A frequency band selection device that can be inserted into a signal transmission line of a catv system on the premise of a user includes at least two signal path sets between a tap side and a premise side. Each signal path set includes two discrete signal paths, a high frequency signal path for a downstream bandwidth and a low frequency signal path for an upstream bandwidth. The high frequency signal path and the low frequency signal path are separated by a cut-off transition frequency that is different for each signal path set. The device further includes a switch controller having at least two discrete switch positions. The switch controller chooses one of the switch positions as a result of an information signal. Each of the switch positions corresponds to a respective one of the signal path sets.
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1. A frequency band selection device that can be inserted into a signal transmission line of a catv system on the premise of a user, the device comprising:
at least two signal path sets between a tap-side and a premise-side, each of the at least two signal path sets comprising:
a first discrete signal path comprising a high frequency signal path allowing a downstream bandwidth to pass from the tap-side to the premise-side,
a second discrete signal path comprising a low frequency signal path allowing an upstream bandwidth to pass from the premise-side to the tap-side, and
the high frequency signal path and the low frequency signal path are separated by a cut-off transition frequency that is different for each of the at least two signal path sets; and
a switch controller having at least two discrete switch positions, the switch controller choosing one of the switch positions as a result of an information signal, each of the switch positions corresponding to a respective one of the at least two signal path sets.
12. A frequency band selection device comprising:
at least two signal path sets between a tap-side and a premise-side, each of the at least two signal path sets comprising:
a first discrete signal path comprising a high frequency signal path allowing a downstream bandwidth to pass from the tap-side to the premise-side,
a second discrete signal path comprising a low frequency signal path allowing an upstream bandwidth to pass from the premise-side to the tap-side, and
the high frequency signal path and the low frequency signal path are separated by a cut-off transition frequency that is different for each of the at least two signal path sets;
a switch controller having at least two discrete switch positions, the switch controller choosing one of the switch positions as a result of an information signal, each of the switch positions corresponding to a respective one of the at least two signal path sets;
a tap-side switch comprising an input terminal connected to a supplier side terminal;
a premise-side switch connected to a premise-side terminal;
a tap-side filter set including a first pair of frequency band splitting devices selectable by the tap-side switch; and
a premise-side filter set including a second pair of frequency band splitting devices selectable by the premise-side switch,
wherein:
each of the at least two signal path sets comprises at least one conductor providing an electrical transmission line between the tap-side and the premise-side,
the tap-side switch and the premise-side switch are actuated by the switch controller,
the tap-side switch comprises a first position directly connected to a first frequency band splitting device of the first pair of frequency band splitting devices,
the first frequency band splitting device of the first pair of frequency band splitting devices is associated with a first signal path set of the at least two signal path sets,
the tap-side switch comprises a second position directly connected to a second frequency band splitting device of the first pair of frequency band splitting devices,
the second frequency band splitting device of the first pair of frequency band splitting devices is associated with a second signal path set of the at least two signal path sets,
the premise-side switch comprises a first position directly connected to a first frequency band splitting device of the second pair of frequency band splitting devices,
the first frequency band splitting device of the second pair of frequency band splitting devices is associated with the first signal path set,
the premise-side switch comprises a second position directly connected to a second frequency band splitting device of the second pair of frequency band splitting devices, and
the second frequency band splitting device of the second pair of frequency band splitting devices is associated with the second signal path set.
2. The frequency band selection device of
a tap-side switch comprising an input terminal connected to a supplier side terminal; and
a tap-side filter set including a pair of frequency band splitting devices selectable by the tap-side switch,
wherein:
the tap-side switch comprises a first position directly connected to a first frequency band splitting device of the pair of frequency band splitting devices,
the first frequency band splitting device of the pair of frequency band splitting devices is associated with a first signal path set of the at least two signal path sets,
the tap-side switch comprises a second position directly connected to a second frequency band splitting device of the pair of frequency band splitting devices,
the second frequency band splitting device of the pair of frequency band splitting devices is associated with a second signal path set of the at least two signal path sets, and
the tap-side switch is actuated by the switch controller.
3. The frequency band selection device of
4. The frequency band selection device of
a premise-side switch connected to a premise-side terminal; and
a premise-side filter set including a pair of frequency band splitting devices selectable by the premise-side switch,
wherein:
the premise-side switch comprises a first position directly connected to a first frequency band splitting device of the pair of frequency band splitting devices,
the first frequency band splitting device of the pair of frequency band splitting devices is associated with the first signal path set,
the premise-side switch comprises a second position directly connected to a second frequency band splitting device of the pair of frequency band splitting devices,
the second frequency band splitting device of the pair of frequency band splitting devices is associated with the second signal path set, and
the premise-side switch is actuated by the switch controller.
5. The frequency band selection device of
6. The frequency band selection device of
a tap-side switch set connected between a first pair of frequency band splitting devices and a second pair of frequency band splitting devices; and
a premise-side switch set connected between the first pair of frequency band splitting devices and the second pair of frequency band splitting devices,
wherein the tap-side switch set and the premise-side switch set are actuated by the switch controller.
7. The frequency band selection device of
8. The frequency band selection device of
9. The frequency band selection device of
10. The frequency band selection device of
11. The frequency band selection device of
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This application is a continuation of, and claims the benefit and priority of, U.S. patent application Ser. No. 12/252,907, filed on Oct. 16, 2008. The entire contents of which are hereby incorporated by reference.
The use of a cable television (“CATV”) system to provide internet, voice over internet protocol (“VOIP”) telephone, television, and radio services is well known in the art. In providing these services, a downstream bandwidth (i.e., radio frequency (“RF”) signals, digital signals, optical signals, etc.) is passed from a supplier of the services to a user and an upstream bandwidth is passed from the user to the supplier. The downstream bandwidth is passed, for example, within relatively higher frequencies from within a total bandwidth of the CATV system while the upstream bandwidth is passed within relatively lower frequencies.
Traditionally, the size of the downstream bandwidth far exceeds the size of the upstream bandwidth due to nature of the services provided. For example, while the downstream bandwidth must accommodate all of the television and radio programming along with internet and VOIP downloading, the upstream bandwidth is only required to accommodate internet, system control signals, and VOIP uploading. Problems are arising, however, due to an increase in upstream bandwidth usage caused by an increasing demand for higher speed internet uploads and the increasing demand for the VOIP telephone services.
VOIP telephone services places significant demands on the upstream bandwidth. When a user uploads a large image file to a photo sharing website, the image file will be parsed into a number of data packets that can be intermixed with other data packets being passed through a particular portion of the upstream bandwidth by other users located on a particular signal transmission line within the CATV system. To optimize a total data throughput on the particular signal transmission line, the data packets may be significantly delayed and/or reorganized without any knowledge of or inconvenience to the user. When a user uses VOIP telephone services, their voice is converted into data packets that are similar in form to the data packets used to upload the image file. Because a typical conversation is carried out in real time, meaning that a contiguous and unbroken flow of data packets is required, any person with whom the user is talking will quickly notice significant delays in the delivery of the data packets and/or reorganization of the data packets that results in audio distortion of the user's voice. Any such reorganization and/or delay in the uploading of data packets carrying VOIP telephone services are measured in terms of jitter, and are closely monitored because of the significant service quality characteristics it represents.
Jitter experienced between the user and their caller is a direct result of network congestion within the upstream bandwidth. Because the upstream bandwidth is shared by all users on the particular signal transmission line, each user is competing with the other users for packet data space within the upstream bandwidth. Even further, each of the users can unknowingly inject interference signals, such as noise, spurious signals, and other undesirable signals, into the upstream bandwidth through the use of common household items and poor quality wiring in the user's premise, the interference signals causing errors that force a slow down and an additional amount of jitter in the upstream flow of packets.
In an effort to increase the upstream flow of packets, several suppliers have a plan to increase the size of the upstream bandwidth from 5-42 Mhz to 5-85 Mhz to allow a greater flow of the upstream content. Along with such an increase, the downstream bandwidth must be correspondingly decreased in size because the total bandwidth is relatively fixed. Such a change is, however, very difficult to implement.
Traditional practices would require that every drop amplifier and two way (diplex) filter in network amplifiers and nodes of the CATV system to be changed as part of the increasing the size of the upstream bandwidth. Compounding the difficulty of implementing such a change, all of the changes must be implemented at various locations throughout the CATV system at a single, particular time. Accordingly, such an implementation is time consuming, costly, and difficult to coordinate.
Further, while increasing the size of the upstream bandwidth may incrementally increase the flow of upstream data packets, the upstream bandwidth remains susceptible to reliability/congestion issues since it is based on an inherent, system wide flaw that leaves the upstream bandwidth open and easily impacted by any single user. For example, while the downstream bandwidth is constantly monitored and serviced by skilled network engineers, the upstream bandwidth is created and passed using an infrastructure within a user's premise that is maintained by the user without the skill or knowledge required to reduce the creation and passage of interference signals into the upstream bandwidth. This issue is further compounded by the fact that over 500 premises can be connected together such that interference signals generated by one of the 500 premises can easily impact all of the remaining premises. It is common in the art for the supplier to add physical filters between the user's premise and a tap from of the main signal distribution system near the users premise to reduce the impact of the interference signals generated on the user's premise, but such a physical filter must be installed manually and does not account for significant, transient interference sources such as garbage disposals, vacuum cleaners, welders, powered hand tools, etc.
Even further, increasing the size of the upstream bandwidth forces suppliers to push their downstream content into increasingly higher frequency portions of the downstream bandwidth. Unfortunately, these higher frequencies are much more susceptible to parasitic losses in signal strength caused by the signal transmission lines, connectors on the user's premise, devices connected to the signal transmission lines on the user's premise, etc. In the past many users have added relatively low-tech drop amplifiers on their premise to account for such losses. Because of the changes to increase the size of the upstream bandwidth, all of these drop amplifiers must be removed and or replaced. Additionally, because of the increased demands placed on the downstream content (e.g., high definition television, increased compression, etc.) the signal strength (i.e., level) of the downstream bandwidth must be maintained to closer tolerances than can typically be provided by the typical low-tech drop amplifier. Accordingly, as a result of increasing the size of the upstream bandwidth, the quality of the content moved to the higher frequencies within the downstream bandwidth may be significantly lessened causing a decrease in customer satisfaction and an increase in costly service calls.
In light of the forgoing, increasing the size of the upstream bandwidth: (i) may require a significant amount of capital expenditure in terms new filter devices and the manpower to install the devices; (ii) may not result in the expected large increases in upstream data throughput because of the interference signals injected from within each user's premise; (iii) may result in lower quality downstream content, and (iv) may inject additional interference signals that now fall within the additional upstream bandwidth, which would have otherwise been filtered out.
Therefore, there is a need to overcome, or otherwise lessen the effects of, the disadvantages and shortcomings described above.
The present invention helps to reduce the complexity and cost involved with changing the size of an upstream bandwidth. Specifically, the present invention allows a CATV supplier to implement such a change in the size at a common, specific time to all users of the CATV services.
Further, the present invention can be added to a variety of other devices that require a defined separation between the upstream bandwidth and the downstream bandwidth. The incorporation of the present invention allows such other devices to remain relevant after a change in the size of the upstream bandwidth.
In accordance with one embodiment of the present invention, a frequency band selection device is provided that can be inserted into a signal transmission line of a CATV system on the premise of a user. The device includes at least two signal path sets between a tap side and a premise side. Each signal path set includes two discrete signal paths, a high frequency signal path allowing a downstream bandwidth to pass from the tap side to the premise side and a low frequency signal path allowing an upstream bandwidth to pass from the premise side to the tap side. The high frequency signal path and the low frequency signal path are separated by a cut-off transition frequency that is different for each signal path set. The device further includes a switch controller having at least two discrete switch positions. The switch controller chooses one of the switch positions as a result of an information signal. Each of the switch positions corresponds to a respective one of the signal path sets.
In accordance with one embodiment of the present invention, a dynamically configurable CATV system is provided. The system includes a plurality of frequency band selection devices, each of the devices being located on a premise of a user. Each device includes at least two signal path sets between a tap side and a premise side. Each signal path set includes two discrete signal paths, a high frequency signal path allowing a downstream bandwidth to pass from the tap side to the premise side and a low frequency signal path allowing an upstream bandwidth to pass from the premise side to the tap side. The high frequency signal path and the low frequency signal path are separated by a cut-off transition frequency that is different for each signal path set. Each device further includes a switch controller having at least two discrete switch positions. The switch controller chooses one of the switch positions as a result of an information signal. Each of the switch positions corresponds to a respective one of the signal path sets. The system further includes a head end transmitter being connected to each of the plurality of devices via a main distribution line, the head end transmitter providing the information signal to the switch controller in each of the devices.
In accordance with one embodiment of the present invention, a method is provided for varying CATV frequency bands on a premise of a user of CATV services. The method includes providing a frequency band selection device on the premise. The device includes at least two signal path sets between a tap side and a premise side. Each signal path set includes two discrete signal paths, a high frequency signal path allowing a downstream bandwidth to pass from the tap side to the premise side and a low frequency signal path allowing an upstream bandwidth to pass from the premise side to the tap side. The high frequency signal path and the low frequency signal path are separated by a cut-off transition frequency that is different for each signal path set. The device further includes a switch controller having at least two discrete switch positions. The switch controller chooses one of the switch positions as a result of an information signal. Each of the switch positions corresponds to a respective one of the signal path sets. The method further includes actuating the switch controller as a result of the information signal.
In accordance with one embodiment of the present invention, the device further includes a tap side filter set including at least two frequency band splitting devices selectable by a tap side switch set, and a premise side filter set including at least two frequency band splitting devices selectable by a premise side switch set. Preferably, the tap side switch set and the premise side switch set are actuated by the switch controller.
In accordance with one embodiment of the present invention, the tap side switch set includes a tap side downstream switch and a tap side upstream switch, and the premise side switch set includes a premise side downstream switch and a premise side upstream switch.
In accordance with one embodiment of the present invention, the information signal is a continuous tone.
In accordance with one embodiment of the present invention, the information signal contains a coded operational signal.
In accordance with one embodiment of the present invention, one of the frequency band splitting devices in each of the tap side filter set and the premise side filter set is configured to separate the upstream bandwidth from the downstream bandwidth according to DOCSIS-1 and DOCSIS-2 standards.
In accordance with one embodiment of the present invention, one of the frequency band splitting devices in each of the tap side filter set and the premise side filter set is configured to separate the upstream bandwidth from the downstream bandwidth according to a DOCSIS-3 standard.
In accordance with one embodiment of the present invention, the device includes three or more signal path sets and three or more discrete switch positions.
For a further understanding of the nature and objects of the invention, references should be made to the following detailed description of a preferred mode of practicing the invention, read in connection with the accompanying drawings in which:
As shown in
Referring still to
As shown in
Additionally, it is common practice to provide a “set-top box” (“STB”) or “set-top unit” (“STU”) for use directly with the television 150. For the sake of clarity, however, there is no representation of an STB or STU included in
Referring to
Because a diagram of a premise device 100 including all three devices is too complex to be clearly represented in one figure, a circuit 205 of the main circuit 200, as it is represented in
Along these lines, alternate embodiments of the premise device 100 are represented in
Individual components that are similar between the embodiments represented in
As shown in
The premise device 100 preferably includes a lightening protection device 230 positioned near the supplier side 210 and a lightening protection device 240 positioned near the premise side 220. Having two lightening protection devices 230, 240 attempts to protect the premise device 100 from energy passing from the drop transmission line 120 from a lighting strike and from energy passing from the premise distribution system 130 from a lighting strike. It should be understood that the lightening protection devices may not be necessary if/when the premise device 100 is configured to be placed in a CATV system that utilizes non-conductive signal transmission lines. Any of the high quality, commercially available lightning protection devices will function well within the specified locations within the premise device 100.
The premise device 100 preferably includes two power bypass failure switches 250, 260 that route all of the upstream\downstream signals through a bypass signal path 270 (e.g. a coaxial cable, an optical cable, a microstrip, a stripline, etc.) in the event of a power outage. The bypass failure switches 250, 260 are preferably located near the supplier end 210 and premise end 220, respectively. In an effort to protect the bypass failure switches 250, 260 from damage due to lightening energy, they are preferably placed between the lightening protection devices 230, 240 and the supplier end 210 and premise end 220.
Each of the bypass failure switches 250, 260 includes a default position bypassing the upstream/downstream signals through the bypass signal path 270 at any time power is removed from the premise device 100. When power is applied, each of the bypass failure switches 250, 260 actuate to a second position that disconnects the bypass signal path 270 and passes all of the upstream\downstream signal transmissions along another path through the circuit 205 (
The premise device 100 preferably includes circuit components creating the frequency band selection device 1 (
A simplified version of the of the frequency band selection device 1 is shown in
Each of the switches 280, 290, 300, 310, 320, 330 is controlled either directly or indirectly by a microprocessor 810 (
The premise device 100 preferably further includes circuit components creating the upstream bandwidth conditioning device 2, which automatically increases the signal to noise ratio of the upstream bandwidth created on the user's premise and passed into the upstream bandwidths on the main signal distribution system 30. It should be understood that with VOIP telephone service, the consistent flow of upstream data packets that lasts as long as the telephone call can appear to be noise (i.e., interference signals). Before VOIP, such continuous upstream flow data of data packets was not likely. Accordingly, the present device purposefully includes logic and structure that will halt the addition of attenuation once the maximum output of the cable modem is sensed even if the upstream data flow is consistent enough to be interpreted as noise.
As shown in
As shown in
In light of the forgoing, the term “variable signal level adjustment device” used herein should be understood to include not only a variable attenuation device, but also circuits containing a variable amplifier, AGC circuits, other variable amplifier/attenuation circuits, and related optical circuits that can be used to reduce the signal strength on the upstream bandwidth.
It should be noted that the term contemporary signal strength is intended to describe a current or present signal strength as opposed to a signal strength measured at a time in the past (i.e., a previous signal strength) such as prior to an application of signal level adjustment or an application of an additional amount of signal level adjustment. The reason for this point should be clear based on the following.
In operation, the microprocessor 810 within the upstream bandwidth conditioning device 2 performs a signal level setting routine 1000 (
Referring now to
Specifically, in step 1030 the microprocessor 810 reads a contemporary signal strength from the signal level detector 390, and the counter is incremented by a predetermined increment, such as one (1) in step 1040. The microprocessor 810 then looks to see if the counter is greater than the predetermined number (i.e., 25). If so, the microprocessor 810 ends the routine, but if not, the microprocessor 810 proceeds to step 1060. In step 1060, the microprocessor 810 compares the contemporary signal strength to a predetermined threshold. If the contemporary signal strength is greater than the predetermined threshold, the microprocessor 810 instructs the variable attenuator 400 to add an amount of additional signal level adjustment (e.g. 1 dB), but if the contemporary signal strength is lower than the predetermined threshold, the microprocessor 810 returns to step 1030.
After adding the amount of additional signal level adjustment, the microprocessor 810 reads a new contemporary signal strength in step 1080 while saving the previously read contemporary signal strength (i.e., from step 1030) as a previous signal strength in preparation for step 1090. In step 1090, the microprocessor 810 compares the contemporary signal strength measured in step 1080 and the previous signal strength measured in step 1030 to one another. If the contemporary signal strength is equal to the previous signal strength then the microprocessor 810 returns to step 1030, but if the contemporary signal strength is less than the previous signal strength the microprocessor 810 proceeds to step 1100 where it instructs the variable attenuator 400 to reduce the amount of signal level adjustment by a predetermined amount (e.g. the amount of additional signal level adjustment added in step 1070 or an amount greater than the additional signal level adjustment added in step 1070). After step 1100, the microprocessor 810 saves the total amount of signal level adjustment in step 1110 and stops the routine at step 1120. Again, it should be understood that the amount of additional signal level adjustment may be added/removed by the variable amplifier 415, or by the AGC discussed above.
As mentioned above, an important aspect of the present signal level setting routine is the comparison step conducted in step 1090. A traditional cable modem 140 (
Because problems could result in the modem 140 from operating it at its maximum output (i.e., signal distortion may be high when the modem 140 is operating at or near a maximum level and/or the durability of the modem 140 may be sacrificed when the modem 140 is operating at or near a maximum level), the amount of signal level adjustment may be reduced by a sufficient amount in step 1100 to ensure quality of the output signal generated by the modem 140 and the durability of the modem 140 once the maximum output strength of the modem 140 is identified.
It is noted that in a system with more than one device passing data packets into the upstream bandwidth, the premise device 100 may identify the maximum output strength of one device and not the other. In other words, the premise device 100 may identify the first device achieving its maximum output strength without proceeding to identify the maximum output strength of any other devices. If the premise device 100 fails to identify the first observed maximum output strength, that device may continue to operate at its maximum output strength until another determination cycle is initiated.
The predetermined number compared in 1050 can be related directly to the amount of signal level adjustment. For example, if the variable signal level adjustment device is a step attenuator including 25 steps of 1 dB attenuation, as is the case in the embodiment represented in
The amount of additional attenuation added in step 1070, and the predetermined amount of attenuation reduced in step 1100 are all variables that are currently based, at least partially, on hardware design limitations and can, depending on the hardware, be adjusted by one skilled in the art based on the conditions experienced in a particular CATV system and with particular CATV equipment. As discussed above, the variable signal level adjustment device in one embodiment of the present invention is a step attenuator having a resolution of 1 dB and a range of 25 dB. Accordingly, the amount of additional attenuation added in step 1070 using the present hardware could be 1 dB or multiples of 1 dB. Similarly, the predetermined amount of attenuation reduced in step 1100 can be 1 dB or multiples of 1 dB. It should be understood that if the amount of additional attenuation added in step 1070 is a multiple of 1 dB, such as 5 dB, the amount of attenuation reduced in step 1100 can be a lesser amount, such as 2 dB or 4 dB. The amount of attenuation reduced in step 1100 can also be greater than the amount of additional attenuation added in step 1070 for the reasons stated above relating to maintaining the quality of the output from the modem 140 and the and durability of the modem 140.
The predetermined threshold compared in step 1060 is a signal level sufficient to distinguish the presence of upstream data packets in the upstream bandwidth from interference signals. This value will vary depending on the output power of any cable modem 140, STB, STU, etc. in the system and the average observed level of interference signals. A goal is, for example, to determine if a device is present that sends upstream data packets via the upstream bandwidth. If the predetermined threshold is set too low, the interference signals may appear to be upstream data packets, but if the predetermined threshold is set too high, the upstream data packets may appear as interference signals.
Any of the high quality, commercially available signal couplers, signal level detectors, variable attenuation devices, filters, amplifiers, and microprocessors will function well within the specified locations within the premise device 100.
Referring now to
The tuner circuit 600 obtains the downstream bandwidth from a coupler 420 drawing the downstream bandwidth off of the high frequency signal path 930 (
Through instructions provided by the microprocessor 810, the tuner 610 scans the coupled downstream bandwidth in an effort to locate and identify a channel having a low frequency, referred to herein as a low band signal channel 1250 (
During the scanning process to locate and identify the low and high band signal channels 1250, 1260, the tuner circuit 600 provides the microprocessor 810 with three types of information. First, a signal indicating that a channel has been identified is provided to the microprocessor 810 through input line 640. Second, a signal indicating signal strength of the identified channel is provided to the microprocessor 810 through input line 630. Third, a signal indicating the format of the identified channel is provided to the microprocessor 810 through input line 620.
The signal indicating that a channel has been identified is created by passing the coupled downstream bandwidth though a band pass filter 650 to remove extraneous noise, a signal level detector 660 to convert signal into a voltage, and another signal level detector 670. The signal leaving the signal level detector 670 is compared to a predetermined threshold voltage using comparator 680. The predetermined threshold voltage is created using a voltage source 690 and an resistive divider 700, and is set such that if the voltage associated with the coupled downstream bandwidth at the tuner frequency is greater than the threshold voltage, it is likely a channel in use by the supplier 20, whereas if the voltage associated with the coupled downstream bandwidth at the tuner frequency is less than the threshold voltage, it is likely interference signals.
The signal indicating signal strength is created similarly to the signal indicating that a channel has been identified. The signal indicating signal strength passes through comparator 720 when it is greater than a threshold voltage created by a voltage source 730 and a resistive divider 740. To clarify the differences, the signal indicating that a channel has been identified may not have any direct relation to the actual signal strength, whereas the signal indicating signal strength is directly proportional to the actual signal strength of the identified channel.
The signal indicating the format of the identified channel is created when the coupled downstream bandwidth passes through a channel analyzer, which includes the band pass filter 650, the signal level detector 660, a synch detector 750, a low pass filter 760, and a signal level detector 770. The resulting signal identifies whether the identified channel is an analog format channel or another type of signal format.
According to current signal transmission specifications, digital format channels have a signal strength that is typically 6 dB less than a corresponding analog channel. Accordingly, the microprocessor 810 must include a level offset calculation that can account for this 6 dB difference when comparing the relative signal strengths of the low and high band signal channels 1250, 1260. If this inherent difference is not accounted for, any resulting comparisons of the two channels 1250, 1260 for the purpose of determining relative signal strengths would necessarily be flawed. For example, if the high band channel 1260 is digital while the low band channel 1250 is analog, the additional, inherent 6 dB difference would incorrectly indicate that there is more parasitic losses than there actually is. Similarly, if the high band channel 1260 is analog and the low band channel 1250 is digital, any resulting comparison would incorrectly indicate that there is less parasitic loss that there actually is. Therefore, it should be understood that it does not matter whether the 6 dB offset is added to the signal strength of a digital format channel or the 6 dB offset is subtracted from the signal strength of an analog format channel. Further, it should be understood that the 6 dB offset can be added to the signal strength of both the low and high band channels 1250, 1260 if they are both digital or the 6 dB offset can be subtracted from the signal strength of both the low and high band channels 1250, 1260 if they are both analog. Even further, it should be understood that the offset value is dictated by the standards observed by a particular supplier and can be, therefore, a value other than 6 dB.
After completing the scanning process and the process of adding/removing any offsets, the microprocessor 810 now has a low band signal strength (including any offset), a low band channel frequency, a high band signal strength (including any offset), and a high band channel frequency. The known information (i.e., the strength and frequency) of the low and high band channels 1250, 1260 are now compared, by the microprocessor 810, to a predetermined signal strength loss curve (i.e., a gain loss curve), which corresponds to the known parasitic losses associated with the type of coaxial/optical cables used, as shown in
It should be understood that parasitic losses affect higher frequencies more than lower frequencies. Accordingly, if a known signal having a −10 dB signal strength, for example, is transmitted at various frequencies across the entire downstream bandwidth and across a length of coaxial/optical cable, a plot of the resulting gain curve would result in a curve, which is known. Because the end goal is to have a gain curve that is a straight line near the original signal strengths or to have a gain curve that has an increasing slope versus frequency, the microprocessor 810 directly controls the variable slope adjustment circuit to adjust the downstream signal transmission in curve such that the lower frequencies are lower in amplitude than the higher frequencies.
For example, as shown in
As with the other devices discussed above, the downstream bandwidth output level and/or output level tilt compensation device 3 can be activated automatically upon initialization of the premise device 100, a set intervals, upon the occurrence of a particular event, and/or upon receipt of an information signal (e.g. a tone, a coded operating signal, etc.) from the supplier 20.
While the present invention has been particularly shown and described with reference to certain exemplary embodiments, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by claims that can be supported by the written description and drawings. Further, where exemplary embodiments are described with reference to a certain number of elements it will be understood that the exemplary embodiments can be practiced utilizing either less than or more than the certain number of elements.
Lai, Joseph, Olson, Thomas A., Kelma, David, Shafer, Steven K.
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