Abstract:
RF front end circuitry includes primary transceiver circuitry associated with a primary antenna and secondary receiver circuitry associated with a secondary antenna. Generally, the primary transceiver circuitry and the primary antenna are located on one end of a mobile communications device, while the secondary receiver circuitry and the secondary antenna are located at an opposite end of the device. Cross-coupling connection lines run between the antenna switching circuitry for the primary antenna and the secondary antenna, and are reused to send a portion of primary RF transmit signals from the primary transceiver circuitry to the secondary receiver circuitry so that primary RF transmit signals coupled into the secondary receiver path via antenna-to-antenna coupling can be reduced.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional patent application No. 62/159,702, filed May 11, 2015, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure relates to radio frequency (RF) front end circuitry, and specifically to RF front end circuitry configured to improve primary RF transmit signal isolation in a secondary receiver signal path. 
       BACKGROUND 
       [0003]    Advances in radio frequency (RF) front end circuitry continue to provide improvements in signal quality and data throughput. One technique for improving signal quality and data throughput is by providing multiple antennas, which are used to simultaneously transmit and/or receive signals.  FIG. 1  shows conventional RF front end circuitry  10  including a primary antenna  12 A, a secondary antenna  12 B, primary antenna switching circuitry  14 A coupled to the primary antenna  12 A, secondary antenna switching circuitry  14 B coupled to the secondary antenna  12 B, a first cross-coupling connection line  16 A and a second cross-coupling line  16 B coupled between the primary antenna switching circuitry  14 A and the secondary antenna switching circuitry  14 B, primary transceiver circuitry  18  coupled to the primary antenna switching circuitry  14 A, and secondary receiver circuitry  20  coupled to the secondary antenna switching circuitry  14 B. 
         [0004]    The primary antenna switching circuitry  14 A includes a primary antenna node  22 , a primary transceiver node  24 , a first cross-coupling connection node  26 , and a second cross-coupling connection node  28 . A first switch  30  is coupled between the primary antenna node  22  and the primary transceiver node  24 . A second switch  32  is coupled between the primary transceiver node  24  and the first cross-coupling connection node  26 . A third switch  34  is coupled between the primary antenna node  22  and the second cross-coupling connection node  28 . The secondary antenna switching circuitry  14 B includes a secondary antenna node  36 , a secondary receiver node  38 , a third cross-coupling connection node  40 , and a fourth cross-coupling connection node  42 . A fourth switch  44  is coupled between the secondary antenna node  36  and the secondary receiver node  38 . A fifth switch  46  is coupled between the secondary receiver node  38  and the third cross-coupling connection node  40 . A sixth switch  48  is coupled between the secondary antenna node  36  and the fourth cross-coupling connection node  42 . The first cross-coupling connection line  16 A is coupled between the first cross-coupling connection node  26  and the third cross-coupling connection node  40 . The second cross-coupling connection line  16 B is coupled between the second cross-coupling connection line  28  and the fourth cross-coupling connection line  42 . 
         [0005]    In a first mode of operation, the first switch  30  and the fourth switch  44  are closed, while the second switch  32 , the third switch  34 , the fifth switch  46 , and the sixth switch  48  are open, thereby coupling the primary transceiver circuitry  18  to the primary antenna  12 A and the secondary receiver circuitry  20  to the secondary antenna  12 B. This configuration is illustrated in  FIG. 2A . Accordingly, in the first mode of operation, primary RF transmit signals are provided from the primary transceiver circuitry  18  to the primary antenna  12 A, primary RF receive signals are provided from the primary antenna  12 A to the primary transceiver circuitry  18 , and secondary RF receive signals are provided from the second antenna  12 B to the secondary receiver circuitry  20 . The secondary RF receive signals may be diversity multiple-input-multiple-output (MIMO) receive signals. In general, the first mode of operation is used when the performance of the primary antenna  12 A is better than that of the secondary antenna  12 B, for example, when the voltage standing wave ratio (VSWR) associated with the primary antenna  12 A is lower than the VSWR associated with the secondary antenna  12 B. 
         [0006]    In a second mode of operation, the second switch  32 , the third switch  34 , the fifth switch  46 , and the sixth switch  48  are closed, while the first switch  30  and the fourth switch  44  are open, thereby coupling the primary transceiver  18  to the secondary antenna  12 B and the secondary receiver circuitry  20  to the primary antenna  12 A. This configuration is illustrated in  FIG. 2B . Specifically, the primary transceiver circuitry  18  is coupled to the secondary antenna  12 B via the first cross-coupling connection line  16 A, while the secondary receiver circuitry  20  is coupled to the primary antenna  12 A via the second cross-coupling connection line  16 B. Accordingly, in the second mode of operation, primary RF transmit signals are provided from the primary transceiver circuitry  18  to the secondary antenna  12 B, primary RF receive signals are provided from the secondary antenna  12 B to the primary transceiver circuitry  18 , and secondary RF receive signals are provided from the primary antenna  12 A to the secondary receiver circuitry  20 . In general, the second mode of operation is used when the performance of the primary antenna  12 A is worse than that of the secondary antenna  12 B, for example, when the VSWR associated with the primary antenna  12 A is higher than the VSWR associated with the secondary antenna  12 B. Those skilled in the art will appreciate that the antenna swapping capability enabled by the conventional RF front end circuitry  10  allows the antenna with the best performance to be used for the primary transmission and reception of RF signals, which generally improves the signal quality of primary RF signals. Switch control circuitry  50  coupled to the first antenna switching circuitry  14 A and the second antenna switching circuitry  14 B may control the switches therein in order to switch between the first mode of operation and the second mode of operation. 
         [0007]    Generally, the primary antenna  12 A is provided at a first end of a mobile communications device, and the secondary antenna  12 B is provided at a second end of the mobile communications device, which is opposite the first end. This is so that an obstruction (e.g., a user&#39;s hand, a surface on which the device is placed, etc.) at one end of a mobile communications device will not affect transmission and/or reception characteristics of both antennas  12  simultaneously, thereby preserving the performance of at least one of the antennas  12 .  FIG. 3  illustrates a mobile communications device  52  including the first antenna  12 A, the second antenna  12 B, the primary transceiver circuitry  18 , and the secondary receiver circuitry  20 . The primary antenna  12 A is designed and placed in the mobile communications device  52  in order to be used for the primary transmission and reception of RF signals during normal operation. It is only when an obstruction of some kind limits the performance of the primary antenna  12 A that the second mode of operation is used. Accordingly, the primary antenna  12 A is used most of the time for the primary transmission and reception of RF signals, while the secondary antenna  12 B is used most of the time for the reception of secondary RF signals. The conventional RF front end circuitry  10  is therefore designed to maximize performance during normal operation (i.e., the first mode of operation discussed above). 
         [0008]    In order to maximize the performance of the conventional RF front end circuitry  10  in the first mode of operation, the distance between the primary antenna  12 A and the primary transceiver circuitry  18  should be minimized. Similarly, the distance between the secondary antenna  12 B and the secondary receiver circuitry  20  should be minimized. This is so that signals provided between the primary antenna  12 A and the primary transceiver circuitry  18  and the secondary antenna  12 B and the secondary receiver circuitry  20  experience minimal insertion loss and distortion that may be introduced by longer signal traces. Since the primary transceiver circuitry  18  and the secondary receiver circuitry  20  are on opposite ends of the mobile communications device  52  in such a configuration, the first cross-coupling connection line  16 A and the second cross-coupling connection line  16 B run the length of the mobile communications device  52  between the primary antenna switching circuitry  14 A and the secondary antenna switching circuitry  14 B to implement the antenna swapping capability discussed above. Generally, the first cross-coupling connection line  16 A and the second cross-coupling connection line  16 B are shielded lines (e.g., coaxial lines) in order to minimize insertion loss and interference. Because the second mode of operation is only temporarily used when the primary antenna  12 A experiences a significant decline in performance, the decrease in performance due to the use of the cross-coupling connection lines  16  is considered an acceptable trade-off in order to increase the performance of the conventional RF front end circuitry  10  during normal operation. 
         [0009]    In some situations, primary RF transmit signals provided at one of the antennas  12  may couple into the other one of the antennas  12 , such that the secondary RF receive signals provided to the secondary receiver circuitry  20  include a portion of the primary RF transmit signals. Filtering circuitry may be provided between the secondary receiver circuitry  20  and the secondary antenna switching circuitry  14 B to reduce the portion of the primary RF transmit signals coupled into the secondary receiver path, however, limits on insertion loss in the secondary receiver path may place design constraints on the filtering circuitry that limit the effectiveness thereof. Accordingly, there is a need for RF front end circuitry with improved primary RF transmit signal isolation in the secondary receive signal path. 
       SUMMARY 
       [0010]    The present disclosure relates to radio frequency (RF) front end circuitry, and specifically to RF front end circuitry configured to improve primary RF transmit signal isolation in a secondary receiver signal path. In one embodiment, RF front end circuitry includes primary antenna switching circuitry coupled to a primary antenna node, secondary antenna switching circuitry coupled to a secondary antenna node, a first cross-coupling connection line and a second cross-coupling connection line coupled between the primary antenna switching circuitry and the second antenna switching circuitry, primary transceiver circuitry coupled to the primary antenna switching circuitry, secondary receiver circuitry coupled to the secondary antenna switching circuitry, and switching control circuitry coupled to the primary antenna switching circuitry and the secondary antenna switching circuitry. The switching control circuitry is configured to operate the primary antenna switching circuitry and the second antenna switching circuitry such that in a first mode of operation, the primary transceiver circuitry is coupled to the primary antenna node, the secondary receiver circuitry is coupled to the secondary antenna node, and a portion of a primary RF transmit signal provided from the primary transceiver circuitry is provided to the secondary receiver circuitry via the first cross-coupling connection line. In a second mode of operation, the primary transceiver circuitry is coupled to the secondary antenna node via the first cross-coupling connection line, the secondary receiver circuitry is coupled to the primary antenna node via the second cross-coupling connection line, and a portion of the primary RF transmit signal from the primary transceiver circuitry is provided to the secondary receiver circuitry via the first cross-coupling connection line. 
         [0011]    Since the first cross-coupling connection line and the second cross-coupling connection line are already provided for antenna swapping, the secondary receiver circuitry can reduce the presence of primary RF transmit signal components in secondary RF receive signals due to antenna-to-antenna coupling of primary RF transmit signals without the addition of connections between the primary antenna switching circuitry and the secondary antenna switching circuitry. Accordingly, the performance of the RF front end circuitry is significantly improved. 
         [0012]    Those skilled in the art will appreciate the scope of the disclosure and realize additional aspects thereof after reading the following detailed description in association with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The accompanying drawings incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure. 
           [0014]      FIG. 1  is a schematic representation of conventional RF front end circuitry. 
           [0015]      FIGS. 2A and 2B  are schematic representations of conventional RF front end circuitry. 
           [0016]      FIG. 3  is a diagram illustrating conventional mobile communications circuitry. 
           [0017]      FIG. 4  is a schematic representation of RF front end circuitry according to one embodiment of the present disclosure. 
           [0018]      FIGS. 5A and 5B  are schematic representations of RF front end circuitry according to various embodiments of the present disclosure. 
           [0019]      FIG. 6  is a schematic representation of RF front end circuitry according to one embodiment of the present disclosure. 
           [0020]      FIG. 7  is a schematic representation of RF front end circuitry according to one embodiment of the present disclosure. 
           [0021]      FIG. 8  is a schematic representation of RF front end circuitry according to one embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the disclosure and illustrate the best mode of practicing the disclosure. Upon reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims. 
         [0023]      FIG. 4  shows radio frequency (RF) front end circuitry  54  according to one embodiment of the present disclosure. The RF front end circuitry  54  includes a primary antenna  56 A, a secondary antenna  56 B, primary antenna switching circuitry  58 A coupled to the primary antenna  56 A, secondary antenna switching circuitry  58 B coupled to the secondary antenna  56 B, a first cross-coupling connection line  60 A and a second cross-coupling connection line  60 B coupled between the primary antenna switching circuitry  58 A and the secondary antenna switching circuitry  58 B, primary transceiver circuitry  62  coupled to the primary antenna switching circuitry  58 A and secondary receiver circuitry  64  coupled to the secondary antenna switching circuitry  58 B. 
         [0024]    The primary antenna switching circuitry  58 A includes a primary antenna node  66 , a primary transceiver node  68 , a first cross-coupling connection node  70  and a second cross-coupling connection node  72 . A first switch  74  is coupled between the primary antenna node  66  and the primary transceiver node  68 . A second switch  76  is coupled between the primary transceiver node  68  and the first cross-coupling connection node  70 . A third switch  78  is coupled between the primary antenna node  66  and the second cross-coupling connection node  72 . A primary signal coupler  80  is electromagnetically coupled with a signal line between the primary transceiver node  68  and the first switch  74 , and is coupled to the first cross-coupling connection node  70 . 
         [0025]    The secondary antenna switching circuitry  58 B includes a secondary antenna node  82 , a secondary receiver node  84 , a third cross-coupling connection node  86 , a fourth cross-coupling connection node  88 , a first feedback signal node  90 , and a second feedback signal node  92 . A fourth switch  94  is coupled between the secondary antenna node  82  and the secondary receiver node  84 . A fifth switch  96  is coupled between the secondary antenna node  82  and the third cross-coupling connection node  86 . A sixth switch  98  is coupled between the secondary receiver node  84  and the fourth cross-coupling connection node  88 . A first feedback signal path is formed between the third cross-coupling connection node  86  and the first feedback signal node  90 . A second feedback signal path is formed by a secondary signal coupler  100 , which is electromagnetically coupled with a signal line between the third cross-coupling connection node  86  and the fifth switch  96 , and is coupled to the second feedback signal node  92 . 
         [0026]    In a first mode of operation, the first switch  74  and the fourth switch  94  are closed, while the second switch  76 , the third switch  78 , the fifth switch  96 , and the sixth switch  98  are open, thereby coupling the primary transceiver circuitry  62  to the primary antenna  56 A and the secondary receiver circuitry  64  to the secondary antenna  56 B. This configuration is illustrated in  FIG. 5A . 
         [0027]    Accordingly, in the first mode of operation, primary RF transmit signals are provided from the primary transceiver circuitry  62  to the primary antenna  56 A, primary RF receive signals are provided from the primary antenna  56 A to the primary transceiver circuitry  62 , and secondary RF receive signals are provided from the secondary antenna  56 B to the secondary receiver circuitry  64 . The secondary RF receive signals may be diversity multiple-input-multiple-output (MIMO) receive signals. In general, the first mode of operation is used when the performance of the primary antenna  56 A is better than that of the secondary antenna  56 B, for example, when the voltage standing wave ratio (VSWR) associated with the primary antenna  56 A is lower than the VSWR associated with the secondary antenna  56 B. 
         [0028]    As discussed above, primary RF transmit signals provided by the primary transceiver circuitry  62  may be radiated from the primary antenna  56 A and at least partially coupled into the secondary antenna  56 B. These relatively high power signals may leak into the secondary receiver signal path, thus degrading the performance of the secondary receiver circuitry  64 . Accordingly, at least a portion of the primary RF transmit signals provided from the primary transceiver circuitry are coupled into the primary signal coupler  80  and delivered from the primary antenna switching circuitry  58 A to the secondary antenna switching circuitry  58 B via the first cross-coupling connection line  60 A. The portion of the primary RF transmit signals are then provided to the secondary receiver circuitry  64 , where they may be used to reduce the presence of primary RF transmit signals in the secondary RF receive signals attributable to antenna-to-antenna coupling of the primary RF transmit signals. The performance of the RF front end circuitry  54  may therefore be improved. 
         [0029]    Using the primary signal coupler  80  to deliver a portion of the RF transmit signals to the secondary receiver circuitry  64  in the first mode of operation allows the RF front end circuitry  54  to implement primary RF transmit signal cancellation without the addition of any additional long-running signal lines between the first antenna switching circuitry  58 A and the second antenna switching circuitry  58 B. In other words, because the first cross-coupling connection line  60 A and the second cross-coupling connection line  60 B are already present in order to implement antenna swapping as discussed above, using the first cross-coupling connection line  60 A to deliver the portion of the primary RF transmit signals is achieved at a minimal cost from a components perspective (i.e., only requires the addition of the primary signal coupler  80  and the secondary signal coupler  100 ), and with minimal modification of the RF front end circuitry  54 . 
         [0030]    In the second mode of operation, the second switch  76 , the third switch  78 , the fifth switch  96 , and the sixth switch  98  are closed, while the first switch  74  and the fourth switch  94  are open, thereby coupling the primary transceiver circuitry  62  to the secondary antenna  56 B and the secondary receiver circuitry  64  to the primary antenna  56 A. This configuration is illustrated in  FIG. 5B . Specifically, the primary transceiver circuitry  62  is coupled to the secondary antenna  56 B via the first cross-coupling connection line  60 A, while the secondary receiver circuitry  64  is coupled to the primary antenna  56 A via the second cross-coupling connection line  60 B. Accordingly, in the second mode of operation, primary RF transmit signals are provided from the primary transceiver circuitry  62  to the secondary antenna  56 B, primary RF receive signals are provided from the secondary antenna  56 B to the primary transceiver circuitry  62 , and secondary RF receive signals are provided from the primary antenna  56 A to the secondary receiver circuitry  64 . In general, the second mode of operation is used when the performance of the primary antenna  56 A is worse than that of the secondary antenna  56 B, for example, when the VSWR associated with the primary antenna  56 A is higher than the VSWR associated with the secondary antenna  56 B. 
         [0031]    The secondary signal coupler  100  is used to obtain a portion of the primary RF transmit signals for reducing the portion of primary RF transmit signals in the secondary RF receive signals. Since primary RF transmit signals are already routed into the secondary antenna switching circuitry  58 B via the first cross-coupling connection line  60 A, the secondary signal coupler  100  couples a portion of these primary RF transmit signals into the secondary receiver circuitry  64 , where they are used as described above to reduce the portion of primary RF transmit signals in the secondary RF receive signals attributable to antenna-to-antenna coupling of the primary RF transmit signals. As discussed above, reusing the cross-coupling connection lines  60  to extract a portion of the primary RF transmit signals is achieved with minor modification of the RF front end circuitry  54 , and enables a significant increase in the performance thereof. Switch control circuitry  101  coupled to the primary antenna switching circuitry  58 A and the secondary antenna switching circuitry  58 B may control the switches therein in order to switch between the first mode of operation and the second mode of operation. 
         [0032]    While the primary antenna switching circuitry  58 A and the secondary antenna switching circuitry  58 B are shown in a particular configuration in  FIG. 4 , the principles of the present disclosure may be accomplished by antenna switching circuitry having many different configurations, all of which are contemplated herein. Further, while the primary transceiver circuitry  62  and the secondary receiver circuitry  64  are shown as single blocks in  FIG. 4 , the primary transceiver circuitry  62  and the secondary receiver circuitry  64  may include multiple different parts. For example, the primary transceiver circuitry  62  and the secondary receiver circuitry  64  may include separate transmit and/or receive signal paths for ultra high-band RF signals, high-band RF signals, mid-band RF signals, and/or low-band RF signals, and may further include filtering circuitry to combine and/or separate the various signals in these separate signal paths. 
         [0033]    The secondary receiver circuitry  64  may use the portion of the primary RF transmit signals to reduce the portion of primary RF transmit signals in the secondary RF receive signals in any number of different ways. For example, the secondary receiver circuitry  64  may adjust a filter response of an adjustable filter based on the portion of the primary RF transmit signals, may provide primary RF transmit signal cancellation in the secondary RF receive signals based on the portion of the primary RF transmit signals, may provide pre-distortion in the secondary RF receive signals based on the portion of the primary RF transmit signals, or the like. As discussed above, in the first mode of operation the portion of the primary RF transmit signals are provided to the secondary receiver circuitry  64  via the first feedback signal node  90 , while in the second mode of operation the portion of the primary RF transmit signals are provided to the secondary receiver circuitry  64  via the second feedback signal node  92 . Accordingly, in some embodiments a switch (not shown) may be provided in the secondary antenna switching circuitry  58 B to isolate the feedback signal path between the third cross-coupling connection node  86  and the first feedback signal node  90  in the second mode of operation. In other embodiments, the secondary receiver circuitry  64  may simply use the signal provided at the first feedback signal node  90  in the first mode of operation and use the signal provided at the second feedback signal node in the second mode of operation. 
         [0034]      FIG. 6  shows the RF front end circuitry  54  including details of the secondary receiver circuitry  64  according to one embodiment of the present disclosure. As shown in  FIG. 6 , the secondary receiver circuitry  64  includes signal processing circuitry  102 , which is coupled to low-noise amplifier (LNA) circuitry  104 , TX cancellation circuitry  106 , and optional filtering circuitry  108 . The signal processing circuitry  102  is coupled to the first feedback signal node  90  and the second feedback signal node  92  of the secondary antenna switching circuitry  58 B. The TX cancellation circuitry  106  is coupled to the secondary receiver node  84  of the secondary antenna switching circuitry  58 B via the optional filtering circuitry  108 . The LNA circuitry  104  may receive the secondary RF receive signals from the secondary receiver node  84  via the TX cancellation circuitry  106  and optional filtering circuitry  108  and amplify the secondary RF receive signals for further processing. The signal processing circuitry  102  may be configured to receive the portion of the primary RF transmit signals from the first feedback signal node  90  or the second feedback signal node  92 , depending upon the mode of operation of the RF front end circuitry  54 , and may generate a control signal for one or both of the TX cancellation circuitry  106  and the LNA circuitry  104  based on the portion of the primary RF transmit signals. The control signal(s) may be configured to reduce (e.g., cancel) the component of the secondary RF receive signals attributable to primary RF transmit signals from the primary transceiver circuitry  62  that are coupled into the secondary receiver path via antenna-to-antenna coupling. In some embodiments, the TX cancellation circuitry  106  and/or the optional filtering circuitry  108  is not provided, such that the LNA circuitry  104  is directly connected to the secondary receiver node  84  of the secondary antenna switching circuitry  58 B. 
         [0035]    The TX cancellation circuitry  106  may reduce the portion of the secondary RF receive signals attributable to coupled primary RF transmit signals in any number of ways known in the art. For example, the TX cancellation circuitry  106  may use the portion of the primary RF transmit signals received at the signal processing circuitry  102  to add an inverted version of the primary RF transmit signals into the secondary RF receive signals in order to cancel that portion of the signals out. Those of ordinary skill in the art will appreciate that any number of different ways to reduce the portion of primary RF transmit signals in the secondary RF receive signals exist, all of which are contemplated herein. In some embodiments, the signal processing circuitry  102  may be omitted such that the TX cancellation circuitry  106  responds directly to the signals provided at the first feedback signal node  90  and the second feedback signal node  92 . 
         [0036]      FIG. 7  shows the RF front end circuitry  54  including further details of the secondary receiver circuitry  64  according to an additional embodiment of the present disclosure. As shown in  FIG. 7 , the optional filtering circuitry  108  is additionally coupled to the signal processing circuitry  102 , such that the signal processing circuitry  102  is coupled to the LNA circuitry  104 , the TX cancellation circuitry  106 , and the optional filtering circuitry  108 . The LNA circuitry  104  may receive the secondary RF receive signal from the secondary receiver node  84  of the secondary antenna switching circuitry  58 B via the optional filtering circuitry  108  and amplify the secondary RF receive signals for further processing. The signal processing circuitry  102  may be configured to receive the portion of the primary RF transmit signal from the first feedback signal node  90  or the second feedback signal node  92 , depending upon the mode of operation of the RF front end circuitry  54 , and may generate a control signal for one or more of the optional filtering circuitry  108 , the TX cancellation circuitry  106 , and the LNA circuitry  104  based on the portion of the primary RF transmit signals. The control signal(s) may be configured to reduce the component of the secondary RF receive signals attributable to primary RF transmit signals from the primary transceiver circuitry  62  that are coupled into the secondary receiver path via antenna-to-antenna coupling. In some embodiments, the TX cancellation circuitry  106  and/or the optional filtering circuitry  108  are not provided, such that the LNA circuitry  104  is directly connected to the secondary receiver node  84  of the secondary antenna switching circuitry  58 B. 
         [0037]    The optional filtering circuitry  108  may be a band-pass filter with edges that are adjustable based on the control signals provided by the signal processing circuitry  102 . In some embodiments, however, the signal processing circuitry  102  may be omitted such that the optional filtering circuitry  108  responds directly to the signals provided at the first feedback signal node  90  and the second feedback signal node  92 . By adjusting the optional filtering circuitry  108  based on the portion of the primary RF transmit signals at one of the first feedback signal node  90  and the second feedback signal node  92 , the portion of primary RF transmit signals in the secondary RF receive signals attributable to antenna-to-antenna coupling may be significantly reduced. Those skilled in the art will appreciate that many different designs and configurations for the optional filtering circuitry  108  and the signal processing circuitry  102  exist, all of which are contemplated herein. 
         [0038]    As discussed above, in some embodiments, the primary transceiver circuitry  62 , the secondary receiver circuitry  64 , or both, may include separate transmit and/or receive paths for ultra high-band signals, high-band signals, mid-band signals, and low-band signals. Accordingly,  FIG. 8  shows the RF front end circuitry  54  wherein the secondary receiver circuitry  64  includes a separate signal path for low-band signals and mid/high-band signals. The RF front end circuitry  54  shown in  FIG. 8  is substantially similar to that shown in  FIG. 7 , except that the LNA circuitry  104  is separated into low-band LNA circuitry  110  and mid/high-band LNA circuitry  112 , and a diplexer  114  is provided between the secondary receiver node  84  of the secondary antenna switching circuitry  58 B and the secondary receiver circuitry  64  in order to separate low-band secondary RF receive signals from mid/high-band secondary RF receive signals and separately deliver the signals to the low-band LNA circuitry  110  and the mid/high-band LNA circuitry  112 , respectively. While the optional filtering circuitry  108  is shown coupled only in the signal path of the low-band LNA circuitry  110 , additional adjustable filtering circuitry (not shown) may be provided in the signal path of the mid/high-band LNA circuitry  112  without departing from the principles of the present disclosure. Further, the separate signal paths shown in  FIG. 8  may be equally applied to any of the other embodiment discussed in the present disclosure. 
         [0039]    In one embodiment, the filter response of the diplexer  114  may reduce the level of the primary RF transmit signals in the secondary RF receive signals from around 23 dB to 13 dB (i.e., the diplexer  114  may provide about a 13 dB reduction due to the filtering response thereof). Due to the stringent requirements of many wireless communications standards, such a level of primary RF transmit signal components may be unacceptable. The optional filtering circuitry  108  may further reduce the level of the primary RF transmit signals by about 8 dB (to about 5 dB), and the TX cancellation circuitry  106  may further reduce the level of the primary RF transmit signals by about 12 db (to about −7 dB). Accordingly, the level of the primary RF transmit signals due to antenna-to-antenna coupling in the secondary RF receive signals may be significantly reduced (e.g., reduced by about 8 dB to about 20 dB) when using the principles described in the present disclosure. 
         [0040]    Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.