Abstract:
Systems and methods for selecting, combining and duplexing signals in a communications network. Several configurations of diplexers and channel selectors are disclosed which use filters, combiners and splitters to select and combine which the signals to be either received or transmitted.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority benefit of U.S. Provisional Patent Application Ser. No. 61/981,629, filed Apr. 18, 2014 and entitled “Method and Apparatus for Band Selection, Switching and Diplexing”, which is herein incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The disclosed method and apparatus relate to communications systems and more particularly to systems for selecting, combining and diplexing signals of a communications system. 
       BACKGROUND 
       [0003]    In many cases, broadband receivers are used to receive signals from several sources. Frequently, one particular signal needs to be selected from among the signals received. Alternatively, more than one signal need to be combined to form a composite signal. Different signals may need to be combined for transmission together over a shared medium, such as coaxial cable within a home. For example, in a home entertainment network, signals may be received from various sources, such as satellite dishes, MoCA (Multimedia over Coax Alliance) networks, or cable television feeds. In some such cases, these signals must be combined for communication over a common medium, such as a coaxial cable that allows components within the home entertainment network to communication with one another. 
         [0004]      FIG. 1  is a simplified block diagram of a signal selector  100 . A first single pole-triple throw switch  102  is used to select one of three filters  104 ,  106 ,  108  to be connected to an input  110 . A second single pole-triple throw switch  112  selects the output of the selected filter  104 ,  106 ,  108  to be coupled to the output  114  of the signal combiner  100 . The first filter  104  has relatively low band pass frequency response that extends from a first frequency of approximately f 1  to a second frequency of approximately f 2 . The second filter  106  has a relatively high band pass frequency response that extends from a third frequency of approximately f 3  to a fourth frequency of approximately f 4 . The third filter  108  has a relatively wide bandpass frequency response that extends from the first frequency of approximately f 1  to approximately the fourth frequency of f 4 . Accordingly, by setting the switches appropriately, the signals with a frequency of f 1  to f 2  that are present at the input  110  can be selected to be coupled through to the output by selecting the first position in both the input switch  102  and the output switch  114 . Likewise, by setting the input and output switches  102 ,  114  to the second position, signals with a frequency of f 3  to f 4  that are present at the input  110  can be selected to be coupled through to the output. Finally, by setting the input and output switches  102 ,  114  to the third position, signals with a frequency of f 1  to f 4  that are present at the input  110  can be selected to be coupled through to the output. 
         [0005]    While this arrangement works well, the fact that it requires two single pole, triple throw switches causes the selector  100  to have a relatively high loss from the input  110  to the output  114 . Furthermore, the two switches add distortion to the signal. Therefore, there is presently a need for a low loss signal combiner that can select between different filters inexpensively. 
         [0006]    In the context of a home entertainment network, selection of signals carried on several different frequency bands is necessary.  FIG. 2  is a simplified block diagram of a universal MoCA diplexer  200 . The diplexer  200  has six filters  202 ,  204 ,  206 ,  208 ,  210 ,  212 . Three of the filters  202 ,  204 ,  206  are used to select satellite television signals and MoCA signals. Another two filters  208 ,  210  are used to select MoCA. The MoCA band is selected based upon whether the frequency band will be shared by satellite television or cable television signals. When satellite signals are present, MoCA signals are modulated on the E-band (500 MHz to 600 MHz) or F-band (675 MHz to 850 MHz). When used with cable television signals, MoCA is typically modulated on the D-band (1150 MHz to 1500 MHz). The sixth filter  212  is used to select cable television (CATV) signals. Two multi-throw switches  214 ,  216  are used to select which filter from among the five filters  202 ,  204 ,  206 ,  208 ,  210  is to be coupled to the output  218  and which filter is to be coupled to the input  220 . A single pole, single throw switch  222  is used to connect the input  220  to the CATV filter  212 . 
