Patent Publication Number: US-2023144780-A1

Title: Circuits for filtering radio-frequency signals

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. 
     BACKGROUND 
     Field 
     Embodiments of the disclosure relate to the field of wireless communication devices, and more particularly, to front end modules for multiple frequency bands. 
     Description of the Related Technology 
     Front-end modules of wireless communication devices are typically configured to condition (for instance, filter and/or amplify) received radio-frequency (RF) signals. The RF signals can be cellular signals, wireless local area network signal (WLAN), e.g., Wi-Fi signals, or the like. Since multiple frequency bands can exist close to each other, the front-end module can be configured to separate frequencies bands adjacent to each other. 
     Front-end modules can be used for transmitting and/or receiving signals of a wide range of frequencies. For example, a front-end modules can be used to wirelessly communicate RF signals in a frequency range of about 30 kHz to 300 GHz, such as in the range of about such as in the range of about 400 MHz to about 7.125 GHz for Frequency Range 1 (FR1) of the Fifth Generation (5G) communication standard or in the range of about 24.250 GHz to about 71.000 GHz for Frequency Range 2 (FR2) of the 5G communication standard. 
     Examples of RF communication systems with front-end modules include, but are not limited to, mobile phones, tablets, base stations, network access points, customer-premises equipment (CPE), laptops, and wearable electronics. 
     SUMMARY 
     According to one embodiment there is provided a radio-frequency switching circuit for multiple signal bands comprising a first signal path for a first frequency range, a second signal path for a second frequency range, the first and second frequency ranges being adjacent to each other, one or more second signal path filters each configured to pass a respective region of the second frequency range, at least one of the respective regions being smaller than the second frequency range, and one or more switches configured to select one of the second signal path filters based on a control signal. 
     In one example the first frequency range includes one or more frequency bands used for cellular communication and wherein the second frequency range includes a frequency band used for WLAN communication. 
     In one example the first frequency range includes a frequency band used for WLAN communication and wherein the second frequency range includes one or more frequency bands used for cellular communication. 
     In one example the first or second frequency ranges includes a frequency band used for WLAN communication having a frequency range of between 2403 MHz to 2483.5 MHz, or 5150 MHz to 5850 MHz, or 5925 MHz to 7125 MHz. 
     In one example the first frequency range is separated from the second frequency range by a frequency gap that is smaller than or equal to approximately 15 MHz. 
     In one example the region of the second frequency range corresponding to the selected second signal path filter is separated from the first frequency range by a frequency gap that is greater than or equal to 20 MHz, 32 MHz, 33 MHz, 37 MHz or 40 MHz. 
     The one or more second signal path filters can include at least first and second signal path filters configured to pass first and second respective regions of the second frequency range, each of the first and second respective regions being smaller than the second frequency range. 
     The first frequency range can include a first band lower than the second frequency range and a second band higher than the second frequency range. A lower end of the first region of the second frequency range can be separated from an upper end of the first band of the first frequency range by a frequency gap that is greater than a gap between the upper end of the first band and a lower end of the second frequency range. An upper end of the second region of the second frequency range can be separated from a lower end of the second band of the first frequency range by a frequency gap that is greater than a gap between the lower end of the second band and an upper end of the second frequency range. 
     In one example a first region of the second frequency range includes frequencies between 2532 MHz to 2463 MHz. 
     In one example a second region of the second frequency range includes frequencies between 2443 MHz to 2483 MHz. 
     In one example a third region of the second frequency range includes frequencies between 2423 MHz to 2483 MHz. 
     Another example further comprises a mode select switch configured to provide the signals from the selected second signal path filter to an output node. 
     According to another embodiment there is provided a radio-frequency switching circuit comprising a first signal path for a first frequency range, a second signal path for a second frequency range, the first and second frequency ranges being adjacent to each other, one or more first signal path filters each configured to pass a respective region of the first frequency range, at least one of the respective regions of the first frequency range being smaller than the first frequency range, one or more second signal path filters each configured to pass a respective region of the second frequency range, at least one of the respective regions being smaller than the second frequency range, and one or more switches configured to select one or more of the first signal path filters and the second signal path filters based on a control signal. 
     In one example the first frequency range includes one or more frequency bands used for cellular communication and wherein the second frequency range includes a frequency band used for WLAN communication. 
     In one example the second frequency range includes a frequency band used for WLAN communication having a frequency range of between 2403 MHz to 2483.5 MHz, or 5150 MHz to 5850 MHz, or 5925 MHz to 7125 MHz. 
     In one example the first frequency range is separated from the second frequency range by a frequency gap that is smaller than or equal to approximately 15 MHz. 
     In one example the region of the first frequency range corresponding to the selected first signal path filter is separated from the second frequency range by a frequency gap that is greater than or equal to 20 MHz, 32 MHz, 33 MHz, 37 MHz or 40 MHz. 
     In one example the region of the second frequency range corresponding to the selected second signal path filter is separated from the first frequency range by a frequency gap that is greater than or equal to 20 MHz, 32 MHz, 33 MHz, 37 MHz or 40 MHz. 
     The one or more first signal path filters can include at least first and second signal path filters configured to pass first and second respective regions of the first frequency range, each of the first and second respective regions being smaller than the first frequency range. The one or more second signal path filters include at least third and fourth signal path filters configured to pass third and fourth respective regions of the second frequency range, each of the third and fourth respective regions being smaller than the second frequency range. The third and fourth respective regions of the second frequency range can be between a first band of the first frequency range and a second band of the first frequency range. 
     In one example a first region of the first frequency range includes frequencies between 2300 MHz to 2370 MHz and between 2515 MHz to 2675 MHz. 
     In one example a first region of the second frequency range includes frequencies between 2532 MHz to 2463 MHz. 
     In one example a second region of the second frequency range includes frequencies between 2443 MHz to 2483 MHz. 
     In one example a third region of the second frequency range includes frequencies between 2423 MHz to 2483 MHz. 
     Another example further comprises a mode select switch for each of the first and second signal paths, each mode select switch configured to provide the signals from the respective signal path filter to a respective output node. 
     According to another embodiment there is provided a method for filtering a radio-frequency signal comprising receiving a first frequency range and a second frequency range, the first and second frequency ranges being adjacent to each other, providing the first frequency range to a first signal path having one or more first signal path filters that each pass a respective region of the first frequency range, at least one of the respective regions of the first frequency range being smaller than the first frequency range, providing the second frequency range to a second signal path having one or more second signal path filters that each pass a respective region of the second frequency range, at least one of the respective regions being smaller than the second frequency range, and in response to receiving a control signal, selecting one or more of the first signal path filters and the second signal path filters. 
     According to another embodiment there is provided a radio-frequency module comprising a packaging substrate configured to receive a plurality of components, and a semiconductor die implemented on the packaging substrate, the semiconductor die including a radio-frequency switching circuit comprising a first signal path for a first frequency range, a second signal path for a second frequency range, the first and second frequency ranges being adjacent to each other, one or more second signal path filters each configured to pass a respective region of the second frequency range, at least one of the respective regions being smaller than the second frequency range, and one or more switches configured to select one of the second signal path filters based on a control signal. 
     According to another embodiment there is provided a wireless device comprising an antenna port coupled to one or more antennas, an antenna switch module, a radio-frequency module, the radio-frequency module including a radio-frequency switching circuit comprising a first signal path for a first frequency range, a second signal path for a second frequency range, the first and second frequency ranges being adjacent to each other, one or more second signal path filters each configured to pass a respective region of the second frequency range, at least one of the respective regions being smaller than the second frequency range, and one or more switches configured to select one of the second signal path filters based on a control signal, and a controller configured to provide a control signal to the radio-frequency switching circuit. 
     Still other aspects, embodiments, and advantages of these exemplary aspects and embodiments are discussed in detail below. Embodiments disclosed herein may be combined with other embodiments in any manner consistent with at least one of the principles disclosed herein, and references to “an embodiment,” “some embodiments,” “an alternate embodiment,” “various embodiments,” “one embodiment” or the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described may be included in at least one embodiment. The appearances of such terms herein are not necessarily all referring to the same embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of at least one embodiment are discussed below with reference to the accompanying figures, which are not intended to be drawn to scale. The figures are included to provide illustration and a further understanding of the various aspects and embodiments, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of the disclosure. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every figure. In the figures: 
         FIG.  1    is a schematic diagram showing example frequency bands for use in wireless communications; 
         FIG.  2    is a schematic diagram of an example switching circuit that uses a ganged band-pass filter configuration in an antenna plexer; 
         FIG.  3    is a schematic diagram showing how a 2.4 GHz Wi-Fi frequency band may be divided into two separate regions; 
         FIGS.  4 A and  4 B  are schematic diagrams showing a first frequency band configuration and a second frequency band configuration; 
         FIG.  5    is a schematic diagram of a first example switching circuit according to aspects of the present disclosure; 
         FIG.  6    is a schematic diagram showing the relative frequency separation between a 2.4 GHz Wi-Fi frequency band, a first frequency range and a second frequency range; 
         FIG.  7    is a schematic diagram of a second example switching circuit according to aspects of the present disclosure; 
         FIG.  8    is a schematic diagram of a third example switching circuit according to aspects of the present disclosure; 
         FIG.  9    is a schematic diagram of an example process for filtering radio-frequency signals; 
         FIGS.  10 A- 10 C  show features of the present disclosure implemented on radio-frequency modules; and 
         FIG.  11    is a schematic diagram of a wireless device that includes one or more of the radio-frequency modules of  FIGS.  10 A- 10 C . 
     
    
    
     DETAILED DESCRIPTION 
     Aspects and embodiments described herein are directed to a switching circuit for filtering radio-frequency signals in two adjacent frequency ranges. The switching circuit may select a filter path to provide a sub-range of frequencies for at least one of the frequency ranges. This can advantageously enables a larger frequency separation between signals in the first frequency range and signals in a second frequency range thereby attenuating emissions and insertion loss and improving the coexistence of both signals on a transmission line as further described below. 
     Shared use of antennas is often facilitated in existing radio architectures through the use of “antenna plexers”, which include banks of filters that enable a filtered merge of many signals in different frequency ranges to a single common antenna feed for a broadband antenna supporting all those bands. These are implemented in a variety of filter technologies, such as low temperature co-fired ceramic technology (LTCC), integrated passive device technology (IPD), discrete surface-mount technology (SMT), or a combination of those for purely L-C-based filters. As the filter band groups of these ganged band pass filters get closer together in frequency offset, the corner frequency roll-off of the band pass filters, which designed in-band from out-of-band (OOB), starts to have more impact in increasing in-band insertion loss at the band edges, and the loading loss of the filters becomes worse as well as the band pass filters move closer together in frequency. 
     Typically, wireless communication frequencies can be divided into a low frequency band (e.g., approximately 698 MHz-approximately 960 MHz, LB), a middle frequency band (e.g., approximately 1427 MHz-approximately 2200 MHz, MB), a high frequency band (e.g., approximately 2300 MHz-approximately 2690 MHz, HB) and ultrahigh frequency band (e.g., approximately 3400 MHz-approximately 3600 MHz, UHB). The frequency bands may be cellular frequency bands, such as UMTS (Universal Mobile Telecommunications System) frequency bands described below in Table 1, or other non-UMTS frequency bands. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                 Tx Frequency 
                 Rx Frequency 
               
               
                   
                 Band 
                 Mode 
                 Range (MHz) 
                 Range (MHz) 
               
               
                   
                   
               
             
            
               
                   
                 B1 
                 FDD 
                 1,920-1,980 
                 2,110-2,170 
               
               
                   
                 B2 
                 FDD 
                 1,850-1,910 
                 1,930-1,990 
               
               
                   
                 B3 
                 FDD 
                 1,710-1,785 
                 1,805-1,880 
               
               
                   
                 B4 
                 FDD 
                 1,710-1,755 
                 2,110-2,155 
               
               
                   
                 B5 
                 FDD 
                 824-849 
                 869-894 
               
               
                   
                 B6 
                 FDD 
                 830-840 
                 875-885 
               
               
                   
                 B7 
                 FDD 
                 2,500-2,570 
                 2,620-2,690 
               
               
                   
                 B8 
                 FDD 
                 880-915 
                 925-960 
               
               
                   
                 B9 
                 FDD 
                 1,749.9-1,784.9 
                 1,844.9-1,879.9 
               
               
                   
                 B10 
                 FDD 
                 1,710-1,770 
                 2,110-2,170 
               
               
                   
                 B11 
                 FDD 
                 1,427.9-1,447.9 
                 1,475.9-1,495.9 
               
               
                   
                 B12 
                 FDD 
                 699-716 
                 729-746 
               
               
                   
                 B13 
                 FDD 
                 777-787 
                 746-756 
               
               
                   
                 B14 
                 FDD 
                 788-798 
                 758-768 
               
               
                   
                 B15 
                 FDD 
                 1,900-1,920 
                 2,600-2,620 
               
               
                   
                 B16 
                 FDD 
                 2,010-2,025 
                 2,585-2,600 
               
               
                   
                 B17 
                 FDD 
                 704-716 
                 734-746 
               
               
                   
                 B18 
                 FDD 
                 815-830 
                 860-875 
               
               
                   
                 B19 
                 FDD 
                 830-845 
                 875-890 
               
               
                   
                 B20 
                 FDD 
                 832-862 
                 791-821 
               
               
                   
                 B21 
                 FDD 
                 1,447.9-1,462.9 
                 1,495.9-1,510.9 
               
               
                   
                 B22 
                 FDD 
                 3,410-3,490 
                 3,510-3,590 
               
               
                   
                 B23 
                 FDD 
                 2,000-2,020 
                 2,180-2,200 
               
               
                   
                 B24 
                 FDD 
                 1,626.5-1,660.5 
                 1,525-1,559 
               
               
                   
                 B25 
                 FDD 
                 1,850-1,915 
                 1,930-1,995 
               
               
                   
                 B26 
                 FDD 
                 814-849 
                 859-894 
               
               
                   
                 B27 
                 FDD 
                 807-824 
                 852-869 
               
               
                   
                 B28 
                 FDD 
                 703-748 
                 758-803 
               
               
                   
                 B29 
                 FDD 
                 N/A 
                 716-728 
               
               
                   
                 B30 
                 FDD 
                 2,305-2,315 
                 2,350-2,360 
               
               
                   
                 B31 
                 FDD 
                 452.5-457.5 
                 462.5-467.5 
               
               
                   
                 B32 
                 FDD 
                 N/A 
                 1,452-1,496 
               
               
                   
                 B33 
                 TDD 
                 1,900-1,920 
                 1,900-1,920 
               
               
                   
                 B34 
                 TDD 
                 2,010-2,025 
                 2,010-2,025 
               
               
                   
                 B35 
                 TDD 
                 1,850-1,910 
                 1,850-1,910 
               
               
                   
                 B36 
                 TDD 
                 1,930-1,990 
                 1,930-1,990 
               
               
                   
                 B37 
                 TDD 
                 1,910-1,930 
                 1,910-1,930 
               
               
                   
                 B38 
                 TDD 
                 2,570-2,620 
                 2,570-2,620 
               
               
                   
                 B39 
                 TDD 
                 1,880-1,920 
                 1,880-1,920 
               
               
                   
                 B40 
                 TDD 
                 2,300-2,400 
                 2,300-2,400 
               
               
                   
                 B41 
                 TDD 
                 2,496-2,690 
                 2,496-2,690 
               
               
                   
                 B42 
                 TDD 
                 3,400-3,600 
                 3,400-3,600 
               
               
                   
                 B43 
                 TDD 
                 3,600-3,800 
                 3,600-3,800 
               
               
                   
                 B44 
                 TDD 
                 703-803 
                 703-803 
               
               
                   
                 B45 
                 TDD 
                 1,447-1,467 
                 1,447-1,467 
               
               
                   
                 B46 
                 TDD 
                 5,150-5,925 
                 5,150-5,925 
               
               
                   
                 B65 
                 FDD 
                 1,920-2,010 
                 2,110-2,200 
               
               
                   
                 B66 
                 FDD 
                 1,710-1,780 
                 2,110-2,200 
               
               
                   
                 B67 
                 FDD 
                 N/A 
                 738-758 
               
               
                   
                 B68 
                 FDD 
                 698-728 
                 753-783 
               
               
                   
                   
               
            
           
         
       
     
     The high frequency band includes, but is not limited to, Band 40 (B40), Band 30 (B30), Band 41 (B41) and Band 7 (B7), etc. B41 is used in time division duplex (TDD) and thus has a single frequency band of approximately 2496 MHz to approximately 2690 MHz, which is utilized for both transmitted (Tx) and received (Rx) operations. Similarly, B40 is used in TDD and thus has a single frequency band of approximately 2300 MHz to approximately 2400 MHz. B41 and B40 can be utilized in cellular communications, e.g., 3rd generation partnership project (3GPP) wireless device. B7 is used in frequency division duplex (FDD) and thus performs simultaneous Tx and Rx operations via different frequencies, for example, Tx (approximately 2500 MHz to approximately 2570 MHz) and Rx (approximately 2620 MHz to approximately 2690 MHz) paths. This is typically accomplished by the use of a duplexer, which combines the Tx and Rx paths into a common terminal. B30 is also used in FDD and thus performs simultaneous Tx and Rx operations via different frequencies, for example, Tx (approximately 2305 MHz to approximately 2315 MHz) and Rx (approximately 2350 MHz to approximately 2360 MHz) paths. 
     The middle frequency band includes, but is not limited to, band 51 (B51) (e.g., approximately 1427 MHz-approximately 1432 MHz, TDD), band 74 (B74) (e.g., approximately 1427 MHz-approximately 1432 MHz and approximately 1475 MHz-approximately 1518 MHz, FDD), band 65 (B65) (e.g., approximately 1920 MHz-approximately 2010 MHz and approximately 2110 MHz-approximately 2200 MHz, FDD) etc. The 2.4 GHz Wi-Fi band has a frequency range of approximately 2403 MHz to approximately 2483 (or approximately 2483.5) MHz, which lies between B40 and B41 and can be utilized in wireless local area network (WLAN). 
       FIG.  1    illustrates an example of frequency bands that can be utilized in wireless communications, according to certain embodiments. For illustration purposes, the frequency range of approximately 1710 MHz to approximately 2400 MHz is illustrated as MB/HB 1 and the frequency range of approximately 2496 MHz to approximately 2690 MHz is illustrated as HB 2 in  FIG.  1   . Band B40 has a frequency range of approximately 2300 MHz to 2400 MHz, and Band B41 has a frequency range of approximately 2496 MHz to 2690 MHz. As illustrated in  FIG.  1   , a frequency gap between an upper channel of the MB/HB 1 band (specifically, an upper channel of B40) and a lower channel of Wi-Fi and is approximately 3 MHz. A frequency gap between an upper channel of Wi-Fi and a lower channel of the HB 2 band (specifically, B41) is approximately 13 MHz. 
     It will be appreciated that although the specific examples described herein relate to enabling the coexistence between 2.4 GHz Wi-Fi signals and adjacent frequency bands B40 and B41, features of the disclosure are not limited to such examples and may be applied to other adjacent frequency bands, e.g., to other Wi-Fi signals and their corresponding adjacent frequency bands. For example, similar principles may be applied when using the 5 GHz Wi-Fi band (ranging from approximately 5.15 GHz to approximately 5.85 GHz) and adjacent frequency band n79 (approximately 4.4 GHz to approximately 5.00 GHz), where the 5 GHz Wi-Fi band is separated from the n79 band by a frequency gap of approximately 15 MHz, or when using the 6 GHz Wi-Fi band (approximately 5.925 GHz to approximately 7.125 GHz) and adjacent frequency band B47 (approximately 5.855 GHz to 5.925 GHz), where there is effectively no frequency gap between the 6 GHz Wi-Fi band and the B47 band. 
     The implementation of the combination of Wi-Fi and cellular bands can be quite difficult on shared antenna systems that support both radio access technologies (RATs). This is because the frequency gap between these bands becomes quite small, as described above, such that the 2.4 GHz Wi-Fi is in extremely close proximity to the HB group, which includes bands both above (for example B41) and below (for example B40) the 2.4 GHz Wi-Fi band. Emissions and isolation between these bands for these RATs is a large challenge for attenuation, isolation, emissions and insertion loss. In particular, emissions due to an Adjacent Channel Leakage Ratio (ACLR), Spectrum Emission Mask (SEM) and out-of-band emissions should in certain cases be attenuated by more than approximately 35 to 40 dB to mitigate receive desense (RxDeSense) of the other RATs. 
     Some configurations use ganged band-pass filters in antenna plexers to facilitate isolation and merging of the various bands on to the common single antenna feed. An example switching circuit  200  is shown in the schematic diagram of  FIG.  2   , which can be implemented in, but is not limited to, a front end module, a front end configuration, a diversity receiver module, a multiple input multiple output (MiMo) module, etc. 
     The switching circuit  200  of  FIG.  2    comprises antennas  202 ,  204  coupled to an antenna port, an antenna switch  206  which may be implemented on an antenna switching module (ASM), ganged filters  212 ,  214 ,  218 , and control signal  208 . The switching circuit  200  is configured to transmit an RF transmit signal to antennas  202 ,  204 , receive an RF receive signal from the antennas  202 ,  204 , and route the RF receive signal to receive circuitry such as the ganged pass-band filters  212 ,  214 ,  218  for subsequent downconversion and baseband processing. The RF receive signal may be received as an FDD signal and/or a TDD signal, and have a specific frequency band configuration. For example, the signals may include single-band signals having data modulated onto a single frequency band, multi-band signals (also referred to as inter-band carrier aggregation signals) having data modulated onto multiple frequency bands and/or data modulated onto multiple frequency bands using different communication protocols. 
     In the illustrated embodiment, the antenna switch  206  is configured to receive an antenna swapping signal through the control signal  208  from a baseband subsystem that includes a processor and/or is based at least in part on the frequency band configuration. The antenna switch  206  is configured to connect the appropriate antenna(s)  202 ,  204  with ganged filters  212 ,  214 ,  218  based on the antenna swapping signal. Further, a sounding reference signal (SRS) is transmitted to a base station through at least one of the antennas  202 ,  204 . The base station may use the SRS for uplink frequency selective scheduling, such as SRS hopping supporting to be able to direct transmit signals to appropriate antennas  202 ,  204 . The connection paths of the antenna switch  206  illustrated in  FIG.  2    are for illustrative purposes only. The antenna switch  206  shown in the example of  FIG.  2    may not be present in some other configurations. However, the use of antenna switch  206  can enable integration of post-antenna plexer switching. 
     The RF signals can include at least one of TDD and/or FDD signal. The switching circuit  200  utilizes a filter  212  for filtering LB signals transmitted to and received from at least one of the antennas  202 ,  204 . The switching circuit  200  utilizes a filter  214  for filtering MB/HB signals transmitted to and received from at least one of the antennas  202 ,  204 . In an embodiment, filter  214  comprises a ganged MB band pass filter and an HB band pass filter. In an alternative embodiment, filter  214  may be a dual-band filter configured to pass both MB band frequencies and HB band frequencies. In an embodiment, the MB comprises a frequency range of approximately 1710 MHz to approximately 2400 MHz and the HB comprises a frequency range of approximately 2496 MHz to approximately 2690 MHz. The switching circuit  200  utilizes a filter  218  for filtering the 2.4 GHz Wi-Fi band signals transmitted to and received from at least one of the antennas  202 ,  204 . 
     In an embodiment, the filters  214 ,  218  can comprise band pass filter(s), whereas the filter  212  can comprise a low pass filter. The filters  212 ,  214 ,  218  can comprise surface acoustic wave (SAW) filters and/or bulk acoustic wave (BAW) filters. SAW and/or BAW devices utilize the piezoelectric effect to convert energy back and forth between the electrical and mechanical realms where the presence of an electrical field causes the material to deform and the application of a mechanical stress induces an electric charge. 
     As indicated above, it can be challenging to sufficiently attenuate OOB signals without suffering band edge insertion loss degradation for frequency bands that are in close proximity, such as where high frequency band B40 is relatively close to the low end of a 2.4 GHz Wi-Fi band and B41 is relatively close to the high end of the 2.4 GHz Wi-Fi band. 
     Embodiments of the disclosure mitigate such problems by providing a switching circuit that can reduce the operational bandwidth of the Wi-Fi and/or cellular RF bands to reduce insertion loss and improve isolation, as further described below. 
     A first embodiment of the disclosure enables reduced bandwidth for Wi-Fi signals by selecting either a high channel Wi-Fi band or a low channel Wi-Fi band. 
       FIG.  3    illustrates an example of how the 2.4 GHz Wi-Fi frequency band may be divided into two regions partially overlapping each other. In the illustrated embodiment, the full Wi-Fi band spanning frequencies from 2403 MHz to 2483 MHz can be divided into two overlapping regions, Wi-Fi A and Wi-Fi B. In one aspect, the overlapping region can support at least a 20 MHz bandwidth channel. For example, Wi-Fi A can have a range of approximately 2403 MHz to 2463 MHz and Wi-Fi B can have a range of approximately 2443 MHz to 2483 MHz. In another aspect, the overlapping region can support at least a 40 MHz bandwidth channel. For example, Wi-Fi A can have a range of approximately 2403 MHz to 2463 MHz and Wi-Fi B can have a range of approximately 2423 MHz to 2483 MHz. The ranges of Wi-Fi A, Wi-Fi B and the overlapping region can vary based on the Wi-Fi standard or required channel bandwidth. Separating the full Wi-Fi band into sub-bands Wi-Fi A and Wi-Fi B facilitates a larger gap between an upper channel of the MB/HB 1 band (B40) and a lower channel of Wi-Fi band (sub-band Wi-Fi B), and a larger gap between an upper channel of Wi-Fi (sub-band Wi-Fi A) and a lower channel of the HB 2 band (B41, or B7 Tx), as shown in  FIGS.  4 A and  4 B . 
       FIG.  4 A  illustrates an example of a frequency band configuration of B40 and sub-band Wi-Fi B without Wi-Fi A, B7 and B41. In this configuration, a gap between B40 and Wi-Fi B is approximately 20 MHz (when Wi-Fi B is selected as approximately 2423 MHz to 2483 MHz) or approximately 40 MHz (when Wi-Fi B is selected as approximately 2443 MHz to 2483 MHz). The gap between B40 and Wi-Fi B can vary depending on the division of the Wi-Fi band.  FIG.  4 B  illustrates an example of a frequency band configuration of B41 and/or B7 Tx and sub-band Wi-Fi A without B40 and Wi-Fi B. In this configuration, a gap between B41 and Wi-Fi A is approximately 33 MHz and a gap between B7 Tx and Wi-Fi A is approximately 37 MHz. These band configurations provide a frequency offset gap that is larger than 3 MHz, resulting in better out of band attenuation and lower in-band insertion loss. 
     Accordingly, the 2.4 GHz Wi-Fi band may be split into two overlapping frequency regions which may each be provided with separate RF filter paths. The frequency overlap is variable and dependent on the implementation, but can support at least 20 MHz channel placements, and potentially 40 MHz channels as illustrated in  FIG.  4 A . This depends on the Wi-Fi a/b/g/n/x standard that is supported by the implementation. Advantageously, splitting the Wi-Fi band into two regions (region “A” with excellent performance for the lower Wi-Fi 2.4 GHz channels, and region “B” with excellent performance for the upper Wi-Fi 2.4 GHz channels) provides that each respective filter is narrower in bandwidth, but also provides better OOB attenuation, lower in-band insertion loss (IL), and also provides a larger gap in frequency offset between its band edges and the cellular bands. 
       FIG.  5    is a schematic diagram of an embodiment of a switching circuit  500  configured to enable a signal to be routed through certain combinations of switches. The switching circuit  500  can be implemented in, but not limited to, a front end module, a front end configuration, a diversity receiver module, a multiple input multiple output (MiMo) module, etc. 
     In the illustrated embodiment, the switching circuit  500  comprises antennas  202 ,  204 , a filtering circuit  500 A comprising ASM  206 , control signal  208 , LB filter  212 , and MB/HB  214  filters as described above. The filtering circuit  500 A further comprises two Wi-Fi filters  512 ,  514  for filtering the 2.4 GHz Wi-Fi band signals transmitted to and received from at least one of the antennas  202 ,  204 . Each filter  512 ,  514  is implemented on a respective Wi-Fi signal path  522 ,  524  that each includes a switch  532 ,  534  for selecting one or more of the Wi-Fi signal paths. Advantageously, switches  532 ,  534  also enable filters  512 ,  514  to be completely disconnected when Wi-Fi is not concurrently active thereby enabling much lower insertion loss due to the reduced loading of filters  212 ,  214 . 
     Switching circuit  500  further comprises a Wi-Fi band select switch  542  that provides either the Wi-Fi A signal or Wi-Fi B signal to an output node on Wi-Fi signal path  552 , and in some embodiments the Wi-Fi band select switch  542  can be a single-pole/multiple-throw (SPMT) switch as shown in  FIG.  5   . A control signal (not shown) determines the configuration of the switches  532 ,  534  and the Wi-Fi band select switch  542  in order to provide either the Wi-Fi A signal or the Wi-Fi B signal to the Wi-Fi signal path  552 . 
     In the embodiment shown, the first filter  512  is configured to filter the low channel Wi-Fi band, e.g., Wi-Fi A having a range of approximately 2403 MHz to 2463 MHz, and the second filter  514  is configured to filter the high channel Wi-Fi band, e.g., Wi-Fi B having a range of approximately 2443 MHz to 2483 MHz or a range of approximately 2423 MHz to 2483 MHz. Switches  532 ,  534  are configured to switch-combine the appropriate Wi-Fi filter  512 ,  514  with the cellular LB filter  212  and/or cellular MB/HB filter  214  according to the received cellular frequency band and desired band separation, as described above. In some embodiments, the switches  532 ,  534  are implemented on the ASM  206 . 
     In the embodiment shown in  FIG.  5   , the filters  212 ,  214  are implemented as ganged filters on a single switchless LB/MB/HB signal path while filters  512 ,  514  are implemented in separate signal paths that may be connected in parallel to the main LB/MB/HB signal path via switch  532  and switch  534  respectively. This configuration can prevent loading of the cellular RF signals by the Wi-Fi signals. However, it will be appreciated that in alternative embodiments each of the cellular filters  212 ,  214  and Wi-Fi filters  512 ,  514  may be provided on separate signal paths having respective switches to route a receive signal to at least one of the plurality of signal paths corresponding to the frequency band of the single-band or multi-band receive signal. In such embodiments, the Wi-Fi band select switch  542  is not included. 
     A second embodiment of the disclosure enables the use of a reduced bandwidth of cellular RF signals. 
     As discussed above, B40 and B41 are commonly used high frequency bands that coexist very close to the 2.4 GHz Wi-Fi band frequency range.  FIG.  6    illustrates the relative separation between the 2.4 GHz Wi-Fi band and the conventional B40 and B41 bands as well as the relative separation between the 2.4 GHz Wi-Fi band and sub-bands B40A and B41N. As shown in  FIG.  6   , the 2.4 GHz Wi-Fi band has a frequency range of 2403 MHz to 2483 MHz, band B40 has a frequency range of 2300 MHz to 2400 MHz, and B41 has a frequency range of 2496 MHz to 2690 MHz. The gap between a lower channel of the Wi-Fi band and an upper channel of Band B40 is 3 MHz, and a gap between an upper channel of the Wi-Fi band and a lower channel of Band B41 is 13 MHz. As also shown in  FIG.  6   , Band B40A has a frequency range of 2300 MHz to 2370 MHz and Band B41N has a frequency range of 2515 MHz to 2675 MHz. Accordingly, a gap between a lower channel of Wi-Fi and an upper channel of B40A is 33 MHz, and a gap between an upper channel of Wi-Fi and a lower channel of B41N is 32 MHz. 
     As indicated above, using a band configuration of B40 and B41 with the 2.4 GHz Wi-Fi band results in a relatively small frequency offset gap of 3 MHz and 13 MHz respectively. However, the use of reduced bandwidth cellular bands B40A and B41N can provide a larger gap in frequency offset, resulting in better out of band attenuation and lower in-band insertion loss. 
       FIG.  7    is a schematic diagram of an embodiment of a switching circuit  700  configured to enable a signal to be routed through certain combinations of switches. The switching circuit  700  can be implemented in, but not limited to, a front end module, a front end configuration, a diversity receiver module, a multiple input multiple output (MiMo) module, etc. 
     In the illustrated embodiment, the switching circuit  700  comprises antennas  202 ,  204 , filtering circuit  700 A comprising ASM  206 , control signal  208 , LB cellular filter  212  and a 2.4 GHz Wi-Fi filter  218  as described above. The filtering circuit  700 A further comprises two cellular filters  712 ,  714  for filtering the MB and HB signals transmitted to and received from at least one of the antennas  202 ,  204 . Each filter  712 ,  714  is implemented on a respective cellular signal path  722 ,  724  that each includes a switch  732 ,  734  for selecting one or more of the cellular signal paths. Advantageously, switches  732 ,  734  also enable filters  512 ,  514  to be completely disconnected when MB/HB cellular signals are not active thereby enabling much lower insertion loss due to the reduced loading of filters  212 ,  218 . 
     The switching circuit  700  further comprises a cellular band select switch  742  that provides the output from either filter  712  or  714  to an output node on cellular MB/HB signal path  752 . Accordingly, the cellular band select switch  742  provides either a first, full bandwidth, RF signal MHB1 or a second, reduced bandwidth, RF signal MHB2 to the cellular signal path  752 . In some embodiments, the first filter  712  is configured to pass frequencies in the range of between 1710 MHz to 2400 MHz and between 2496 MHz to 2690 MHz while the second filter  714  is configured to pass a reduced frequency range of between 1710 MHz to 2370 MHz and between 2515 MHz to 2675 MHz. In some embodiments, the first filter  712  is configured to filter at least bands B40 and B41 while the second filter  714  is configured to filter sub-bands B40A and B41N. 
     Switches  732 ,  734  are configured to switch-combine the appropriate MB/HB filter  712 ,  714  with the cellular LB filter  212  and 2.4 GHz Wi-Fi filter  218  according to whether the Wi-Fi band is being used and the desired band separation. In some embodiments the cellular band select switch  742  can be a single-pole/multiple-throw (SPMT) switch, as shown in  FIG.  7   . A control signal (not shown) may determine the configuration of the switches  732 ,  734  and the cellular band select switch in order to provide either the full bandwidth (e.g. B40 and B41) signal or the reduced bandwidth (e.g. B40A and B41N) signal to the cellular signal path  752 . 
     In the embodiment shown in  FIG.  7   , the filters  212 ,  218  are implemented as switchless signal paths while filters  712 ,  714  are implemented in separate signal paths that may be connected in parallel to the LB signal path and Wi-Fi signal path via switches  732 ,  734  respectively. This configuration can prevent loading of the Wi-Fi signals by the cellular HB signals. However, it will be appreciated that in alternative embodiments each filter may be implemented on a separate signal path having a respective switch to route a receive signal to at least one of the plurality of signal paths that corresponds to the frequency band of the single-band or multi-band receive signal. In such embodiments, the cellular band select switch  742  is not included. 
     A third embodiment of the disclosure enables the reduction in bandwidth of either or both Wi-Fi and cellular RF signals. 
       FIG.  8    is a schematic diagram of an embodiment of a switching circuit  800  comprising antennas  202 ,  204 , filtering circuit  800 A comprising ASM  206 , control signal  208  and LB cellular filter  212  as described above. The filtering circuit  800 A further comprises two Wi-Fi filters  512 ,  514  for filtering the 2.4 GHz Wi-Fi band signals and two cellular filters  712 ,  714  for filtering the MB and HB signals transmitted to and received from at least one of the antennas  202 ,  204 . 
     As described above, each filter  512 ,  514 ,  712 ,  714  is implemented on a respective cellular signal path  522 ,  524 ,  722 ,  724  that each includes a switch  532 ,  534 ,  732 ,  734  for selecting one or more of the Wi-Fi or cellular signal paths. A Wi-Fi band select switch  542  provides either the Wi-Fi A signal or Wi-Fi B signal to a Wi-Fi signal path  552  while a cellular band select switch  742  provides either the full bandwidth MB/HB signal band (e.g. bands B40 and B41) or a reduced bandwidth MB/HB signal (e.g. sub-bands B40A and B41N) to cellular MB/HB signal path  752 . Although filter  212  is implemented as a switchless signal path it will be appreciated that in alternative embodiments each filter may be implemented on a separate signal path having a respective switch to route a receive signal to at least one of the plurality of signal paths that corresponds to the frequency band of the single-band or multi-band receive signal. 
     The third embodiment advantageously enables optimization of the insertion loss and attenuation by selecting the appropriate Wi-Fi and/or cellular band signal path. 
       FIG.  9    shows an example method  900  that can be implemented by a switching circuit to filter received radio-frequency signals as described herein. In a first step  902  the process starts. In a second step  904  the switching circuit filters a first frequency range with a first filter. In a third step  906  the switching circuit filters a first region of the first frequency range with a second filter. In a fourth step  908  the switching circuit filters a second frequency range with a third filter. In a fifth step  910  the switching circuit selects the first filter or the second filter based on a control signal using one or more switches. The process ends at a final step  912 . 
       FIG.  10 A  is an exemplary block diagram of switching module  1000 . In the illustrated embodiment, a multimode semiconductor die  1002  can include one or more of the switching circuits  500 ,  700 ,  800  of  FIGS.  5 ,  7 , and  8    respectively, that include filtering circuits  500 A,  700 A and  800 A and switches  552 ,  752 .  FIG.  10 B  is an exemplary block diagram of a multi-chip switching module  1010 . In an embodiment, filter circuits  500 A,  700 A and  800 A may be implemented on a filter die  1012  while switches  552 ,  752  may be implemented on switch die  1014 .  FIG.  10 C  is an exemplary block diagram of a multi-chip switching module  1020  including the switch die  1014  and a plurality of SAW or BAW filters  1022 , which can form some or all of the filters in the filter circuits  500 A,  700 A,  800 A. The multi-chip module  1020  can further include power amplifier (PA) circuitry  1024 . 
     The modules  1000 ,  1010 ,  1020  can further include connectivity  1032  to provide signal interconnections, packaging  1034 , such as for example, a package substrate, for packaging of the circuitry, and other circuitry die  1036 , such as, for example amplifiers, pre-filters, post filters modulators, demodulators, down converters, and the like, as would be known to one of skill in the art of semiconductor and multi-chip module fabrication in view of the disclosure herein. 
       FIG.  11    is an exemplary block diagram illustrating a simplified wireless device  1100 . The wireless device  1100  can include one or more of the switching circuits  500 ,  700 ,  800  of  FIGS.  5 ,  7 , and  8   , respectively, for example. 
     The wireless device  1100  includes a speaker  1102 , a display  1104 , a keyboard  1106 , and a microphone  1108 , all connected to a baseband subsystem  1110 . A power source  1142 , which may be a direct current (DC) battery or other power source, is also connected to the baseband subsystem  1110  to provide power to the wireless device  1100 . In a particular embodiment, the wireless device  1100  can be, for example but not limited to, a portable telecommunication device such as a mobile cellular-type telephone. The speaker  1102  and the display  1104  receive signals from baseband subsystem  1110 , as known to those skilled in the art. Similarly, the keyboard  1106  and the microphone  1108  supply signals to the baseband subsystem  1110 . The baseband subsystem  1110  includes a microprocessor (μP)  1120 , memory  1122 , analog circuitry  1124 , and a digital signal processor (DSP)  1126  in communication via bus  1128 . Bus  1128 , although shown as a single bus, may be implemented using multiple busses connected as necessary among the subsystems within the baseband subsystem  1110 . The baseband subsystem  1110  may also include one or more of an application specific integrated circuit (ASIC)  1132  and a field programmable gate array (FPGA)  1130 . 
     The microprocessor  1120  and memory  1122  provide the signal timing, processing, and storage functions for wireless device  1100 . The analog circuitry  1124  provides the analog processing functions for the signals within baseband subsystem  1110 . The baseband subsystem  1110  provides control signals to a transmitter  1150 , a receiver  1170 , a power amplifier  1180 , and a switching module  1190 , for example. 
     It should be noted that, for simplicity, only the basic components of the wireless device  1100  are illustrated herein. The control signals provided by the baseband subsystem  1110  control the various components within the wireless device  1100 . Further, the function of the transmitter  1150  and the receiver  1170  may be integrated into a transceiver. 
     The baseband subsystem  1110  also includes an analog-to-digital converter (ADC)  1134  and digital-to-analog converters (DACs)  1136  and  1138 . In this example, the DAC  1136  generates in-phase (I) and quadrature-phase (Q) signals  1140  that are applied to a modulator  1152 . The ADC  1134 , the DAC  1136 , and the DAC  1138  also communicate with the microprocessor  1120 , the memory  1122 , the analog circuitry  1124 , and the DSP  1126  via bus  1128 . The DAC  1136  converts the digital communication information within baseband subsystem  1110  into an analog signal for transmission to the modulator  1152  via connection  1140 . Connection  1140 , while shown as two directed arrows, includes the information that is to be transmitted by the transmitter  1150  after conversion from the digital domain to the analog domain. 
     The transmitter  1150  includes the modulator  1152 , which modulates the analog information on connection  1140  and provides a modulated signal to upconverter  1154 . The upconverter  1154  transforms the modulated signal to an appropriate transmit frequency and provides the upconverted signal to the power amplifier  1180 . The power amplifier  1180  amplifies the signal to an appropriate power level for the system in which the wireless device  1100  is designed to operate. 
     Details of the modulator  1152  and the upconverter  1154  have been omitted, as they will be understood by those skilled in the art. For example, the data on connection  1140  is generally formatted by the baseband subsystem  1110  into in-phase (I) and quadrature (Q) components. The I and Q components may take different forms and be formatted differently depending upon the communication standard being employed. 
     The power amplifier  1180  supplies the amplified signal to a front-end module  1162 , where the amplified signal is conditioned and filtered by one or more signal conditioning filters for transmission. The front end module  1162  comprises an antenna system interface that may include, for example, the switching circuit  1190  configured to switch a signal between the antenna  1160 , the receiver  1170 , and the power amplifier  1180  (receiving the RF transmit signal from the transmitter  1150 ), as described herein to implement FDD and TDD in a shared band. For example, the switching circuit  1190  can include one or more of the switching circuits  500 ,  700 ,  800  of  FIGS.  5 ,  7 , and  8   , respectively. The RF transmit signal is supplied from the front-end module  1162  to the antenna  1160 . In an embodiment, the antenna  1160  comprises an FDD/TDD antenna. 
     In an embodiment, the switching circuit  1190  comprises the switching module  1000  including the semiconductor die  1002 . In another embodiment, switching circuit  1190  comprises the switching module  1010  including the filtering semiconductor die  1012  and the switching semiconductor die  1014 . In a further embodiment, the switching circuit  1190  comprises the multi-chip module  1020  including one or more SAW or BAW filters  1022  and the switching semiconductor die  1014 . In such embodiments, the switching circuit  1190  can comprises one or more of the switching circuits  500 ,  700 ,  800  of  FIGS.  5 ,  7 , and  8   , respectively. 
     A signal received by antenna  1160  will be directed from the front-end module  1162  to the receiver  1170 . The receiver  1170  includes low noise amplifier circuitry  1172 , a downconverter  1174 , a filter  1176 , and a demodulator  1178 . 
     If implemented using a direct conversion receiver (DCR), the downconverter  1174  converts the amplified received signal from an RF level to a baseband level (DC), or a near-baseband level (approximately 100 kHz). Alternatively, the amplified received RF signal may be downconverted to an intermediate frequency (IF) signal, depending on the application. The downconverted signal is sent to the filter  1176 . The filter  1176  comprises a least one filter stage to filter the received downconverted signal as known in the art. 
     The filtered signal is sent from the filter  1176  to the demodulator  1178 . The demodulator  1178  recovers the transmitted analog information and supplies a signal representing this information via connection  1186  to the ADC  1134 . The ADC  1134  converts these analog signals to a digital signal at baseband frequency and transfers the signal via bus  1128  to the DSP  1126  for further processing. 
     Having described above several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only, and the scope of the invention should be determined from proper construction of the appended claims, and their equivalents. 
     It is to be appreciated that embodiments of the methods and apparatuses discussed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The methods and apparatuses are capable of implementation in other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. 
     Throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” The words “coupled” or “connected”, as generally used herein, refer to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word “or” in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. 
     Moreover, conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment. 
     The above detailed description of certain embodiments is not intended to be exhaustive or to limit the invention to the precise form disclosed above. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those ordinary skilled in the relevant art will recognize in view of the disclosure herein. 
     For example, while processes or blocks are presented in a given order, alternative embodiments may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified. Each of these processes or blocks may be implemented in a variety of different ways. In addition, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel, or may be performed at different times. 
     The teachings of the invention provided herein can be applied to other systems, not necessarily the systems described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments. 
     While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions, and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.