Various envelope tracking amplifiers are presented that can be switched between an ET (envelope tracking) mode and a non-ET mode. switches and/or tunable components are utilized in constructing the envelope tracking amplifiers that can be switched between the ET mode and the non-ET mode.
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40. An amplifier arrangement configured to operate based on a mode of operation, comprising:
an adjustable power supply controlled by a first control signal to provide either a variable supply or a constant supply to the amplifier arrangement; and
a power amplifier comprising a configuration arrangement controlled by secondary control signals, the configuration arrangement adapted to configure the power amplifier based on the mode of operation,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on an input signal to the power amplifier, and
the first mode of operation comprises one of: a) envelope tracking, b) envelope following, c) average power tracking, and d) polar modulation.
1. An amplifier arrangement configured to operate based on a mode of operation, comprising:
an adjustable power supply controlled by a first control signal to provide either a variable supply or a constant supply to the amplifier arrangement;
a power amplifier comprising a configuration arrangement controlled by secondary control signals, the configuration arrangement adapted to configure the power amplifier based on the mode of operation, and
one or more tunable matching networks, the one or more tunable matching networks connected to the input and/or output of the amplifier arrangement to provide a desired matching based on the mode of operation,
wherein the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on an input signal to the power amplifier.
5. An amplifier arrangement configured to operate based on a mode of operation, comprising:
an adjustable power supply controlled by a first control signal to provide either a variable supply or a constant supply to the amplifier arrangement;
a power amplifier comprising a configuration arrangement controlled by secondary control signals, the configuration arrangement adapted to configure the power amplifier based on the mode of operation, and
one or more voltage divider resistors in series connection with the adjustable power supply, the one or more voltage divider resistors adapted to generate a proportioned bias voltage to one or more gates of the power amplifier,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on an input signal to the power amplifier, and
the adjustable power supply is adapted to provide bias voltages to the power amplifier, the bias voltages used to bias a drain and/or one or more gates of the power amplifier.
13. A method for configuring an amplifier arrangement to operate based on a mode of operation comprising:
providing an adjustable power supply adapted to provide either variable supply or constant supply to the amplifier arrangement;
providing a first control signal to control the adjustable power supply, wherein the first control signal controls which supply to be provided to the amplifier arrangement;
providing a power amplifier adapted to amplify an input signal, the power amplifier further comprising a configuration arrangement adapted to configure the power amplifier based on the mode of operation;
providing a second control signal to control the configuration arrangement; and
providing one or more tunable matching networks,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on the first control signal and the second control signal, and
the one or more tunable matching networks connected to the input and/or output of the amplifier arrangement are used to provide a desired matching based on the mode of operation.
4. An amplifier arrangement configured to operate based on a mode of operation, comprising:
an adjustable power supply controlled by a first control signal to provide either a variable supply or a constant supply to the amplifier arrangement;
a power amplifier comprising a configuration arrangement controlled by secondary control signals, the configuration arrangement adapted to configure the power amplifier based on the mode of operation, and
a feedback loop, the feedback loop being connected between an input and an output of the amplifier arrangement and is adapted to adjust an amplitude and/or a phase response of the amplifier arrangement based on the mode of operation,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on an input signal to the power amplifier, and
the feedback loop comprises a tunable resistor and a tunable capacitor, the tunable resistor and the tunable capacitor adapted to tune the feedback loop with respect to the amplifier arrangement and controlled by secondary control signals based on the mode of operation.
3. An amplifier arrangement configured to operate based on a mode of operation, comprising:
an adjustable power supply controlled by a first control signal to provide either a variable supply or a constant supply to the amplifier arrangement;
a power amplifier comprising a configuration arrangement controlled by secondary control signals, the configuration arrangement adapted to configure the power amplifier based on the mode of operation, and
a feedback loop, the feedback loop being connected between an input and an output of the amplifier arrangement and is adapted to adjust an amplitude and/or a phase response of the amplifier arrangement based on the mode of operation,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on an input signal to the power amplifier, and
the feedback loop comprises a resistor, a capacitor and a feedback loop switch, the feedback loop switch adapted to enable/disable an operation of the feedback loop with respect to the amplifier arrangement and is controlled by secondary control signals based on the mode of operation.
6. An amplifier arrangement configured to operate based on a mode of operation, comprising:
an adjustable power supply controlled by a first control signal to provide either a variable supply or a constant supply to the amplifier arrangement;
a power amplifier comprising a configuration arrangement controlled by secondary control signals, the configuration arrangement adapted to configure the power amplifier based on the mode of operation,
an envelope detector operative to receive an input rf signal and configured to provide as an output an envelope signal corresponding to an envelope of the input rf signal; and
a control unit connected with the envelope detector, the control unit operative to receive the envelope signal from the envelope detector and configured to generate the first control signal,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on an input signal to the power amplifier, and
the adjustable power supply is adapted to provide bias voltages to the power amplifier, the bias voltages used to bias a drain and/or one or more gates of the power amplifier.
12. A circuital arrangement comprising:
a) an amplifier arrangement configured to operate based on a mode of operation, comprising:
an adjustable power supply controlled by a first control signal to provide either a variable supply or a constant supply to the amplifier arrangement; and
a power amplifier comprising a configuration arrangement controlled by secondary control signals, the configuration arrangement adapted to configure the power amplifier based on the mode of operation;
wherein the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on an input signal to the power amplifier;
b) one or more additional power amplifiers adapted to further amplify an input rf signal provided on one or more separate paths, the one or more separate paths each providing a different amplification level for the input rf signal; and
c) one or more path switches, the one or more path switches adapted to select one particular path to provide an amplified input rf signal to an output port of the arrangement, the one or more path switches being controlled by secondary control signals based on a desired mode of operation.
25. A method for configuring an amplifier arrangement to operate based on a mode of operation comprising:
providing an adjustable power supply adapted to provide either variable supply or constant supply to the amplifier arrangement;
providing a first control signal to control the adjustable power supply, wherein the first control signal controls which supply to be provided to the amplifier arrangement;
providing a power amplifier adapted to amplify an input signal, the power amplifier further comprising a configuration arrangement adapted to configure the power amplifier based on the mode of operation;
providing a second control signal to control the configuration arrangement;
providing one or more additional amplifiers to further amplify an input signal; and
providing one or more bypass switches adapted to include or exclude the one or more additional amplifiers with respect to the amplifier arrangement,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on the first control signal and the second control signal, and
the one or more bypass switches are controlled by secondary control signals based on the mode of operation.
32. An amplifier arrangement configured to operate based on a mode of operation, comprising:
an adjustable power supply controlled by a first control signal to provide either a variable supply or a constant supply to the amplifier arrangement;
a power amplifier comprising a configuration arrangement controlled by secondary control signals, the configuration arrangement adapted to configure the power amplifier based on the mode of operation;
a constant power supply, and
a supply switch adapted to select between the constant power supply and the adjustable power supply to bias the power amplifier, the supply switch controlled by the secondary control signals based on the mode of operation,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on an input signal to the power amplifier,
the adjustable power supply is configured to provide constant supply to bias the drain of the power amplifier when the supply switch selects the constant power supply, and
the mode of operation is based on a combination of: a) a power consumption of the adjustable power supply, b) a power level of an input signal to the amplifier arrangement, and c) a power level of an output signal of the amplifier arrangement.
26. A method for configuring an amplifier arrangement to operate based on a mode of operation comprising:
providing an adjustable power supply adapted to provide either variable supply or constant supply to the amplifier arrangement;
providing a first control signal to control the adjustable power supply, wherein the first control signal controls which supply to be provided to the amplifier arrangement;
providing a power amplifier adapted to amplify an input signal, the power amplifier further comprising a configuration arrangement adapted to configure the power amplifier based on the mode of operation;
providing a second control signal to control the configuration arrangement;
providing one or more additional amplifiers adapted to further amplify an input signal provided on one or more separate paths, wherein the one or more separate paths each provide a different amplification level for the input signal; and
providing one or more path switches, the one or more path switches adapted to select one particular path and are controlled by secondary control signals based on the mode of operation,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on the first control signal and the second control signal.
17. A method for configuring an amplifier arrangement to operate based on a mode of operation comprising:
providing an adjustable power supply adapted to provide either variable supply or constant supply to the amplifier arrangement;
providing a first control signal to control the adjustable power supply, wherein the first control signal controls which supply to be provided to the amplifier arrangement;
providing a power amplifier adapted to amplify an input signal, the power amplifier further comprising a configuration arrangement adapted to configure the power amplifier based on the mode of operation;
providing a second control signal to control the configuration arrangement; and
providing one or more voltage divider resistors in series connection with the adjustable power supply,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on the first control signal and the second control signal,
the adjustable power supply is adapted to provide bias voltages to the power amplifier, the bias voltages used to bias a drain and/or one or more gates of the power amplifier, and
the one or more voltage divider resistors are adapted to generate a proportioned bias voltage to one or more gates of the power amplifier.
11. An amplifier arrangement configured to operate based on a mode of operation, comprising:
an adjustable power supply controlled by a first control signal to provide either a variable supply or a constant supply to the amplifier arrangement;
a power amplifier comprising a configuration arrangement controlled by secondary control signals, the configuration arrangement adapted to configure the power amplifier based on the mode of operation,
a second plurality of stacked fet transistors, wherein the second plurality of stacked fet transistors comprises a number of stacked fet transistors different from a first plurality of stacked fet transistors of the power amplifier; and
a stack switch connected to the adjustable power supply and operative to select between the first plurality of stacked fet transistors or the second plurality of stacked fet transistors, the stack switch is controlled by secondary control signals based on the mode of operation,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on an input signal to the power amplifier, and
the adjustable power supply is adapted to provide bias voltages to the power amplifier, the bias voltages used to bias a drain and/or one or more gates of the power amplifier.
16. A method for configuring an amplifier arrangement to operate based on a mode of operation comprising: providing an adjustable power supply adapted to provide either variable supply or constant supply to the amplifier arrangement;
providing a first control signal to control the adjustable power supply, wherein the first control signal controls which supply to be provided to the amplifier arrangement;
providing a power amplifier adapted to amplify an input signal, the power amplifier further comprising a configuration arrangement adapted to configure the power amplifier based on the mode of operation;
providing a second control signal to control the configuration arrangement; and
providing a feedback loop connected between an input and an output of the amplifier arrangement;
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on the first control signal and the second control signal,
the feedback loop is adapted to adjust an amplitude and/or a phase response of the amplifier arrangement based on the mode of operation, and
the feedback loop comprises a tunable resistor and a tunable capacitor, the tunable resistor and the tunable capacitor being adapted to tune the feedback loop with respect to the amplifier arrangement and being controlled by secondary control signals based on the mode of operation.
24. A method for configuring an amplifier arrangement to operate based on a mode of operation comprising:
providing an adjustable power supply adapted to provide either variable supply or constant supply to the amplifier arrangement;
providing a first control signal to control the adjustable power supply, wherein the first control signal controls which supply to be provided to the amplifier arrangement;
providing a power amplifier adapted to amplify an input signal, the power amplifier further comprising a configuration arrangement adapted to configure the power amplifier based on the mode of operation;
providing a second control signal to control the configuration arrangement;
providing a second plurality of stacked fet transistors, wherein the second plurality of stacked fet transistors comprises a number of stacked fet transistors different from a first plurality of stacked fet transistors of the power amplifier; and
providing a stack switch connected to the adjustable power supply and operative to select between the first plurality of stacked fet transistors or the second plurality of stacked fet transistors, the stack switch is controlled by secondary control signals based on the mode of operation
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on the first control signal and the second control signal.
15. A method for configuring an amplifier arrangement to operate based on a mode of operation comprising:
providing an adjustable power supply adapted to provide either variable supply or constant supply to the amplifier arrangement;
providing a first control signal to control the adjustable power supply, wherein the first control signal controls which supply to be provided to the amplifier arrangement;
providing a power amplifier adapted to amplify an input signal, the power amplifier further comprising a configuration arrangement adapted to configure the power amplifier based on the mode of operation;
providing a second control signal to control the configuration arrangement; and
providing a feedback loop connected between an input and an output of the amplifier arrangement;
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on the first control signal and the second control signal,
the feedback loop is adapted to adjust an amplitude and/or a phase response of the amplifier arrangement based on the mode of operation, and
the feedback loop comprises a resistor, a capacitor and a feedback loop switch, the feedback loop switch being adapted to enable or disable an operation of the feedback loop with respect to the amplifier arrangement and being controlled by secondary control signals based on the mode of operation.
19. A method for configuring an amplifier arrangement to operate based on a mode of operation comprising:
providing an adjustable power supply adapted to provide either variable supply or constant supply to the amplifier arrangement;
providing a first control signal to control the adjustable power supply, wherein the first control signal controls which supply to be provided to the amplifier arrangement;
providing a power amplifier adapted to amplify an input signal, the power amplifier further comprising a configuration arrangement adapted to configure the power amplifier based on the mode of operation;
providing a second control signal to control the configuration arrangement;
providing an envelope detector operative to receive an input signal and configured to provide as an output an envelope signal corresponding to an envelope of the input signal; and
providing a control unit connected with the envelope detector, the control unit operative to receive the envelope signal from the envelope detector and configured to generate the first control signal,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on the first control signal and the second control signal, and
the adjustable power supply is adapted to provide bias voltages to the power amplifier, the bias voltages used to bias a drain and/or one or more gates of the power amplifier.
18. A method for configuring an amplifier arrangement to operate based on a mode of operation comprising:
providing an adjustable power supply adapted to provide either variable supply or constant supply to the amplifier arrangement;
providing a first control signal to control the adjustable power supply, wherein the first control signal controls which supply to be provided to the amplifier arrangement;
providing a power amplifier adapted to amplify an input signal, the power amplifier further comprising a configuration arrangement adapted to configure the power amplifier based on the mode of operation;
providing a second control signal to control the configuration arrangement; and
providing one or more bias terminal supply switches,
wherein:
the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on the first control signal and the second control signal,
the adjustable power supply is adapted to provide bias voltages to the power amplifier, the bias voltages used to bias a drain and/or one or more gates of the power amplifier and
the bias terminal supply switches are connected to one or more gate bias terminals of the power amplifier and are adapted to select between providing one or more gate bias terminals with bias voltages from either an external power supply or the adjustable power supply, the one or more bias terminal supply switches controllable by secondary control signals based on the mode of operation.
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a) a power level of the input signal, and b) a desired amplification level of the input signal.
28. The circuital arrangement of
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33. The amplifier according to any one of
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37. The method according to
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42. The amplifier arrangement according to
a constant power supply, and
a supply switch adapted to select between the constant power supply and the adjustable power supply to bias the power amplifier, the supply switch controlled by the secondary control signals based on the mode of operation.
43. The amplifier arrangement according to
44. The amplifier arrangement according to
45. The amplifier arrangement according to
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The present application claims priority to U.S. provisional application No. 61/747,009 entitled “Amplifier Dynamic Bias Adjustment for Envelope Tracking” filed on Dec. 28, 2012 and incorporated herein by reference in its entirety. The present application also claims priority to U.S. provisional application No. 61/747,016 entitled “Optimization Methods for Amplifiers with Variable Supply Power” filed on Dec. 28, 2012 and incorporated herein by reference in its entirety. The present application also claims priority to U.S. provisional application No. 61/747,025 entitled “Amplifiers Operating in Envelope Tracking Mode or Non-Envelope Tracking Mode” filed on Dec. 28, 2012 and incorporated herein by reference in its entirety. The present application also claims priority to U.S. provisional application No. 61/747,034 entitled “Control Systems and Methods for Power Amplifiers Operating in Envelope Tracking Mode” filed on Dec. 28, 2012 and incorporated herein by reference in its entirety.
The present application is related to U.S. application Ser. No. 13/829 946 entitled “Amplifier Dynamic Bias Adjustment for Envelope Tracking” filed on even date herewith and incorporated herein by reference in its entirety. The present application is also related to U.S. application Ser. No. 13/830,070 entitled “Optimization Methods for Amplifier with Variable Supply Power” filed on even date herewith and incorporated herein by reference in its entirety. The present application is also related to U.S. application Ser. No. 13/830,555, entitled “Control Systems and Methods for Power Amplifiers Operating in Envelope Tracking Mode” filed on even date herewith and incorporated herein by reference in its entirety.
1. Field
The present disclosure relates to envelope tracking amplifiers. In particular, the present disclosure relates to amplifiers operating in envelope tracking mode or non-envelope tracking mode.
2. Description of Related Art
Although nonlinear amplifiers can exhibit higher efficiency than linear amplifiers, until recently nonlinear power amplifiers were undesirable for use with radio frequency (RF) signals produced by linear modulation schemes. A technique known as “envelope tracking” (ET) was developed that allows use of linear amplifiers to approach the efficiency of non-linear power amplifiers with RF signals produced by linear modulation schemes (e.g. where it is important to maintain relative variation within an envelope of an RF signal). By dynamically adjusting a DC bias voltage at a drain terminal of an output transistor of a power amplifier in a manner that roughly follows a time varying envelope of the RF signal, a signal produced by a linear modulation scheme can be amplified by a power amplifier without undesirable envelope distortion. Effectively, the technique of envelope tracking shifts a burden of linearity away from the power amplifier to an ETPS (envelope tracking power supply) that is connected to the drain terminal of the output transistor of the nonlinear power amplifier.
According to a first aspect of the present disclosure, an amplifier arrangement configured to operate based on a mode of operation is provided, the amplifier arrangement comprising: an adjustable power supply controlled by a first control signal to provide either a variable supply or a constant supply to the amplifier arrangement; and a power amplifier comprising a configuration arrangement controlled by secondary control signals, the configuration arrangement adapted to configure the power amplifier based on the mode of operation, wherein the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on an input signal to the power amplifier.
According to a second aspect of the present disclosure, a method for configuring an amplifier arrangement to operate based on a mode of operation is presented, the method comprising: providing an adjustable power supply adapted to provide either variable supply or constant supply to the amplifier arrangement; providing a first control signal to control the adjustable power supply, wherein the first control signal controls which supply to be provided to the amplifier arrangement; providing a power amplifier adapted to amplify an input signal, the power amplifier further comprising a configuration arrangement adapted to configure the power amplifier based on the mode of operation; and providing a second control signal to control the configuration arrangement, wherein the mode of operation comprises a first mode of operation and a second mode of operation, the first mode of operation corresponding to the adjustable power supply providing variable supply to the power amplifier, the second mode of operation corresponding to the adjustable power supply providing constant supply to the power amplifier, the mode of operation switching between the first mode of operation and the second mode of operation and vice versa based on the first control signal and the second control signal.
The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more embodiments of the present disclosure and, together with the description of example embodiments, serve to explain the principles and implementations of the disclosure.
The present disclosure describes methods and arrangements for amplifiers operating in envelope tracking mode or non-envelope tracking mode. Furthermore, configuration methods and arrangements using such amplifiers as well as related system integration and controls are presented. Such amplifiers may be used within mobile handsets for current communication systems (e.g. WCMDA, LTE, etc. . . . ) wherein amplification of signals with frequency content of above 100 MHz and at power levels of above 50 mW is required. Such amplifiers may also be used to transmit power at frequencies and to loads as dictated by downstream splitters, cables, or feed network(s) used in delivering cable television service to a consumer, a next amplifier in an RF chain at a cellular base station; or a beam forming network in a phased array radar system, and other. The skilled person may find other suitable implementations for the present disclosure, targeted at lower (e.g. audio) frequency systems as well, such as audio drivers, high bandwidth laser drivers and similar. As such, it is envisioned that the teachings of the present disclosure will extend to amplification of signals with frequency content of below 100 MHz as well.
Throughout the present disclosure, embodiments and variations are described for the purpose of illustrating uses and implementations of inventive concepts of various embodiments. The illustrative description should be understood as presenting examples of the inventive concept, rather than as limiting the scope of the concept as disclosed herein.
Throughout the present disclosure, the terms “linear region” and “compression region” refer to basic operations of an amplifier stage. When operating in the linear region, the amplifier output response is linear, in other words, the change in the output power of the amplifier is linear with respect to a corresponding change in input power. This is the typical response of the amplifier at low input power levels. Typically there is minimal change in the amplifier's gain or phase response as a function of input power in this region. As the input power level to the amplifier increases and the amplifier output approaches its maximum output level, known as the saturation level, the output response of the amplifier becomes non-linear. In this case, the change in output power of the amplifier for a given change in input power decreases as the output power approaches the saturation level. Once the output power reaches saturation level, any incremental increase in input power will not affect the output power level (zero incremental gain), thus remaining at saturation. The transition region between the linear region and the region of zero incremental gain is referred to as the compression region of operation of the amplifier. The region of zero incremental gain wherein the output power remains at the saturation level is referred to as the saturation region. One measure of the amount of compression typically used in the industry is the −1 dB compression point. This is the point at which the gain has been reduced by 1 dB. Furthermore, it is common in the industry to refer to the saturation level as the −3 dB compression point.
Operating an amplifier from a fixed supply results in degraded efficiency when the peak-to-average ratio of the modulation is large. This is because the supply voltage needs to be high enough to accommodate the peak, even though most of the time a much lower supply voltage could be used. The voltage from the supply that is not needed for the RF signal is wasted as heat in the amplifier as depicted by
One could imagine coarsely following the envelope of the modulated signal with a variable power supply. This provides an advantage if the variable power supply is efficient. The applied variable supply voltage can be relatively slow or fast compared to the modulation frequency and still provide a benefit, as all cases would result in less power dissipated in the amplifier. In this variable supply case, it is assumed that the supply is always some level above the instantaneous supply voltage needed, which means that all amplitude information is from the RF input waveform, and the amplifier remains as a linear amplifier (operates in the linear region). The amplifier would remain as a linear amplifier throughout (constant gain and phase), but may experience distortion such as AM-PM (amplitude modulation-to-phase modulation) due to the supply voltage changes. Although industry standard definitions don't exist at this time, some refer to this method as envelope following. The supply is following the envelope at some level, but doesn't have to follow it exactly.
The next level of improvement comes when the dynamic supply voltage no longer maintains headroom or some margin between the needed voltage and the supplied voltage. In this case, the amplitude of the amplifier's output is set or limited by the supply voltage. This puts the amplifier in compression at these instants, which typically further improves the efficiency because now the efficiency of the amplifier has improved along with the reduced power due to excess voltage wasted as heat. Transition from linear to compressed regions of operation obviously results in reduced gain for the amplifier. Additionally, the phase response often changes as this transition occurs. The transition from compression to linear regions of operation will have the equal but opposite change in gain and phase.
Operating in this mode where the envelope signal from the dynamic supply puts the amplifier into compression means that the output of the dynamic supply must be exact in time or phase and also amplitude, otherwise distortion will result at the output of the amplifier. In other words, the amplitude or envelope path is separate from the phase path, but both must have acceptable time alignment when the two components are combined. This time alignment must be preserved over the bandwidth of the modulation, thus imposing limits on the phase distortion allowed in the paths.
The bandwidth of the envelope signal needs to be several times larger than the baseband modulation bandwidth. This is because a polar decomposition of the modulation into magnitude and phase shows much wider bandwidth for the amplitude portion. Another way to think of it is by considering the modulation in an IQ constellation format. A transition from one symbol to the next may make a phase change of up to 180 degrees, but it may go from the outermost symbol's amplitude, through a peak, then approach or even reach zero, and return to an outermost symbol's amplitude, all within one symbol transition. That translates into a fast amplitude component. This mode of operation, where the envelope must track the signal amplitude precisely, is often referred to as envelope tracking.
In the envelope tracking case, the amplitude and phase information are being supplied at the input to the amplifier (complex modulation). The dynamic supply voltage may further set the amplitude, but isn't required at all signal levels. The dynamic supply voltage may apply the envelope signal at the peaks and through some portion of the modulation, but then reach a minimum value and let the amplitude information at the amplifier's input continue to provide the amplitude or envelope through other portions of the modulation. This minimum value of the dynamic supply is typically chosen based on the capabilities of the dynamic supply and also the minimum acceptable supply voltages for the amplifier.
If the supply were to follow the envelope all the way through every symbol transition and thus impart all amplitude modulation through the envelope path, the result would be a polar modulator. A polar modulator or polar amplifier has all phase information applied at one port, usually the RF input of an amplifier, and all amplitude information applied at a second port, usually the output bias for an amplifier. Polar modulators or amplifiers are challenging for several reasons: 1) the bandwidth of the amplitude signal is much wider than the baseband modulation and wider than the ET envelope bandwidth, 2) the amplitude signal may approach or even reach zero in the modulation, which is difficult to do in a real amplifier setup without significant distortion, and 3) it is difficult to create a modulated signal over a large range of output powers.
It should be noted that although envelope tracking is used throughout the current disclosure to showcase the various embodiments, many of the teachings of the present disclosure apply not only to envelope tracking, but to envelope following, average power tracking, and polar modulation as well.
Memory effects are also important in amplifiers. Memory effects are when the response of the amplifier is dependent on a previous state of the amplifier. For example, if the input modulation hits a peak and causes increased power dissipation in the amplifier device, the device may experience self-heating or a device temperature increase from the power dissipation. If the modulation amplitude decreases a moment later, the amplifier's gain and phase may still be altered due to the heating associated with the modulation from the previous time. There are many possible sources of memory effects, including thermal, bias circuits, and matching components. Operation in envelope following, envelope tracking, and polar modulation modes can further introduce memory effects due to the dramatically changing bias conditions. These effects must be considered by the amplifier and system designers.
An envelope tracking power supply (ETPS) (180), such as, for example, a variable voltage or current source (e.g. variable DC-DC converter), can be connected to receive power from power supply VDD (185) and output a dynamic bias voltage to a third resistor (175) with a resistance value represented by RD3, and to an inductor (170). The dynamic bias output from the ETPS can be controlled by a control voltage or current signal “ctrl” (190). As a consequence of the control signal (190) applied to the ETPS (180) the dynamic bias voltages ETRD3 and ETDR are functions of a time varying envelope of an RF input signal (e.g.
Envelope tracking power supplies need to have a bandwidth wide enough to support the amplitude component of the modulation. As mentioned, this can be many times greater than the baseband bandwidth. To accomplish this, many ETPSs are built using a combination of a DC-DC switching converter and an analog error amplifier. They can be constructed in many ways, including serial and parallel combinations. The switching DC-DC converter is typically more efficient than the analog amplifier, but has a more limited bandwidth. This is because the DC-DC converter can support a modulation bandwidth that is approximately a factor of 5 to 10 lower than its switching frequency. Faster DC-DC converters are desired. The process choice plays an important role in setting the bandwidth of the DC-DC converter. While hybrid technologies such as CMOS (control circuits) and GaN (switchers) might offer high speed and efficiency, monolithic integration benefits such as cost and size may push the solution to a process such as CMOS, CMOS SOI, or CMOS SOS. The benefits of the SOI and SOS processes include a variety of benefits, one of which is lower parasitic capacitance, and thus faster speeds. If the DC-DC converter is fast enough, the analog amp would not be required.
There are numerous benefits to integration of these functions and even integration with the amplifier itself. Integration of the ETPS or portions of it with the amplifier can result in reduced parasitic inductance, reduced parasitic capacitance, reduced phase delays and distortion, and device matching. With monolithic integration of circuit blocks that may include the amplifier, ETPS, and/or control circuits, one can make use of the matching between devices to track and adjust variations due to manufacturing tolerances, temperature and others in ways that can't be supported across multiple ICs and possibly multiple technologies.
The term “port” refers to a two terminal pair, where a signal can be applied across the two terminals. As used herein, the term “dynamic bias voltage” may refer to a bias voltage that can vary with respect to time. The envelope signal may be extracted from the RF input signal by way of an envelope detector.
Turning back to
The third, second, and first resistors (175), (140), and (130), respectively, form a voltage divider network such that a set of bias voltages ETG2, ETG3 are scaled versions of the dynamic bias voltage ETRD3 and therefore vary as a function of the envelope signal. For example, the bias voltage ETG2 can be expressed according to the following equation as per standard voltage division:
ETG2=ETRD3*(R20)/(R20+R32+RD3).
The voltage divider network may be considered to be an example embodiment of bias adjustment circuitry. As used herein, the term “bias adjustment circuitry” may refer to circuitry that is configured to perform an adjustment operation on a dynamic bias voltage signal prior to applying the dynamic bias voltage signal to bias terminals of an amplifier that comprises stacked FETs. In the embodiment shown in
During operation of the envelope tracking amplifier (100), a bias voltage at the drain of the third FET (155), delivered through the inductor (170), in addition to the bias voltages ETG2 and ETG3 at the gate of the second FET and the gate of the third FET, respectively, vary as a function of the envelope signal as dictated by the ETPS control signal (190).
Additionally, a bias voltage ETG1 can be applied to a first gate bias node (110) to bias a gate of the first FET (115). The bias voltage ETG1 can be either a fixed voltage or a dynamic bias voltage. One or more of the gate bias voltages ETG1, ETG2, ETG3 can be scaled, amplitude shifted, phase shifted, inverted, and/or subject to any mathematical operation (e.g. implemented by an op-amp circuit) with relation to the dynamic bias voltage ETDR supplied to the inductor (170), such operations performed by other embodiments of bias adjustment circuitry. Introducing a phase shift in one or more of the gate bias voltages ETG1, ETG2, ETG3 can compensate for unintended effects of the envelope tracking amplifier (100) by pre-distorting phase(s) of the first, second and/or third FET (115, 120, 155). In some embodiments, the bias voltage ETG1 is held fixed while the other two bias voltages ETG2 and ETG3 vary as a function of the envelope signal. In other possible embodiments, one or more of the gate bias voltages ETG1, ETG2, ETG3 are dynamic bias voltages while other gate bias voltages are fixed bias voltages. By way of example, and not of limitation,
The envelope tracking amplifier (100) can be used as a driver, a final, or any other type of amplifier. For example, such an amplifier may be used within a mobile handset for current communication systems to amplify signals with frequency content above 100 MHz and at power levels of above 50 mW. The stack of FETs may comprise any number of FETs (e.g.
In some embodiments, the control signal (190), that is used to determine the dynamic bias voltages ETRD3 and ETDR, closely follows the envelope signal. In other embodiments, the control signal (190) closely follows peaks of the envelope signal and can be slightly higher than the troughs of the envelope signal. In yet other embodiments, the control signal (190) may alternate between following the envelope signal during certain periods of time, and being constant during other periods of time.
In some embodiment it may be desirable to modulate the gate voltage via an envelope signal, such as ETRD3, while letting the gate float with the RF signal as described earlier. In this situation and considering the third FET transistor (155), the corresponding gate capacitor (150) and resistor (R144) have to be chosen such as the low pass filter seen by ETRD3 passes the entire frequency spectrum of the envelope signal, and at the same time the impedance seen by the RF signal looking from the gate of the transistor (e.g. capacitor (150) in parallel with resistor (R144)) is such that the RF signal attenuation is set by the capacitor as designed and not by the bias and envelope path. Given these constraints, derivation of corresponding resistor and capacitor values, as well as derivation of the more generalized formula taking into account for example transistor's model and other components within the circuit, are well within the reach of the skilled person.
Alternatively, the dynamic bias voltage ETRD3 can be inversely related to the envelope signal. As voltage at a drain terminal of the third FET (155) becomes sufficiently low, the third FET (155) and/or the second FET (120) begin(s) to act as a gate voltage controlled resistor (triode) instead of a gate voltage controlled current source (saturation). If the dynamic bias voltage ETRD3 becomes high as the third FET (155) and/or the second FET (120) begin(s) to act as a gate voltage controlled resistor, an equivalent resistance presented by the third FET (155) and/or the second FET (120) can become low since an equivalent resistance presented by a FET in triode operation can be inversely proportional to a gate bias voltage of the FET in triode operation. As a result, when the dynamic bias voltage ETRD3 is inversely related to the envelope signal, it is possible that the third FET (155) and/or the second FET (120) do(es) not significantly hinder operation of the envelope tracking amplifier (100) when voltage at a drain terminal of the third FET (155) becomes sufficiently low that the third FET (155) and/or the second FET (120) begin(s) to act as a gate voltage controlled resistor (triode).
In some embodiments it may be desirable to replace the R-C networks (e.g. 134, 125 of
In some embodiments, the baseband controller can be used to generate the envelope signal, whether from the baseband signal or directly from the RF signal. Furthermore, the baseband controller can generate the gate bias voltages ETG1, ETG2, and ETG3 in a manner similar to the embodiments previously discussed by scaling, amplitude shifting, phase shifting, inverting, and/or performing any mathematical operation (e.g. implemented by an op-amp circuit or digital signal processors) on the envelope signal. By way of example, and not of limitation, digital techniques (e.g. look-up tables, D/A and A/D converters) can be used to generate arbitrary voltage signals that are then used as the gate bias voltages ETG1, ETG2, and ETG3. Analog circuit techniques may be used to generate arbitrary voltage signals (including fixed voltages) that can then be used as the gate bias voltages ETG1, ETG2, and ETG3 as well. Example embodiments of such configurations can be found in
The embodiments shown in
The capacitor (510) may block a DC component of the dynamic bias voltage ETRD3 and pass a time-varying component of the dynamic bias voltage ETRD3. The DC voltage VDC3 can restore the DC component of the dynamic bias voltage ETRD3 to the gate of transistor (155). In a similar manner, VDC2 can restore the DC component to the gate of transistor (120). The embodiment of
Capacitor (510) may be used to create a desired phase shift between the dynamic bias voltage ETRD3 and the third gate bias voltage ETG3. Circuit analysis that accounts for the resistor (520), the third gate capacitor (150), possibly a parasitic gate capacitance of the third FET (155), and other components surrounding node (145) to derive an equation for the amount of phase shift is within the capability of a person skilled in the art. Results of such analysis can be used to determine appropriate values of C3, RD3, RG3, and the third gate capacitor (150) and resistor (144) that can yield a desired phase shift.
With further reference to
ETG2=ETRD3*(R20//RG2/(R20//RG2+RD2+jωL32)
The // sign indicates a parallel combination of resistors where: Rparallel=(R1*R2)/(R1+R2)
Complex number analysis of the equation stated above can reveal that a phase shift in an amount equal to an inverse tangent of a quantity represented by ω*L32/(R20+RD2) can occur between the dynamic bias voltage ETRD3 to the second gate bias voltage ETG2. A more complete analysis that accounts for the second gate capacitor (125) and possibly a parasitic gate capacitance of the second FET (120) is within the capability of a person skilled in the art. Results of such analysis can be used to determine appropriate values of L32, RD2, R20, and the second gate capacitor (125) that can yield a desired phase shift.
In other embodiments similar to
In some embodiments, a capacitive-resistive network can be connected between the first gate bias node (110) and the gate of the first FET (115). In circuits where the capacitive-resistive network is connected between the first gate bias node (110) and the gate of the first FET (115), a DC voltage can also be applied to the gate of the first FET (115) to restore a DC component of a dynamic bias voltage that is applied to the first gate bias node (110), in a manner similar to the capacitive-resistive network shown in
As previously discussed, in the case of an amplifier configured for ET operation, also referred to as “ET mode of operation”, such amplifier is susceptible to operate in either the linear or the compression region, latter being the desired region of operation. Furthermore, when the amplifier is not configured for ET mode of operation (non-ET mode), for example by virtue of supplying a fixed supply voltage to the amplifier, the amplifier is also susceptible to operate in either linear or compression regions, but in such case the desired region of operation is the linear region.
As discussed in prior sections, ET amplifiers operate as a function of an envelope of the input RF signal, referred to as the envelope signal, to the amplifier which may be applied to their supply and biasing inputs. The envelope signal can be equivalent to the time varying tracking signal corresponding to the successive peaks of the input RF signal. When the output of the amplifier tracks the envelope signal due to a change in the applied supply level, the amplifier operates mainly in the highly efficient compression region. When operating in this region, the applied supply restores the amplitude of the output which is lost due to operation in the compression region of the amplifier (AM/AM distortion). Alternatively and mainly at low input power levels, the amplifier output follows the envelope of the input RF signal and operates in the linear region, which is a less efficient region of operation typical to non-ET configurations.
One of the main drives for ET implementation within power amplifiers is the improvement in power efficiency while maintaining a good linear response of the amplifier. ET seeks to improve efficiency by adjusting the supply power based on roughly following the time varying envelope signal thereby adjusting the supply power to the amplifier based on the potential demand. Thus less supply power is provided for lower level input signals, thereby reducing wasted power provided to the amplifiers. Adjustment of the supply power for ET implementation can be done by either adjusting the supply voltage (
The supply control signal is constructed using the envelope signal and such as to reflect limitations associated with ET mode of operation, such as bandwidth limitation of the dynamic output of the variable power supply as well as limitations in output linearity of the amplifier at low power levels when operating in the compression region (e.g. due to low VDS voltage across one or more of the stack transistors), latter limitation defining a minimum preset power level for ET mode of operation. Additional scaling and offset components are applied to the control signal such as to map the output signal of the amplifier to the desired operational range.
Even though the amplifier is set to operate in ET mode, there are instances when the combination of low input RF power level to the amplifier and the ET supply power level (controlled by the supply control signal) removes the amplifier from the compression region and puts it into the traditional linear region of operation typical to non-ET configurations. This switching from compression region to linear region of operation and vice versa, is dependent on the modulation scheme used on the input RF signal, but expected to occur especially in RF signals with high peak-to-average power ratio.
As discussed earlier, operating in the compression region has the advantage of linearity and reduced power dissipation to some degree.
When the amplifier makes the transition from the compression region to the linear region, it operates with less power efficiency and with some added level of distortion to the amplified output as the benefit of AM/AM amplitude correction via supply power modulation is lost. Another undesired side effect of the switching between regions of operation of the amplifier is the change in gain at the output of the amplifier stage; when in the compression region the output signal is clipped and thus reduces the gain of the amplifier as compared to the gain obtained when operating in the linear region.
The present disclosure provides systems and methods by which said limitations can be overcome or at least reduced by some degree. For example, a feedback network can be used within a feedback path around an ET amplifier to create a closed loop configuration such as to optimize response when the amplifier is pushed into operating in the linear region. Given the electrical characteristics of the amplifier, traditional feedback amplifier design techniques can be used to optimize amplifier performance in the linear region and thus positively affect corresponding vital parameters such as gain, phase, distortion and stability. This feedback network can be switched in and out, to effectively activate and de-activate the feedback loop, in unison with the desired operational mode and/or region of operation of the amplifier (ET versus non-ET modes or compression versus linear regions) and under control of a main controller unit which may be aware of the input RF signal to the amplifier or the corresponding envelope signal.
One example of this benefit is that by using feedback in the linear region and removing the feedback in the compressed region is that the gain and efficiency are maximized in the compressed region, while linearity is maximized in the linear region. Another example is that using feedback in the linear region and removing the feedback in the compressed region lets one choose how much gain and thus gain compression (e.g. amount of gain less than the equivalent gain in the linear region) they want in their system as a design parameter, not just a device property.
In another embodiment further linearization of the amplifier can be obtained by adjusting the various gate bias supplies (e.g. ETG1, ETG2, ETG3 of
Such a controller mentioned in the above embodiments can be the transceiver unit traditionally used in modern communication systems. The controller can generate a switch control signal which is synchronized to the change in operational mode/region of the amplifier.
Furthermore and in order to compensate for possible mismatch of the output impedance of the amplifier stage between the two distinct configurations (feedback loop active and feedback loop not active), and thus loss of effective output power seen by the next stage, a tunable matching network can be added at the output stage of the power amplifier (e.g.
In another example, a two-stage amplification can be used wherein the first stage preconditions the input RF power level to the second stage such as to reduce switching of the second stage to the linear region of operation, thus enhancing overall power efficiency and linearity of the output stage; since minimum RF input power level to the second amplifier is increased by the first amplification stage, second amplifier will operate more time in the compression region for an increase in overall efficiency. In this configuration, both stages can be ET amplifiers, each with its own ET power supply and each fitted with a switchable feedback network for optimal overall performance.
The feedback network (2100) is used within a feedback path to create a feedback loop around the driver stage (2115), such as when the feedback loop is active, the output of the driver stage (2115) is taken and combined with the input of the same driver stage (2115) after being subjected to the transformation defined by the feedback network (2100). Such feedback loop is active when the switch (2112) is closed, thus engaging the feedback network (2100) into creating the loop. Control signal to switch (2112) is provided at terminal (2102). By way of example and not limitation, feedback network (2100) is comprised of the switch (2102) and RC series network (2110) in series.
As shown in
A possible circuital connection between the amplifier stage (e.g. a driver stage or a final stage) and the dynamic power source is shown in
Going back to
Furthermore and as depicted in
As previously noted, control signals for input controls (2132, 2142) can be generated within a transceiver unit, which typically generates the modulated RF input signal to the amplifier arrangement at input terminal (2105), and thus has full knowledge of the input data used to generate the RF signal. As such, the transceiver unit can be fitted with dedicated circuitry and lookup tables suitable to generate the desired control signals not only for the supply voltages (e.g. gates and drain bias supplies) but also for controlling the switch unit (2112) via input control (2102) and the tunable matching network unit (2120) via input control (2103). For example, when a control signal to input (2132) dictates an ET operational mode for the amplifier unit (2115), the transceiver unit concurrently generates a control signal (2102) to the switch unit (2112) to open the switch and a control signal (2103) to tunable matching network unit (2120) to optimize impedance matching between input stage to amplifier unit (2125) and output stage of amplifier unit (2115) when in ET mode. Alternatively, when control signal to input (2132) dictates a non-ET operational mode, control signals to close the switch unit (2112) and to set the tunable matching network unit (2120) for non-ET impedance matching are concurrently generated by such transceiver unit. In this case, the feedback network (2100) and tunable matching network unit (2120) determine the response of the amplifier. Furthermore and as previously mentioned, gate bias supplies to various transistors within the stack may additionally be adjusted, by same controller unit, to control amplifier's response in either modes of operation.
The person skilled in the art will understand that a transceiver unit is just one example of a controller capable of performing the task of configuration control for elements (2112, 2115, 2120) of
While the control signal used to control the output level of the variable power supply can steer a corresponding amplifier stage to operate in a desired region, due to limitations discussed earlier when operating in an ET mode, exclusive operation in more efficient compression region is not always possible as there will be instances where the input RF power level is smaller than the supply power level, since latter is bounded by the minimum preset level, causing the amplifier to operate in the non-compression (linear) region.
As such, the control signal fed to input (2132) of the variable power supply unit (2130) defines the operational strategy of the amplifier unit (2115) with respect to the input RFin signal fed to input (2105). In other words, the switching of the amplifier unit (2115) between operating in the compression and linear regions is not only function of the input control (2132), but also function of input RFin signal (2105). That is, when operating in the ET mode, for a given power level of the RFin signal (2105) at a given instance, compression occurs if such power is larger than the dynamic power supplied to the amplifier unit (2115), thus causing the amplifier to operate in the compression region. Alternatively, when power level of the RFin signal (2105) is below the threshold set by the variable power supply, compression does not occur and amplifier (2115) operates in the linear region. As previously mentioned, this switching of the amplifier operation from one region to the other is dependent on the modulation scheme used to generate the input RF signal and becomes more pronounced in cases where modulation schemes with high peak-to-average power ratio are used.
Considering the embodiment of
The above changes in amplifier configuration and various adjustments affecting its operation may engender some undesired effects measurable at the output signal of the amplifier. In one embodiment, these undesired effects may be further controlled by pre-distortion (e.g. phase, amplitude) of the input RF signal to the amplifier stage, in a manner to compensate for these effects. Simulation results may be used to create lookup tables which may be subsequently used by the controller during operation. These lookup tables may include mapping of the various changes and adjustments to pre-distortion coefficients to be applied to the input RF signal.
Although
In a similar manner and as depicted in
In yet another embodiment and as depicted by
Furthermore, although two amplifiers are currently shown in
In
In the above embodiments a switch unit is used to activate or de-activate a feedback loop around an amplifier stage with the overall goal of controlling differences in the amplifier's response function when the amplifier's region of operation changes from linear to compression. Additionally, it was noted that in a two stage configuration (e.g. a driver stage followed by a final stage), the first stage amplifier gain when operating in the linear region (feedback network is engaged) can be selected such as to reduce the switching of the final stage to the linear region, thus increasing the time the final stage operates in the more efficient compression region.
In yet another embodiment of the present disclosure, as shown in
The person skilled in the art will know that he feedback function or variable gain function can be realized in various ways. For example, the feedback can be in the form of a shunt resistor from the source of the input device to ground (degeneration), or a variable gain amplifier topology, many of which are common in the industry. The feedback can be switched, variable, or variable and switched.
It should be noted that although the inventors have discussed a “feedback network” as a means to optimize and adapt gain/response of an amplifier stage when switching between regions of operation (e.g. linear region vs. compression region), for the sake of simplicity and not by limitation of the embodiments, all figures show the feedback network as an RC series network with the addition, in some cases, of a switch. A person skilled in the art will understand that the presented embodiments allow for various types of feedback networks, whether tunable or fixed and/or using active or passive elements, to be used, based on the desired overall response of the corresponding amplifier stage and governed by known amplifier feedback design techniques. Tuning of such a feedback network is merely limited by the elements comprised in the network and can be easily adapted for given the built-in intelligence in the controller.
Furthermore, it should also be noted that although
In
In
As previously discussed, the term “ET” mode can refer to the mode of operation where one or more bias voltages or bias currents are varied as a function of an envelope signal. Such mode can be used to cause the envelope tracking amplifier to operate in a compression region thereby increasing amplifier efficiency. Also, the term “non-ET” mode can refer to the mode of operation where no bias voltages and no bias currents are varied (e.g. as a function of an envelope signal). Such mode can be used to cause the envelope tracking amplifier to operate in a linear region.
Going back to
In one embodiment, the amplifier system would be switched from ET mode to non-ET mode of operation when the input and thus output power level drops to a point that the power consumption in the ETPS is more than the power it saves. As an example, the amplifier may operate in ET mode from the maximum average output power down to the maximum average power −10 dB. At that time the ETPS would be switched off, bypassed, or switched to an average power tracking mode, (average power tracking mode is one where a DC-DC converter slowly follows the average power of the amplifier and an analog error amp would not be required). The non-ET mode would be used at this power and all lower power levels. The example of Pmax-10 dB is an example. The actual value depends on the system optimization, including amplifier efficiency with and without ET and the power consumption of the ETPS.
A transceiver can be such an example of a source that could be used to provide control signals to the envelope tracking amplifier (100) indicating a desired mode of operation and thereby configure the envelope tracking amplifier (100) to adapt to the desired mode of operation. The transceiver used to provide an input signal to the envelope tracking amplifier (100) could know a desired mode of operation for a particular input signal being provided. Thus an embodiment could be imagined where the transceiver also provides control signals to the ETPS and/or related switches and tunable elements of an embodiment to configure the embodiment to operate accordingly.
Furthermore, the control unit (3420) can also provide one or more secondary control signals (3430) to other components (e.g. a configuration arrangement comprising switches and/or tunable elements such as tunable resistors and tunable capacitors) within the envelope tracking amplifier (3400). The one or more secondary control signals (3430) can configure one or more switches and/or one or more tunable components within the envelope tracking amplifier (3400) described below such that the one or more switches and/or one or more tunable components are adapted to operate according to the desired mode of operation.
As stated above, other devices external to the envelope tracking amplifier can provide one or more control signals to the ETPS (180) and/or related switches and tunable elements. For example, a transceiver can be used to provide an input signal to the envelope tracking amplifier. Since the transceiver would know what is being provided to the envelope tracking amplifier, the transceiver could also provide an indication (either through an envelope signal and/or control signal) to the ETPS (180) and/or related switches and tunable elements to configure the envelope tracking amplifier to operate in a desired mode of operation (ET mode or non-ET mode) adapted for the input signal provided.
The envelope tracking amplifier (100, 800) shown in
As stated above, it is desirable to have an envelope tracking amplifier be configurable to operate between operating in ET and non-ET mode. In such situations the envelope tracking amplifier (such as the envelope tracking amplifier (100) of
In some other embodiments switching between other modes, not just ET and non-ET may be desired. This may include such modes as polar, ET, envelope following, and fixed supply.
Alternatively,
Generally speaking, embodiments comprising a plurality of amplifiers that are operatively connected in cascade, where one or more of the amplifiers are envelope tracking amplifiers, configured to switch between the ET mode and the non-ET mode, can be accommodated by using one or more switches to selectively include or bypass one or more amplifiers from among the plurality of amplifiers. When operating in the ET mode, appropriate operation of the switches can increase the total number of amplifiers present in a signal amplification path. Conversely, when operating in the non-ET mode, appropriate operation of the switches can decrease the total number of amplifiers present in the signal amplification path. The term “signal amplification path” can refer to a path which an input signal flows through while being amplified by successive amplifiers operating in cascade. Numerous embodiments that operate by using switches to selectively include or omit one or more amplifiers in the signal amplification path are possible, two of which will be described below. Implementations of such embodiments are alternative ways to configure a particular embodiment to operate according to a desired mode of operation (ET or non-ET mode).
Alternatively, a second through path can be added to the embodiment shown in
Furthermore,
Returning to
When switching between ET mode and the non-ET mode, a resistance value and/or a capacitance value present at a gate of any FET in a stack of FETs used in constructing an envelope tracking amplifier, except a first FET (e.g. the first FET (115) in
For the ET mode operation, as seen in
With reference to the embodiment shown in
Another alternative can be seen in
Furthermore,
Alternately, the embodiments shown in
The embodiment shown in
Alternatively, the gate resistor switch (4610) of the embodiment shown in
Generally speaking, when switching between the ET mode and the non-ET mode, an effective number of FETs in a stack of FETs used to construct an envelope tracking amplifier can be configured based on the selected mode of operation. By way of example, and not of limitation, if the ET mode of operation is desired and higher amplification is needed (e.g. a higher output power from the variable power supply across the stack of FETs), an effective number of FETs in the stack of FETs used to construct an envelope tracking amplifier can be increased. Conversely, if the non-ET mode of operation is desired, the effective number of FETs in the stack of FETs used to construct an envelope tracking amplifier can be decreased. Selection of a desired number of FETs to be active can be provided based on a particular biasing of individual FETs of the stack of FETs. Numerous embodiments that operate by changing the effective number of FETs in the stack of FETs used to construct the envelope tracking amplifier are possible, two of which are presented in the following paragraphs.
Biasing the third FET (155) to operate in the triode region (and thus having the third FET (155) act as a resistor rather than an amplifier) reduces the effective number of FETs in the stack of FETs used to construct the envelope tracking amplifier (100) of
Modifications similar to the embodiment shown in
With the above two embodiments, biasing a gate voltage of the FET is used to reduce the stack height. Alternatively, embodiments could be provided where amplifier arrangements of different stack heights are chosen directly. For example,
As seen in
As discussed above in
Given that the embodiment of
For all of the embodiments previously discussed in the present disclosure in relation to switching an amplifier operation mode between ET and non-ET, control of switches and/or tuning of tunable elements can be performed by control signals that are provided by a transceiver, a microprocessor (e.g. a control unit of a cell phone or wireless device), a control circuit corresponding to any amplifier within a given embodiment, or some other unit that is configured to provide appropriate control signals, whether implemented in hardware (e.g. simple/complex digital logic, analog), software and/or a combination thereof. Any and all parts of these various embodiments can be monolithically integrated for better overall performance as well as reduced manufacturing cost, assembly cost, testing cost and form factor.
Going back to
Furthermore and as discussed in prior embodiments, in order to optimize operation (e.g. linearity, efficiency, ACLR) of the amplifier (100) in the envelope tracking mode, each of the bias voltages ETG1, ETG2, ETG3 can independently be scaled, amplitude shifted, phase shifted, inverted, and/or subject to any mathematical operation (e.g. implemented by an op-amp circuit or lookup table) with relation to the bias voltage supplied to the inductor (170) prior to being applied to gate bias nodes (110, 135, 145). In some embodiments, the bias voltage ETG1 may be held fixed while the other two bias voltages ETG2 and ETG3 vary as a function of the control voltage connected to the input terminal (190) of the ETPS (180), but with differing gains and/or phases. In yet another embodiment, ETG3 may be set to a high voltage to put transistor (155) strongly in the triode region when the envelope voltage on its drain (through inductor 170) goes very low and thus removing transistor (155) from the cascode configuration, while decreasing ETG2 to follow the envelope and maintain the cascode effect. These techniques can be applied to any or all of the gates in a stack and the stack can be anywhere from a stack of 1 to a stack of n (n>1, e.g. n=3, 4, 7, . . . ).
This added flexibility of independently and dynamically controlling the various gate bias voltages provides for better control of the response of the ET amplifier as compared to the traditional ET implementation, wherein only the drain voltage is controlled using an envelope signal. For example, knowing the operational characteristics of the ET amplifier with respect to its drain input voltage, one can further optimize using any one or combination of the controlling gate biases and create lookup tables to provide corrections to the gate biases based on the input voltage to the drain. Corrections can be made to optimize response of the ET amplifier for one or multiple of linearity, efficiency, output power and adjacent channel leakage ratio (ACLR) and using various strategies (e.g. keep one gate constant and correct for other two). These lookup tables can subsequently be used by some circuitry (e.g. waveform generation) to generate corrections during operation (e.g. increase output power request by a base station). Although these types of corrections can be completely predicted by the drain input or corresponding control signal, other type of corrections can be generated as well. For example:
In such cases, the lookup tables described above may include additional dimensions to describe corrections based on the real time and/or estimated operating temperature of the amplifier. The person skilled in the art will see that same correction/compensation method can be used with respect to other parameters which may affect operation of the amplifier.
Going back to
The envelope tracking amplifier (100) shown in
For the sake of simplicity, the transceiver (720) of
In the embodiment shown in
Similar to the embodiment of
In one embodiment of
It should also be noted that the ETPS, as used throughout the present disclosure, needs to have sufficient bandwidth to accommodate the bandwidth of the amplitude component of the modulation, which is typically 5-10 times wider than the modulation bandwidth. The ETPS must have minimal distortion (amplitude and phase) over this bandwidth. It is common for the ETPS to be built using a DC-DC converter to provide the low frequency portion of the amplitude path and an analog amplifier for the high frequency portion, along with some analog control circuitry to control overall operation of the unit. The DC-DC converter has a higher efficiency than the analog amplifier, but suffers from challenges in bandwidth as well as spurs due to the switching nature of the DC-DC. The analog amplifier covers the DC-DC converter's shortfalls. Noise, in addition to the spurs, must also be considered. A faster DC-DC converter will improve the overall efficiency of the ETPS by requiring less help from the analog amplifier. In the limit case, the ETPS consists of solely of a DC-DC converter. Using a semiconductor process such as silicon on sapphire (SOS), or even silicon on insulator (SOI), reduces the parasitic capacitances and offers several device advantages that result in faster DC-DC converters.
As it was the case in the embodiment depicted by
The examples set forth above are provided to give those of ordinary skill in the art an overview of various control systems and methods related to the implementation of the envelope tracking method as related to the present disclosure. As mentioned before, these are only implementation examples and not limiting the scope of what the inventors regard as their disclosure.
Based on these examples, one can derive the following set of functional units and system functions to be implemented therein through some dedicated circuitry, which together implement the envelope tracking method. Any combination of these functional units may be integrated in one IC and/or module.
Functional Units:
The person skilled in the art will understand that known design techniques are available for implementation of the presented system functions. For example:
The various examples set forth above represent some possible implementations of the envelope tracking method by placing such system functions in newly defined modules (i.e. 730, 740, 780A) and/or in specific functional units. As such, the input/output configurations of said units reflect the chosen implementation. For example, input to the PA unit (750) is modified in order to adapt to each of the configurations of
Furthermore, a person of ordinary skill will understand that any of such system functions can be implemented within a plurality of functional units given some design modification to said unit. For example, the transceiver can be made to perform envelope detection based on its input data at terminal (710), but so can the PA unit based on the input RFin signal at terminal (105), or the waveform shaping unit (780A) of
This apparent flexibility of mixing and matching system functions within functional units, and adapting I/O's accordingly, is however limited by the choice of good and sound design principles and integration. For example, any integration of waveform generation into the PA is beneficial because monolithic integration means the waveform signals will be matched and the amplitude/phase response will be well controlled. In contrast, splitting the gate and drain waveform generation across multiple ICs and packages introduces potential amplitude, phase and delay issues subject to PCB design and part variation. In another example and as previously mentioned, due to its high current requirement, it is desirable to keep the drain voltage supply generation close to the PA unit and within the ETPS, since latter is designed for high currents and good heat dissipation. This in turn limits the PA input configuration for its drain bias to an analog input, in contrast to a possible digital input for the gates biases, whereby internal D/A conversion units can generate the analog gate bias voltages.
Given the above, Table 1 is a proposed embodiment of design and integration constraints for the system functions. It defines possible functional integrations for each of the system functions.
TABLE 1
Functional
Input
I/O Signal
Unit
Source
Type
Envelope
Tx/Rx, ETPS,
RFin/Analog
Analog/Digital
detection
PA, WS
Data/Digital
data
Gate waveform
Tx/Rx, ETPS,
Envelope
Analog/Digital
generation
PA, WS
Detection
Drain waveform
Tx/Rx, ETPS,
Envelope
Analog/Digital
generation
PA, WS
detection
PA Drain input
ETPS
Drain
Analog/Digital
generation
waveform
Input Analog
generation
Output
PA Gate input
Tx/Rx, ETPS,
Gate
Analog/Digital
generation
PA, WS
waveform
Input Analog
generation
Output
As per Table 1, the following constraints are defined:
Modules presented in
In
For example,
Equivalently,
System functions of embodiment presented in
As a summary, in the previous paragraphs, various system level embodiments for controls and methods implementation of the envelope tracking amplifier using some functional units; the transceiver unit (720), the ETPS unit (180) and the amplifier unit (750), surrounded by some external enabling modules (730, 740, 780A) were presented. Subsequently a set of enabling system functions required to generate the presented embodiments as well as associated design constraints were defined which together allowed to define a generic system configuration for the envelope tracking method and controls thereof (
It should be noted that in the case of an ET implementation, traditional filtering of the supply input to the amplifier via a large bypass capacitor to reduce feedback between the various amplification stages, and thus possible oscillation, is not possible, since such a capacitor would distort the supply envelope modulation and thus the RF output, as well as reduce any efficiency improvement obtainable from the ET design.
The person skilled in the art will now notice that the embodiments presented in
Embodiments as depicted by
As described earlier, close proximity of the ETPS unit to the amplifier unit is desirable, such as to reduce any phase/amplitude degradation of the envelope supply to the amplifier unit, as the supply directly affects the output of the amplifier. As such, monolithic integration of these two units, using for example Silicon on Insulator technology, which allows for high transistor stacks (e.g. 3, 4 or greater) and higher breakdown voltages, is disclosed. This integration also allows for better stability when feedback is used around the amplifier as all the components affecting the output may be integrated.
The presented optimization modules may be used in different context and for optimizing different parameters at different stages of operation. For example, the temperature detector module (920), may be used during amplifier transmission and provide feedback to main controller of operating temperature, which may prompt the controller to modify controls (supplies or other amplifier configuration related) to the amplifier. Such controls may cause for example selection of different waveforms for the ETPS unit to shift biasing or supply of the amplifier in a manner to maintain a specific response characteristic (e.g. ACLR, linearity, efficiency, power output, etc. . . . ). If lookup tables are used in the waveform generation module, controls may result in selection of a different lookup table in response to a temperature shift detected by the temperature detection module. In other cases, controls may prompt injection of a compensation error component (e.g. offset, gain) into the waveform generation module. Other parameters can be monitored and used to drive the configuration and control loop. Examples include detecting threshold voltages of devices in the PA IC or ETPS or other related circuits, detecting voltage and current levels, input or output power, and the status/health of circuits and devices. Monitoring information such as this can be used to drive a configuration setting (slow changes, for example at power up) or in a real-time closed loop system.
Another optimization module, the Non-Volatile RAM module (910), may be used in different manners. For example during the manufacturing stage of the amplifier unit (100), module (910) may be programmed to contain characteristic data specific to the amplifier unit, not only vis-à-vis biasing and supply variation, but also with respect to temperature and other parameters. In turn, during final integration of the amplifier unit into a target device (e.g. cellular phone), NV-RAM content is used to expedite calibration, testing and troubleshooting of the target device. Availability of data within module (910) not only expedites calibration/testing/troubleshooting of the target device, possibly allowing bypass of certain steps required in the absence of the data provided by the NV-RAM, but also guarantees that the final device is “optimized” for operation with respect to the specific amplifier unit, thus rendering issues associated with batch to batch manufacturing variability moot. During operation of the device, the NV-RAM content can also be used to provide correction factors based on operating conditions (e.g. temperature and other). The person skilled in the art will understand the flexibility of providing such a programmed NV-RAM coupled with a temperature detector or some other type of transducer (930), and will be able to use teaching from the present disclosure to adapt to various conditions and requirements. In some embodiments, this calibration can be done at factory test of the PA, the ETPS, the PA+ETPS if integrated, factory test of the radio system, or in-situ by detectors in the radio system. The calibration can also be based on characterization. Typical parameters that would be monitored during the calibration process include output power, gain, AM-AM, AM-PM, ACLR, EVM, receive band noise, efficiency, and voltage levels.
Although throughout the present disclosure envelope tracking was used as an amplification method in the various embodiments, it should be noted that the techniques for stacking, mode switching optimization, and system partitioning used in said embodiments apply to envelope tracking as well as envelope following, polar amplifiers/systems, and average power tracking described in the early sections of this disclosure. These techniques can be further applied in conjunction with other amplifier efficiency improvement and performance techniques such as analog pre-distortion, digital pre-distortion, Doherty amplifiers, LINC or outphasing amplifiers, switching amplifiers such as Class S and Class M, and also distributed amplifiers, among others. The skilled person will thus appreciate the flexibility and adaptability of the various embodiments of this disclosure to other known configurations and techniques.
Finally, as integration is usually synonymous to reduced cost and reduced form factor, it is envisioned, as another embodiment of the current disclosure, that the entirety of the components of
The examples set forth above are provided to give those of ordinary skill in the art a complete disclosure and description of how to make and use the embodiments of the amplifiers operating in envelope tracking mode or non-envelope tracking mode of the disclosure, and are not intended to limit the scope of what the inventors regard as their disclosure. Such embodiments may be, for example, used within mobile handsets for current communication systems (e.g. WCMDA, LTE, etc. . . . ) wherein amplification of signals with frequency content of above 100 MHz and at power levels of above 50 mW may be required. The skilled person may find other suitable implementations of the presented embodiments.
Modifications of the above-described modes for carrying out the methods and systems herein disclosed that are obvious to persons of skill in the art are intended to be within the scope of the following claims. All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the disclosure pertains. All references cited in this disclosure are incorporated by reference to the same extent as if each reference had been incorporated by reference in its entirety individually.
It is to be understood that the disclosure is not limited to particular methods or systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. The term “plurality” includes two or more referents unless the content clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosure pertains.
A number of embodiments of the disclosure have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of the present disclosure. Accordingly, other embodiments are within the scope of the following claims.
Nobbe, Dan William, Dykstra, Jeffrey A., Olson, Chris, Cable, James S.
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