         [0007]    The use of multi-throw switches increases the loss in the circuit substantially. Therefore, there is a need for a universal diplexer that can select from among several frequency bands without encountering the substantial losses associated with multi-throw switches. 
       SUMMARY 
       [0008]    Various embodiments of the disclosed method and apparatus for selecting, combining and duplexing signals are presented. In accordance with one embodiment of the disclosed method and apparatus, an input signal is coupled to two filters. The first filter has a relatively low pass band. The second filter has a relatively high pass band. In one embodiment the 3 dB cutoff at the high end of the low pass filter is at the same frequency as the 3 dB cutoff at the low end of the high pass filter. A single pole, single throw switch coupled to the output of the filters selects between one, the other or both filters. The output of the two switches are coupled to two inputs to a combiner/splitter. In another embodiment, amplifiers are provided between the filter and the switch. 
         [0009]    In another embodiment, a receive/transmit diplexer is achieved using two single pole, double throw (SPDT) switches, one at the output of each filter. The two SPDT switches select between transmit and receive modes. In receive mode, each SPDT switch allows the associated filter to be selectively coupled to a low noise amplifier (LNA) for amplifying received signals output from the filter. In transmit mode the switches couple a power amplifier (PA) to the filters to amplify signals to be transmitted prior to entering the filter. The input to each PA is coupled to one of two inputs to a splitter. The splitter receives an input signal to be transmitted. The signal is split and the output coupled to the two PAs. The output of each PA is coupled to one of the throws of one of the two SPDT switches. In receive mode, a combiner receives the output from the two LNAs. Each LNA is coupled to the output of one of the filters through the second throw of one of the SPDT switches. 
         [0010]    In another embodiment, a MoCA universal diplexer is achieved using two SPDT switches. The first of the two switches is used to select whether a first group of filters or a second group of filters are coupled to an F connector. The F connector couples the filters to a coaxial cable for receiving and transmitting to the networks. The first group of filters include an E-band and an F-band filter. The second group of filters include a D-band low filter, a D-band high filter and a set of switched CATV filters. The second of the two switches is used to select between the E-band and an F-band filter. In an alternative embodiment of the MoCA universal diplexer, the second SPDT switch is eliminated. This is achieved by limiting the F-band filter to frequencies that do no overlap with the frequencies of the E-band filter. Therefore, the outputs of the E-band filter and the partial F-band filter can be directly coupled to the first switch (i.e., both can be selected concurrently). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The disclosed method and apparatus, in accordance with one or more various embodiments, is described with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict examples of some embodiments of the disclosed method and apparatus. These drawings are provided to facilitate the reader&#39;s understanding of the disclosed method and apparatus. They should not be considered to limit the breadth, scope, or applicability of the claimed invention. It should be noted that for clarity and ease of illustration these drawings are not necessarily made to scale. 
           [0012]      FIG. 1  is a simplified block diagram of a prior art signal selector. 
           [0013]      FIG. 2  is a simplified block diagram of a prior art universal MoCA diplexer. 
           [0014]      FIG. 3  is a simplified block diagram of a passive band switch in accordance with the disclosed method and apparatus. 
           [0015]      FIG. 4  is a simplified block diagram of an active transmitter band switch. 
           [0016]      FIG. 5  is a simplified block diagram of a receiver band switch. 
           [0017]      FIG. 6  is a simplified block schematic of a transmit/receive diplexer. 
           [0018]      FIG. 7  is a simplified block diagram of a universal diplexer. 
           [0019]      FIG. 8  provides details regarding one embodiment of the Rx/Tx selection and combining module of  FIG. 7 . 
           [0020]      FIG. 9  is a simplified block diagram of an alternative embodiment of a universal diplexer. 
       
    
    
       [0021]    The figures are not intended to be exhaustive or to limit the claimed invention to the precise form disclosed. It should be understood that the disclosed method and apparatus can be practiced with modification and alteration, and that the invention should be limited only by the claims and the equivalents thereof. 
       DETAILED DESCRIPTION 
       [0022]      FIG. 3  is a simplified block diagram of a passive band switch  300  in accordance with the disclosed method and apparatus. The band switch  300  includes a first filter  302 , a second filter  304 , a first SPST switch  306 , a second SPST switch  308  and a combiner/splitter  310 . Signals in one of three frequency bands (high, low and bandpass band) can be selected by selectively opening or closing the first and second SPDT switches  306 ,  308 . The first filter  302  has a relatively low pass-band, having a low frequency 3 dB cutoff at a first frequency f 1  and high frequency 3 dB cutoff at a second frequency f 2 . The second filter has a low frequency 3 dB cutoff at a third frequency f 3  and a high frequency 3 dB cutoff at a fourth frequency f 4 . The third frequency f 3  can be any frequency equal to or greater than the second frequency f 2 . The two filters  302 ,  304  are coupled together at a common connection point  312  at a first terminal of each filter  302 ,  304 . A second terminal of the first filter  302  is coupled to the first terminal of the first switch  306 . The second terminal of the first switch  306  is coupled to a first isolated port of the combiner/splitter  310 . A second terminal of the second filter  304  is coupled to the first terminal of the second switch  308 . The second terminal of the second switch  308  is coupled to the second isolated port of the combiner/splitter  310 . 
         [0023]    It should be noted that because the band switch  300  is passive, it can be used for receiving signals at the common port  314  of the combiner/splitter  310  and passing them through to the common port  312 . Alternatively, operation in the opposite direction is possible. That is, signals can be received at the filter common port  312  and the output of the filters combined at the combiner/splitter  310  to be output at the port  314 . The combiner/splitter  310  provides isolation that prevents the filters from interacting badly with one another (e.g., forming resonant circuits that may oscillate, etc.). 
         [0024]    The band switch  300  has three modes. The first mode is “low pass” mode. In low pass mode, the first switch  306  is closed and the second switch  308  is open. Accordingly, if an input signal is applied to the common connection point  312 , the output at the common port  314  of the combiner/splitter  310  will have only those frequencies passed by the first filter  302 . Likewise, if an input signal is applied to the common port  314  of the combiner/splitter  310 , the output at the common connection point  312  will have only those frequencies passed by the first filter  302 . 
         [0025]    The second mode is “high pass” mode. In high pass mode, the first switch  306  is open and the second switch  308  is closed. Accordingly, if an input signal is applied to the common connection point  312 , the output at the common port  314  of the combiner/splitter  310  will have only those frequencies passed by the second filter  304 . Likewise, if an input signal is applied to the common port  314  of the combiner/splitter  310 , the output at the common connection point  312  will have only those frequencies passed by the second filter  304 . 
         [0026]    The third mode is “band pass” mode. In band pass mode, both switches  306 ,  308  are closed. In band pass mode, when the third frequency f 3  is equal to the second frequency f 2 , the frequency response through the band switch  300  will be relatively flat across the band from f 1  to f 4 . The combiner/splitter  310  provides isolation between the two filters  302 ,  304  and the two switches  306 ,  308 . Therefore, switching between modes will not cause distortion at the common port  314  of the combiner/splitter  310 . In addition, the combiner/splitter  310  allows the two filters  302 ,  304  to be used together to make a composite band pass filter that will allow signals in the range from f 1  to f 4  to pass from the input to the output without the need for a third filter. 
         [0027]    By eliminating one switch and using a SPST switch rather than a SPSD switch, the loss through the band switch  300  is reduced. However, the addition of the combiner/splitter  310  offsets some of the gains achieved by simplifying the switches. 
         [0028]      FIG. 4  is a simplified block diagram of an active transmitter band switch  400 . Two power amplifiers (PAs)  416 ,  418  are included. A signal to be transmitted is coupled to the common port of a splitter  410 . A first isolation port of the splitter  410  is coupled to a first terminal of a first switch  406 . The input of the first PA  416  is coupled to a second terminal of the first switch  406 . The output of the PA  416  is coupled to a first terminal of a first filter  402 . A second isolation port of the splitter  410  is coupled to the first terminal of a second switch  408 . The input to the second PA  418  is coupled to a second terminal of the second switch  408 . The output of the second PA  418  is coupled to a first terminal of a second filter  404 . Due to the use of active components (i.e., the PAs  416 ,  418 ), the band switch  400  can only be used for transmitting. In a manner similar to that described with respect to the band switch  300 , the active transmitter band switch  400  has three modes: “low pass” mode; “high pass” mode and “band pass” mode. Using the switches  406 ,  408  in a similar manner to that described above, one of the three modes can be selected. In an alternative embodiment, each power amplifier  416 ,  418  can be placed between the splitter  410  and the respective switch  406 ,  408 . 
         [0029]      FIG. 5  is a simplified block diagram of a receiver band switch  500 . In the receiver band switch  500 , two low noise amplifiers (LNAs)  516 ,  518  are used. An input signal is received at a common connection point  512 . The input signal is coupled to a first terminal of each of two filters  502 ,  504 . A second terminal of the first filter  502  is coupled to the input of the first LNA  516 . The output of the first LNA  516  is coupled to a first isolation port of a combiner  510 . A second terminal of the second filter  504  is coupled to the input of the second LNA  518 . The output of the second LNA  518  is coupled to the second isolation port of the combiner  510 . In a manner similar to that described with respect to the band switch  300 , the active receiver band switch  500  has three modes: “low pass” mode; “high pass” mode and “band pass” mode. Using the switches  406 ,  408  in a similar manner to that described above, one of the three modes can be selected. In an alternative embodiment, each low noise amplifier  516 ,  518  can be placed between the combiner  510  and the respective switch  506 ,  508 . 
         [0030]    The use of active elements in the transmitter band switch  400  and receiver band switch  500  provide gain that compensates for losses incurred in the filter and splitter/combiner. It should be noted that removing the switch  102  from the prior art band switch  100  shown in  FIG. 1  will reduce the noise figure incurred in the band switch  500 . It can be seen that, even though there is an additional loss incurred due to the combiner  510 , that loss occurs after the LNA. Thus, the noise figure of the receiver band switch  500  will be better than would be the case if an LNA were introduced in the band switch  100 . 
         [0031]      FIG. 6  is a simplified block schematic of a transmit/receive diplexer  600 . In one of the three transmit modes, the diplexer  600  couples signals to be transmitted from diplexer transmit input port  602  onto a coaxial cable or other medium connected to a diplexer coaxial cable port  604 . In one of the three receive modes, the diplexer  600  will receive signals at the diplexer coaxial cable port  604  and couple them to the diplexer receive output port  624 . It will be understood by those skilled in the art that the diplexer coaxial cable port  604  can be coupled to any medium or circuit. However, in order to make clear the context of one embodiment of the disclosed method and apparatus, the diplexer coaxial cable port  604  is discussed in the context of a coaxial cable port. 
         [0032]    The diplexer  600  has two filters  608 ,  610  and operates in one of four modes. In the first mode, the first Tx/Rx switch  612  is set to couple the output of a first PA  616  to a first terminal of the first filter  608 . The input to the PA  616  is coupled to a first isolation port  603  of a splitter  618 . The second terminal of the first filter  608  is coupled to a common connection point  620 . The second Tx/Rx switch  614  is set to couple the input of a first LNA  621  to a first terminal of the second filter  610 . The output of the first LNA  621  is coupled to the first isolation port  605  of a combiner  619 . A second terminal of the second filter  610  is coupled to the common connection point  620 . 
         [0033]    Accordingly, signals that are input at the diplexer transmit input port  602  of the diplexer  600  are coupled to the common port of the splitter  618 . Those signals that are within the pass band of the first filter  608  are transmitted out the diplexer coaxial cable port  604  to a coaxial cable or other medium. Signals presented to the diplexer transmit input port  602  of the diplexer and that are outside of the pass band of the filter  608  are rejected. 
         [0034]    Concurrently, signals received at the diplexer coaxial cable port  604  are applied to the filter  610 . Signals within the pass band of the filter  610  are coupled through the second switch  614  to the input to first LNA  621 . These signals are then applied to the first isolation port  605  of the combiner  619  and output from the common port of the combiner  619  to the diplexer receive output port  624 . 
         [0035]    Therefore, in the first mode, signals in the passband of the first filter  608  are transmitted and signals in the passband of the second filter  610  received. 
         [0036]    In the second mode, the Tx/Rx switches  612 ,  614  are each thrown in the other direction (the opposite position from the position of the first mode). Therefore, the first filter  608  is coupled to the input of the LNA  626 . The output of the LNA  626  is coupled a second isolation port  607  of the combiner  619 . The second filter  610  is coupled to the output of the second PA  622 . The input to the PA  622  is coupled to the second isolation port  609  of the splitter  618 . Accordingly, in the second mode, signals in the passband of the first filter  608  are received and signals in the passband of the second filter  610  are transmitted. 
         [0037]    In the third mode, the first Tx/Rx switch  612  is set to couple the output of the first PA  616  to a first terminal of the filter  608 . The input to the PA  616  is coupled to the first isolation port  603  of the splitter  618 . A second terminal of the first filter  608  is coupled to the common connection point  620  which is coupled to the diplexer coaxial cable port  604 . The second Tx/Rx switch  614  is set to couple the output of a second PA  622  to a first terminal of the second filter  610 . The input to the second PA  622  is coupled to the second isolation port of the splitter  618 . A second terminal of the second filter  610  is coupled to the common connection point  620 . Accordingly, signals that are applied to the diplexer transmit input port  602  are split and coupled to the two filters  608 ,  610 . The signals are then recombined at the common connection point  620  and output together at the diplexer coaxial cable port  604 . 
         [0038]    In the fourth mode, both filters  608 ,  610  are used for receiving. The first Tx/Rx switch  612  is set to couple the first filter  608  to the LNA  626 . The second Tx/Rx switch  614  is set to couple a first terminal of the second filter  610  to the LNA  621 . Accordingly, signals that are presented at the diplexer coaxial cable port  604  and that are within the pass band of the first filter  608  are coupled to the first isolation port  607  of the combiner  619 . Signals presented at the diplexer coaxial cable port  604  that are within the pass band of the second filter  610  are coupled to the second isolation port  605  and combined with the signals at the first isolation port  607 . The combined signals are output from the combiner  619  to the diplexer receive output port  624 . 
         [0039]    The diplexer  600  allows for selection of a low pass band, a high pass band or a broad band in both the receive and transmit modes. The diplexer  600  requires only two filters and two SPDT switches. In an alternative embodiment, the Tx/Rx switches  612 ,  614  have a third position in which the associated filter  608 ,  610  is disconnected. When one of the Tx/Rx switches is in this third position, either one frequency band is received or one frequency band is transmitted. 
         [0040]    In one embodiment of the diplexer  600 , the high frequency 3 dB cutoff for the filter  608  is at the same frequency as the low frequency 3 dB cutoff for the filter  610 . Accordingly, when both filters are used in receive mode or both filters are used in transmit mode, a flat frequency response will be achieved from the low frequency end f 1  of the filter  608  to the high frequency end f 4  of the filter  610 . In another embodiment, the high frequency 3 dB cutoff for the filter  608  is at a lower frequency than the low frequency 3 dB cutoff for the filter  610 . Thus, a notch will be created in the frequency response of the diplexer at frequencies between the high frequency 3 dB cutoff for the filter  608  and the low frequency 3 dB cutoff for the filter  610 . In one embodiment, the filters are dynamically tunable to determine the bandwidth of each filter in each mode. 
         [0041]    The amplifiers  616 ,  621 ,  622 ,  626  provide gain to compensate for the insertion loss suffered through the splitter  618  and combiner  619 . In one embodiment, when a switch  612 ,  614  removes an amplifier from the signal path, that amplifier can be turned off to both save power and reduce the amount of noise coupled to the output signal. 
         [0042]    It should be noted that the isolation through the switches  612 ,  614  in the off position should be at least as great as the rejection of the filter that is operational for those frequencies that are in the pass band of the filter that is not operational. That is, if there is significant leakage through the switches  612 ,  614 , the selection of just one band will not be effective, since some of the power in the other band will leak through the switch  612 ,  614 . While the noise of the two LNAs  621 ,  626  will increase the overall noise figure of the diplexer, the elimination of one switch before the LNA (i.e., on the other side of the filters  608 ,  610 ) offsets the increase in noise figure. 
         [0043]      FIG. 7  is a simplified block diagram of a diplexer  700 . The diplexer  700  includes an Rx/Tx selection and combining module  800 . The Rx/Tx selection and combining module  800  includes a first MoCA Tx/Rx module  702 , a second MoCA Tx/Rx module  704 , and a combining/splitter module  706 . The diplexer  700  also includes five filters  708 ,  710 ,  712 ,  714 ,  716 , a cable/satellite switch  718 , an E-band/F-band switch  720  and an “F connector”  722 . The diplexer  700  has two high level modes. The first high level mode is cable mode. The second high level mode is satellite mode. In cable mode, the cable/satellite switch  718  is in the cable position (the position that is not shown in the  FIG. 7 ). 
         [0044]    In cable mode, the F connector  722  is coupled through the pole of the cable/satellite switch  718  to the cable throw  724 . The cable throw  724  of the switch  718  is coupled to three of the filters  708 ,  710 ,  712 . In one embodiment, the first filter  708  passes signals in the CATV band. Accordingly, satellite television signals received on the F-connector  722  are passed through the filter  708  to tuners required to display the television signals for viewing. The second filter  710  is a D band-low filter that passes signals in the range of 1125 to 1225 MHz. The third filter  712  is a D band-high filter that passes signals in the range of 1350 to 1675 MHz. These frequency bands commonly carry communications that conform to the well-known MoCA standard for home entertainment network communications. In particular, these frequency bands are typically used together when a medium, such as coaxial cabling, is shared by a MoCA network and CATV signals. 
         [0045]    In satellite mode, the F connector  722  is coupled through the pole of the cable/satellite switch  718  to the satellite throw  726 . The satellite throw  726  is coupled to the pole of the E-band/F-band switch  720 . The E-band/F-band switch  720  has two positions. In the first position, the pole is connected to the E-band filter  714  having a pass band in the range of 650 to 875 MHz. In the second position, the pole of the E-band/F-band switch  720  is connected to the F-band filter  716  having a pass band of 400 to 700 MHz. These two filters commonly carry MoCA signals when a medium, such as coaxial cabling, is shared by a MoCA network and satellite television signals. 
         [0046]    In the satellite mode, the satellite signals are rejected from being passed to the MoCA Rx/Tx modules  702 ,  704 . Since satellite signals are in the pass band of the D-band filters  710 ,  712 , the isolation of the cable/satellite switch  724  must be at least greater than the rejection of the E-band and F-band filters  714 ,  716 . 
         [0047]      FIG. 8  provides details regarding one embodiment of the Rx/Tx selection and combining module  800 . A first filter port  801  of the Rx/Tx selection and combining module  800  couples two of the filters  710 ,  714  (see  FIG. 7 ) to the first MoCA Rx/Tx module  702 . The first MoCA Rx/Tx module  702  includes a PA  803 , LNA  805  and Rx/Tx switch  807 . In accordance with one embodiment, the combining/splitting module  706  includes a splitter  809  and a combiner  811 . The input to the PA  803  is coupled to one of two isolation outputs  813  of the splitter  809 . The output from the LNA  805  is coupled to one two isolation inputs to the combiner  811 . Accordingly, when the Rx/Tx switch  807  is in the transmit mode, inputs received from the filters  710 ,  714  through the port filter  801  are amplified by the PA  803  and coupled to a transmit output port  817 . 
         [0048]    When the Rx/Tx switch  807  is in the receive mode, the filters  710 ,  714  are coupled to the input of the LNA  805 . The output of the LNA  805  is coupled to a first of two isolation inputs  815  to the combiner  811 . 
         [0049]    An Rx/Tx switch  820  within the second MoCA Rx/Tx module  704  selects between transmit and receive modes for signals that fall within the pass band of either the F-band filter  716  or the D band-High filter  712 . When the MoCA Rx/Tx module  704  is in transmit mode, the output of the PA  821  is coupled to a second filter port  823 . The input to the PA  821  is coupled to a second isolated output  825  of the splitter  809 . The second filter port  823  is coupled to the D band-High filter  712  and to the F-band filter  716 . Thus, when the cable/satellite switch  718  shown in  FIG. 7  is in cable mode, signals in the frequency range D band-High (i.e., 1350-1675 MHz) coupled to the transmit output port  817  will be amplified by and routed through the Rx/Tx selection and combining module  800  to the F-connector  722 . Likewise, when the cable/satellite switch  718  is in the satellite mode, signals in the frequency range F-band (i.e., 400-700 MHz) coupled to the transmit input port  817  will be amplified by and routed through the Rx/Tx selection and combining module  800  to the F-connector  722  for transmission. 
         [0050]    When the Rx/Tx switch  820  in the MoCA Rx/Tx module  704  is in receive mode, the input to the LNA  827  is coupled to the second filter port  823 . The output from the LNA  827  is coupled to a second isolated output  829  of the combiner  811 . As noted above, the second filter port  823  is coupled to the D band-High filter  712  and to the F-band filter  716 . Thus, when the cable/satellite switch  718  shown in  FIG. 7  is in cable mode, signals in the frequency range D band-High (i.e., 1350-1675 MHz) coupled to the F-connector  722  will be amplified by and routed through the Rx/Tx selection and combining module  800  to the receiver output port  831 . Likewise, when the cable/satellite switch  718  is in the satellite mode, signals in the frequency range F-band (i.e., 400-700 MHz) coupled to the F-connector  722  will be amplified by and routed through the Rx/Tx selection and combining module  800  to the receive output port  831 . 
         [0051]    When the diplexer  700  is in satellite mode (i.e., the cable/satellite switch  718  is in satellite position) there are four modes possible. In the first mode, the MoCA Rx/Tx  702  is in transmit mode and the E-band/F-band switch  720  is in E-band mode. In the second mode, the MoCA Rx/Tx  702  is in receive mode and the E-band/F-band switch  720  is in E-band mode. In the third mode, the MoCA Rx/Tx  704  is in transmit mode and the E-band/F-band switch  720  is in F-band mode. In the fourth mode, the MoCA Rx/Tx  704  is in receive mode and the E-band/F-band switch  720  is in F-band mode. It should be noted that when the E-band/F-band switch  720  is in E-band mode, the amplifiers in the MoCA Rx/Tx module  704  can be turned off. Likewise, when the E-band/F-band switch  720  is in F-band mode, the amplifiers in the MoCA Rx/Tx module  702  can be turned off. 
         [0052]    There are also four possible modes when the diplexer  700  is in cable mode. In the first mode, the MoCA Rx/Tx module  702  is in transmit mode and the MoCA Rx/Tx module  704  is in receive mode. In this case, MoCA signals are received on the D band-High frequency and transmitted on the D band-low frequency. In the second mode, the MoCA Rx/Tx module  702  is in receive mode and the MoCA Rx/Tx modules  704  is in transmit mode. In this case, MoCA signals are transmitted on the D band-High frequency and received on the D band-low frequency. In the third mode, both MoCA Rx/Tx modules  702 ,  704  are in transmit mode. Accordingly, MoCA signals are transmitted on the full D-band. In the fourth mode, both MoCA Rx/Tx modules  702 ,  704  are in receive mode. Therefore, MoCA signals are received on the full D-band. 
         [0053]    In one embodiment, either the high frequency 3 dB cutoff of the filter  710  can be shifted up or the low frequency 3 dB cutoff of the filter  712  can be shifted down such that the two filters to cross over at the same point 3 dB cutoff frequency. Alternatively, these 3 dB cutoff frequencies can both be shifted to meet in the middle. Such filter adjustments can be done dynamically using tunable filters, or the filters can be designed with a fixed band having the adjusted 3 dB cutoff frequencies. By adjusting these 3 dB cutoff frequencies, the combined pass band created when the MoCA Rx/Tx modules  702 ,  704  are either both in transmit mode or both in receive mode will cover the full spectrum from the lower end 
         [0054]    of the filter  710  to the upper end of the filter  712 . 
         [0055]      FIG. 9  is a simplified block diagram of an alternative embodiment of a diplexer  900 . The diplexer  900  is essentially identical to the diplexer  700  except that the F-band filter  902  passes only a portion (400-600 MHz) of the full F-band passed by the F-band filter  716 . Therefore, the pass band of the E-band filter  904  and the partial F-band filter  902  do not overlap. Since the pass band of the E-band filter  904  and the partial F-band filter  902  do not overlap, the E-band/F-band switch  720  can be eliminated from the diplexer  900 . Accordingly, the filters  902 ,  904  are each coupled directly to the cable/satellite switch  718 . 
         [0056]    Therefore, when both MoCA Rx/Tx modules  702 ,  704  are in transmit mode, and the cable/satellite switch  718  is in satellite mode, the full Mid-RF band (i.e., 400-875 MHz) is available for MoCA transmissions. Likewise, when both MoCA Rx/Tx modules  702 ,  704  are in receive mode, and the cable/satellite switch  718  is in satellite mode, the full Mid-RF band (i.e., 400-875 MHz) is available to receive MoCA signals. 
         [0057]    Although the disclosed method and apparatus is described above in terms of various examples of embodiments and implementations, it should be understood that the particular features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described. Thus, the breadth and scope of the claimed invention should not be limited by any of the examples provided in describing the above disclosed embodiments. 
         [0058]    It should be understood by those skilled in the art that while the particular embodiments disclosed are described in the context of a system in which MoCA, cable television, and satellite signals share a common medium, the particular frequencies of the filters may vary without departing from the scope of the invention. Furthermore, the particular types of signals and networks that are being diplexed and combined should not be taken as a limitation on the scope of the claimed invention. The presently disclosed method and apparatus can be implemented with any type of signals and networks. Furthermore, the concepts that are disclosed herein can be expanded to systems in which more filters are used by daisy chaining several of the disclosed diplexers together. Alternatively, transmit/receive diplexers like those of  FIG. 6  can be selected from a bank of diplexers. When a particular diplexer is selected, the diplexer can pass signals that are within the pass band of only one or only the other filter or that are in the pass band of either one of the two filters. 
         [0059]    Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide examples of instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future. 
         [0060]    A group of items linked with the conjunction “and” should not be read as requiring that each and every one of those items be present in the grouping, but rather should be read as “and/or” unless expressly stated otherwise. Similarly, a group of items linked with the conjunction “or” should not be read as requiring mutual exclusivity among that group, but rather should also be read as “and/or” unless expressly stated otherwise. Furthermore, although items, elements or components of the disclosed method and apparatus may be described or claimed in the singular, the plural is contemplated to be within the scope thereof unless limitation to the singular is explicitly stated. 
         [0061]    The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term “module” does not imply that the components or functionality described or claimed as part of the module are all configured in a common package. Indeed, any or all of the various components of a module, whether control logic or other components, can be combined in a single package or separately maintained and can further be distributed in multiple groupings or packages or across multiple locations. 
         [0062]    Additionally, the various embodiments set forth herein are described with the aid of block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives can be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration.