Abstract:
Systems and methods are provided for implementing and using multiband transceiver architectures. In a transmit subsystem that comprises a plurality of transmit paths, a frequency spectrum that is used for transmission of signals may be segmented into a plurality of segments, and each of the segments may be allocated to one of the plurality of transmit paths. Further, performance in each of the plurality of transmit paths may be monitored during transmission of signals, and operation of the transmit subsystem and each of the plurality of transmit paths may be controlled based on the monitored performance. Such control may comprise dynamically performing one or more of modifying operation of one or more of the plurality of transmit paths, modifying assignment of plurality of segments to the plurality of transmit paths, and modifying segmentation of the frequency spectrum.

Description:
CLAIM OF PRIORITY 
       [0001]    This patent application makes reference to, claims priority to and claims benefit from the U.S. Provisional Patent Application Ser. No. 61/888,963, filed Oct. 9, 2013. The above identified application is hereby incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    Aspects of the present disclosure relate to electronics. More specifically, certain implementations of the present disclosure relate to methods and systems for power combining power amplifier architectures and methods. 
       BACKGROUND 
       [0003]    Conventional power amplifier architectures and methods can be inefficient. Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present disclosure as set forth in the remainder of the present application with reference to the drawings. 
       BRIEF SUMMARY 
       [0004]    System and methods are provided for power combining power amplifier architectures and methods, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims. 
         [0005]    These and other advantages, aspects and novel features of the present disclosure, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         [0006]      FIG. 1  depicts a portion of an example transmitter comprising multiple power amplifiers operating in parallel. 
           [0007]      FIGS. 2A-2C  depict portions of example transmitters operable to dynamically allocate frequency segments among a plurality of transmit paths operating in parallel. 
           [0008]      FIG. 2D  depicts an example implementation of circuitry operable to dynamically allocate frequency segments among a plurality of transmit paths based on peak to average power ratio (PAPR). 
           [0009]      FIG. 3A  depicts a flowchart of an example process for dynamically allocating frequency segments among a plurality of transmit paths based on peak to average power ratio (PAPR). 
           [0010]      FIG. 3B  depicts an example result of dynamic allocation of segments of DOCSIS upstream spectrum. 
           [0011]      FIG. 4A  depicts a portion of an example transmitter comprising multiple transmit paths for multiple DOCSIS upstream bands. 
           [0012]      FIG. 4B  depicts example allocation of spectrum among the transmit paths of the transmitter shown in  FIG. 4A . 
           [0013]      FIG. 5  depicts example system operable to dynamically allocate frequency segments among a pair of multiband transmitters. 
           [0014]      FIG. 6  depicts an example result of dynamic allocation of segments among multiband transmitters. 
           [0015]      FIGS. 7A-7D  depict example architectures for a transceiver comprising multiple transmit paths and multiple receive paths. 
           [0016]      FIG. 8A  depicts an example allocation of spectrum among paths of the transceivers shown in  FIGS. 7A-7C . 
           [0017]      FIG. 8B  depicts an example allocation of spectrum among transmit and receive paths of the transceivers shown in  FIGS. 7D . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    As utilized herein the terms “circuits” and “circuitry” refer to physical electronic components (e.g., hardware) and any software and/or firmware (“code”) which may configure the hardware, be executed by the hardware, and or otherwise be associated with the hardware. As used herein, for example, a particular processor and memory may comprise a first “circuit” when executing a first one or more lines of code and may comprise a second “circuit” when executing a second one or more lines of code. As utilized herein, “and/or” means any one or more of the items in the list joined by “and/or”. As an example, “x and/or y” means any element of the three-element set {(x), (y), (x, y)}. In other words, “x and/or y” means “one or both of x and y.” As another example, “x, y, and/or z” means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means “one or more of x, y, and z.” As utilized herein, the term “exemplary” means serving as a non-limiting example, instance, or illustration. As utilized herein, the terms “for example” and “e.g.” set off lists of one or more non-limiting examples, instances, or illustrations. As utilized herein, circuitry is “operable” to perform a function whenever the circuitry comprises the necessary hardware and code (if any is necessary) to perform the function, regardless of whether performance of the function is disabled, or not enabled, by some user-configurable setting. Further, although the following description uses DOCSIS (Data Over Cable Service Interface Specification) based transmitters/receivers and network as an example use case, various aspects of this disclosure may be used in wired and wireless transmitters and networks of all kinds. 
