PATENT DOCUMENT

Publication Number: US-11817896-B2
Application Number: US-202217582872-A
Country: US
Kind Code: B2

Title: Wideband balanced duplexer

Abstract:
Embodiments disclosed herein relate to isolating a receiver circuit of an electronic device from a transmission signal and leakage of the transmission signal. To do so, an isolation circuit is disposed between the receiver circuit and a transmission circuit. The isolation circuit may include multiple variable impedance devices and one or more antennas. The impedances of the variable impedance devices may be balanced such that a signal at a particular frequency or within a particular frequency band can pass through or is blocked by the isolation circuit. The isolation circuit may include one or more double balanced duplexers to achieve the improved isolation. The isolation circuit may also increase bandwidth available for wireless communications of the electronic device.

Claims:
The invention claimed is: 
     
       1. An electronic device comprising:
 one or more antennas; 
 transmit circuitry configured to send a transmission signal to the one or more antennas; 
 receive circuitry configured to receive a reception signal from the one or more antennas; and 
 isolation circuitry configured to isolate the receive circuit from the transmission signal, the isolation circuitry comprising
 a first balun coupled between the one or more antennas and the receive circuitry, 
 a first variable impedance device coupled to the first balun, 
 a second variable impedance device coupled to the first balun, 
 a second balun coupled to the one or more antennas and the transmit circuitry, 
 a third variable impedance device coupled to the second balun, and 
 a fourth variable impedance device coupled to the second balun. 
 
 
     
     
       2. The electronic device of  claim 1 , wherein the isolation circuitry is configured to isolate the receive circuitry from the transmission signal when the first variable impedance device and the second variable impedance device are in a balanced state. 
     
     
       3. The electronic device of  claim 1 , wherein the first variable impedance device and the second variable impedance device are coupled to opposing ends of a first set of coils of the first balun, and wherein the third variable impedance device and the fourth variable impedance device are coupled to opposing ends of a second set of coils of the first balun. 
     
     
       4. The electronic device of  claim 3 , wherein the receive circuitry is coupled to the first balun between the first set of coils, and wherein the transmit circuitry is coupled to the second balun between the second set of coils. 
     
     
       5. The electronic device of  claim 1 , comprising
 a fifth variable impedance device coupled to the first balun, 
 a sixth variable impedance device coupled to the first balun, 
 a seventh variable impedance device coupled to the second balun, and 
 an eighth variable impedance device coupled to the second balun. 
 
     
     
       6. The electronic device of  claim 5 , wherein the first balun is configured to isolate the receive circuitry from the transmission signal when the fifth variable impedance device and the sixth variable impedance device are in a balanced state at a frequency of the transmission signal. 
     
     
       7. The electronic device of  claim 1 , wherein the isolation circuitry comprises
 a third balun coupled between one or more antennas and the receive circuitry configured to prevent a leakage current at a frequency of the transmission signal from entering the receive circuitry, and 
 a fourth balun coupled to the one or more antennas and the transmit circuitry configured to isolate the transmit circuitry from the reception signal. 
 
     
     
       8. The electronic device of  claim 1 , wherein the first balun is disposed in parallel with the second balun. 
     
     
       9. Radio frequency transceiver circuitry comprising:
 transmit circuitry communicatively coupled to one or more antennas, the transmit circuitry configured to send a transmission signal to the one or more antennas; 
 receive circuitry communicatively coupled to the one or more antennas, the receive circuitry configured to receive a reception signal from the one or more antennas; and 
 isolation circuitry comprising
 a first balun transformer coupled between the one or more antennas and the receive circuitry, 
 a first set of variable impedance devices coupled to the first balun transformer, the first set of variable impedance devices configured to isolate the receive circuitry from the transmission signal when the first set of variable impedance devices are in a balanced state, 
 a second balun transformer coupled between the one or more antennas and the transmit circuitry, and 
 a second set of variable impedance devices coupled to the second balun transformer, the second set of variable impedance devices configured to isolate the transmit circuitry from the reception signal when the second set of variable impedance devices are in the balanced state. 
 
 
     
     
       10. The radio frequency transceiver circuitry of  claim 9 , wherein the first balun transformer comprises a first set of coils, the first set of variable impedance devices comprises first and second variable impedance devices coupled to opposing ends of the first set of coils, the second balun transformer comprises a second set of coils, and the second set of variable impedance devices comprises third and fourth variable impedance devices coupled to opposing ends of the second set of coils. 
     
     
       11. The radio frequency transceiver circuitry of  claim 9 , wherein the first set of variable impedance devices and the second set of variable impedance devices are configured to isolate the receive circuitry from the transmission signal when in the balanced state and enable the receive circuitry to receive the reception signal from the one or more antennas when in an unbalanced state. 
     
     
       12. The radio frequency transceiver circuitry of  claim 9 , wherein the reception signal is within a first frequency range, and the transmission signal is within a second frequency range. 
     
     
       13. The radio frequency transceiver circuitry of  claim 12 , wherein the first frequency range is greater than 100 megahertz (MHz) and the second frequency range is between 10 MHz and 100 MHz. 
     
     
       14. An electronic device comprising:
 one or more antennas; 
 first isolation circuitry coupled to the one or more antennas, the first isolation circuitry comprising a first balun coupled to the one or more antennas and a first set of variable impedance devices; 
 a first duplexer coupled to the first balun; 
 second isolation circuitry coupled to the one or more antennas, the second isolation circuitry comprising a second balun coupled to a second set of variable impedance devices; and 
 a second duplexer coupled to the second balun. 
 
     
     
       15. The electronic device of  claim 14 , wherein the first isolation circuitry comprises
 a third balun coupled to the one or more antennas and a third set of impedance devices, the first duplexer coupled to the third balun. 
 
     
     
       16. The electronic device of  claim 15 , wherein the second isolation circuitry comprises
 a fourth balun coupled to the one or more antennas and a fourth set of impedance devices, the second duplexer coupled to the fourth balun. 
 
     
     
       17. The electronic device of  claim 16 , the first duplexer comprising
 a first plurality of variable impedance devices coupled to opposing ends of a first set of coils of the first balun, and 
 a second plurality of variable impedance devices coupled to opposing ends of a second set of coils of the second balun. 
 
     
     
       18. The electronic device of  claim 14 , wherein the first balun is coupled in parallel with the second balun. 
     
     
       19. The electronic device of  claim 14 , wherein the first duplexer comprises
 a third balun coupled to the one or more antennas and receive circuitry, the receive circuitry configured to receive a reception signal from the one or more antennas, and 
 a fourth balun coupled to the one or more antennas and transmit circuitry, the transmit circuitry configured to send a transmission signal to the one or more antennas. 
 
     
     
       20. The electronic device of  claim 19 , wherein the second duplexer comprises
 a fifth balun coupled to the one or more antennas and the receive circuitry, 
 a first plurality of variable impedance devices coupled to the fifth balun, 
 a sixth balun coupled to the one or more antennas and the transmit circuitry, and 
 a second plurality of variable impedance devices coupled to the sixth balun.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and benefit of U.S. patent application Ser. No. 17/116,360, filed Dec. 9, 2020, and entitled “WIDEBAND BALANCED DUPLEXER,” which is incorporated herein by reference in its entirety for all purposes. 
     BACKGROUND 
     The present disclosure relates generally to wireless communication, and more specifically to isolation of high bandwidth wireless signals between transmitters and receivers in wireless communication devices. 
     In an electronic device, a transmitter and a receiver may each be coupled to an antenna to enable the electronic device to both transmit and receive wireless signals. The electronic device may include an electrical balanced duplexer (EBD) that isolates the transmitter from received signals of a first frequency range, and isolates the receiver from transmission signals of a second frequency range (e.g., thus implementing frequency division duplex (FDD) operations). In this manner, interference between the transmission and received signals may be reduced when communicating using the electronic device. However, these communications may be negatively impacted by insertion loss resulting from components of the EBD providing less than ideal isolation of the transmission and/or received signals. Moreover, a bandwidth of an EBD or conventional double balanced duplexer may not be sufficient to support high bandwidth (e.g., greater than 10 MHz) operations. 
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     An aspect of the disclosure provides an electronic device that may have one or more antennas. The electronic device may have transmit circuitry that sends a transmission signal to the one or more antennas and receive circuitry that receives a reception signal from the one or more antennas. The electronic device may have isolation circuitry including a first balun coupled to the one or more antennas and the transmit circuitry may isolate the transmit circuitry from the reception signal. The isolation circuitry may have a second balun coupled to the one or more antennas and the transmit circuitry in parallel with the first balun. The second balun may prevent a leakage signal from the transmit circuitry from entering the receive circuitry. 
     Another aspect of the disclosure provides radio frequency transceiver circuitry that may have transmit circuitry communicatively coupled to one or more antennas. The radio frequency transceiver circuitry may have receive circuitry communicatively coupled to the one or more antennas. The radio frequency transceiver circuitry may have a first duplexer coupled to and disposed between the receive circuitry and the one or more antennas. The first duplexer may have a first balun transformer and a first set of variable impedance devices coupled to the first balun transformer. The radio frequency transceiver circuitry may have a second duplexer coupled to and disposed between the receive circuitry and the one or more antennas. The second duplexer may have a second balun transformer and a second set of variable impedance devices coupled to the second balun transformer. 
     Another aspect of the disclosure provides a user equipment including one or more antennas and a power amplifier. The user equipment may have isolation circuitry having a first transformer coupled to and disposed between the power amplifier and the one or more antennas. The isolation circuitry may have a first variable impedance device coupled to the first transformer, and a second variable impedance device coupled to the first transformer. The isolation circuitry may have a second transformer coupled to and disposed between the power amplifier and the one or more antennas. The second transformer may be disposed in parallel with the first transformer. The isolation circuitry may have a third variable impedance device coupled to the second transformer, and a fourth variable impedance device coupled to the second transformer. 
     Various refinements of the features noted above may exist in relation to various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings described below in which like numerals refer to like parts. 
         FIG.  1    is a block diagram of an electronic device, according to an embodiment of the present disclosure. 
         FIG.  2    is a functional block diagram of the electronic device of  FIG.  1    that may implement the components shown in  FIG.  1    and/or the circuitry and/or components described in the following figures, according to embodiments of the present disclosure. 
         FIG.  3    is a block diagram of example transceiver circuitry of the electronic device of  FIG.  1   , according to an embodiment of the present disclosure. 
         FIG.  4 A  is a schematic diagram of a receiver circuit of the example transceiver circuitry of  FIG.  3   , according to an embodiment of the present disclosure. 
         FIG.  4 B  is a schematic diagram of a transmitter circuit of the example transceiver circuitry of  FIG.  3   , according to an embodiment of the present disclosure. 
         FIG.  5    is a schematic diagram of the example transceiver circuitry of  FIG.  3    having baluns to isolate the transmitter/receiver circuits from received/transmission signals and baluns to reduce insertion loss, according to an embodiment of the present disclosure. 
         FIG.  6    is a schematic diagram of an example duplexer of the transceiver circuitry of  FIG.  3    having additional variable impedance devices to enhance isolation, according to an embodiment of the present disclosure. 
         FIG.  7    is a schematic diagram of an example double balanced duplexer implemented with the duplexer of  FIG.  6   , according to an embodiment of the present disclosure. 
         FIG.  8    is a schematic diagram of an example quadplexer module of the transceiver circuitry of the electronic device of  FIG.  1   , according to an embodiment of the present disclosure. 
         FIG.  9    is a schematic diagram illustrating example components of the example quadplexer module of  FIG.  8   , according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Use of the term “approximately,” “near,” “about”, and/or “substantially” should be understood to mean including close to a target (e.g., design, value, amount), such as within a margin of any suitable or contemplatable error (e.g., within 0.1% of a target, within 1% of a target, within 5% of a target, within 10% of a target, within 25% of a target, and so on). 
     This disclosure is directed to isolation of wireless signals between transmitters and receivers in wireless communication devices using a double balanced duplexer (DBD). When using a DBD in an electronic device to isolate a transmitter from received signals and isolate a receiver from transmission signals, variable impedance devices (e.g., impedance gradients, impedance tuners) may be used to place baluns (e.g., transformers) of the DBD in balanced and unbalanced states to block and enable pass-through of signals. For example, an impedance gradient coupled to a balun may function as a filter with a high impedance in a pass band and a low impedance in the block (e.g., stop) band. Conversely, an impedance tuner coupled to the balun may function as a filter with a low impedance in the pass band and a high impedance in the block band. As a result, in the pass band, the balun is unbalanced, and signals having frequencies in the pass band pass through the balun. In the block band, the balun is balanced, and signals are destructively combined at the balun. However, the bandwidth of the pass band of the DBD may be limited (e.g., to about 10 megahertz (MHz)). Further, insertion loss (e.g., lost power) caused by non-ideal components of the DBD operating in real-world conditions may degrade communication capabilities of the DBD. 
     Embodiments herein provide various apparatuses and techniques to reduce insertion loss while increasing the bandwidth of the DBD and maintaining or improving isolation of the transmitter and receiver of an electronic device. To do so, the embodiments disclosed herein include isolation circuitry that may have a first balun coupled between a transmitter and an antenna that isolates the transmitter from received signals received by the antenna, and enables transmission signals sent from the transmitter to pass through to the antenna. The isolation circuitry may also have a second balun coupled between the transmitter and the antenna that substantially prevents, reduces, or mitigates a leakage signal from the transmitter to a receiver. The isolation circuitry may further include a third balun coupled between the antenna and the receiver that isolates the receiver from the transmission signals, and enables the received signals to pass from the antenna to the receiver. The isolation circuitry may additionally include a fourth balun that substantially prevents, reduces, or mitigates a leakage signal from the antenna to the transmitter. 
     Each balun may include a set of coils, such as four coils. In some embodiments, one pair of the coils (e.g., on a transmitter side of the balun, on a receiver side of the balun, on an antenna side of the balun) may be coupled to variable impedance devices that are tunable to place the respective balun in a balanced or unbalanced state. In such embodiments, the other pair of coils may not be coupled to such variable impedance devices. However, in some embodiments, each pair of coils of the balun may be coupled to variable impedance devices, such that each pair may operate in the balanced state to enhance isolation of the receiver from transmission signals and/or enhance isolation of the transmitter from received signals. 
       FIG.  1    is a block diagram of an electronic device  10 , according to an embodiment of the present disclosure. The electronic device  10  may include, among other things, one or more processors  12  (collectively referred to herein as a single processor for convenience, which may be implemented in any suitable form of processing circuitry), memory  14 , nonvolatile storage  16 , a display  18 , input structures  22 , an input/output (I/O) interface  24 , a network interface  26 , and a power source  29 . The various functional blocks shown in  FIG.  1    may include hardware elements (including circuitry), software elements (including computer code stored on a computer-readable medium) or a combination of both hardware and software elements. The processor  12 , memory  14 , the nonvolatile storage  16 , the display  18 , the input structures  22 , the input/output (I/O) interface  24 , the network interface  26 , and/or the power source  29  may each be communicatively coupled directly or indirectly (e.g., through or via another component, a communication bus, a network) to one another to transmit and/or receive data between one another. It should be noted that  FIG.  1    is merely one example of a particular implementation and is intended to illustrate the types of components that may be present in electronic device  10 . 
     By way of example, the electronic device  10  may represent a block diagram of any suitable computing device, including a desktop computer, a notebook computer, a portable electronic or handheld electronic device (e.g., a wireless electronic device or smartphone), a tablet, a wearable electronic device, and other similar devices. It should be noted that the processor  12  and other related items in  FIG.  1    may be generally referred to herein as “data processing circuitry.” Such data processing circuitry may be embodied wholly or in part as software, software, hardware, or any combination thereof. Furthermore, the processor  12  and other related items in  FIG.  1    may be a single contained processing module or may be incorporated wholly or partially within any of the other elements within the electronic device  10 . The processor  12  may be implemented with any combination of general-purpose microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate array (FPGAs), programmable logic devices (PLDs), controllers, state machines, gated logic, discrete hardware components, dedicated hardware finite state machines, or any other suitable entities that may perform calculations or other manipulations of information. The processors  12  may perform the various functions described herein and below. 
     In the electronic device  10  of  FIG.  1   , the processor  12  may be operably coupled with a memory  14  and a nonvolatile storage  16  to perform various algorithms. Such programs or instructions executed by the processor  12  may be stored in any suitable article of manufacture that includes one or more tangible, computer-readable media. The tangible, computer-readable media may include the memory  14  and/or the nonvolatile storage  16 , individually or collectively, to store the instructions or routines. The memory  14  and the nonvolatile storage  16  may include any suitable articles of manufacture for storing data and executable instructions, such as random-access memory, read-only memory, rewritable flash memory, hard drives, and optical discs. In addition, programs (e.g., an operating system) encoded on such a computer program product may also include instructions that may be executed by the processor  12  to enable the electronic device  10  to provide various functionalities. 
     In certain embodiments, the display  18  may facilitate users to view images generated on the electronic device  10 . In some embodiments, the display  18  may include a touch screen, which may facilitate user interaction with a user interface of the electronic device  10 . Furthermore, it should be appreciated that, in some embodiments, the display  18  may include one or more liquid crystal displays (LCDs), light-emitting diode (LED) displays, organic light-emitting diode (OLED) displays, active-matrix organic light-emitting diode (AMOLED) displays, or some combination of these and/or other display technologies. 
     The input structures  22  of the electronic device  10  may enable a user to interact with the electronic device  10  (e.g., pressing a button to increase or decrease a volume level). The I/O interface  24  may enable electronic device  10  to interface with various other electronic devices, as may the network interface  26 . The network interface  26  may include, for example, one or more interfaces for a personal area network (PAN), such as a BLUETOOTH® network, for a local area network (LAN) or wireless local area network (WLAN), such as a network employing one of the IEEE 802.11x family of protocols (e.g., WI-FI®), and/or for a wide area network (WAN), such as any standards related to the Third Generation Partnership Project (3GPP), including, for example, a 3 rd  generation (3G) cellular network, universal mobile telecommunication system (UMTS), 4 th  generation (4G) cellular network, long term evolution (LTE®) cellular network, long term evolution license assisted access (LTE-LAA) cellular network, 5 th  generation (5G) cellular network, and/or New Radio (NR) cellular network. In particular, the network interface  26  may include, for example, one or more interfaces for using a Release-15 cellular communication standard of the 5G specifications that include the millimeter wave (mmWave) frequency range (e.g., 24.25-300 gigahertz (GHz)). The network interface  26  of the electronic device  10  may allow communication over the aforementioned networks (e.g., 5G, Wi-Fi, LTE-LAA, and so forth). 
     The network interface  26  may also include one or more interfaces for, for example, broadband fixed wireless access networks (e.g., WIMAX®), mobile broadband Wireless networks (mobile WIMAX®), asynchronous digital subscriber lines (e.g., ADSL, VDSL), digital video broadcasting-terrestrial (DVB-T®) network and its extension DVB Handheld (DVB-H®) network, ultra-wideband (UWB) network, alternating current (AC) power lines, and so forth. 
     As illustrated, the network interface  26  may include a transceiver  30 . In some embodiments, all or portions of the transceiver  30  may be disposed within the processor  12 . The transceiver  30  may support transmission and receipt of various wireless signals via one or more antennas (not shown in  FIG.  1   ). In some cases, an impedance of the one or more antennas may disturb the duplex function and degrade isolation between the transmit path and the receive path. To prevent such disruption by the one or more antennas, a variable impedance device, such as an impedance tuner, may be used to substantially match an impedance of the antenna. 
     In some embodiments, the transceiver  30  may include a duplexer (not shown in  FIG.  1   ). A duplexer enables bidirectional communication over a single path while separating signals traveling in each direction from one another. For example, the duplexer may enable frequency division duplexing (FDD), such that the duplexer may isolate a transmitter of the electronic device  10  from a received signal of a first frequency band while isolating a receiver of the electronic device  10  from a transmission signal of a second frequency band (e.g., isolate the transmitter from the receiver, and vice versa). In some embodiments, the duplexer may include multiple variable impedance devices that isolate the transmitter from a received signal and/or isolates the receiver from a transmission signal. The duplexer may include an electrical balanced duplexer, a double balanced duplexer, or any other suitable form of duplexer. 
     The power source  29  of the electronic device  10  may include any suitable source of power, such as a rechargeable lithium polymer (Li-poly) battery and/or an alternating current (AC) power converter. In certain embodiments, the electronic device  10  may take the form of a computer, a portable electronic device, a wearable electronic device, or other type of electronic device. 
       FIG.  2    is a functional block diagram of the electronic device  10  that may implement the components shown in  FIG.  1    and/or the circuitry and/or components described in the following figures, according to embodiments of the present disclosure. As illustrated, the processor  12 , the memory  14 , the transceiver  30 , the transmitter  52 , the receiver  54 , and/or the antennas  55  (illustrated as  55   a - 55   n ) may be communicatively coupled directly or indirectly (e.g., through or via another component, a communication bus, a network) to one another to transmit and/or receive data between one another. 
     The electronic device  10  may include the transmitter  52  and/or the receiver  54  that respectively enable transmission and reception of data between the electronic device  10  and a remote location via, for example, a network or direction connection associated with the electronic device  10  and an external transceiver (e.g., in the form of a cell, eNB (E-UTRAN Node B or Evolved Node B), base stations, and the like. As illustrated, the transmitter  52  and the receiver  54  may be combined into the transceiver  30 . The electronic device  10  may also have one or more antennas  55   a  through  55   n  electrically coupled to the transceiver  30 . The antennas  55   a - 55   n  may be configured in an omnidirectional or directional configuration, in a single-beam, dual-beam, or multi-beam arrangement, and so on. Each antenna  55  may be associated with a one or more beams and various configurations. In some embodiments, each beam, when implement as multi-beam antennas, nay have its own transceiver  30 . The electronic device  10  may include (not shown) multiple transmitters, multiple receivers, multiple transceivers, and/or multiple antennas as needed for various communication standards. 
     The transmitter  52  may be configured to wirelessly transmit packets having different packet types or functions. For example, the transmitter  52  may be configured to transmit packets of different types generated by the processor  12 . The receiver  54  may be configured to wirelessly receive packets having different packet types. In some examples, the receiver  54  may be configured to detect a type of a packet used and to process the packet accordingly. In some embodiments, the transmitter  52  and the receiver  54  may be configured to transmit and receive information via other wired or wireline systems or means. 
     As illustrated, the various components of the electronic device  10  may be coupled together by a bus system  56 . The bus system  56  may include a data bus, for example, as well as a power bus, a control signal bus, and a status signal bus, in addition to the data bus. The components of the electronic device  10  may be coupled together or accept or provide inputs to each other using some other mechanism. 
     As mentioned above, the transceiver  30  of the electronic device  10  may include a transmitter and a receiver that are coupled to at least one antenna to enable the electronic device  10  to transmit and receive wireless signals. The electronic device  10  may include isolation circuity having one or more baluns coupled to multiple variable impedance devices that isolate the transmitter from received signals, and the receiver from transmission signals, thus reducing interference when communicating. In particular, a pair of variable impedance devices coupled to a balun may be tuned to a balanced state to block signals of a certain frequency range (e.g., a block band) from passing through, and may be tuned to an unbalanced state to enable signals of another frequency range (e.g., a pass band) to pass through. However, the transmission path for transmission signals sent from the transmitter may branch from the antenna toward the receiver. Accordingly, the branched transmission signal that travels in the direction of the receiver may be a leakage signal that can interfere with signals received by the antenna. Further, in some cases, a portion of the signals received by the antennas may branch toward the transmitter. The branched received signal that travels in the direction of the transmitter may be an additional or alternative leakage signal that can interfere with signals to be transmitted via the antenna. 
     Embodiments herein provide various apparatuses and techniques to reduce or substantially prevent such interference by maintaining isolation of the transmitter and receiver of the electronic device  10 . To do so, the embodiments disclosed herein include isolation circuitry that may have a first balun coupled between the transmitter and the antenna that isolates the transmitter from received signals received by the antenna, and enables transmission signals sent from the transmitter to pass through to the antenna. The isolation circuitry may also have a second balun coupled between the transmitter and the antenna that substantially prevents, reduces, or mitigates a leakage signal from the transmitter to a receiver. The isolation circuitry may further include a third balun coupled between the antenna and the receiver that isolates the receiver from the transmission signals, and enables the received signals to pass from the antenna to the receiver. The isolation circuitry may additionally include a fourth balun that substantially prevents, reduces, or mitigates a leakage signal from the antenna to the transmitter. 
     Each balun may include a set of coils, such as four coils. In some embodiments, one pair of the coils (e.g., on a transmitter side of the balun, on a receiver side of the balun, on an antenna side of the balun) may be coupled to variable impedance devices that are tunable to place the respective balun in a balanced or unbalanced state. In such embodiments, the other pair of coils may not be coupled to such variable impedance devices. However, in some embodiments, each pair of coils of the balun may be coupled to variable impedance devices, such that each pair may operate in the balanced state to enhance isolation of the receiver from transmission signals and/or enhance isolation of the transmitter from received signals. 
       FIG.  3    is a block diagram of example transceiver circuitry  50  of the electronic device  10 , according to an embodiment of the present disclosure. In some embodiments, the example transceiver circuitry  50  may be disposed in the transceiver  30  discussed with respect to  FIG.  1   . In other embodiments, the transceiver circuitry  50  may be disposed in the network interface  26  and coupled to the transceiver  30 . 
     As illustrated, the transceiver circuitry  50  includes an isolation circuit  58  disposed between a transmit (TX) circuit  52  and a receive (RX) circuit  54 . The isolation circuit  58  is communicatively coupled to the TX circuit  52  and the RX circuit  54 . In some embodiments, the isolation circuit  58  is coupled to one or more antennas  55 . In some alternative embodiments, the one or more antennas  55  may be disposed within the isolation circuit  58 . The isolation circuit  58  enables signals (e.g., transmission signals) of a first frequency range from the TX circuit  52  to pass through to the one or more antennas  55  and blocks the signals of the first frequency range from passing through to the RX circuit  54 . The isolation circuit  58  also enables signals (e.g., received signals) of a second frequency range received via the one or more antennas  55  to pass through to the RX circuit  54  and blocks the received signals of the second frequency range from passing through to the TX circuit  52 . Each frequency range may be of any suitable bandwidth greater than about 10 MHz, such as between 1 and 100 gigahertz (GHz) (e.g., 10 megahertz (MHz)), and include any suitable frequencies. For example, the first frequency range (e.g., the TX frequency range) may be between 880 and 890 MHz, and the second frequency range (e.g., the RX frequency range) may be between 925 and 936 MHz. 
     In some embodiments, the isolation circuit  58  isolates the RX circuit  54  from a transmission (TX) signal generated by the TX circuit  52 . For example, when transmitting a TX signal, some of the TX signal (e.g., a TX leakage signal) may propagate toward the RX circuit  54 . If a frequency of the TX leakage signal is within the RX frequency range (e.g., is a frequency supported by the RX circuit  54 ), the TX leakage signal may interfere with an RX signal and/or the RX circuit  54 . To prevent such interference, the isolation circuit  58  may isolate the RX circuit  54  from the TX leakage signal. 
     In additional or alternative embodiments, the isolation circuit  58  isolates the TX circuit  52  from a received (RX) signal received via the one or more antennas  55 . For example, when receiving an RX signal from the one or more antennas  55 , some of the RX signal (e.g., an RX leakage signal) may propagate toward the TX circuit  52 . If a frequency of the RX leakage signal is within the TX frequency range (e.g., is a frequency supported by the TX circuit  52 ), the RX leakage signal may interfere with the TX signal and/or the TX circuit  52 . To prevent such interference, the isolation circuit  58  may isolate the TX circuit  52  from the RX leakage signal. 
       FIG.  4 A  is a schematic diagram of the receive circuit (e.g., the RX circuit)  54 , according to an embodiment of the present disclosure. As illustrated, the RX circuit  54  may include, for example, a low noise amplifier (LNA)  60 , filter circuitry  61 , a demodulator  62 , and an analog-to-digital converter (ADC)  63 . One or more signals received by the one or more antennas  55  may be sent to the RX circuit  54  via the isolation circuit  58 . In some embodiments, the RX circuit  54  may include components in addition to or alternative to the LNA  60 , filter circuitry  61 , the demodulator  62 , and the ADC  63 , such as a mixer, a digital down converter, and the like. 
     The LNA  60  and filter circuitry  61  may receive the RX signal received by the one or more antennas  55 . The LNA  60  may amplify the RX signal to a suitable level for the rest of the circuitry to process. The filter circuitry  61  may include one or more types of filters such as bandpass filter, a low pass filter, or a decimation filter, or any combination thereof. The filter circuitry  61  may remove undesired noise from the RX signal, such as cross-channel interference. The filter circuitry  61  may also remove additional signals received by the one or more antennas  55  which are at frequencies other than the desired signal. The filtered RX signal is sent to the demodulator  62 . The demodulator  62  may remove the RF envelope and extract a demodulated signal from the filtered RX signal for processing. The ADC  63  receives the demodulated analog signal and converts the signal to a digital signal so that it can be further processed by the electronic device  10 . 
       FIG.  4 B  is a schematic diagram of the transmission circuit (e.g., the TX circuit)  52 , according to an embodiment of the present disclosure. As illustrated, the TX circuit  52  may include, for example, filter circuitry  64 , a power amplifier (PA)  65 , a modulator  66 , and a digital-to-analog converter (DAC)  67 . In some embodiments, the TX circuit  52  may include components in addition to or alternative to the filter circuitry  64 , the PA  65 , the modulator  66 , and the DAC  67  such as a digital up converter, etc. 
     A digital signal containing information to be transmitted via the one or more antennas  55  is provided to the DAC  67 . The DAC  67  converts the digital signal to an analog signal. The modulator  66  may combine the converted analog signal with a carrier signal to generate a radio wave. The PA  65  receives signal the modulated signal from the modulator  66 . The PA  65  amplifies the modulated signal to a suitable level to drive transmission of the signal via the one or more antennas  55 . Similar to the filter circuitry  61 , the filter circuitry  64  of the TX circuit  52  may remove undesirable noise from the amplified signal to be transmitted via the one or more antennas  55 . 
       FIG.  5    is a schematic diagram of the transceiver circuitry  50  of  FIG.  3    having baluns (e.g.,  70 ,  72 ) to isolate the transmitter/receiver circuits from received/transmission signals and baluns (e.g.,  74 ,  76 ) to reduce insertion loss, according to an embodiment of the present disclosure. As illustrated, the isolation circuitry  58  two baluns  70 ,  72  disposed in parallel between the TX circuit  52  and the one or more antennas  55 , and two baluns  74 ,  76  disposed in parallel between the RX circuit  54  and the one or more antennas  55 . The baluns  70 ,  72  are coupled to the one or more antennas  55  via a first node  94 , and the two baluns  74 ,  76  are coupled to the one or more antennas  55  via a second node  96 . 
     Variable impedance devices  78 ,  80 ,  82 ,  84 ,  86 ,  88 ,  90 ,  92  are coupled to each of the baluns  70 ,  72 ,  74 ,  76 . As illustrated, the variable impedance devices  78 ,  80  are coupled to the balun  70 , the variable impedance devices  82 ,  84  are coupled to the balun  72 , the variable impedance devices  86 ,  88  are coupled to the balun  74 , and the variable impedance devices  90 ,  92  are coupled to the balun  76 . In some embodiments, the variable impedance devices  78 ,  80 ,  82 ,  84 ,  86 ,  88 ,  90 ,  92  may be implemented as impedance tuners, impedance gradients, or both. 
     An impedance gradient, such as the variable impedance device  78 , may operate as an impedance switch, and provide a first impedance state (e.g., a lower impedance) in a first operating mode and a second impedance state (e.g., a higher impedance than the first impedance state) in a second operating mode. For example, the first impedance state may approach or appear as a short or closed circuit (e.g., approaching or approximately equal to zero ohms, such as between 0 and 100 ohms, 0.1 and 10 ohms, 0.5 and 2 ohms, and so on), while the second impedance state may approach or appear as an open circuit (e.g., providing an impedance greater than the first impedance state, such as greater than 10000 ohms, greater than 1000 ohms, greater than 100 ohms, greater than 10 ohms, greater than 5 ohms, and so on). The impedance gradient may be made of any suitable circuit components that enable the first and second impedance states, such as, for example, any suitable combination of inductors and capacitors. 
     An impedance tuner, such as the variable impedance device  80 , may operate as a tunable impedance device, and provide multiple impedance states. For example, the impedance states may include a first impedance state approaching or appearing as a short or closed circuit (e.g., approaching or approximately equal to zero ohms, such as between 0 and 100 ohms, 0.1 and 10 ohms, 0.5 and 2 ohms, and so on), a second impedance state approaching or appearing as an open circuit (e.g., providing an impedance greater than the first impedance state, such as greater than 50000 ohms, such as greater than 10000 ohms, greater than 1000 ohms, greater than 100 ohms, greater than 10 ohms, greater than 5 ohms, and so on), and multiple states providing impedances (e.g., between 0 and 50000 ohms) in between the first and second impedance states. An impedance tuner may be made of any suitable circuit components that enable the multiple impedance states, such as, for example, any suitable combination of inductors and capacitors. It should be understood that these impedance devices are provided as examples, and any suitable device that provides different impedance states and/or values, such as an impedance switch or variable impedance device, is contemplated. 
     Each variable impedance device (e.g.,  78 ,  82 ,  86 ,  90  is paired with a corresponding variable impedance device (e.g.,  80 ,  84 ,  88 ,  92 ). That is, the variable impedance device  78  is paired with the variable impedance device  80 , the variable impedance device  82  is paired with the variable impedance device  84 , the variable impedance device  86  is paired with the variable impedance device  88 , and the variable impedance device  90  is paired with the variable impedance device  92 . These pairs of variable impedance devices can be balanced (or unbalanced) to block (or enable) a signal to pass therethrough. Advantageously, blockage of a signal (e.g., isolation provided by the pairs of variable impedance devices) may be independent of an impedance mismatch of the one or more antennas  55 . That is, the impedance of the one or more antennas  55  may not affect the effectiveness of blocking a signal resulting from placing a pair of variable impedance devices in a balanced state. 
     The balun  70  may isolate the TX circuit  52  from the RX signal when the corresponding variable impedance devices  78 ,  80  are in a balanced state for a reception frequency (e.g., a frequency supported by the RX circuit  54 ) of the RX signal. That is, the variable impedance devices  78 ,  80  may block the RX signal from passing through to the TX circuit  52  when the impedances of the variable impedance devices  78 ,  80  are in a balanced state (e.g., correlate or approximately match in impedance). At the same time, the balun  70  may enable the TX signal to pass therethrough from the TX circuit  52  to the one or more antennas  55  when the corresponding variable impedance devices  78 ,  80  are in an unbalanced state (e.g., not correlate or approximately match in impedance) for a transmission frequency (e.g., a frequency supported by the TX circuit  52 ) of the TX signal. 
     Additionally, the balun  72  may substantially prevent (e.g., mitigate or reduce an occurrence of) a TX leakage signal from the TX circuit  52  to the RX circuit  54  by reducing or cancelling the TX leakage signal. For example, the balun  70  may generate the TX leakage signal. The balun  72  may generate a TX leakage cancellation signal that is equal and opposite to (e.g., equal in amplitude and opposite in phase) the TX leakage signal generated by the balun  70 . In some embodiments, to generate the cancellation signal, the balun  72  may be configured in an opposite polarity from the balun  70 . Thus, the TX leakage signal generated by the balun  72  destructively combines with the TX leakage cancellation signal generated by the balun  72 , effectively cancelling the TX leakage signal generated by the balun  70  and substantially preventing the TX leakage signal generated by the balun  70  from propagating to the baluns  74 ,  76 . 
     Similarly, the balun  76  may substantially prevent (e.g., mitigate or reduce) an RX leakage signal generated by the balun  74  by generating an RX leakage cancellation signal that is equal and opposite to (e.g., equal in amplitude and opposite in phase) the RX leakage signal generated by the balun  74 . In some embodiments, to generate the cancellation signal, the balun  76  may be configured in an opposite polarity from the balun  74 . The RX leakage signal generated by the balun  76  destructively combines with the RX leakage cancellation signal generated by the balun  74 , effectively cancelling the RX leakage signal generated by the balun  74  and substantially preventing the RX leakage signal generated by the balun  74  from propagating to the baluns  70 ,  72 . Thus, the baluns  70 ,  72 ,  74 ,  76  may prevent or mitigate (or reduce an occurrence of) interference between the TX and RX signals while reducing an occurrence of damage to the TX circuit  52  and the RX circuit  54 . As discussed above, the baluns  72 ,  76  may improve isolation effectiveness of the isolation provided by the baluns  70 ,  74  of the RX circuit  54  from the TX signal and isolation of the TX circuit  52  from the RX signal received via the one or more antennas  55 . 
     That is, the balun  70  may isolate the TX circuit  52  from the RX signal while the balun  72  may substantially prevent (or mitigate) a leakage signal (e.g., leakage from the TX signal) from the TX circuit  52  to the RX circuit  54 . Similarly, the balun  74  isolates the RX circuit  54  from the TX signal while the balun  76  substantially prevents (or substantially reduce an occurrence of) an RX leakage signal (e.g., leakage from the RX signal) from the one or more antennas  55  to the TX circuit  52  by cancelling the RX leakage signal. 
     During operation, a combination of the baluns  72 ,  76  and corresponding variable impedance devices  82 ,  84 ,  90 ,  92  (e.g., without the baluns  70 ,  74  and corresponding variable impedance devices  78 ,  80 ,  86 ,  88 ) may function similar to a double-balanced duplexer (e.g., without the baluns  70 ,  74 ). Similarly, a combination of the baluns  70 ,  74  and corresponding variable impedance devices  78 ,  80 ,  86 ,  88  (e.g., without the baluns  72 ,  76  and corresponding variable impedance devices  82 ,  84 ,  90 ,  92 ) may function similar to a double-balanced duplexer. However, as discussed above, each combination of the baluns  70 ,  74  or  72 ,  76  may not have sufficient bandwidth to support high bandwidth operation due to the relatively large insertion loss caused by the baluns  70 ,  74  or  72 ,  76 . 
     In combination, the baluns  70  with  72  and/or  74  with  76  (and corresponding variable impedance devices) may increase the bandwidth of the transceiver circuitry  50  by reducing or mitigating the leakage signals. That is, the baluns  70 ,  72  (and corresponding variable impedance devices) may enable a bandwidth of the TX signal of the transceiver circuitry  50  to be greater than 10 MHz, such as between 10 MHz and 1 gigahertz (GHz) (e.g., 300 MHz). Similarly, the baluns  74 ,  76  may enable a bandwidth of the RX signal of the transceiver circuitry  50  to be greater than 10 MHz, such as between 10 MHz and 1 gigahertz (GHz) (e.g., 300 MHz). That is, the baluns  70 ,  72 ,  74 ,  76  may enable transmission of a TX signal via the one or more antennas within a frequency range of greater than 10 MHz and block a reception signal within a frequency range of greater than 10 MHz from passing through to the TX circuit  52 . In some embodiments, the frequency range of the transmitted TX signal and a blocked RX signal may be greater than 100 MHz, greater than about 200 MHz, and the like. Accordingly, the baluns  70 ,  72 ,  74 ,  76  improve effectiveness of the isolation of the RX circuit  54  from the TX signal transmitted by the TX circuit  52  and isolation of the TX circuit  52  from the RX signal received via the one or more antennas  55 . Thus, the transceiver circuitry  50  may support increased data transfer speeds, reduce an occurrence of interference between the TX and RX signals, and reduce an occurrence of damage caused to the TX circuit  52  and the RX circuit  54  due to signal leakage. While the transceiver circuitry  50  is illustrated in  FIG.  5    including baluns  70 ,  72 ,  74 ,  76 , it should be understood that any suitable isolation circuitry can be used to isolate the RX circuit  54  from the TX signal (and TX noise signal) transmitted by the TX circuit  52  and isolate the TX circuit  52  from the RX signal (and RX noise signal) received via the one or more antennas  55 . 
       FIG.  6    is a schematic diagram of an example duplexer  100  of the transceiver circuitry  50  of  FIG.  3    having additional variable impedance devices to enhance isolation, according to an embodiment of the present disclosure. The duplexer  100  is similar to the baluns  70 ,  72 ,  74 ,  76  of the transceiver circuitry of  FIG.  5   , with additional variable impedance devices coupled to each coil of a balun  102 . In some embodiments, the transceiver circuitry  50  of  FIG.  5    may be implemented by replacing any or all of the baluns  70 ,  72 ,  74 ,  76  and corresponding variable impedance devices  78 ,  80 ,  82 ,  84 ,  86 ,  88 ,  90 ,  92  with the duplexer  100  and corresponding variable impedance devices  112 ,  114 ,  116 ,  118  of  FIG.  6   . As illustrated, the duplexer  100  may be disposed between and communicatively coupled to the RX circuit  54  and the one or more antennas  55 . In additional or alternative embodiments, the duplexer  100  may be disposed between and communicatively coupled to the TX circuit  52  and the one or more antennas  55 . The duplexer  100  includes the balun  102  and a number of variable impedance devices  112 ,  114 ,  116 ,  118  coupled to the balun  102 . The variable impedance devices  112 ,  114 ,  116 ,  118  may be implemented as impedance tuners, impedance gradients, LC matching networks, or a combination thereof. 
     A first side  120  of the balun  102  includes a first set of coils (windings)  104 ,  108  coupled to the RX circuit  54 . A first variable impedance device  112  and a second variable impedance device  114  are coupled to opposing ends of the first set of coils  104 ,  108 . The RX circuit  54  is coupled to a first variable impedance device  112  via a first coil  104  of the first set of coils and coupled to a second variable impedance device  114  via a second coil  108  of the first set of coils. 
     A second side  122  of the balun  102  includes a second set of coils  106 ,  110  coupled to the one or more antennas  55 . A third variable impedance device  116  and a fourth variable impedance device  118  are coupled to opposing ends of the second set of coils  104 ,  108 . The one or more antennas  55  is coupled to a third variable impedance device  116  via a third coil  106  of the second set of coils and coupled to a fourth variable impedance device  118  via a fourth coil  110  of the second set of coils. 
     During operation, the third variable impedance device  116  may have a low impedance in the pass band of the RX frequency and a high impedance in the block band of the RX frequency. The fourth variable impedance device  118  may have a high impedance in the pass band and a high impedance in the block band of the RX frequency. That is, the third variable impedance device  116  and the fourth variable impedance device are in an unbalanced state in the pass band and in a balanced state in the block band. The unbalanced state enables pass-through of signals having a frequency in the pass band. Similarly, the balanced state blocks signals having a frequency in the block band. The first variable impedance device  112  may have a high impedance in the pass band and a high impedance in the block band, of the RX frequency. The second variable impedance device  114  may have a low impedance in the pass band and a high impedance in the block band. That is, the first variable impedance device  112  and the second variable impedance device  114  are in an unbalanced state in the pass band an in a balanced state in the block band, of the RX frequency. 
     While the duplexer  100  is illustrated to include the balun  102  disposed between the RX circuit  54  and the one or more antennas  55 , it should be understood that other arrangements are possible. For example, the duplexer  100  may be disposed between the TX circuit  52  and the one or more antennas  55 . That is, the RX circuit  54  in  FIG.  6    may be replaced by the TX circuit  52 . In that case, the first variable impedance device  112  and the third variable impedance device  116  may be open and the second variable impedance device  114  and the fourth variable impedance device  118  may be closed, at the frequency of the TX signal. That is, the first and third variable impedance devices  112 ,  116  may have a high impedance in the pass band of the TX frequency and the second and fourth variable impedance devices  114 ,  118  may have a low impedance at the TX frequency. 
     The duplexer  100  provides additional isolation between the RX signal and the TX circuit  52  and between the TX signal and the RX circuit  54  when both the first side  120  and the second side  122  of the balun  102  are in a balanced state. Advantageously, the substantial balancing of the impedances in the transceiver circuitry  50  (e.g., the substantial equivalence of the impedance ratios) provides an improved isolation of the RX circuit  54  from the TX signal and improved isolation of the TX circuit  52  from the RX signal. The improved isolation provided by the duplexer  100  is discussed in more detail with respect to  FIG.  7    below. 
       FIG.  7    is a schematic diagram of an example double balanced duplexer (DBD)  130  implemented with the duplexer  100  of  FIG.  6   , according to an embodiment of the present disclosure. The DBD  130  includes a first duplexer  168  and a second duplexer  170 . The first duplexer  168  and the second duplexer  170  are substantially similar to the duplexer  100  discussed with respect to  FIG.  6   . As illustrated, the first duplexer  168  is disposed between the TX circuit  52  and the one or more antennas  55 . The second duplexer  170  is disposed between the RX circuit  54  and the one or more antennas  55 . 
     The first duplexer  168  includes a balun  132  having a first set of coils  136 ,  140  and a second set of coils  138 ,  142 . A first variable impedance device  154  is coupled to a first coil  136  of the first set of coils and a second variable impedance device  156  is coupled to a second coil  140  of the first set of coils. That is, the first variable impedance device  154  and the second variable impedance device  156  are coupled to opposite ends of the first set of coils  136 ,  140 . Similarly, a third variable impedance device  152  is coupled to a third coil  138  of the second set of coils and a fourth variable impedance device  158  is coupled to a fourth coil  142  of the second set of coils. That is, the third variable impedance device  152  and the fourth variable impedance device  158  are coupled to opposite ends of the second set of coils  138 ,  142 . 
     The second duplexer  170  includes a balun  134  having a first set of coils  144 ,  148  and a second set of coils  146 ,  150 . A fifth variable impedance device  162  is coupled to a first coil  144  of the first set of coils and a sixth variable impedance device  164  is coupled to a second coil  148  of the first set of coils. That is, the fifth variable impedance device  162  and the sixth variable impedance device  164  are coupled to opposite ends of the first set of coils  144 ,  148 . Similarly, a seventh variable impedance device  160  is coupled to a third coil  146  of the second set of coils and an eighth variable impedance device  166  is coupled to a fourth coil  150  of the second set of coils. That is, the seventh variable impedance device  160  and the eighth variable impedance device  166  are coupled to opposite ends of the second set of coils  146 ,  150 . 
     As discussed with respect to the duplexer  100  in  FIG.  6   , each of the duplexers  168 ,  170  may operate in a balanced or unbalanced state depending on the frequency ranges of the TX signal and RX signal. That is, the first duplexer  168  may provide isolation of the TX circuit  52  from the RX signal in the RX frequency range when the balun  132  is in a balanced state. Similarly, the second duplexer  170  may provide isolation of the RX circuit from the TX signal (e.g., leakage of the TX signal) in the TX frequency range when the balun  134  is in a balanced state. In some embodiments, the DBD  130  is tunable by changing an impedance of one or more of the variable impedance devices  152 ,  154 ,  156 ,  158 ,  160 ,  162 ,  164 ,  166 . 
     The variable impedance devices  154 ,  156  provide isolation of the TX circuit from the RX signal and the variable impedance devices  152 ,  158  provide additional isolation of the TX circuit  52  from the RX signal. Similarly, the variable impedance devices  160 ,  166  provide isolation of the RX circuit from the TX signal and the variable impedance devices  162 ,  164  provide additional isolation of the RX circuit  54  from the TX signal. Thus, the first duplexer  168  (e.g., the balun  132  and the variable impedance devices  152 ,  154 ,  156 ,  158 ) improves isolation between the RX signal and the TX circuit  52  and the second duplexer  170  (e.g., the balun  134  and the variable impedance devices  160 ,  162 ,  164 ,  166 ) improves isolation between the TX signal (and TX signal leakage) and the RX circuit  54 . Further, the DBD  130  provides an increases bandwidth available for the TX signal to greater than 10 MHz, such as about 100 MHz, compared to a conventional DBD with a single impedance device on each side of the baluns. 
       FIG.  8    is a schematic diagram of an example quadplexer module  180  of the transceiver circuitry  50  of the electronic device of  FIG.  1   , according to an embodiment of the present disclosure. The quadplexer module  180  may split one input signal into four output signals. In particular, the quadplexer module  180  may route an RX signal received via the one or more antennas  55  to multiple RX circuits  54 . Similarly, the quadplexer module  180  may route TX signals from multiple TX circuits  52  to the one or more antennas  55 . As illustrated, the quadplexer module  180  includes a quadplexer  186  coupled to a first DBD  182  and a second DBD  184 . The first DBD  182  and the second DBD  184  may be substantially similar to the DBD  130  discussed with respect to  FIG.  7   . That is, each of the first DBD  182  and the second DBD  184  include the first duplexer  168  and the second duplexer  170  discussed with respect to  FIG.  7   . As illustrated, the first DBD  182  and the second DBD  184  are coupled to a common set of (e.g., one or more) antennas  55 . In some embodiments, each of the first DBD  182  and the second DBD  184  may be coupled to separate antennas among the antennas  55 . 
     As discussed above, the first DBD  182  and the second DBD  184  may be tunable by adjusting an impedance of the variable impedance devices  152 ,  154 ,  156 ,  158 ,  160 ,  162 ,  164 ,  166 . In some embodiments, in addition to or in the alternative of the first DBD  182  and the second DBD  184  being tunable, the quadplexer module  180  may include additional DBDs to enable further increase bandwidth available for the TX signal and the RX signal. 
     In operation, the quadplexer  186  may receive RX signals from the one or more antennas  55  in different frequency bands to be sent to respective RX circuits  54 . The quadplexer  186  may also receive TX signals in different frequency bands from respective TX circuits  52  and route the TX signals to the one or more antennas  55 . In some embodiments, each of the frequency bands of the various RX signals and TX signals may each be different. In additional or alternative embodiments, at least some of the frequency bands of the various RX signals and TX signals may overlap. As discussed below with respect to  FIG.  9   , the quadplexer  186  may function as a tunable filter to enable transmission and/or receipt of signals having various frequencies or frequency bands. Similarly, the quadplexer may be tunable to block transmission and/or receipt of signals having various frequencies or frequency bands. Thus, the quadplexer  186  enables improved isolation within the transceiver circuitry  50  discussed with respect to  FIG.  3   . 
       FIG.  9    is a schematic diagram illustrating example components of the example quadplexer module  180  of  FIG.  8   , according to an embodiment of the present disclosure. As illustrated, the quadplexer  186  includes first isolation circuitry  188  coupled to and disposed between the first DBD  182  and the one or more antennas  55 . The quadplexer  186  also includes second isolation circuitry  190  coupled to and disposed between the second DBD  184  and the one or more antennas  55 . 
     The first isolation circuitry  188  includes a first balun  200  coupled in parallel to a second balun  202 . The first balun  200  includes a first set of coils  208 ,  212  and a second set of coils  210 ,  214 . A first variable impedance device  242  is coupled to a first coil  208  of the first set of coils and a second variable impedance device  244  is coupled to a second coil  212  of the first set of coils. That is, the first variable impedance device  242  and the second variable impedance device  244  are coupled to opposite ends of the first set of coils  208 ,  210 . Similarly, a third variable impedance device  240  is coupled to a third coil  210  of the second set of coils and a fourth variable impedance device  246  is coupled to a fourth coil  214  of the second set of coils. That is, the third variable impedance device  240  and the fourth variable impedance device  246  are coupled to opposite ends of the second set of coils  210 ,  214 . 
     The first balun  200 , in conjunction with the third variable impedance device  240  and the fourth variable impedance device  246 , may provide isolation between the first DBD  182  and signals from and to the second DBD  184 . The first balun  200 , in conjunction with the first variable impedance device  242  and the second variable impedance device  244 , may provide additional isolation between the first DBD  182  and signals from and to the second DBD  184 , essentially implementing the duplexer  100  of  FIG.  10   . 
     The second balun  202  includes a third set of coils  216 ,  220  and a fourth set of coils  218 ,  222 . A fifth variable impedance device  248  is coupled to a first coil  216  of the third set of coils and a sixth variable impedance device  254  is coupled to a second coil  220  of the third set of coils. That is, the fifth variable impedance device  248  and the sixth variable impedance device  254  are coupled to opposite ends of the third set of coils  216 ,  220 . Similarly, a seventh variable impedance device  250  is coupled to a third coil  218  of the fourth set of coils and an eighth variable impedance device  252  is coupled to a fourth coil  222  of the fourth set of coils. That is, the seventh variable impedance device  250  and the eighth variable impedance device  252  are coupled to opposite ends of the fourth set of coils  218 ,  222 . 
     The second balun  202  may mitigate (or substantially prevent or reduce an occurrence of) a leakage signal from the first DBD  182  to the second isolation circuitry  190 . Moreover, the second balun  202 , in conjunction with the fifth variable impedance device  248  and the sixth variable impedance device  254 , may provide isolation between the first DBD  182  and signals from and to the second DBD  184 . The second balun  202 , in conjunction with the seventh variable impedance device  250  and the eighth variable impedance device  252 , may provide additional isolation between the first DBD  182  and signals from and to the second DBD  184 . 
     The second isolation circuitry  190  includes a third balun  204  coupled in parallel to a fourth balun  206 . The third balun  204  includes a first set of coils  224 ,  228  and a second set of coils  226 ,  230 . A ninth variable impedance device  258  is coupled to a first coil  224  of the first set of coils and a tenth variable impedance device  260  is coupled to a second coil  228  of the first set of coils. That is, the ninth variable impedance device  258  and the tenth variable impedance device  260  are coupled to opposite ends of the first set of coils  224 ,  228 . Similarly, an eleventh variable impedance device  256  is coupled to a third coil  226  of the second set of coils and a twelfth variable impedance device  262  is coupled to a fourth coil  230  of the second set of coils. That is, the eleventh variable impedance device  256  and the twelfth variable impedance device  262  are coupled to opposite ends of the second set of coils  226 ,  230 . 
     The third balun  204 , in conjunction with the eleventh variable impedance device  256  and the twelfth variable impedance device  262 , may provide isolation between the second DBD  184  and signals from and to the first DBD  182 . The third balun  204 , in conjunction with the ninth variable impedance device  258  and the tenth variable impedance device  260 , may provide additional isolation between the second DBD  184  and signals from and to the first DBD  182 . 
     The fourth balun  206  includes a third set of coils  232 ,  236  and a fourth set of coils  234 ,  238 . A thirteenth variable impedance device  264  is coupled to a first coil  232  of the third set of coils and a fourteenth variable impedance device  272  is coupled to a second coil  236  of the third set of coils. That is, the thirteenth variable impedance device  264  and the fourteenth variable impedance device  272  are coupled to opposite ends of the third set of coils  232 ,  236 . Similarly, a fifteenth variable impedance device  268  is coupled to a third coil  234  of the fourth set of coils and a sixteenth variable impedance device  270  is coupled to a fourth coil  238  of the fourth set of coils. That is, the fifteenth variable impedance device  268  and the sixteenth variable impedance device  270  are coupled to opposite ends of the fourth set of coils  234 ,  238 . 
     The fourth balun  206  may mitigate (or substantially prevent or reduce an occurrence of) a leakage signal from the second DBD  184  to the first isolation circuitry  188 . Moreover, the fourth balun  206 , in conjunction with the thirteenth variable impedance device  264  and the fourteenth variable impedance device  272  may provide isolation between the second DBD  184  and signals from and to the first DBD  182 . The fifteenth variable impedance device  268  and the sixteenth variable impedance device  270  (in conjunction with the fourth balun  206 ) may provide additional isolation between the second DBD  184  and signals from and to the first DBD  182 . 
     Similar to the variable impedance devices  152 ,  154 ,  156 ,  158 ,  160 ,  162 ,  164 ,  166  discussed with respect to  FIG.  7   , the impedances of the variable impedance devices  240 ,  242 ,  244 ,  246 ,  248 ,  250 ,  252 ,  254 ,  256 ,  258 ,  260 ,  262 ,  264 ,  266 ,  268 ,  270 ,  272  can be tuned such that each of the baluns  200 ,  202 ,  204 ,  206  are in a balanced state to improve isolation of the TX signal and TX signal leakage and the RX circuits  54  and isolation of the RX signal and the TX circuits  52 . That is, the quadplexer  186  is similar to the isolation circuitry  58  discussed with respect to  FIG.  5   , with additional variable impedance devices coupled to the baluns  200 ,  202 ,  204 ,  206 . That is, the quadplexer  186  is a combination of the isolation circuitry  58  of  FIG.  5    and the duplexer  100  discussed with respect to  FIG.  6   . Thus, the quadplexer  186  provides improved isolation between the DBDs  182 ,  184  and increases bandwidth for wireless communications available to the electronic device  10 . 
     The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure. 
     The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ,” it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Metadata:
Filing Date: 20220124
Publication Date: 20231114
Grant Date: 20231114
Priority Date: 20201209
Inventors: MUHAREMOVIC, NEDIM
HUR, JOONHOI
VAZNY, RASTISLAV
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B1/48", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03F3/245", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03H7/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F2200/294", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F2200/451", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B1/525", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/48", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/48", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L5/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F1/565", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F3/19", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F3/245", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F3/245", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F2200/294", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F2200/451", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F3/19", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F1/565", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03H7/463", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03H7/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F2200/451", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F2200/294", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F3/245", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 80442492