Tuning matching circuits for transmitter and receiver bands as a function of the transmitter metrics

Abstract

A system can obtain an operational metric associated with the transceiver, determine a target figure of merit based on a compromise between a desired transmitter performance and a desired receiver, determine a current figure of merit based on the operational metric, and adjust the variable reactance component of the impedance matching circuit based on a comparison of the current figure of merit with the target figure of merit. Other embodiments are disclosed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

It should be noted that this equation is only a non-limiting example of an equation that could be used for a particular circuit under particular operating conditions and the present invention is not limited to utilization of this particular equation.

FIG. 5 is a flow diagram illustrating the steps involved in an exemplary embodiment of the present invention operating in a TDM environment. During the transmitter time slot, the AIMM algorithm presented in FIG. 3, or some other suitable algorithm, can be applied on a continual basis to move operation of the transmitter towards the target FOM. However, when the receive time slot is activated 505, the AIMM should be adjusted to match for the receiver frequency. The adjustment to the receiver mode of operation may initially involve determining the current operating conditions of the device 510. Based on the current operating conditions, a translation for tuning of the various circuits in the AIMM 100 are identified 520. For instance, various states, components or conditions can be sensed and analyzed to determine or detect a current state or a current use case for the device. Based on this information, a particular translation value or function may be retrieved and applied. It should also be appreciated that such translations can be determined during the design phase and loaded into the device. Finally, the translations are applied to the AIMM 100 530. When operation returns to the transmitter time slot 535, the AIMM algorithm again takes over to optimize operation based on the target FOM.

It should be understood that the translation applied to tuning of the AIMM 100 during the receiver time slot is based on the particular circuit and device and can be determined during design or even on an individual basis during manufacturing and testing. As such, the specific translations identified herein are for illustrative purposes only and should not be construed to limit the operation of the present invention.

Thus, for TDM systems, embodiments of the present invention operate to optimize operation of a device by tuning the matching circuit for an antenna to optimize operation based on a target FOM. During the receiver time slot, a translation is applied to the tuned components to improve receiver performance. The target FOM can be based on a variety of performance metrics and a typical such metric is the reflection loss of the transmitter. The values for the tuned components can be set based on operational conditions and using a look-up table, can be initially set by using such a look-up table and then heuristically fine tuned, or may be heuristically determined on the fly during operation. The translations applied during the receiver operation are determined empirically based on the design of the circuitry and/or testing and measurements of the operation of the circuit. However, a unique aspect of the present invention is tuning of the matching circuit during transmit mode and based on non-receiver related metrics and then retuning the circuit during receive mode operation based on a translation to optimize or attain a desired level of receiver operation.

In an exemplary embodiment of the present invention operating within an FDM environment, the AIMM 100 can be adjusted to so that the matching characteristics represent a compromise between optimal transmitter and receiver operation. Several techniques can be applied to achieve this compromise. In one technique, the translation applied in the TDM example could be modified to adjust the AIMM 100 as a compromise between the optimal transmit and receive settings. For instance, in the example illustrated in FIG. 2, the value of PTC1 and PTC2 can be determined and adjusted periodically, similar to TDM operation (even though such action would temporarily have an adverse effect on the receiver). Then, a translation could be applied to the values of PTC1 and PTC2 for the majority of the operation time. For instance, in the TDM example shown in FIG. 4, the transmitter values were adjusted by multiplying the PTC2 value by 0.6 in three modes of operation and using the above-identified equation during a forth mode of operation. This same scheme could be used in the FDM mode of operation however, the scaling factor would be different to obtain operation that is compromised between the optimal transmitter setting and optimal receiver setting. For example, multiplying the PTC2 value by 0.8 could attain an acceptable compromise.

However, another technique of an embodiment of the present invention is to apply an algorithm that operates to attain a target FOM that is based on one or more transmitter related metrics (such as return loss) and the values of the adjustable components in the AIMM. Advantageously, this aspect of the present invention continuously attempts to maintain a compromised state of operation that keeps the operation of the transmitter and the receiver at a particular target FOM that represents a compromise performance metric level.

In the particular example illustrated in FIG. 2, such an algorithm could be based on a target FOM that is an expression consisting of the transmitter return loss and the values of PTC1 and PTC2. Because the algorithm is not operating to minimize the transmitter return loss in this embodiment of an FDM system, a compromised value is specified. For instance, a specific target transmitter return loss can be pursued for both transmitter and receiver operation by tuning the AIMM based on a FOM that is not only a function of the return loss, but also a function of the values of PTC1 and PTC2 that will encourage operation at a specific level. The target FOM is attained when the actual transmitter return loss is equal to the target transmitter return loss and, specified preferences for PTC1 and PTC2 are satisfied. The preferences illustrated are for the value of PTC1 to be the highest possible value and the value of PTC2 to be the lowest possible value while maintaining the transmit return loss at the target value and satisfying the PTC1 and PTC2 preferences.

FIG. 6 is a return loss contour diagram in the PTC plane for a particular frequency (i.e., 825 MHz/870 MHz operation). Obviously, optimal operation in an FDM system cannot typically be attained because the settings for optimal transmitter operation most likely do not coincide with those for optimal receiver operation. As such, a compromise is typically selected. For instance, a compromise may include operating the transmitter at a target return loss value of −12 dB and at a point at which the transmitter −12 dB contour is closest to a desired receiver contour (i.e., −12 dB).

The operational goal of the system is to attempt to maintain the matching circuit at a point where the operational metrics for the transmitter are at a target value (eg. −12 dB) and the estimated desired receiver operation is most proximate. In an exemplary embodiment of the present invention, an equation used to express the target FOM for such an arrangement can be stated as follows:
Target FOM=f(Tx_RL,TX_RL_Target)+f(PTC2,PTC1)
Where: TX_RL is the measure transmitter return loss
TX_RL_Target is the targeted transmitter return loss

In an exemplary embodiment suitable for the circuit provided in FIG. 2, the FOM may be expressed as:
FOM=(Tx_RL−Tx_RL_Target)+C2*PTC2−C1*PTC1), where,
C1 and C2 are preference constants or scaled values, and
if Tx_RL>Tx_RL_Target then Tx_RL=Tx_RL_Target.

In operation, exemplary embodiments of the present invention optimize the transmitter based on the target reflected loss to attain operation on the desired contour 610 (as shown in FIG. 6) and also adjusts the values of PTC1 and PTC2 to attain operation at the desired location 630 (or minimum FOM) on the contour. The portion of the FOM equation including the TxRL and TX_RL_Target values ensures operation on the targeted RL contour 610 (i.e., the −12 db RL contour). By observing the contour 610, it is quite apparent that not all points on the target reflected loss contour have the same value for the PTC1 and PTC2. Because of this, the values of PTC1 and PTC2 can be incorporated into the target FOM equation to force or encourage operation at a particular location on the reflected loss contour. In the illustrated example, the target FOM is the point at which the reflected loss contour is closest to the expected same valued reflected loss contour for the receiver. However, it will be appreciated that other performance goals may also be sought and the present invention is not limited to this particular example. For instance, in other embodiments, the target FOM may be selected to encourage operation at a mid-point between optimal transmitter performance and expected optimal receiver performance. In yet another embodiment, the target FOM may be selected to encourage operation at a point that is mid-point between a desired transmitter metric and an estimated or measured equivalent for the receiver metric.

In the provided example illustrated in FIG. 6, the optimum, compromised or desired point on the target contour is the point that minimizes the value of PTC2 and maximizes the value of PTC1 in accordance with the equation C2*PTC2-C1*PTC1. Thus, the portion of the expression including PTC1 and PTC2 ensures that operation is at a particular location on the contour that is desired—namely on the lower portion of the contour and closest to the RX_RL contour 620. In general, the algorithm operates to optimize the current FOM or, more particularly in the illustrated embodiment, to minimize the expression of C2*PTC2−C1*PTC1 as long as the desired TX_RL parameter is also met. It should be appreciated that the details associated with this example are associated with a specific circuit design and a wide variety of relationships between the adjustable components of the AIMM would apply on a circuit by circuit basis and as such, the present invention is not limited to this specific example.

Another embodiment of the present invention may take into consideration historical performance of the tunable components as well as current values. As an example, as the tunable components are adjusted, changes in the current FOM will occur in a particular direction (i.e., better or worse). As an example, if the AIMM adjustments 26 result in the current FOM falling on the top portion of a desired performance contour, making a particular adjustment may result in making the current FOM worse or better. If the adjustment was known to cause a certain result when the current FOM is located on the bottom of the contour and this time, the opposite result occurs, then this knowledge can help identify where the current FOM is located on the contour. Thus, knowing this information can be used in combination with the operation metric to attain the operation at the target FOM. For instance, the target FOM may be a function of the operational metrics, the current states of the tunable components, and the knowledge of previous results from adjusting the tunable components.

Stated another way, when a current FOM is calculated, the adjustments to reach the target FOM may take into consideration past reactions to previous adjustments. Thus, the adjustment to the tunable components may be a function of the FOM associated with a current setting and, the change in the current FOM resulting from previous changes to the tunable components.

In another embodiment of the present invention operating in an FDM environment, the FOM may be optimized similar to operation in the TDM environment. For example, the FOM may be a function of the transmitter reflected loss metric and the system may function to optimize the FOM based on this metric. Once optimized, the tunable components can be adjusted based on a predetermined translation to move the FOM from the optimized for the transmitter position to a position that is somewhere between the optimal transmitter setting and the optimal receiver setting.

FIG. 7 is a flow diagram illustrating the steps involved in an exemplary embodiment of the present invention in obtaining the preference values for PTC1 and PTC2. Initially, the process 700 involves plotting of the return loss contours for the various modes of operation, or a reasonable subset thereof 710. FIG. 6 is an example of such a plot generated as a result of performing this step. Next, the compromised tuning location is identified 720. As previously mentioned, a variety of factors may be weighed to determine the compromised tuning location and one example, as illustrated in FIG. 6, is the point at which a target reflected loss for the transmitter is the most proximate to a target reflected loss for the receiver. In a typical embodiment, this is the point at which the target transmitter and receiver contours at the desired reflected loss are closest to each other and nearly parallel. Once the compromised location is determined, the preference values can be characterized 730. For instance, in the example in FIG. 6, by drawing a perpendicular line between the two contours and passing through the compromised location, the slope and hence the preferences can be identified. These preference values can then be determined and then applied across the broad spectrum of frequencies and usage scenarios 740.

It should be appreciated that the values of C1 and C2 are constants and can vary among embodiments of the invention, as well as among devices employing the invention. As such, the values are determined empirically as described above. In an exemplary embodiment, the values of C1 and C2 are 0.7 and 2 respectively for a given circuit and a given antenna, given mode of operation, etc. Thus, any given set of constants are determined empirically and only apply to a specific antenna design, circuit and mode of operation and, although the use of these specific values may in and of itself be considered novel, the present invention is not limited to the particular expression. In fact, depending on particular goals, design criteria, operational requirements, etc. different values may be required to attain the compromised performance. It will also be appreciated that in various embodiments, it may be desired to have a different targeted reflection loss for the transmitter than for the receiver.

In another embodiment of the present invention, rather than analyzing the transmitter reflected power as the performance metric, the reflection coefficient vector may be measured. In this embodiment, the phase information of the reflection coefficient may be included within the FOM. For example, FIG. 8 is a contour plot showing the magnitude and the phase of the reflection coefficient. The preferred point of operation 830 is shown as falling on the −12 dB contour 810 and at a phase of 45 degrees. In such an embodiment, the components of the matching circuit of the AIMM 100 can be adjusted to meet a reflected loss value that falls on the −12 db contour and that also approaches the specific point on the contour—namely at the point where the reflection coefficient differs by 45 degrees.

As mentioned, mobile and transportable transceivers are subjected to a variety of use cases. For instance, a typical cellular telephone could be operated in various scenarios including speaker phone mode, ear budded, with the antenna in the up position or the down position, in the user's hand, holster, pocket, with a slider closed or extended, in a holster or out of a holster, etc. All of these scenarios, as well as a variety of other environmental circumstances can drastically alter the matching characteristics of the cellular telephone's antenna circuitry. As such, not only do the various embodiments of the present invention operate to tune the matching circuitry based on the operational frequency, but in addition, adjust the matching characteristics based on changes in the modes of operation. Advantageously, this greatly improves the performance of the device without requiring separate matching circuitry for the various modes of operation of the device. Thus, it will be appreciated that various other parameters can be monitored to identify various use cases and then adjustments to the tuning circuitry can be immediately deployed followed by fine tuning adjustments to optimize the FOM. The other parameters in which the embodiments of the present invention may function are referred to as modes of operation. The various modes of operation include the use cases as previously described, along with operating environments, bands of operation, channel frequencies, modulation formats and schemes, and physical environments. Thus, the various embodiments of the present invention may make changes, select default values, calculate adjustment values, etc., all as a function of one or more of the modes of operation.

One embodiment of the present invention may maintain a set of initial starting values based on the various use cases and operational environments. For instance, each use case may include a default value. Upon detection or activation of the device in a new use case, the default value is obtained from memory and the components in the AIMM are tuned accordingly. From that point on, the adjustment algorithm can then commence fine tuning of the operation. As previously mentioned, each time the target FOM is attained for a particular use case, the new values may be written into the default location as the new default values. Thus, every time the operational state of the device changes, such as changing between bands of operation etc., the default values are obtained and applied, and then adjustments can resume or, operation can simply be held at the default value.

Numerous specific details have now been set forth to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.

Unless specifically stated otherwise, as apparent from the description, it is appreciated that throughout the specification discussions that different electronic devices could be used to create a variable tuner network. The embodiments used in the examples discussed were specific to variable capacitor devices, however variable inductors, or other tunable networks, built out of elements such as Micro-Electro-Mechanical Systems (MEMS) and/or other tunable variable impedance networks could be used in such an AIMM system.

Unless specifically stated otherwise, as apparent from the description, it is appreciated that throughout the specification discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining,” or the like, refer to the action and/or processes of a microprocessor, microcontroller, computer or computing system, or similar electronic computing device, that manipulate and/or transform data represented as physical, such as electronic, quantities within the computing system's registers and/or memories into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices.

Embodiments of the present invention may include apparatuses for performing the operations herein. An apparatus may be specially constructed for the desired purposes, or it may comprise a general purpose computing device selectively activated or reconfigured by a program stored in the device. Such a program may be stored on a storage medium, such as, but not limited to, any type of disk including floppy disks, optical disks, compact disc read only memories (CD-ROMs), magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), electrically programmable read-only memories (EPROMs), electrically erasable and programmable read only memories (EEPROMs), magnetic or optical cards, or any other type of media suitable for storing electronic instructions, and capable of being coupled to a system bus for a computing device.

The processes presented herein are not inherently related to any particular computing device or other apparatus. Various general purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct a more specialized apparatus to perform the desired method. The desired structure for a variety of these systems will appear from the description below. In addition, embodiments of the present invention are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. In addition, it should be understood that operations, capabilities, and features described herein may be implemented with any combination of hardware (discrete or integrated circuits) and software.

Use of the terms “coupled” and “connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Rather, in particular embodiments, “connected” may be used to indicate that two or more elements are in direct physical or electrical contact with each other. “Coupled” may be used to indicated that two or more elements are in either direct or indirect (with other intervening elements between them) physical or electrical contact with each other, and/or that the two or more elements co-operate or interact with each other (e.g. as in a cause an effect relationship).

In the description and claims of the present application, each of the verbs, “comprise,” “include,” and “have”, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of members, components, elements, or parts of the subject or subjects of the verb.

The present invention has been described using detailed descriptions of embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. The described embodiments comprise different features, not all of which are required in all embodiments of the invention. Some embodiments of the present invention utilize only some of the features or possible combinations of the features. Variations of embodiments of the present invention that are described and embodiments of the present invention comprising different combinations of features noted in the described embodiments will occur to persons of the art.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described herein above. Rather the scope of the invention is defined by the claims that follow.

Claims

1. A method comprising:

obtaining, by a processor of a communication device, an operational metric for a transceiver of the communication device;

identifying a desired transmitter performance and a desired receiver performance;

determining, by the processor, a target figure of merit based on a compromise between the desired transmitter performance and the desired receiver performance;

determining, by the processor, a current figure of merit based on the operational metric;

comparing, by the processor, the current figure of merit to the target figure of merit; and

adjusting, by the processor, a variable reactance component of an impedance matching circuit a variable tuner network operably coupled with an antenna of the communication device, the adjusting of the variable reactance component being performed based on the comparing of the current and the target figures of merit, wherein the obtaining of the operational metric is during a transmit mode of the transceiver of the communication device, wherein the variable reactance component is adjusted without utilizing operational metrics measured during a receive mode of the communication device.

2. The method of claim 1, wherein the obtaining of the operational metric is during a transmit mode of the transceiver, wherein the variable reactance component is adjusted without utilizing operational metrics measured during a receive mode of the communication device.

3. The method of claim 1, comprising communicating, by the communication device, utilizing frequency division multiplexing.

4. The method of claim 1, wherein the determining of the target figure of merit includes selecting a mid-point between the desired transmitter performance and the desired receiver performance.

5. The method of claim 1, wherein the determining of the current figure of merit is based on known parameters associated with the variable reactance component and is not based on phase information.

6. The method of claim 1, comprising:

storing a tuning value based on the adjusting of the variable reactance component; and

utilizing the tuning value as a default value for subsequent tuning of the antenna.

7. The method of claim 6, comprising:

determining an operational state of the communication device; and

utilizing information associated with the operational state as a default value for subsequent tuning of the antenna.

8. The method of claim 7, wherein the operational state comprises a use case scenario selected from the group consisting essentially of hand held operation, antenna position and slider position.

9. The method of claim 1, wherein the compromise between the desired transmitter performance and the desired receiver performance is based on an evaluation of total radiated power, isotropic power or a combination thereof.

10. The method of claim 1, wherein the compromise between the desired transmitter performance and the desired receiver performance is based on an evaluation of total isotropic sensitivity a type of communication service.

11. The method of claim 1, wherein the compromise between the desired transmitter performance and the desired receiver performance is based on an evaluation of transmitter linearity.

12. The method of claim 1, wherein the compromise between the desired transmitter performance and the desired receiver performance is based on an evaluation of transmitter efficiency.

13. A communication device comprising:

an antenna;

a transceiver;

an impedance matching a variable tuner network coupled with the antenna and the transceiver, wherein the impedance matching variable tuner network includes a variable reactance component;

a memory to store computer instructions; and

a controller coupled with the memory and the impedance matching variable tuner network, wherein the controller, responsive to executing the computer instructions, performs operations comprising:

obtaining an operational metric associated with the transceiver communication device;

identifying a desired transmitter performance and a desired receiver performance;

determining a target figure of merit based on a compromise between the desired transmitter performance and the desired receiver performance;

determining a current figure of merit based on the operational metric; and

adjusting the variable reactance component of the impedance matching circuit variable tuner network based on a comparison of the current figure of merit with and the target figure of merit, wherein the obtaining of the operational metric is during a transmit mode of the transceiver, and wherein the variable reactance component is adjusted without utilizing operational metrics measured during a receive mode of the communication device.

14. The communication device of claim 13, further comprising a transceiver, wherein the variable reactance component includes a voltage tunable capacitor, and wherein the operations of the controller further comprise:

determining a use case for the communication device; and

performing an initial adjustment of the voltage tunable capacitor based on the use case without utilizing any operational metrics associated with the transceiver, wherein the initial adjustment of the voltage tunable capacitor is performed prior to the adjusting based on the comparison of the current figure of merit with the target figure of merit.

15. The communication device of claim 13, wherein the variable reactance component includes a Micro-Electro-Mechanical Systems (MEMS) variable reactance component.

16. The communication device of claim 13, wherein the operations of the controller further comprise:

storing a tuning value based on the adjusting of the variable reactance component; and

utilizing the tuning value as a default value for subsequent tuning of the antenna.

17. The communication device of claim 13, wherein the obtaining of the operational metric is during a transmit mode of the transceiver, and wherein the variable reactance component is adjusted without utilizing operational metrics measured during a receive mode of the communication device.

18. The communication device of claim 13, wherein the adjusting of the variable reactance component is associated with a communication session that utilizes frequency division multiplexing.

19. A method comprising:

obtaining an operational metric for a transceiver of a communication device;

determining a target figure of merit based on transceiver performance of the communication device;

determining a current figure of merit based on the operational metric, wherein the determining of the target figure of merit is not based on phase information;

comparing the current figure of merit to the target figure of merit to determine a figure of merit comparison; and

adjusting, by a processor of the communication device, a variable reactance component of an impedance matching circuit a variable tuner network operably coupled with an antenna of the communication device, the adjusting of the variable reactance component being performed based on the figure current and target figures of merit comparison and based on previous tuning results associated with previous adjusting of the variable reactance component the variable tuner network, wherein the obtaining of the operational metric is during a transmit mode of the transceiver, and wherein the variable reactance component is adjusted without utilizing operational metrics measured during a receive mode of the communication device.

20. The method of claim 19, comprising monitoring the previous tuning results by determining a change in the current figure of merit based on different reactance values for the variable reactance component.

21. The method of claim 19, wherein the operational metric comprises a return loss.

22. The method of claim 19, wherein the variable reactance component includes at least one of a Micro-Electro-Mechanical Systems (MEMS) variable reactance component and a voltage tunable capacitor.

23. The method of claim 19, wherein the current figure of merit, the target figure of merit or both is according to a vector measurement of a transmission reflection coefficient.

24. The method of claim 1, wherein the adjusting of the variable reactance component is based on tuning values stored in a lookup table.

25. A communication device comprising:

an antenna;

a transceiver;

a variable tuner network coupled with the antenna;

a memory that stores computer instructions; and

a controller coupled with the memory and the variable tuner network, wherein the controller, responsive to executing the computer instructions, performs operations comprising:

obtaining a non-receiver operational metric;

identifying a first desired performance of the communication device;

identifying a second desired performance of the communication device;

determining a target figure of merit based on a compromise between the first desired performance and the second desired performance;

determining a current figure of merit based on the non-receiver operational metric; and

adjusting a variable reactance of the variable tuner network based on the current figure of merit and the target figure of merit, wherein the obtaining of the operational metric is during a transmit mode of the transceiver, and wherein the variable reactance component is adjusted without utilizing operational metrics measured during a receive mode of the communication device.

26. The communication device of claim 25, wherein the target figure of merit is stored in a lookup table.

27. The communication device of claim 25, wherein the first desired performance is associated with a first component of the communication device, and wherein the second desired performance is associated with a second component of the communication device.

28. The communication device of claim 25, wherein the variable tuner network includes a Micro-Electro-Mechanical Systems (MEMS) variable reactance component.

29. The communication device of claim 25, wherein the variable tuner network includes a voltage tunable capacitor.

30. A communication device comprising:

an antenna;

a transceiver;

a variable tuner network coupled with the antenna;

a memory that stores computer instructions; and

a controller coupled with the memory and the variable tuner network, wherein the controller, responsive to executing the computer instructions, performs operations comprising:

obtaining an operational metric for communications of a communication device;

determining a target figure of merit based on communications performance of the communication device;

determining a current figure of merit based on the operational metric, wherein the determining of the target figure of merit is not based on phase information; and

adjusting the variable tuner network based on the current and target figures of merit, wherein the obtaining of the operational metric is during a transmit mode of the transceiver, and wherein the variable tuner network is adjusted without utilizing operational metrics measured during a receive mode of the communication device.

31. The communication device of claim 30, wherein the adjusting of the variable tuner network is further based on previous tuning results associated with previous adjusting of the variable tuner network.

32. The communication device of claim 30, wherein the operational metric comprises a return loss.

33. The communication device of claim 30, wherein the communications performance is associated with total radiated power, total isotropic sensitivity, linearity or a combination thereof.

34. The communication device of claim 30, wherein the variable tuner network includes a Micro-Electro-Mechanical Systems (MEMS) variable reactance component.

35. The communication device of claim 30, wherein the variable tuner network includes a voltage tunable capacitor.