         [0019]      FIG. 1  depicts a portion of an example transmitter comprising multiple power amplifiers operating in parallel. The depicted portion of the transmitter may comprise a digital-to-analog converter (DAC) circuit  104 , a filter circuit  106 , a splitter circuit  108 , power amplifier circuits  110   1  and  110   2 , and a combiner circuit  112 . 
         [0020]    In the example implementation shown in  FIG. 1 , the transmitter transmits (e.g., signal  113 ) into a hybrid-fiber coaxial (HFC) network  114 . The transmitter may be part of a DOCSIS modem or cable modem termination system (CMTS). Using multiple power amplifiers (PAs) in parallel, as shown in  FIG. 1 , may improve heat dissipation and maximum output power of the transmitter relative to using only a single PA. 
         [0021]    In operation, a time-domain digital signal  103  may be converted by DAC  104  to an analog signal, which may be filtered by filter  106  and then split by the splitter  108  into two substantially identical signals, each of which may be amplified by a respective one of PAs  110   1  and  110   2 . The amplified outputs may then be recombined in combiner  112 . 
         [0022]    In another example implementation, the combiner  112  may be replaced by a circulator, which may be less lossy than a passive implementation of combiner  112 . 
         [0023]      FIGS. 2A-2C  depict portions of example transmitters operable to dynamically allocate frequency segments among a plurality of transmit paths operating in parallel. For example, shown in  FIG. 2A  is a portion of a transmitter, which may have parallel PAs like the transmitter shown in  FIG. 1 . However, the transmitter (or portion thereof) shown in  FIG. 2A  may additionally have parallel DACs  104   1  and  104   2  and parallel filters  106   1  and  106   2  as well as a path assignment circuit  202 . The path assignment circuit  202  may comprise suitable circuitry for assigning signals, corresponding to one or more input signals into the path assignment circuit  202 , onto a plurality of paths (e.g., a plurality of transmit paths within a transmitter). For example, the path assignment circuit  202  may comprise suitable circuitry to dynamically allocate frequency segments among a plurality of transmit paths based on peak to average power ratio (PAPR). An example implementation of the path assignment circuit  202  is described in more detail in  FIG. 2D . 
         [0024]    In operation, X (an integer) time-domain signals  201  (e.g., carriers modulated in accordance with DOCSIS 3.0) and/or frequency-domain signals (e.g., OFDM subcarriers modulated in accordance with DOCSIS 3.1) may arrive at the path assignment circuit  202 . The path assignment circuit  202  may divide the transmit frequency spectrum into a plurality of segments and then, for each of the plurality of frequency segments, assign the carriers and/or subcarriers falling within that segment to one of a plurality of transmit paths within the transmitter. For example, the path assignment circuit  202  may assign (via signals  203   1 ,  203   2 ) the carriers and/or subcarriers falling within a particular segment to either transmit path 1 (comprising DAC  104   1 , filter  106   1 , and PA  110   1 ) or transmit path 2 (comprising DAC  104   2 , filter  106   2 , and PA  110   2 ). The outputs of the transmit paths 1 and 2 may be recombined by the combiner  112 . 
         [0025]    In an example implementation, the use of two PAs in parallel (as opposed to using a single PA) may reduce the number of carriers/subcarriers per PA, and may reduce the peak to average power ratio (PAPR) by, for example, ˜1 to 2 dB. Further, the dynamic assignment of frequency segments among the multiple transmit paths may reduce PAPR by an additional 3 dB or more, for example. 
         [0026]    In an example implementation, the assignments of each carrier and/or subcarrier to one of the two paths may be performed based on the PAPR of the signals  203   1 ,  203   2 , and/or  113 . 
         [0027]    While the example implementation depicted in  FIG. 2A  (and similarly in  FIGS. 2B-2C ) comprises two transmit paths, it should be understood that the use of implementation with only two transmit path is for illustration, and that different number of transmit paths (and/or different manner for use thereof when assigning carriers and/or subcarriers) may be used. For example, other implementations may dynamically assign carriers and/or subcarriers to a subset of three or more transmit paths (e.g., each assigned to 1 of 3 paths, each assigned to 2 of 3 paths, each assigned to 1 of 4 paths, etc.). 
         [0028]    In various implementations, the components of the transmitter shown in  FIG. 2A  may be realized in any combination of one or more integrated circuits and/or one or more discrete components residing on one or more printed circuit boards (PCBs). As just one example, the components to the left of the PAs  110   1  and  110   2  may reside on a first semiconductor (e.g., silicon) die, the PAs  110   1  and  110   2  may reside on a second and third, respectively, semiconductor (e.g., Gallium Arsenide) die, and the combiner  112  may reside on a fourth semiconductor die or be realized using discrete components (e.g., SMT resistors and/or capacitors). 
         [0029]    Now referring to  FIG. 2B , the transmitter portion shown therein may be similar to the one shown in  FIG. 2A  but an output power amplifier (PA) and active combiner circuit  204  instead of the passive combiner  112  of  FIG. 2A . The active combiner circuit  204  may comprise suitable circuitry for combining a plurality of inputs, and also for applying additional adjustment, such as power amplification. The active combiner circuit  204  may reduce or eliminate losses that may be introduced by the passive combiner  112 . One consideration for the circuit  204  in  FIG. 2B  is that it needs to be capable of supporting the full PAPR of signal  113 . Accordingly, the transmitter shown in  FIG. 2B  may be operable to provide substantially similar handling of the time-domain signals  201  as described with respect to  FIG. 2A  (but with enhanced performance as result of the use of ‘active’ circuit  204  instead of the ‘passive’ combiner  112 ). 
         [0030]    In various implementations, the components of the transmitter shown in  FIG. 2B  may be realized in any combination of one or more integrated circuits and/or one or more discrete components residing on one or more printed circuit boards (PCBs), for example as described with respect to transmitter shown in  FIG. 2A . For example, the circuit  204  may reside on the same semiconductor die as one of the PAs  110   1  and  110   2 , or may reside on its on semiconductor die. 
         [0031]    Now referring to  FIG. 2C , the transmitter portion shown therein may be similar to the one shown in  FIG. 2B  but may comprise two of the circuits  204  in parallel and feeding the combiner  112 . The circuits  204   1  and  204   2 , arranged in the manner shown in  FIG. 2C , may generate substantially identical signals to drive the combiner  112 . Each of the circuits  204   1  and  204   2  in  FIG. 2C  may need drive only half the power driven by circuit  204  in  FIG. 2B . The implementation shown in  FIG. 2C  may spread the heat among two circuits  204   1  and  204   2  rather than just a single active combiner circuit  204 . 
         [0032]    In various implementations, the components of the transmitter shown in  FIG. 2C  may be realized in any combination of one or more integrated circuits and/or one or more discrete components residing on one or more printed circuit boards (PCBs). For example, the circuit  204   1  may reside on the same semiconductor die as PA  110   1 , and the circuit  204   2  may reside on the same semiconductor die as  110   2 . 
         [0033]    For each of the transmitters shown in  FIGS. 1-2C , the signal  113  may be standard-compliant (e.g., DOCSIS 3.0 and/or DOCSIS 3.1). Further, the dynamic assignment of subcarriers may be transparent to the receiver (e.g., a CMTS). 
         [0034]    In various implementations, each of the transmitters shown in  FIGS. 2A-2C  may be operable to dynamically control power consumption by enabling and disabling transmit paths. For example, transmit paths may be enabled/disabled based on spectrum usage and/or PAPR. If the PAPR is below a determined threshold and/or the number of carriers/subcarriers being utilized is below a threshold (which may correlate to low PAPR), then one or more transmit paths may be disabled. The path(s) may be enabled upon the PAPR and/or usage rising above a determined threshold. 
         [0035]      FIG. 2D  depicts an example implementation of circuitry operable to dynamically allocate frequency segments among a plurality of transmit paths based on peak to average power ratio (PAPR). Shown in  FIG. 2D  is an example implementation for the path assignment circuit  202  of  FIGS. 2A-2C . 
         [0036]    In the example implementation shown, inputs to the path assignment circuit  202  may be: (1) j (an integer) signals C, each corresponding to one of a respective j DOCSIS 3.0 upstream channels; and (2) k (an integer) signals SC, each corresponding to a respective one of k DOCSIS 3.1 subcarriers. The inputs may be applied to a circuit  220 . The circuit  220  may select which N (an integer) of signals C 1 -C j  to output to a first transmit path (e.g., to a combiner circuit  224   1 ) and which Q (an integer) of signals C 1 -C j  to output to a second transmit path (e.g., to a combiner circuit  224   2 ). Similarly, the circuit  220  may select which M (an integer) of signals SC 1 -SC k  to output to a first transmit path (e.g., to an inverse fast Fourier transform (IFFT) circuit  222   1 ) and which R (an integer) of signals SC 1 -SC j  to output to a second transmit path (e.g., to an IFFT circuit  222   2 ). 
         [0037]    The selections performed by the circuit  220  may be based on a control signal  229 , which may be generated by a circuit  228 . In the example implementation shown, the circuit  228  may be a random generator and the signal  229  may be a random number, and thus determining which signals are output to which transmit path may be random. In an example implementation, the random number may be constrained such that the number of signals, or percentage of spectrum, assigned to each transmit path may be a determined value or within a determined range of values (e.g., to ensure that signals occupying ˜50% of the spectrum are routed to each of the transmit paths). 
         [0038]    Each of the IFFT circuits  222   1  and  222   2  may be operable to transform the spectrum containing the respective assigned OFDM subcarriers from the frequency domain OFDM subcarriers to a respective one of time-domain signals  223   1  and  223   2 . 
         [0039]    The combiner circuit  224   1  may be operable to combine the selected N time-domain signals with the time-domain signal  223   1  to generate signal  225   1 . Similarly, the combiner circuit  224   2  may be operable to combine the selected Q time-domain signals with the time-domain signal  223   2  to generate signal  225   2 . The signals  225   1  and  225   2  may be output to an output latch circuit  230 . 
         [0040]    The circuit  226  may be operable to calculate the PAPR of the signals  225   1  and  225   2 . Further, the circuit  226  may be operable to perform certain action under certain conditions based on the PAPR values. For example, if the PAPR values are below a threshold, then the circuit  225  may trigger the output latch circuit  230  to output the signals  225   1  and  225   2 , as signals  203   1  and  203   2 , respectively. If the PAPR values are above the threshold, the circuit  226  may trigger the circuit  228  to generate a new random value (new value for signal  229 ) resulting in a different mapping between the input signals and the transmit paths. This may be repeated, such as until a mapping with an acceptable PAPR is found or a timeout occurs for example. 
         [0041]      FIG. 3A  depicts a flowchart of an example process for dynamically allocating frequency segments among a plurality of transmit paths based on peak to average power ratio (PAPR). Shown in  FIG. 3A  is a flow chart  300  comprising a plurality of steps (represented as blocks  302 - 310 ). 
         [0042]    The example process begins with block  302  and proceeds to block  308 . In block  302 , transmit spectrum may be divided into multiple segments. In block  304 , each segment may be randomly assign to one of the transmit paths. In block  306 , the resulting PAPR for each transmit path may be calculated. 
         [0043]    In block  308 , a check may be performed to determine whether the PAPR for each path is less than the desired threshold or a timeout had occurred. If the result of block  308  is no, the process returns to block  304 . If the result of block  308  is yes, the process may proceeds to block  310 , to proceed with the transmitting based on the current spectrum assignment, thus completing the process. The process of block  3 A may be executed for each transmit time interval. 
         [0044]      FIG. 3B  depicts an example result of dynamic allocation of segments of DOCSIS upstream spectrum. In the example spectrum allocation shown in  FIG. 3B , the spectrum (e.g., corresponding to signals  201  input into the path assignment circuit  202 ) may be divided into eight segments, which may or may not be uniformly sized (e.g., some segments may be wider than others). The segments may then be allocated among the transmit paths in the receiver. For example, in the particular example spectrum allocation shown in  FIG. 3B , as a result of a random assignment of each of the eight segments, segments 2, 5, and 8 may be assigned to signals  203   1  corresponding to transmit path 1, and segments 1, 3, 4, 6, and 7 may be assigned signals  203   1  corresponding to transmit path 2. Thus, in the example implementation there is an uneven distribution of segments (5 vs. 3) and bandwidth (50% vs. 30%) among the two paths. 
         [0045]    In some implementations, the distribution may be constrained to be 50% (or some other percentage, or within some range of percentages) of segments and/or 50% (or some other percentage, or within some range of percentages) of bandwidth. 
         [0046]      FIG. 4A  depicts a portion of an example transmitter comprising multiple transmit paths for multiple DOCSIS upstream bands. For example, the transmitter (or portion thereof) shown in  FIG. 4A  may comprise a pre-equalizer  402 , and a plurality of transmit paths (e.g., 3 transmit paths, as shown in the implementation depicted in FIG.  4 A), with each of the transmit paths (transmit path ‘i’) comprising a DAC  404   i , a first filter  406   i , a PA  408   i , and a second filter  410   i . 
         [0047]    The architecture of  FIG. 4A  may enable dynamically reconfiguring the transmitter bandwidth without need for high-power switches in the analog domain. The elimination of such switches may reduce cost, board area, and power loss. Dividing the upstream spectrum among multiple paths may reduce the performance requirements of the components of the transmitter (e.g., DACs  404 , filters  406 , PAs  408 , and filters  410  in the example implementation shown in  FIG. 4A ) of the paths relative to an implementation where each path has to handle more bandwidth (and likely more PAPR as a result). 
         [0048]    One advantage of the transmitter architecture of  FIG. 4A  is that filtering for each transmit path may be broken into two filters, namely filter  406  and filter  410 . Accordingly, the filters  406  may be readily integrated on chip with the DACs  404  whereas filters  410  may be off-chip components. 
         [0049]    In some instances, due to non-idealities of the filters  406 , there may be some overlap in their passbands (the overlaps may be referred to as “transition bands”). This is illustrated in the  FIG. 4B , which depicts example allocation of spectrum among the transmit paths of the transmitter architecture shown in  FIG. 4A . In this regard, the first transmit path may be allocated a first band  412   1  (“Band 1”), the second transmit path may be allocated a second band  412   2  (“Band 2”), and the third transmit path may be allocated a third band  412   3  (“Band 3.”) 
         [0050]    In an example implementation, pre-equalizer  402  may be operable to compensate for the transition band roll-off and group delay variation. There may be a feedback path from the output (or some intermediate stage of one or more of the transmit paths) for adapting/calibrating the pre-equalization. 
         [0051]    In an example implementation, the architecture of  FIG. 4A  may provide for suppression of harmonic distortion in the outputs of the PAs  408 . 
         [0052]    In an example implementation, the various transmit paths of the transmitter shown in  FIG. 4A  may be dynamically enabled/disabled as needed. For example, the first transmit path may be enabled only when the transmitter needs/desires to transmit on a first band (e.g., Band 1), the second transmit path may be enabled only when the needs/desires to transmit on a second band (e.g., Band 2), and the third transmit path may be enabled only when the needs/desires to transmit on a third band (e.g., Band 3). 
         [0053]    In an example DOCSIS-based implementation, Band 1 may go up to 42 MHz, Band 2 may go up to 85 MHz, and Band 3 may go up to 192 MHz. In such an implementation, only the first path may be enabled when supporting DOCSIS 3.0 using a “low split,” Bands 1 and 2 may be enabled when supporting DOCSIS 3.1 with a “mid split” or when supporting DOCSIS 3.0 below the low split and DOCSIS 3.1 between the low split and the mid split, and Bands 1, 2, and 3 may be enabled when supporting DOSCIS 3.1 with a “high split” or for concurrently supporting backwards compatibility for DOCSIS 3.0 when supporting DOCSIS 3.0 below the low split and DOCSIS 3.1 between the low split and the high split. 
         [0054]    A transmitter may use the multiband architecture of  FIG. 4A  in combination with the dynamic path assignment circuit  202  described above with reference to  2 A- 3 B. An example implementation of such a transmitter is shown in  FIG. 5   
         [0055]      FIG. 5  depicts example system operable to dynamically allocate frequency segments among a pair of multiband transmitters. For example, the transmitter architecture (or portion thereof) shown in  FIG. 5  may comprise path assignment circuit  202  and two instances of the multiband architecture shown in  FIG. 4A . The transmitter architecture shown in  FIG. 5  may comprise two pre-equalizers  402   1  and  402   2 , each of which coupled to three transmit paths, with each transmit path comprising a DAC (e.g., one of DACs  404   1 - 404   6 ), a first filter (e.g., one of filters  406   1 - 406   6 ), a PA (e.g., one of PAs  408   1 - 408   6 ). Further, one or more second filters (e.g., filters  410   1 - 410   3 ) may be used to provide filtering in the manner described with respect to  FIG. 4A . 
         [0056]    In the example implementation shown in  FIG. 5 , Band 1 output from first set of transmit paths may be combined with Band 1 output from second set of transmit paths via a circuit  502   1 . Similarly, Band 2 outputs may be combined by a circuit  502   2 , and Band 3 outputs may be combined by a circuit  502   3 . Each of the circuits  502   1 ,  502   2 , and  502   3  may be a passive or active combiner or circulator. The outputs of the circuits  502   1 ,  502   2 , and  502   3  may be input into corresponding one of the second filters  410   1 - 410   3 . 
         [0057]    In various implementations, the transmitter shown in  FIG. 5  may be realized in any combination of one or more integrated circuits and/or one or more discrete components residing on one or more printed circuit boards (PCBs). As just one example, each of the dashed rectangles in  FIG. 5  may correspond to an integrated circuit or discrete element, and the integrated circuits and discrete elements may reside on one or more printed circuit boards (PCBs). 
         [0058]      FIG. 6  depicts an example result of dynamic allocation of segments among the multiband transmitters, such as the pair of multiband transmitters of the transmitter architecture shown in  FIG. 5 . In  FIG. 6 , spectrum (e.g., corresponding to signals  201  input into the path assignment circuit  202 ) may be divided into twelve segments during spectrum allocation among the transmit paths in the transmitter shown in  FIG. 5 . In an example implementation, a different segment size (bandwidth) is used for each of the three bands, but this disclosure is not so limited. As a result of a random assignment of each of the twelve segments, segments B1 — 2, B2 — 2, B2 — 3, B2 — 1, B3 — 3, and B3 — 6 may be assigned to signal  203   1  (input into pre-equalizer  402   1 ) and segments B1 — 1, B2 — 1, B2 — 4, B3 — 2, B3 — 4, B3 — 5 may be assigned to signal  203   2  (input into pre-equalizer  402   2 ). 
         [0059]      FIGS. 7A-7D  depict example architectures for a transceiver comprising multiple transmit paths and multiple receive paths. 
         [0060]    Each of the example architectures shown in  FIGS. 7A-7D  may comprise a multiband transmit subsystem, a multiband receive subsystem, a plurality of filters (e.g., filters  406   1 - 406   4  in the example architectures shown in  FIGS. 7A-7C ; and filters  406   1 - 406   6  in the example architecture shown in  FIG. 7D ), and network  114  (e.g., a HFC network). The multiband transmit subsystem may comprise, in each of the example architectures shown in  FIGS. 7A-7D , pre-equalizer  402 , DACs  404   1 - 404   3 , PAs  408   1 - 408   3 . The multiband transmit subsystem may vary among the example architectures shown in  FIGS. 7A-7D . Each of the circuits shown in  FIGS. 7A-7D  and previously mentioned may be as described above. 
         [0061]    In  FIG. 7A , the example multiband receive subsystem may comprise an equalizer  702 , analog-to-digital converters (ADCs)  704   1 - 704   3 , and low-noise amplifiers (LNAs)  706   1 - 706   3 . Also shown are filters  406   1 - 406   4 , where filters  406   1 - 406   3  are shared by the transmitter subsystem and the receive subsystem, whereas filter  406   4  is used only by the receive subsystem. The passbands of the filters  406   1 - 406   4  may be the bands  412   1 - 412   4  (corresponding to Bands 1 through 4), respectively, as shown in  FIG. 8A . 
         [0062]    In a first configuration, the transceiver of  FIG. 7A  may support transmit on Band 1 and receive on Bands 2, 3, and 4. In such a configuration, PA  408   1  may be configured to amplify transmit signals, PAs  408   2  and  408   3  may be configured as short circuits (or may be bypassed via one or more switching elements) such that received signals from the filters  404   2  and  406   3  may pass through the PAs  408   2  and  408   3 , and each of LNAs  706   1 - 706   3  may be configured to amplify a respective received signal from filters  406   2 ,  406   3 , and  406   4 . The output of each of LNAs  706   1 - 706   3  may then be digitized by a respective one of ADCs  704   1 - 704   3 . The outputs of the ADCs may then be equalized by equalizer  702 . 
         [0063]    In a second configuration, the transceiver of  FIG. 7A  may support transmit on Bands 1 and 2 and receive on Bands 3 and 4. In such a configuration, PAs  408   1  and  408   2  may be configured to amplify respective transmit signals, PA  408   3  may be configured as a short circuit (or may be bypassed via one or more switching elements) such that received signals from the filter  406   3  may pass through the PA  408   3 , LNA  706   1  may be powered down, and each of LNAs  706   2 - 706   3  may be configured to amplify a respective one of received signals from filters  406   3  and  406   4 . The output of the LNAs  706   2  and  706   3  may then be digitized by the ADCs  704   2  and  704   3  and then equalized by equalizer  702 . 
         [0064]    In a third configuration, the transceiver of  FIG. 7A  may support transmit on Bands 1, 2, and 3 and receive on a fourth band  412   4  (“Band 4.”) In such a configuration, PAs  408   1 - 408   3  may be configured to amplify respective transmit signals, LNAs  706   1 - 706   2  may be powered down, and LNA  706   3  may be configured to amplify received signals from filter  406   4 . The output of the LNA  706   3  may then be digitized by the ADC  704   3  and then equalized by equalizer  702 . Equalizer  702  may also be operable to filter out-of-band noise from LNAs  706   1 - 706   3 . 
         [0065]    The configurability of the PAs into a short circuit may eliminate the need for switches (a source of loss) in the upstream and downstream paths. 
         [0066]    In  FIG. 7B  the example multiband receive subsystem comprises the equalizer  702 , the low-noise amplifiers (LNAs)  706   1 - 706   3 , a leakage suppression circuit  720 , a DAC  722 , an ADC  726 , and a combiner  728 . 
         [0067]    The transceiver of  FIG. 7B  may support the same configurations of LNAs and PAs as described above with respect to  FIG. 7A . Rather than applying outputs of the LNAs  706   1 - 706   3  to the equalizer  704  through respective and dedicated ADCs (e.g., the ADCs  704   1 - 704   3  in  FIG. 7A ), the outputs of the LNAs  706   1 - 706   3  may be instead combined via the combiner  728 , and may then be applied through a single ADC—e.g., the ADC  726 . The combiner  728  may be, for example, a passive or active combiner or circulator. Further, the leakage suppression circuit  720  may be operable to cancel out effects of overlap in the passbands of the filters  406   1 - 406   4  and/or non-idealities in the received signals, similar to how the pre-equalizer compensates for such overlaps and non-idealities for transmitted signals. For example, the digital output of the leakage suppression circuit  720  may be converted to analog via the DAC  722 , and may then be combined with the outputs of the LNAs  706   1 - 706   3  via the combiner  728 . 
         [0068]    In  FIG. 7C  the example multiband receive subsystem comprises the equalizer  702 , the ADC  726 , combiner  728 , the LNAs  706   1 - 706   3 , the leakage suppression circuit  720 , DAC  722 , and overvoltage protection circuits  732   1  and  732   2 . 
         [0069]    In a first configuration, the transceiver of  FIG. 7C  may support transmit on Band 1 and receive on Bands 2, 3, and 4. In such a configuration, PA  408   1  may be configured to amplify transmit signals, PAs  408   2  and  408   3  may be configured as open circuits so as not to load down or interfere with signals received via the filters  406   2  and  406   3  which then pass through the circuits  732   1  and  732   2 , for amplification by LNAs  706   1  and  706   2 . 
         [0070]    In a second configuration, the transceiver of  FIG. 7C  may support transmit on Bands 1 and 2 and receive on Bands 3 and 4. In such a configuration, PAs  408   1  and  408   2  may be configured to amplify respective transmit signals, PA  408   3  may be configured as an open circuit so as not to load down or interfere with signals received via the filters  406   3  which then pass through the circuit  732   2 , for amplification by LNAs  706   2 . In this configuration, LNA  706   1  may be disabled and may be protected being damaged by the output of PA  408   2  by circuit  732   1 . 
         [0071]    In a third configuration, the transceiver of  FIG. 7C  may support transmit on Bands 1, 2, and 3 and receive on Band 4. In such a configuration, PAs  408   1 - 408   3  may be configured to amplify respective transmit signals, LNAs  706   1 - 706   2  may be disabled and may be protected by circuits  732   1  and  732   2 . 
         [0072]    Shown in  FIG. 7D  is an example multiband receive subsystem similar to the embodiment shown in  FIG. 7A , but additionally including filters  406   5  and  406   6 , and switches  406   7  and  406   8 . The filters  406   5  and  406   6  may be configured based on spectrum allocation that accommodate sharing circuitry between transmit and receive paths. For example, the passbands of the filters  406   5  and  406   6  may be bands  412   5  and  412   6  respectively, as shown in  FIG. 8B . The filters  406   5  and  406   6  may provide additional (relative to the embodiment of  FIG. 7A ) filtering of undesired signals through bands  412   5  and  412   6  respectively, while allowing filters  406   2  and  406   3  to be designed with greater flexibility (relative to the embodiment of  FIG. 7A ). Switches  406   7  and  406   8  may be dynamically configurable during operation of the transceiver to couple and decouple the receive subsystem from the transmit subsystem as desired/necessary. Furthermore, when Band 2 and Band 3 are used for filtering received signals, DACs  404   2  and  404   3  may drive filters  406   9  and  406   10  respectively in order to cancel or otherwise suppress undesired signals. This may avoids the need to add additional component, such as a separate DAC (e.g., DAC  722  of  FIGS. 7B and 7C ). 
         [0073]    Although each of  FIGS. 7A-7D  depict only a single transmit subsystem, there may be two such subsystem in parallel and fed by circuit  202 , substantially in the similar manner as described with respect to the architecture shown in such as in  FIG. 5  for example. 
         [0074]    In  FIGS. 7A-7C , the use of four narrower-band filters instead of two (one for Bands 1, 2, and 3) or one (one for all bands) wider-band filter may reduce cost and complexity. Additionally, the depicted filter configuration may suppress noise and/or distortion (e.g., harmonic distortion generated by the PAs, noise created by the DACs, and/or distortion introduced by the DACs) that falls in both the upstream and downstream paths, which may enable reducing the cost and complexity of the PAs and the DACs. 
         [0075]    In various implementations, the components of each of the transceivers shown in  FIG. 7A-7C  may be realized in any combination of one or more integrated circuits and/or one or more discrete components residing on one or more printed circuit boards (PCBs). As just one example, in  FIG. 7C , the components  402 ,  404 ,  720 ,  702 ,  722 ,  726 ,  728 , and  706  may reside on a first semiconductor (e.g., silicon) die,  408   1  may reside on a second semiconductor (e.g., Gallium Arsenide) die,  408   2  and  732   1  may reside on a third semiconductor (e.g., Gallium Arsenide) die,  408   3  and  732   2  may reside on a fourth semiconductor (e.g., Gallium Arsenide) die and the filters  406   1 - 406   4  may be discrete components. As another example, in  FIG. 7C , the circuits  732  may be on-chip with the LNAs  706 . As another example, in  FIG. 7C , the components  402 ,  404 ,  720 ,  702 ,  722 ,  726 , and  728  may reside on a first semiconductor die;  408   1 ,  706   1 , and  732   1  may reside on a second die;  408   2 ,  706   2 , and  732   2  may reside on a third die,  408   3  and  706   3  may reside on a fourth die, and the filters  406   1 - 406   4  may reside on a fifth die. Any other partitioning is possible. 
         [0076]      FIG. 8A  depicts an example allocation of spectrum among paths of the transceivers shown in  FIGS. 7A-7C . 
         [0077]    In an example implementation, Band 1 may be ˜5 MHz to ˜42 MHz, Band 2 may be ˜42 MHz to ˜85 MHz, Band 3 may be ˜85 MHz to ˜192 MHz, and Band 4 may be approximately 200 MHz to ˜1003 MHz. In such an implementation, for DOCSIS 3.0 or DOCSIS 3.1 with a “low split,” the transceiver may be configured into configuration 1 described above, for DOCSIS 3.1 with a “mid split,” the transceiver may be configured into configuration 2 described above, for DOCSIS 3.1 with a “high split” the transceiver may be configured into configuration 3 described above. 
         [0078]      FIG. 8B  depicts an example allocation of spectrum among transmit and receive paths of the transceivers shown in  FIGS. 7D . In an example implementation, bands  412   5  and  412   6  may be allocated in addition to the other bands allocated as described in  FIG. 8A . In this regard, the bands  412   5  and  412   6  may be allocated such that may be used as passbands of the filters  406   5  and  406   6 . Bands  412   5  and  412   6  may be allocated, for example, when circuitry is shared between transmit and receive path in the transceivers, with some of shared circuitry in the same paths is assigned other allocated bands. For example, bands  412   5  and  412   6  may be determined and/or allocated based on bands  412   2  and  412   3 , which may be used as passbands of the filters  406   2  and  406   3  that are part of the receive paths that use filters  406   5  and  406   6 , respectively. 
         [0079]    Other embodiments of the invention may provide a non-transitory computer readable medium and/or storage medium, and/or a non-transitory machine readable medium and/or storage medium, having stored thereon, a machine code and/or a computer program having at least one code section executable by a machine and/or a computer, thereby causing the machine and/or computer to perform the processes as described herein. 
         [0080]    Accordingly, various embodiments in accordance with the present invention may be realized in hardware, software, or a combination of hardware and software. The present invention may be realized in a centralized fashion in at least one computing system, or in a distributed fashion where different elements are spread across several interconnected computing systems. Any kind of computing system or other apparatus adapted for carrying out the methods described herein is suited. A typical combination of hardware and software may be a general-purpose computing system with a program or other code that, when being loaded and executed, controls the computing system such that it carries out the methods described herein. Another typical implementation may comprise an application specific integrated circuit or chip. 
         [0081]    Various embodiments in accordance with the present invention may also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein, and which when loaded in a computer system is able to carry out these methods. Computer program in the present context means any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following: a) conversion to another language, code or notation; b) reproduction in a different material form. 
         [0082]    While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims.