Abstract:
Circuitry includes a primary antenna node, a secondary antenna node, a first set of input/output nodes, a second set of input/output nodes, a first diplexer, a second diplexer, and switching circuitry. The switching circuitry is arranged such that any one of the first set of input/output nodes and the second set of input/output nodes can be connected to the primary antenna node or the secondary antenna node, either through the first diplexer, the second diplexer, or directly by bypassing the first diplexer and the second diplexer while providing minimal insertion loss. In particular, the number of closed series switches in the signal paths provided between the one of the first set of input/output nodes and the second set of input/output nodes is minimized while still providing a large amount of flexibility in the switching paths that can be created by the switching circuitry.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of provisional patent application Ser. No. 62/293,838, filed Feb. 11, 2016, the disclosure of which is hereby 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 designed for reduced insertion loss. 
       BACKGROUND 
       [0003]    As wireless communications technology continues to evolve, there is a focus on improving both reliability and speed. In recent years, technologies such as multiple-input-multiple-output (MIMO) and carrier aggregation have been used to increase both speed and reliability of a wireless connection. At a high level, MIMO and carrier aggregation allow multiple radio frequency (RF) signals to be simultaneously transmitted and/or received by a device. These RF signals are generally transmitted at different frequencies and then separated by a receiving device to obtain the data therein. While this process is relatively straightforward when the frequencies of the RF signals are far apart, it becomes significantly more complex when they are not. This is due to the RF front end circuitry that is responsible for separating the received RF signals. Conventional RF front end circuitry often utilizes a tiered filtering approach in which RF signals are first separated into relatively large RF frequency bands, and then filtered with increasing granularity as they move downstream from an antenna, ultimately being separated into one or more RF operating bands. For example, a first filter in conventional RF front end circuitry may separate low-band RF signals (i.e., RF signals with a frequency between 700 MHz to 1000 MHz) from mid/high-band RF signals (i.e., RF signals with a frequency between 1800 MHz and 2700 MHz), a second filter downstream from the first filter may separate mid-band RF signals (i.e., RF signals with a frequency between 1800 MHz and 2200 MHz) from high-band RF signals (i.e., RF signals with a frequency between 2300 MHz and 2700 MHz), and a number of band filters downstream from the second filter may separate the mid-band RF signals and the high-band RF signals into separate RF operating bands (e.g., 3 rd  Generation Partnership (3GPP) Long Term Evolution (LTE) operating bands). 
         [0004]    Due to the relatively large separation between low-band RF signals and mid/high-band RF signals (i.e., ˜800 MHz), the first filter in such a system is generally capable of separating these signals without issue. However, the narrow separation between mid-band RF signals and high-band RF signals (i.e., ˜100 MHz) makes such a task much more difficult. Designing a filter with the required bandwidth to pass both mid-band RF signals and high-band RF signals may reduce the achievable selectivity of the filter. Due to this limited selectivity, mid-band RF signals at the upper end of the frequency band and high-band RF signals at the lower end of the frequency band will be cross-contaminated, and may reduce the performance of the RF front end circuitry such that certain combinations of operating bands are not usable for carrier aggregation and/or MIMO. 
         [0005]    To address these issues, RF front end circuitry  10  has been proposed as shown in  FIG. 1 . The RF front end circuitry  10  includes a primary antenna  12 , a secondary antenna  14 , primary antenna swapping circuitry  16 , secondary antenna swapping circuitry  18 , a front end diplexer  20 , reconfigurable RF filtering circuitry  22 , first band filtering circuitry  24 , and second band filtering circuitry  26 . The primary antenna swapping circuitry  16  is coupled between the front end diplexer  20  and the primary antenna  12 . The secondary antenna swapping circuitry  18  is coupled between a secondary RF signal node  28  and the secondary antenna  14 . The reconfigurable RF filtering circuitry  22  is coupled between the first band filtering circuitry  24 , the second band filtering circuitry  26 , and the front end diplexer  20 . 
         [0006]    The primary antenna swapping circuitry  16  includes a number of primary antenna swapping switches SW PAS . The secondary antenna swapping circuitry  18  includes a number of secondary antenna swapping switches SW PAS . Together, the primary antenna swapping switches SW PAS  and the secondary antenna swapping switches SW PAS  are configured to couple one of the primary antenna  12  and the secondary antenna  14  to the front end diplexer  20  and couple the other one of the primary antenna  12  and the secondary antenna  14  to the secondary RF signal node  28 . While not shown in order to avoid obscuring the drawings, the secondary RF signal node  28  is generally coupled to secondary RF filtering circuitry in order to separate secondary RF receive signals into their constituent RF operating bands for further processing. Those skilled in the art will appreciate that the one of the primary antenna  12  and the secondary antenna  14  coupled to the front end diplexer  20  is dependent on current signal conditions, and that the primary antenna  12  and the secondary antenna  14  may be dynamically swapped as desired in order to improve transmission and/or reception characteristics. 
         [0007]    The front end diplexer  20  is configured to separate RF receive signals from one of the primary antenna  12  and the secondary antenna  14  into low-band RF receive signals and mid/high-band RF receive signals, separately delivering the low-band RF receive signals to a low-band RF signal node  30  and the mid/high-band RF receive signals to the reconfigurable RF filtering circuitry  22 . Further, the front end diplexer  20  is configured to combine RF transmit signals from the low-band RF signal node  30  and the reconfigurable RF filtering circuitry  22  and provide these RF transmit signals to one of the primary antenna  12  and the secondary antenna  14  for transmission. 
         [0008]    As discussed above, it is generally difficult for a filter to achieve the necessary bandwidth for passing mid-band RF signals and high-band signals while maintaining adequate selectivity to separate RF signals at the edges of these frequency bands. Accordingly, the reconfigurable RF filtering circuitry  22  includes a first reconfigurable RF filtering circuitry diplexer  32 A, a second reconfigurable RF filtering circuitry diplexer  32 B, and a number of reconfigurable RF filtering circuitry switches SW RFC . The first reconfigurable RF filtering circuitry diplexer  32 A is configured to separate RF signals within the mid-band from RF signals within a first subset of the high-band, while the second reconfigurable RF filtering circuitry diplexer  32 B is configured to separate RF signals within the mid-band from RF signals within a second subset of the high-band. The first subset of the high-band may include a relatively narrow portion thereof at the lower end of the band (e.g., from 2300 MHz to 2400 MHz), while the second subset of the high-band may include the remaining portion of the high-band (e.g., 2400 MHz to 2700 MHz). Due to the relatively narrow portion of the high-band passed by the first reconfigurable RF filtering circuitry diplexer  32 A, the selectivity of this portion of the diplexer may be significantly improved such that the first reconfigurable RF filtering circuitry diplexer  32 A can adequately separate mid-band RF signals (even those at the upper end of the mid-band) from high-band RF signals at the lower end thereof. 
         [0009]    In carrier aggregation configurations in which mid-band RF signals are simultaneously received along with high-band RF signals and the mid-band RF signals are relatively close in frequency to the high-band RF signals, the reconfigurable RF filtering circuitry switches SW RFC are configured to couple the first reconfigurable RF filtering circuitry diplexer  32 A between the first band filtering circuitry  24 , the second band filtering circuitry  26 , and the front end diplexer  20 . Accordingly, RF receive signals within the mid-band and the high-band that are relatively close in frequency can be adequately separated by the first reconfigurable RF filtering circuitry diplexer  32 A and delivered to the first band filtering circuitry  24  and the second band filtering circuitry  26 . In carrier aggregation configurations in which mid-band RF signals are simultaneously received along with high-band RF signals and the mid-band RF signals are relatively far apart in frequency to the high-band RF signals, the reconfigurable RF filtering circuitry switches SW RFC are configured to couple the second reconfigurable RF filtering circuitry diplexer  32 B between the first band filtering circuitry  24 , the second band filtering circuitry  26 , and the front end diplexer  20 . Accordingly, RF receive signals within the mid-band and the high-band that are relatively far apart in frequency can be adequately separated by the second reconfigurable RF filtering circuitry diplexer  32 B and delivered to the first band filtering circuitry  24  and the second band filtering circuitry  26 . In non-carrier aggregation configurations, the reconfigurable RF filtering switches SW RFC are configured to directly couple one of the first band filtering circuitry  24  and the second band filtering circuitry  26  to the front end diplexer  20 . The first reconfigurable RF filtering circuitry diplexer  32 A and the second reconfigurable RF filtering circuitry diplexer  32 B can by bypassed in this case since the RF receive signals will fall within a single one of the mid-band and the high-band. Accordingly, in non-carrier aggregation configurations in which the first reconfigurable RF filtering circuitry diplexer  32 A and the second reconfigurable RF filtering circuitry diplexer  32 B are not necessary, the insertion loss associated therewith can be avoided. 
         [0010]    The first band filtering circuitry  24  and the second band filtering circuitry  26  include a number of band filtering switches SW BF  and a number of band filters  34 . The band filtering switches SW BF  are configured to couple one or more of the band filters  34  to the reconfigurable RF filtering circuitry  22 . Each one of the band filters  34  is configured to isolate an RF signal within a particular RF operating band (or in some cases, RF signals within multiple RF operating bands) from other RF signals. RF receive signals from the reconfigurable RF filtering circuitry  22  are isolated via an appropriate band filter  34  and delivered to an appropriate one of a number of input/output nodes  36 . RF transmit signals from downstream circuitry are received at one of the input/output nodes  36 , isolated from other RF signals via an appropriate band filter  34 , and delivered to the reconfigurable RF filtering circuitry  22  for transmission from one of the primary antenna  12  and the secondary antenna  14 . Generally, only the band filters  34  associated with the particular RF operating bands being transmitted or received are coupled to the reconfigurable RF filtering circuitry  22  to avoid excessive loading of the signal paths. 
         [0011]    Control circuitry  38  is coupled to each one of the primary antenna swapping circuitry  16 , the secondary antenna swapping circuitry  18 , the reconfigurable RF filtering circuitry  22 , the first band filtering circuitry  24 , and the second band filtering circuitry  26  in order to control the state of the switches therein and effectuate the functionality discussed below. 
         [0012]    Due to the reconfigurable RF filtering circuitry  22 , the RF front end circuitry  10  is capable of separating any combination of mid-band RF signals and high-band RF signals, thereby expanding the range of band combinations for carrier aggregation and/or MIMO. However, the configuration of the switches in the primary antenna swapping circuitry  16 , the secondary antenna swapping circuitry  18 , the reconfigurable RF filtering circuitry  22 , the first band filtering circuitry  24 , and the second band filtering circuitry  26  may introduce excessive insertion loss in the signal paths thereof.  FIG. 2A  shows a switch configuration in which the first reconfigurable RF filtering circuitry diplexer  32 A in the reconfigurable RF filtering circuitry  22  is used to perform carrier aggregation between one or more mid-band RF signals and one or more high-band RF signals via the primary antenna  12 . As shown, a second one of the primary antenna swapping switches SW PAS2  is closed, while the remaining primary antenna swapping switches SW PAS  are open. Further, a second one of the reconfigurable RF filtering circuitry switches SW RFC2 , a sixth one of the reconfigurable RF filtering circuitry switches SW RFC6 , and a seventh one of the reconfigurable RF filtering circuitry switches SW RFC7 , are closed, while the remaining reconfigurable RF filtering circuitry switches SW RFC  are open. For exemplary purposes, a fourth one of the band filtering switches SW BF4  is closed in the first band filtering circuitry  24  while the remaining band filtering switches SW BF  are open. Similarly, a first one of the band filtering switches SW BF1  is closed in the second band filtering circuitry  26  while the remaining band filtering switches SW BF  are open. 
         [0013]    Assuming a 0.20 dB insertion loss for each closed series switch in the signal path and a 0.025 dB insertion loss for each open parallel switch, a signal path from the primary antenna  12  to a second one of the input/output nodes  36 B includes four closed series switches and ten open parallel switches for a total insertion loss of 1.05 dB. Notably, this is a conservative estimate of the actual insertion loss, as a number of band filtering switches SW BF  associated with additional band filters  34  in the first band filtering circuitry  24  and the second band filtering circuitry  26  are not shown to avoid obscuring the drawings. A similar result is achieved when the second reconfigurable RF filtering circuitry diplexer  32 B in the reconfigurable RF filtering circuitry  22  is used to perform carrier aggregation between one or more mid-band RF signals and one or more high-band RF signals via the primary antenna. Additional switches are added in the signal path when the secondary antenna  14  is used in these configurations. 
         [0014]      FIG. 2B  shows a switch configuration in which the first reconfigurable RF filtering circuitry diplexer  32 A and the second reconfigurable RF filtering circuitry diplexer  32 B are bypassed in a non-carrier aggregation mode. In the particular example shown in  FIG. 2B , the primary antenna  12  is coupled via the front end diplexer  20  to the first band filtering circuitry  24 . Accordingly, a second one of the primary antenna swapping switches SW PAS2  is closed, while the remaining primary antenna swapping switches SW PAS  are open. Further, a first one of the reconfigurable RF filtering circuitry switches SW RFC1  is closed while the remaining reconfigurable RF filtering circuitry switches SW RFC  are open. For purposes of example, a fourth one of the band filtering switches SW BF4  in the first band filtering circuitry  24  is closed while the remaining band filtering switches SW BF  are open. 
         [0015]    Again assuming a 0.20 dB insertion loss for each closed series switch in the signal path and a 0.025 dB insertion loss for each open parallel switch, a signal path from the primary antenna  12  to the second one of the input/output nodes  36 B includes three closed series switches and ten open parallel switches for a total insertion loss of 0.825 dB. Once again, this is a conservative estimate of the actual insertion loss, as a number of band filtering switches SW BF  associated with additional band filters  34  in the first band filtering circuitry  24  and the second band filtering circuitry  26  are not shown to avoid obscuring the drawings. A similar result is achieved when only the second band filtering circuitry  26  is coupled to the front end diplexer  20 . 
         [0016]    The insertion loss added by the switching elements in the RF front end circuitry  10  may degrade the performance thereof, causing excessive power loss and thus reducing battery life of mobile wireless devices. Accordingly, there is a need for improved RF front end circuitry capable of supporting carrier aggregation and/or MIMO configurations between RF signals that are relatively close in frequency to one another. 
       SUMMARY 
       [0017]    The present disclosure relates to radio frequency (RF) front end circuitry, and specifically to RF front end circuitry designed for reduced insertion loss. In one embodiment, circuitry includes a primary antenna node, a secondary antenna node, a first set of input/output nodes, a second set of input/output nodes, a first diplexer, a second diplexer, switching circuitry, and control circuitry. The first set of input/output nodes are each associated with RF signals within a first RF frequency band. The second set of input/output nodes are each associated with RF signals within a second RF frequency band. The first diplexer is configured to separate RF signals within the first RF frequency band from RF signals within a first subset of the second RF frequency band. The second diplexer is configured to separate RF signals within the first RF frequency band from RF signals within a second subset of the second RF frequency band. The switching circuitry is coupled between the primary antenna node, the secondary antenna node, the first set of input/output nodes, the second set of input/output nodes, the first diplexer, and the second diplexer. The control circuitry is coupled to the switching circuitry. In a carrier aggregation configuration, the control circuitry is configured to cause the switching circuitry to couple at least one of the first set of input/output nodes and at least one of the second set of input/output nodes to one of the primary antenna node and the secondary antenna node via one of the first diplexer and the second diplexer such that an insertion loss due to switching elements in the path between the at least one of the first set of input/output nodes and the primary antenna node is less than or equal to 0.9 dB. In a non-carrier aggregation configuration, the control circuitry is configured to cause the switching circuitry to couple at least one of the first set of input/output nodes and the second set of input/output nodes to one of the primary antenna node and the secondary antenna node such that the first diplexer and the second diplexer are bypassed and an insertion loss due to switching elements in the path between the primary antenna node and the at least one of the first set of input/output nodes and the second set of input/output nodes and the primary antenna node is less than or equal to 0.9 dB. 
         [0018]    By operating the circuitry as described above, the performance of the circuitry is significantly improved by reducing the insertion loss due to switching elements, while still providing great flexibility in the number of switching configurations that the circuitry is capable of providing. 
         [0019]    Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         [0020]    The accompanying drawing figures 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. 
           [0021]      FIG. 1  is a functional schematic illustrating conventional radio frequency (RF) front end circuitry. 
           [0022]      FIGS. 2A and 2B  are functional schematics illustrating different switching configurations for the RF front end circuitry shown in  FIG. 1 . 
           [0023]      FIG. 3  is a functional schematic illustrating RF front end circuitry according to one embodiment of the present disclosure. 
           [0024]      FIGS. 4A through 4C  are functional schematics illustrating different switching configurations for the RF front end circuitry shown in  FIG. 3  according to various embodiments of the present disclosure. 
           [0025]      FIG. 5  is a functional schematic illustrating RF front end circuitry according to one embodiment of the present disclosure. 
           [0026]      FIGS. 6A through 6C  are functional schematics illustrating different switching configurations for the RF front end circuitry shown in  FIG. 5  according to various embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, 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. 
         [0028]    It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0029]    It will be understood that when an element such as a layer, region, or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. Likewise, it will be understood that when an element such as a layer, region, or substrate is referred to as being “over” or extending “over” another element, it can be directly over or extend directly over the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly over” or extending “directly over” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. 
         [0030]    Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. 
         [0031]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0032]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0033]      FIG. 3  shows radio frequency (RF) front end circuitry  40  according to one embodiment of the present disclosure. The RF front end circuitry  40  includes a primary antenna  42 , a secondary antenna  44 , primary antenna swapping circuitry  46 , secondary antenna swapping circuitry  48 , a front end diplexer  50 , reconfigurable RF filtering circuitry  52 , first band filtering circuitry  54 , and second band filtering circuitry  56 . The primary antenna swapping circuitry  46  is coupled between the front end diplexer  50  and the primary antenna  42 . The secondary antenna swapping circuitry  48  is coupled between a secondary RF signal node  58  and the secondary antenna  44 . The reconfigurable RF filtering circuitry  52  is coupled between the first band filtering circuitry  54 , the second band filtering circuitry  56 , and the front end diplexer  50 . 
         [0034]    The primary antenna swapping circuitry  46  includes a number of primary antenna swapping switches SW PAS . The secondary antenna swapping circuitry  48  includes a number of secondary antenna swapping switches SW PAS . Together, the primary antenna swapping switches SW PAS  and the secondary antenna swapping switches SW PAS  are configured to couple one of the primary antenna  42  and the secondary antenna  44  to the front end diplexer  50  and couple the other one of the primary antenna  42  and the secondary antenna  44  to the secondary RF signal node  58 . While not shown in order to avoid obscuring the drawings, the secondary RF signal node  58  is generally coupled to secondary RF filtering circuitry in order to separate secondary RF receive signals into their constituent operating bands for further processing. Those skilled in the art will appreciate that the one of the primary antenna  42  and the secondary antenna  44  coupled to the front end diplexer  50  is dependent on current signal conditions, and that the primary antenna  42  and the secondary antenna  44  may be dynamically swapped as desired in order to improve transmission and/or reception characteristics. 
         [0035]    The front end diplexer  50  is configured to separate RF receive signals from one of the primary antenna  42  and the secondary antenna  44  into those RF receive signals within a first RF frequency band and those RF receive signals within a second RF frequency band. In one embodiment, the first RF frequency band is a low-band, encompassing frequencies between 700 MHz and 1000 MHz, and the second RF frequency band is a mid/high-band, encompassing frequencies between 1800 MHz and 2700 MHz. Those skilled in the art will appreciate that the principles of the present disclosure may be applied to RF signals falling within any number of different frequency bands or combinations of frequency bands, all of which are contemplated herein. The RF receive signals within the first RF frequency band are delivered to a low-band RF signal node  60 , while the RF receive signals within the second RF frequency band are delivered to the reconfigurable RF filtering circuitry  52 . Further, the front end diplexer  50  is configured to combine RF transmit signals from the low-band RF signal node  60  and the reconfigurable RF filtering circuitry  52  and provide these RF transmit signals to one of the primary antenna  42  and the secondary antenna  44  for transmission. 
         [0036]    In order to address the issues discussed above with respect to separating RF signals that are relatively close together in frequency, the reconfigurable RF filtering circuitry  52  includes a first diplexer  62 A and a second diplexer  62 B. The first diplexer  62 A is configured to separate RF signals within a third RF frequency band from RF signals within a first subset of a fourth RF frequency band, while the second diplexer  62 B is configured to separate RF signals within the third RF frequency band from RF signals within a second subset of the fourth RF frequency band. In one embodiment, the third RF frequency band and the fourth RF frequency bands are subsets of the second RF frequency band. For example, the third RF frequency band may be a mid-band encompassing frequencies between 1800 MHz and 2200 MHz, and the fourth RF frequency band may be a high-band encompassing frequencies between 2300 MHz and 2700 MHz. Those skilled in the art will appreciate that the principles of the present disclosure may be applied to RF signals falling within any number of different frequency bands, all of which are contemplated herein. The first subset of the fourth RF frequency band may include a relatively narrow portion thereof nearest the third RF frequency band (e.g., from 2300 MHz to 2400 MHz in the exemplary embodiment discussed above). The second subset of the fourth RF frequency band may include the remainder of the fourth RF frequency band (e.g., from 2500 MHz to 2700 MHz). In various embodiments, the first subset and the second subset may overlap. Due to the relatively narrow portion of the fourth RF frequency band passed by the first diplexer  62 A, the selectivity of this portion of the diplexer may be significantly improved such that the first diplexer  62 A can adequately separate RF signals within the third RF frequency band from RF signals within the fourth RF frequency band, even when they are relatively close to one another in frequency. 
         [0037]    The first band filtering circuitry  54  and the second band filtering circuitry  56  include a number of band filtering switches SW BF  and a number of band filters  64 . The band filtering switches SW BF  are configured to couple one or more of the band filters  64  to one of the first diplexer  62 A and the second diplexer  62 B in the reconfigurable RF filtering circuitry  52 , or to bypass the reconfigurable RF filtering circuitry  52  in order to couple the one or more band filters  64  directly to the front end diplexer  50 . In comparison to the conventional RF front end circuitry shown in  FIG. 1 , the switches that were previously included in the reconfigurable RF filtering circuitry  52  are moved into the first band filtering circuitry  54  and the second band filtering circuitry  56 . Such a change in the configuration of the RF front end circuitry  40  reduces the insertion loss in the signal paths thereof as discussed below. 
         [0038]    Each one of the band filters  64  is configured to isolate an RF signal within a particular operating band (or in some cases, RF signals within multiple operating bands) from other RF signals. RF receive signals from one of the front end diplexer  50  and the reconfigurable RF filtering circuitry  52  are isolated via an appropriate one of the band filters  64  and delivered to an appropriate one of a number of input/output nodes  66 . RF transmit signals from downstream circuitry are received at one of the input/output nodes  66 , isolated by an appropriate one of the band filters  64 , and delivered to one of the front end diplexer  50  and the reconfigurable RF filtering circuitry  52  for transmission from one of the primary antenna  42  and the secondary antenna  44 . Generally, only the band filters  64  associated with the particular operating bands being transmitted or received are coupled to the one of the front end diplexer  50  and the reconfigurable RF filtering circuitry  52  to avoid excessive loading of the signal paths. 
         [0039]    Control circuitry  68  is coupled to each one of the primary antenna swapping circuitry  46 , the secondary antenna swapping circuitry  48 , the first band filtering circuitry  54 , and the second band filtering circuitry  56  in order to control the state of the switches therein and effectuate the functionality discussed herein. A first signal coupler  70  and a second signal coupler  72  may be provided at the output of each one of the first band filtering circuitry  54  and the second band filtering circuitry  56  in order to detect a signal strength of transmission signals therefrom for a power control loop. Those skilled in the art will appreciate the details of these signal couplers, and thus a discussion of the specifics thereof is not included herein. 
         [0040]    In carrier aggregation configurations in which RF signals within the third RF frequency band are simultaneously received along with RF signals within the fourth RF frequency band and there is a relatively small frequency delta (e.g., &lt;150 MHz) between the RF signals, the band filtering switching elements SW BF  are configured to couple the first diplexer  62 A between the first band filtering circuitry  54 , the second band filtering circuitry  56 , and the front end diplexer  50 . Accordingly, RF receive signals within the third RF frequency band and RF receive signals within the fourth RF frequency band that are relatively close in frequency can be adequately separated by the first diplexer  62 A and delivered to the first band filtering circuitry  54  and the second band filtering circuitry  56 . In carrier aggregation configurations in which RF signals within the third RF frequency band are simultaneously received along with RF signals within the fourth RF frequency band and there is a relatively large frequency delta (e.g., &gt;150 MHz) between the RF signals, the band filtering switching elements SW BF  are configured to couple the second diplexer  62 B between the first band filtering circuitry  54 , the second band filtering circuitry  56 , and the front end diplexer  50 . Accordingly, RF receive signals within the third RF frequency band and RF receive signals within the fourth RF frequency band that are relatively far apart in frequency can be adequately separated by the second diplexer  62 B and delivered to the first band filtering circuitry  54  and the second band filtering circuitry  56 . In non-carrier aggregation configurations, the band filtering switches SW BF  are configured to directly couple one of the first band filtering circuitry  54  and the second band filtering circuitry  56  to the front end diplexer  50 . The first diplexer  62 A and the second diplexer  62 B can be bypassed in this case since the RF receive signals will fall within a single one of the third RF frequency band and the fourth RF frequency band. Accordingly, in non-carrier aggregation configurations in which the first diplexer  62 A and the second diplexer  62 B are not necessary, the insertion loss associated therewith can be avoided. 
         [0041]    In order to separate RF signals within the third RF frequency band from RF signals within the fourth RF frequency band when there is a relatively small frequency delta between the RF signals, the first diplexer  62 A may be a bandpass-bandstop architecture wherein a bandpass filter response passes RF signals within the first subset of the fourth RF frequency band and the bandstop response blocks signals within the first subset of the fourth RF frequency band. Details of such a diplexer configuration are discussed at length in U.S. patent application Ser. No. 15/194,804, the contents of which are hereby incorporated by reference in their entirety. Due to the bandpass-bandstop architecture of the first diplexer  62 A, the diplexer may also be used to separate RF signals within the first subset of the fourth RF frequency band from RF signals within the second subset of the fourth RF frequency band such that these signals can also be carrier aggregated. 
         [0042]      FIG. 4A  shows a switch configuration for the RF front end circuitry  40  in which the first diplexer  62 A in the reconfigurable RF filtering circuitry  52  is used to perform carrier aggregation between one or more RF signals within the third RF frequency band and one or more RF signals within the fourth RF frequency band via the primary antenna  42 . As shown, a second one of the primary antenna swapping switches SW PAS2  is closed, while the remaining primary antenna swapping switches SW PAS  are open. Further, an eighth one of the band filtering switches SW BFB  in the first band filtering circuitry  54  is closed while the remaining band filtering switches SW BF  therein are open. A second one of the band filtering switches SW BF2  and an eleventh one of the band filtering switches SW BF11  are closed in the second band filtering circuitry  56 , while the remaining band filtering switches SW BF  therein are open. Assuming a 0.20 dB insertion loss for each closed series switch in the signal path and a 0.025 dB insertion loss for each open parallel switch, a signal path from the primary antenna  42  to a fifth one of the input/output nodes  66 E of the first band filtering circuitry  54  includes three closed series switches and twelve open parallel switches for a total insertion loss of 0.9 dB. A similar result is achieved when the second diplexer  62 B in the reconfigurable RF filtering circuitry  52  is used to perform carrier aggregation between one or more RF signals within the third RF frequency band and one or more RF signals within the fourth RF frequency band. Additional switches are added in the signal path when the secondary antenna  44  is used in these configurations, however, this is generally of little concern since the primary antenna  42  is used most of the time when transmission and/or reception characteristics are favorable. 
         [0043]      FIG. 4B  shows a switch configuration in which the first diplexer  62 A and the second diplexer  62 B are bypassed in a non-carrier aggregation mode. In the particular example shown in  FIG. 4B , the primary antenna  42  is coupled via the front end diplexer  50  to the first band filtering circuitry  54 . Accordingly, a second one of the primary antenna swapping switches SW PAS2  is closed, while the remaining primary antenna swapping switches SW PAS  are open. Further, a fourth one of the band filtering switches SW BF4  in the first band filtering circuitry  54  is closed while the remaining band filtering switches SW BF  therein are open. A first one of the band filtering switches SW BF1  in the second band filtering circuitry  56  is closed, while the remaining band filtering switches SW BF  therein are open. Again assuming a 0.20 dB insertion loss for each closed series switch in the signal path and a 0.025 dB insertion loss for each open parallel switch, a signal path from the primary antenna  42  to the fifth one of the input/output nodes  66 E of the first band filtering circuitry  54  includes three closed series switches and eleven open parallel switches for a total insertion loss of 0.875 dB. 
         [0044]      FIG. 4C  shows a switch configuration in which the first diplexer  62 A is used for carrier aggregation between RF signals within the first subset of the fourth RF frequency band and RF signals within the second subset of the fourth RF frequency band. As discussed above, the first diplexer  62 A may have a bandpass-bandstop architecture that may be used to separate RF signals within the first subset of the fourth RF frequency band from RF signals within the second subset of the fourth RF frequency band. Accordingly, a second one of the primary antenna swapping switches SW PAS2  is closed, while the remaining primary antenna swapping switches SW PAS  are open. Further, a seventh one of the band filtering switches SW BF7  and a tenth one of the band filtering switches SW BF10  in the first band filtering circuitry  54  are closed while the remaining band filtering switches SW BF  therein are open. A second one of the band filtering switches SW BF2  and a fourteenth one of the band filtering switches SW BF14  in the second band filtering circuitry  56  are closed, while the remaining band filtering switches SW BF  therein are open. In this configuration, RF signals within the first subset of the fourth RF frequency band are routed to a second one of the band filters  64 B in the first band filtering circuitry  54  while RF signals within the second subset of the fourth RF frequency band are routed to a third one of the band filters  64 C in the first band filtering circuitry  54 , thereby allowing carrier aggregation between these RF signals. Again assuming a 0.20 dB insertion loss for each closed series switch in the signal path and a 0.025 dB insertion loss for each open parallel switch, a signal path from the primary antenna  42  to the second one of the input/output nodes  66 B and the fourth one of the input/output nodes  66 D of the first band filtering circuitry  54  includes three closed series switches and ten open parallel switches for a total insertion loss of 0.85 dB. 
         [0045]      FIG. 5  shows RF front end circuitry  74  according to an additional embodiment of the present disclosure. The RF front end circuitry  74  includes a primary antenna  76 , a secondary antenna  78 , primary antenna swapping and reconfigurable RF filtering circuitry  80 , secondary antenna swapping circuitry  82 , first band filtering circuitry  84 , and second band filtering circuitry  86 . The primary antenna swapping and reconfigurable RF filtering circuitry  80  is coupled between the first band filtering circuitry  84 , the second band filtering circuitry  86 , and the primary antenna  76 . The secondary antenna swapping circuitry  82  is coupled between a number of secondary RF signal nodes  88  and the secondary antenna  78 . 
         [0046]    The primary antenna swapping and reconfigurable RF filtering circuitry  80  includes a first front end diplexer  90 A, a first reconfigurable RF filtering circuitry diplexer  92 A, a second reconfigurable RF filtering circuitry diplexer  92 B, and a number of primary antenna swapping and reconfigurable RF filtering circuitry switches SW PFRC . The secondary antenna swapping circuitry  82  includes a second front end diplexer  90 B and a number of secondary antenna swapping switches SW SAS . Together, the primary antenna swapping and reconfigurable RF filtering circuitry switches SW PFRC  and the secondary antenna swapping switches SW SAS  are configured to couple one or more of the first band filtering circuitry  84 , the second band filtering circuitry  86 , the first reconfigurable RF filtering circuitry diplexer  92 A, the second reconfigurable RF filtering circuitry diplexer  92 B, a low-band RF signal node  94 , and the secondary RF signal nodes  88  to one of the primary antenna  76  (via the first front end diplexer  90 A) and the secondary antenna  78  (via the second front end diplexer  90 B), and couple the other one of the primary antenna  76  and the secondary antenna  78  to one or more of the secondary RF signal nodes  88 . While not shown to avoid obscuring the drawings, the secondary RF signal nodes  88  are generally coupled to secondary RF filtering circuitry in order to separate secondary RF receive signals into their constituent RF operating bands for further processing. Those skilled in the art will appreciate that the connections to the primary antenna  76  and the secondary antenna  78  may be dependent on current signal conditions, and that the primary antenna  76  and the secondary antenna  78  may be dynamically swapped as desired in order to improve transmission and/or reception characteristics. 
         [0047]    The first front end diplexer  90 A is configured to separate RF receive signals from the primary antenna  76  into those RF receive signals within a first RF frequency band and those RF receive signals within a second RF frequency band. In one embodiment, the first RF frequency band is a low-band, encompassing frequencies between 700 MHz and 1000 MHz, and the second RF frequency band is a mid/high-band, encompassing frequencies between 1800 MHz and 2700 MHz. Those skilled in the art will appreciate that the principles of the present disclosure may be applied to RF signals falling within any number of different frequency bands or combinations of frequency bands, all of which are contemplated herein. The RF receive signals within the first RF frequency band are delivered to a number of the primary antenna swapping and reconfigurable RF filtering circuitry switches SW PFRC , which may then route the signals to one of the low-band RF signal node  94  and the secondary antenna swapping circuitry  82 . The RF receive signals within the second RF frequency band are delivered to different ones of the primary antenna swapping and reconfigurable RF filtering switches RF PSRF , which may then route the signals to one of the first reconfigurable RF filtering circuitry diplexer  92 A, the second reconfigurable RF filtering circuitry diplexer  92 B, the first band filtering circuitry  84 , the second band filtering circuitry  86 , and the secondary antenna swapping circuitry  82 . Further, the first front end diplexer  90 A is configured to combine RF transmit signals within the first RF frequency band and RF transmit signals within the second RF frequency band received from various ones of the primary antenna swapping and reconfigurable RF filtering switches SW PSRF and provide these RF transmit signals to the primary antenna  76  for transmission. The second front end diplexer  90 B functions similarly to the first front end diplexer  90 A. 
         [0048]    By combining the switches for antenna swapping and routing of RF signals between the first reconfigurable RF filtering circuitry diplexer  92 A, the second reconfigurable RF filtering circuitry diplexer  92 B, the first band filtering circuitry  84 , and the second band filtering circuitry  86 , the number of switches in any given signal path during operation of the RF front end circuitry  74  may be reduced, thereby reducing insertion loss and improving performance as discussed below. 
         [0049]    In order to address the issues discussed above with respect to separating RF signals that are relatively close together in frequency, the primary antenna swapping circuitry and reconfigurable RF filtering circuitry  80  includes the first reconfigurable RF filtering circuitry diplexer  92 A and the second reconfigurable RF filtering circuitry diplexer  92 B. The first reconfigurable RF filtering circuitry diplexer  92 A is configured to separate RF signals within a third RF frequency band from RF signals within a first subset of a fourth RF frequency band, while the second reconfigurable RF filtering circuitry diplexer  92 B is configured to separate RF signals within the third RF frequency band from RF signals within a second subset of the fourth RF frequency band. In one embodiment, the third RF frequency band and the fourth RF frequency band are subsets of the second RF frequency band. For example, the third RF frequency band may be a mid-band encompassing frequencies between 1800 MHz and 2200 MHz, and the fourth RF frequency band may be a high-band encompassing frequencies between 2300 MHz and 2700 MHz. Those skilled in the art will appreciate that the principles of the present disclosure may be applied to RF signals falling within any number of different frequency bands, all of which are contemplated herein. The first subset of the fourth RF frequency band may include a relatively narrow portion thereof nearest the third RF frequency band (e.g., from 2300 MHz to 2400 MHz in the exemplary embodiment discussed above). The second subset of the fourth RF frequency band may include the remainder of the fourth RF frequency band (e.g., from 2500 MHz to 2700 MHz). In various embodiments, the first subset and the second subset may overlap. Due to the relatively narrow portion of the fourth RF frequency band passed by the first reconfigurable RF filtering circuitry diplexer  92 A, the selectivity of this portion of the diplexer may be significantly improved such that the first reconfigurable RF filtering circuitry diplexer  92 A can adequately separate RF signals within the third RF frequency band from RF signals within the fourth RF frequency band, even when they are relatively close to one another in frequency. 
         [0050]    The first band filtering circuitry  84  and the second band filtering circuitry  86  include a number of band filtering switches SW BF  and a number of band filters  96 . The band filtering switches SW BF  are configured to couple one or more of the band filters  96  to the primary antenna swapping and reconfigurable RF filtering circuitry  80 . Each one of the band filters  96  is configured to isolate an RF signal within a particular RF operating band (or in some cases, RF signals within multiple RF operating bands) from other RF signals. In one embodiment, the band filters  96  in the first band filtering circuitry  84  are associated with RF operating bands located in the third RF frequency band, while the band filters  96  in the second band filtering circuitry  86  are associated with RF operating bands located in the fourth RF frequency band. In operation, RF receive signals from the primary antenna swapping and reconfigurable RF filtering circuitry  80  are isolated via an appropriate one of the band filters  96  and delivered to an appropriate one of a number of input/output nodes  98 . RF transmit signals from downstream circuitry are received at one of the input/output nodes  98 , isolated by an appropriate one of the band filters  96 , and delivered to the primary antenna swapping and reconfigurable RF filtering circuitry  80  for transmission from one of the primary antenna  76  and the secondary antenna  78 . Generally, only the band filters  96  associated with the particular RF operating bands being transmitted or received are coupled to the primary antenna swapping and reconfigurable RF filtering circuitry  80  to avoid excessive loading of the signal paths. 
         [0051]    Similar to the first diplexer  62 A discussed above with respect to  FIG. 3 , the first reconfigurable RF filtering circuitry diplexer  92 A may have a bandpass-bandstop architecture that allows for the separation of RF signals within the first subset of the fourth RF frequency band and the second subset of the RF frequency band. 
         [0052]    Control circuitry  100  is coupled to each one of the primary antenna swapping and reconfigurable RF filtering circuitry  80 , the secondary antenna swapping circuitry  82 , the first band filtering circuitry  84 , and the second band filtering circuitry  86  in order to control the state of the switches therein and effectuate the functionality discussed herein. A first signal coupler  102  and a second signal coupler  104  may be provided at the output of each one of the first band filtering circuitry  84  and the second band filtering circuitry  86 , respectively, in order to detect a signal strength of transmission signals therefrom for a power control loop. However, since multiple outputs from each one of the first band filtering circuitry  84  and the second band filtering circuitry  86  exist in the RF front end circuitry  74 , a first additional signal coupler  106  and a second additional signal coupler  108  are added to ensure that transmission signals can be measured for power control. Providing the first additional signal coupler  106  and the second additional signal coupler  108  covers each egress path for a transmission signal in the RF front end circuitry  74 , such that measurements for power control are possible with a minimal number of signal couplers. Those skilled in the art will appreciate the details of the signal couplers, and thus a discussion of the specifics thereof is not included herein. 
         [0053]    In carrier aggregation configurations in which RF signals within the third RF frequency band are simultaneously received along with RF signals within the fourth RF frequency band at the primary antenna  76  and there is a relatively small frequency delta (e.g., &lt;150 MHz) between the RF signals, the primary antenna swapping and reconfigurable RF filtering circuitry switches SW PFRC  along with the band filtering switches SW BF  are configured to couple the first reconfigurable RF filtering circuitry diplexer  92 A between the first band filtering circuitry  84 , the second band filtering circuitry  86 , and the first front end diplexer  90 A. Accordingly, RF receive signals can be adequately separated by the first front end diplexer  90 A and the first reconfigurable RF filtering circuitry diplexer  92 A and delivered to the first band filtering circuitry  84  and the second band filtering circuitry  86  for separation into their constituent RF operating bands. 
         [0054]    In carrier aggregation configurations in which RF signals within the third RF frequency band are simultaneously received along with RF signals within the fourth RF frequency band at the primary antenna  76  and there is a relatively large frequency delta (e.g., &gt;150 MHz) between the RF signals, the primary antenna swapping and reconfigurable RF filtering circuitry switches SW PFRC  along with the band filtering switches SW BF  are configured to couple the second reconfigurable RF filtering circuitry diplexer  92 B between the first band filtering circuitry  84 , the second band filtering circuitry  86 , and the first front end diplexer  90 A. Accordingly, RF receive signals can be adequately separated by the first front end diplexer  90 A and the second reconfigurable RF filtering circuitry diplexer  92 B and delivered to the first band filtering circuitry  84  and the second band filtering circuitry  86  for separation into their constituent RF operating bands. 
         [0055]    In non-carrier aggregation configurations, the primary antenna swapping and reconfigurable RF filtering circuitry switches SW PFRC  along with the band filtering switches SW BF  are configured to bypass the first reconfigurable RF filtering circuitry diplexer  92 A and the second reconfigurable RF filtering circuitry diplexer  92 B, directly coupling one of the first band filtering circuitry  84  and the second band filtering circuitry  86  to the first front end diplexer  90 A. The first reconfigurable RF filtering circuitry diplexer  92 A and the second reconfigurable RF filtering circuitry diplexer  92 B may be bypassed in this case since the RF receive signals will fall within a single one of the third RF frequency band and the fourth RF frequency band. Accordingly, in non-carrier aggregation configurations in which the first reconfigurable RF filtering circuitry diplexer  92 A and the second reconfigurable RF filtering circuitry diplexer  92 B are not necessary, the insertion loss associated therewith can be avoided. 
         [0056]      FIG. 6A  shows a switch configuration for the RF front end circuitry  74  in which the first reconfigurable RF filtering circuitry diplexer  92 A in the primary antenna swapping and reconfigurable RF filtering circuitry  80  is used to perform carrier aggregation between one or more RF signals within the third RF frequency band and one or more RF signals within the fourth RF frequency band via the primary antenna  76 . As shown, a fifth one of the primary antenna swapping and reconfigurable RF filtering circuitry switches SW PFRCS  is closed, while the remaining primary antenna swapping and reconfigurable RF filtering circuitry switches SW PFRC  are open. Further, an eighth one of the band filtering switches SW BFB  in the first band filtering circuitry  84  is closed while the remaining band filtering switches SW BF  therein are open. A tenth one of the band filtering switches SW BF10  in the second band filtering circuitry  86  is closed while the remaining band filtering switches SW BF  therein are open. Assuming a 0.20 dB insertion loss for each closed series switch in the signal path and a 0.025 dB insertion loss for each open parallel switch, a signal path from the primary antenna  76  to a fifth one of the input/output nodes  98 E of the first band filtering circuitry  84  includes two closed series switches and seven open parallel switches for a total insertion loss of 0.575 dB. A similar result is achieved when the second reconfigurable RF filtering circuitry diplexer  92 B is used to perform carrier aggregation between one or more RF signals within the third RF frequency band and one or more RF signals within the fourth RF frequency band. Additional switches are added in the signal path when the secondary antenna  78  is used in these configurations, however, this is generally of little concern since the primary antenna  76  is used most of the time when transmission and/or reception characteristics are favorable. 
         [0057]      FIG. 6B  shows a switch configuration in which the first reconfigurable RF filtering circuitry diplexer  92 A and the second reconfigurable RF filtering circuitry diplexer  92 B are bypassed in a non-carrier aggregation mode. In the particular example shown in  FIG. 6B , the primary antenna  76  is coupled via the first front end diplexer  90 A to the first band filtering circuitry  84 . Accordingly, a fourth one of the primary antenna swapping and reconfigurable RF filtering circuitry switches SW PFRC4  is closed, while the remaining primary antenna swapping and reconfigurable RF filtering switches SW PSRF  are open. Further, a fourth one of the band filtering switches SW BF4  in the first band filtering circuitry  84  is closed while the remaining band filtering switches SW BF  therein are open. Again assuming a 0.20 dB insertion loss for each closed series switch in the signal path and a 0.025 dB insertion loss for each open parallel switch, a signal path from the primary antenna  76  to the fifth one of the input/output nodes  98 E of the first band filtering circuitry  84  includes two closed series switches and nine open parallel switches for a total insertion loss of 0.625 dB. 
         [0058]      FIG. 6C  shows a switch configuration in which the first reconfigurable RF filtering circuitry diplexer  92 A is used for carrier aggregation between RF signals within the first subset of the fourth RF frequency band and RF signals within the second subset of the fourth RF frequency band. As discussed above, the first reconfigurable RF filtering circuitry diplexer  92 A may have a bandpass-bandstop architecture that may be used to separate RF signals within the first subset of the fourth RF frequency band from RF signals within the second subset of the fourth RF frequency band. Accordingly, a fifth one of the primary antenna swapping and reconfigurable RF filtering circuitry switches SW PFRC5  is closed, while the remaining primary antenna swapping and reconfigurable RF filtering switches SW PSRF  are open. Further, a seventh one of the band filtering switches SW BP7  and a tenth one of the band filtering switches SW BF10  in the first band filtering circuitry  84  are closed while the remaining band filtering switches SW BF  therein are open. An eleventh one of the band filtering switches SW BF11  in the second band filtering circuitry  86  is closed while the remainder of the band filtering switches SW BF  are open. Again assuming a 0.20 dB insertion loss for each closed series switch in the signal path and a 0.025 dB insertion loss for each open parallel switch, a signal path from the primary antenna  76  to the second one of the input/output nodes  98 B of the first band filtering circuitry  84  includes three closed series switches and eight open parallel switches for a total insertion loss of 0.8 dB, while a signal path from the primary antenna  76  to the fourth one of the input/output nodes  98 D of the first band filtering circuitry  84  includes two closed series switches and eight open parallel switches for a total insertion loss of 0.6 dB. 
         [0059]    Those skilled in the art will recognize improvements and modifications to the preferred 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.