PATENT DOCUMENT

Publication Number: US-11881715-B2
Application Number: US-202217751482-A
Country: US
Kind Code: B2

Title: Electronic device having reconfigurable multi-coil transformer with frequency selective filtering

Abstract:
An electronic device may include wireless circuitry having a transformer adjustable between first, second, and third modes. The transformer may have first, second, third, and fourth inductors. The third inductor may be magnetically coupled to the first and second inductors with equal coupling constants. The fourth inductor may be magnetically coupled to the first and second inductors with inverse coupling constants. First and second adjustable capacitors coupled to the third and fourth inductors may receive control signals that place the transformer into a selected one of the first, second, or third modes. In the first mode the transformer exhibits a passband that overlaps first and second bands. In the second mode, the transformer passes signals in the second band while filtering interference in the first band. In the third mode, the transformer passes signals in the first band while filtering interference in the second band.

Claims:
What is claimed is: 
     
       1. A transformer configured to receive radio-frequency signals conveyed along a signal path, comprising:
 a first inductor disposed on the signal path; 
 a second inductor disposed on the signal path and at least partially overlapping the first inductor; 
 a third inductor disposed adjacent a portion of the first inductor and at least partially overlapping the second inductor; and 
 a fourth inductor at least partially overlapping the first inductor, the second inductor, and the third inductor. 
 
     
     
       2. The transformer of  claim 1 , further comprising:
 a first adjustable capacitor coupled between terminals of the fourth inductor. 
 
     
     
       3. The transformer of  claim 2 , further comprising:
 a second adjustable capacitor coupled between terminals of the third inductor. 
 
     
     
       4. The transformer of  claim 3 , wherein the first adjustable capacitor is configured to receive control signals that selectively control the first adjustable capacitor to form an open circuit between the terminals of the fourth inductor and the second adjustable capacitor is configured to receive control signals that selectively control the second adjustable capacitor to form an open circuit between the terminals of the third inductor. 
     
     
       5. The transformer of  claim 3 , wherein the first adjustable capacitor and the second adjustable capacitor are configured to receive control signals that selectively configure the transformer to pass the radio-frequency signals in a first frequency band and a second frequency band that is higher than the first frequency band, in the first frequency band but not the second frequency band, or in the second frequency band but not the first frequency band. 
     
     
       6. The transformer of  claim 1 , wherein the first inductor and the fourth inductor have a first magnetic coupling characterized by a first coupling constant and the second inductor and the fourth inductor have a second magnetic coupling characterized by a second coupling constant equal to the first coupling constant. 
     
     
       7. The transformer of  claim 6 , wherein the first inductor and the third inductor have a third magnetic coupling characterized by a third coupling constant and the second inductor and the third inductor have a fourth magnetic coupling characterized by a fourth coupling constant equal to a negative of the third coupling constant. 
     
     
       8. The transformer of  claim 1 , wherein the first inductor and the third inductor have a first magnetic coupling characterized by a first coupling constant and the second inductor and the third inductor have a second magnetic coupling characterized by a second coupling constant equal to a negative of the first coupling constant. 
     
     
       9. The transformer of  claim 1 , wherein the fourth inductor surrounds an entirety of the fourth inductor and wherein the third inductor does not overlap the first inductor. 
     
     
       10. The transformer of  claim 1 , wherein the third inductor and the fourth inductor are floating with respect to the signal path. 
     
     
       11. An electronic device comprising:
 an antenna; 
 a signal path communicably coupled to the antenna and configured to convey radio-frequency signals for the antenna; and 
 an impedance matching network comprising
 a first inductor disposed on the signal path, 
 a second inductor disposed on the signal path, the first inductor being magnetically coupled to the second inductor with a first coupling constant, and 
 a third inductor magnetically coupled to the first inductor with a second coupling constant and magnetically coupled to the second inductor with a third coupling constant equal to a negative of the second coupling constant. 
 
 
     
     
       12. The electronic device of  claim 11 , wherein the impedance matching network further comprises:
 a fourth inductor magnetically coupled to the first inductor with a fourth coupling constant and magnetically coupled to the second inductor with a fifth coupling constant equal to the fourth coupling constant. 
 
     
     
       13. The electronic device of  claim 11 , further comprising:
 an adjustable capacitor coupled between terminals of the third inductor. 
 
     
     
       14. The electronic device of  claim 13 , wherein the adjustable capacitor has a first state in which the adjustable capacitor forms an open circuit in the third inductor and has a second state in which the adjustable capacitor forms a non-open circuit capacitance in the third inductor. 
     
     
       15. The electronic device of  claim 14 , further comprising:
 a peak detector configured to detect a frequency of an interference signal in the radio-frequency signals; and 
 control circuitry configured to tune the non-open circuit capacitance of the adjustable capacitor based on the detected frequency of the interference signal. 
 
     
     
       16. The electronic device of  claim 11 , wherein the third inductor overlaps the second inductor but not the first inductor. 
     
     
       17. The electronic device of  claim 11 , further comprising:
 a low noise amplifier disposed on the signal path, wherein the impedance matching network is interposed between stages of the low noise amplifier. 
 
     
     
       18. A method of operating an electronic device having a signal path with a transformer that includes a first coil, a second coil, a third coil, a fourth coil, a first adjustable capacitor coupled to the third coil, and a second adjustable capacitor coupled to the fourth coil, the method comprising:
 forming a first open circuit in the third coil and a second open circuit in the fourth coil, the first open circuit in the third coil and the second open circuit in the fourth coil configuring the transformer to pass radio-frequency signals in a first frequency band and a second frequency band higher than the first frequency band; and 
 forming the second open circuit in the fourth coil and controlling the first adjustable capacitor to form a non-open circuit capacitance in the third coil, the second open circuit in the fourth coil and the non-open circuit capacitance in the third coil configuring the transformer to pass the radio-frequency signals in the second frequency band while filtering out the first frequency band. 
 
     
     
       19. The method of  claim 18 , further comprising:
 forming the first open circuit in the third coil and controlling the second adjustable capacitor to form a non-open circuit capacitance in the fourth coil, the first open circuit in the third coil and the non-open circuit capacitance in the fourth coil configuring the transformer to pass the radio-frequency signals in the first frequency band while filtering out the second frequency band. 
 
     
     
       20. The method of  claim 19 , further comprising:
 with a peak detector, detecting a frequency of signal interference in the radio-frequency signals; and 
 with one or more processors, adjusting the first adjustable capacitor and the second adjustable capacitor based on the detected frequency of the signal interference.

Description:
FIELD 
     This disclosure relates generally to electronic devices and, more particularly, to electronic devices with wireless communications circuitry. 
     BACKGROUND 
     Electronic devices are often provided with wireless communications capabilities. An electronic device with wireless communications capabilities has wireless communications circuitry with radio-frequency components that include one or more antennas. Wireless transceiver circuitry in the wireless communications circuitry uses the antennas to transmit and receive radio-frequency signals. 
     It can be challenging to form satisfactory radio-frequency wireless communications circuitry for an electronic device. If care is not taken, the wireless communications circuitry can be subject to undesirable signal interference in one or more frequency bands used to convey radio-frequency signals. 
     SUMMARY 
     An electronic device may include wireless circuitry for performing wireless communications. The wireless circuitry may include a transceiver, an antenna, and front end circuitry between the antenna and the transceiver. The front end circuitry may include an impedance matching network. The impedance matching network may be in a low noise amplifier, as one example. The impedance matching network may have a multi-coil transformer. The multi-coil transformer may be adjustable between a wideband operating mode, a first band rejection operating mode, and a second band rejection operating mode. 
     The multi-coil transformer may have first, second, third, and fourth inductors. The first inductor may be magnetically coupled to the second inductor via a first magnetic coupling with a first coupling constant. The third inductor may be magnetically coupled to the first inductor via a second magnetic coupling with a second coupling constant and may be magnetically coupled to the second inductor via a third magnetic coupling with a third coupling constant. The fourth inductor may be magnetically coupled to the first inductor via a fourth magnetic coupling with a fourth coupling constant and may be magnetically coupled to the second inductor via a fourth magnetic coupling with a fourth coupling constant. The layout of the first, second, third, and fourth coils may be selected so that the second coupling constant is equal to the third coupling constant and so that the fourth coupling constant is equal to a negative of the fifth coupling constant. 
     A first adjustable capacitor may be coupled between terminals of the third inductor. A second adjustable capacitor may be coupled between terminals of the fourth inductor. The first and second adjustable capacitors may receive control signals that place the impedance matching network into a selected one of the first, second, and third operating modes. In the first operating mode, the first and second adjustable capacitors form open circuits and the transformer exhibits a first transfer function with a passband that overlaps a first frequency band and a second frequency band higher than the first frequency band. In the second operating mode, the second adjustable capacitor forms an open circuit in the fourth inductor and the transformer exhibits a second transfer function that passes signals in the second frequency band while filtering interference in the first frequency band. In the third operating mode, the first adjustable capacitor forms an open circuit in the third inductor and the transformer exhibits a third transfer function that passes signals in the first frequency band while filtering interference in the second frequency band. A peak detector may be used to detect the frequency of the interference and the adjustable capacitors may be tuned based on the detected frequency. This may allow the impedance matching circuitry to cover inter-band carrier aggregation (CA) communications while also dynamically mitigating interference without unnecessary increases in chip area. 
     An aspect of the disclosure provides a transformer configured to receive radio-frequency signals conveyed along a signal path. The transformer can include a first inductor disposed on the signal path. The transformer can include a second inductor disposed on the signal path and at least partially overlapping the first inductor. The transformer can include a third inductor disposed adjacent to a portion of the first inductor and partially overlapping the second inductor. The transformer can include a fourth inductor at least partially overlapping the first inductor, the second inductor, and the third inductor. 
     An aspect of the disclosure provides an electronic device. The electronic device can include an antenna. The electronic device can include a signal path communicably coupled to the antenna and configured to convey radio-frequency signals for the antenna. The electronic device can include an impedance matching network comprising. The electronic device can include a first inductor disposed on the signal path. The electronic device can include a second inductor disposed on the signal path, the first inductor being magnetically coupled to the second inductor with a first coupling constant. The electronic device can include a third inductor magnetically coupled to the first inductor with a second coupling constant and magnetically coupled to the second inductor with a third coupling constant equal to a negative of the second coupling constant. 
     An aspect of the disclosure provides a method of operating an electronic device having a signal path with a transformer that includes a first coil, a second coil, a third coil, a fourth coil, a first adjustable capacitor coupled to the third coil, and a second adjustable capacitor coupled to the fourth coil. The method can include forming a first open circuit in the third coil and a second open circuit in the fourth coil, the first open circuit in the third coil and the second open circuit in the fourth coil configuring the transformer to pass radio-frequency signals in a first frequency band and a second frequency band higher than the first frequency band. The method can include forming the second open circuit in the fourth coil and controlling the first adjustable capacitor to form a non-open circuit capacitance in the third coil, the second open circuit in the fourth coil and the non-open circuit capacitance in the third coil configuring the transformer to pass the radio-frequency signals in the second frequency band while filtering out the first frequency band. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an illustrative electronic device having wireless circuitry in accordance with some embodiments. 
         FIG.  2    is a diagram of illustrative wireless circuitry having front end circuitry adjustable between different operating modes for performing communications across first and second frequency bands or filtering out signal interference in one of the frequency bands in accordance with some embodiments. 
         FIG.  3    is a schematic diagram of an illustrative low noise amplifier having an adjustable matching network in accordance with some embodiments. 
         FIG.  4    is a circuit diagram of an illustrative multi-coil transformer in an adjustable matching network that may be switched between wideband, first band rejection, and second band rejection operating modes in accordance with some embodiments. 
         FIGS.  5 A-C  are layout diagrams of an illustrative multi-coil transformer that may be switched between wideband, first band rejection, and second band rejection operating modes in accordance with some embodiments. 
         FIG.  6    is a circuit diagram showing how the illustrative multi-coil transformer of  FIG.  4    may be represented by a balanced input/output impedance network followed by an ideal impedance transformer in accordance with some embodiments. 
         FIG.  7    is a diagram showing how an illustrative multi-coil transformer placed in a wideband operating mode may be decomposed into even and odd modes for performing communications across first and second frequency bands in accordance with some embodiments. 
         FIG.  8    is a plot of the transfer function of an illustrative multi-coil transformer placed in a wideband operating mode in accordance with some embodiments. 
         FIG.  9    is a diagram showing how an illustrative multi-coil transformer placed in a first band rejection operating mode may be decomposed into even and odd modes for performing communications in a second frequency band while rejecting interference in a first frequency band in accordance with some embodiments. 
         FIG.  10    is a plot of the transfer function of an illustrative multi-coil transformer placed in a first band rejection operating mode in accordance with some embodiments. 
         FIG.  11    is a diagram showing how an illustrative multi-coil transformer placed in a second band rejection operating mode may be decomposed into even and odd modes for performing communications in a first frequency band while rejecting interference in a second frequency band in accordance with some embodiments. 
         FIG.  12    is a plot of the transfer function of an illustrative multi-coil transformer placed in a second band rejection operating mode in accordance with some embodiments. 
         FIG.  13    is a flow chart of illustrative operations that may be performed by wireless circuitry to convey radio-frequency signals while adjusting a multi-coil transformer between wideband, first band rejection, and second band rejection operating modes. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic device  10  of  FIG.  1    may be a computing device such as a laptop computer, a desktop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wristwatch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, a wireless internet-connected voice-controlled speaker, a home entertainment device, a remote control device, a gaming controller, a peripheral user input device, a wireless base station or access point, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     As shown in the schematic diagram  FIG.  1   , device  10  may include components located on or within an electronic device housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, metal alloys, etc.), other suitable materials, or a combination of these materials. In some situations, parts or all of housing  12  may be formed from dielectric or other low-conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may include control circuitry  14 . Control circuitry  14  may include storage such as storage circuitry  16 . Storage circuitry  16  may include hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid-state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Storage circuitry  16  may include storage that is integrated within device  10  and/or removable storage media. 
     Control circuitry  14  may include processing circuitry such as processing circuitry  18 . Processing circuitry  18  may be used to control the operation of device  10 . Processing circuitry  18  may include on one or more microprocessors, microcontrollers, digital signal processors, host processors, baseband processor integrated circuits, application specific integrated circuits, central processing units (CPUs), graphics processing units (GPUs), etc. Control circuitry  14  may be configured to perform operations in device  10  using hardware (e.g., dedicated hardware or circuitry), firmware, and/or software. Software code for performing operations in device  10  may be stored on storage circuitry  16  (e.g., storage circuitry  16  may include non-transitory (tangible) computer readable storage media that stores the software code). The software code may sometimes be referred to as program instructions, software, data, instructions, or code. Software code stored on storage circuitry  16  may be executed by processing circuitry  18 . 
     Control circuitry  14  may be used to run software on device  10  such as satellite navigation applications, internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, control circuitry  14  may be used in implementing communications protocols. Communications protocols that may be implemented using control circuitry  14  include internet protocols, wireless local area network (WLAN) protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol or other wireless personal area network (WPAN) protocols, IEEE 802.11ad protocols (e.g., ultra-wideband protocols), cellular telephone protocols (e.g., 3G protocols, 4G (LTE) protocols, 3GPP Fifth Generation (5G) New Radio (NR) protocols, Sixth Generation (6G) protocols, sub-THz protocols, THz protocols, etc.), antenna diversity protocols, satellite navigation system protocols (e.g., global positioning system (GPS) protocols, global navigation satellite system (GLONASS) protocols, etc.), antenna-based spatial ranging protocols, optical communications protocols, or any other desired communications protocols. Each communications protocol may be associated with a corresponding radio access technology (RAT) that specifies the physical connection methodology used in implementing the protocol. 
     Device  10  may include input-output circuitry  20 . Input-output circuitry  20  may include input-output devices  22 . Input-output devices  22  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  22  may include user interface devices, data port devices, and other input-output components. For example, input-output devices  22  may include touch sensors, displays, light-emitting components such as displays without touch sensor capabilities, buttons (mechanical, capacitive, optical, etc.), scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, buttons, speakers, status indicators, audio jacks and other audio port components, digital data port devices, motion sensors (accelerometers, gyroscopes, and/or compasses that detect motion), capacitance sensors, proximity sensors, magnetic sensors, force sensors (e.g., force sensors coupled to a display to detect pressure applied to the display), etc. In some configurations, keyboards, headphones, displays, pointing devices such as trackpads, mice, and joysticks, and other input-output devices may be coupled to device  10  using wired or wireless connections (e.g., some of input-output devices  22  may be peripherals that are coupled to a main processing unit or other portion of device  10  via a wired or wireless link). 
     Input-output circuitry  20  may include wireless circuitry  24  to support wireless communications. Wireless circuitry  24  (sometimes referred to herein as wireless communications circuitry  24 ) may include baseband circuitry such as baseband circuitry  26  (e.g., one or more baseband processors and/or other circuitry that operates at baseband), radio-frequency (RF) transceiver circuitry such as transceiver  28 , radio-frequency front end circuitry such as front end circuitry  30 , and one or more antennas  34 . If desired, wireless circuitry  24  may include multiple antennas  34  that are arranged into a phased antenna array (sometimes referred to as a phased array antenna) that conveys radio-frequency signals within a corresponding signal beam that can be steered in different directions. Baseband circuitry  26  may be coupled to transceiver  28  over one or more baseband data paths. Transceiver  28  may be coupled to antennas  34  over one or more radio-frequency transmission line paths  32 . Front end circuitry  30  may be disposed on radio-frequency transmission line path(s)  32  between transceiver  28  and antennas  34 . 
     In the example of  FIG.  1   , wireless circuitry  24  is illustrated as including only a single transceiver  28  and a single radio-frequency transmission line path  32  for the sake of clarity. In general, wireless circuitry  24  may include any desired number of transceivers  28 , any desired number of radio-frequency transmission line paths  32 , and any desired number of antennas  34 . Each transceiver  28  may be coupled to one or more antennas  34  over respective radio-frequency transmission line paths  32 . Each radio-frequency transmission line path  32  may have respective front end circuitry  30  disposed thereon. If desired, front end circuitry  30  may be shared by multiple radio-frequency transmission line paths  32 . 
     Radio-frequency transmission line path  32  may be coupled to antenna feeds on one or more antenna  34 . Each antenna feed may, for example, include a positive antenna feed terminal and a ground antenna feed terminal. Radio-frequency transmission line path  32  may have a positive transmission line signal path that is coupled to the positive antenna feed terminal and may have a ground transmission line signal path that is coupled to the ground antenna feed terminal. This example is merely illustrative and, in general, antennas  34  may be fed using any desired antenna feeding scheme. 
     Radio-frequency transmission line path  32  may include transmission lines that are used to route radio-frequency antenna signals within device  10 . Transmission lines in device  10  may include coaxial cables, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, transmission lines formed from combinations of transmission lines of these types, etc. Transmission lines in device such as transmission lines in radio-frequency transmission line path  32  may be integrated into rigid and/or flexible printed circuit boards. In one embodiment, radio-frequency transmission line paths such as radio-frequency transmission line path  32  may also include transmission line conductors integrated within multilayer laminated structures (e.g., layers of a conductive material such as copper and a dielectric material such as a resin that are laminated together without intervening adhesive). The multilayer laminated structures may, if desired, be folded or bent in multiple dimensions (e.g., two or three dimensions) and may maintain a bent or folded shape after bending (e.g., the multilayer laminated structures may be folded into a particular three-dimensional shape to route around other device components and may be rigid enough to hold its shape after folding without being held in place by stiffeners or other structures). All of the multiple layers of the laminated structures may be batch laminated together (e.g., in a single pressing process) without adhesive (e.g., as opposed to performing multiple pressing processes to laminate multiple layers together with adhesive). In performing wireless transmission, baseband circuitry  26  may provide baseband signals to transceiver  28 . Transceiver  28  may include circuitry for converting the baseband signals received from baseband circuitry  26  into corresponding radio-frequency signals. For example, transceiver  28  may include mixer circuitry for up-converting the baseband signals to radio frequencies prior to transmission over antennas  34 . Transceiver  28  may also include digital to analog converter (DAC) and/or analog to digital converter (ADC) circuitry for converting signals between digital and analog domains. Transceiver  28  may transmit the radio-frequency signals over antennas  34  via radio-frequency transmission line path  32  and front end circuitry  30 . Antennas  34  may transmit the radio-frequency signals to external wireless equipment by radiating the radio-frequency signals into free space. 
     In performing wireless reception, antennas  34  may receive radio-frequency signals from the external wireless equipment. The received radio-frequency signals may be conveyed to transceiver  28  via radio-frequency transmission line path  32  and front end circuitry  30 . Transceiver  28  may include circuitry for converting the received radio-frequency signals into corresponding baseband signals. For example, transceiver  28  may include mixer circuitry for down-converting the received radio-frequency signals to baseband frequencies prior to conveying the baseband signals to baseband circuitry  26 . 
     Front end circuitry  30  may include radio-frequency front end components that operate on radio-frequency signals conveyed over radio-frequency transmission line path  32 . If desired, the radio-frequency front end components may be formed within one or more radio-frequency front end modules (FEMs). Each FEM may include a common substrate such as a printed circuit board substrate for each of the radio-frequency front end components in the FEM. The radio- frequency front end components in front end circuitry  30  may include switching circuitry (e.g., one or more radio-frequency switches), radio-frequency filter circuitry (e.g., low pass filters, high pass filters, notch filters, band pass filters, multiplexing circuitry, duplexer circuitry, diplexer circuitry, triplexer circuitry, etc.), impedance matching circuitry (e.g., circuitry that helps to match the impedance of antennas  34  to the impedance of radio-frequency transmission line path  32 ), antenna tuning circuitry (e.g., networks of capacitors, resistors, inductors, and/or switches that adjust the frequency response of antennas  34 ), radio-frequency amplifier circuitry (e.g., power amplifier circuitry and/or low-noise amplifier circuitry), radio-frequency coupler circuitry, charge pump circuitry, power management circuitry, digital control and interface circuitry, and/or any other desired circuitry that operates on the radio-frequency signals transmitted and/or received by antennas  34 . 
     While control circuitry  14  is shown separately from wireless circuitry  24  in the example of  FIG.  1    for the sake of clarity, wireless circuitry  24  may include processing circuitry that forms a part of processing circuitry  18  and/or storage circuitry that forms a part of storage circuitry  16  of control circuitry  14  (e.g., portions of control circuitry  14  may be implemented on wireless circuitry  24 ). As an example, baseband circuitry  26  and/or portions of transceiver  28  (e.g., a host processor on transceiver  28 ) may form a part of control circuitry  14 . 
     Wireless circuitry  24  may transmit and/or receive wireless signals within corresponding frequency bands of the electromagnetic spectrum (sometimes referred to herein as communications bands or simply as “bands”). The frequency bands handled by wireless circuitry  24  may include wireless local area network (WLAN) frequency bands (e.g., Wi-Fi®(IEEE 802.11) or other WLAN communications bands) such as a 2.4 GHz WLAN band (e.g., from 2400 to 2480 MHz), a 5 GHz WLAN band (e.g., from 5180 to 5825 MHz), a Wi-Fi® 6E band (e.g., from 5925-7125 MHz), and/or other Wi-Fi® bands (e.g., from 1875-5160 MHz), wireless personal area network (WPAN) frequency bands such as the 2.4 GHz Bluetooth® band or other WPAN communications bands, cellular telephone frequency bands (e.g., bands from about 600 MHz to about 5 GHz, 3G bands, 4G LTE bands, 5G New Radio Frequency Range 1 (FR1) bands below 10 GHz, 5G New Radio Frequency Range 2 (FR2) bands between 20 and 60 GHz, etc.), other centimeter or millimeter wave frequency bands between 10-100 GHz, near-field communications (NFC) frequency bands (e.g., at 13.56 MHz), satellite navigation frequency bands (e.g., a GPS band from 1565 to 1610 MHz, a Global Navigation Satellite System (GLONASS) band, a BeiDou Navigation Satellite System (BDS) band, etc.), ultra-wideband (UWB) frequency bands that operate under the IEEE 802.15.4 protocol and/or other ultra-wideband communications protocols, communications bands under the family of 3GPP wireless communications standards, communications bands under the IEEE 802.XX family of standards, and/or any other desired frequency bands of interest. 
     Antennas  34  may be formed using any desired antenna structures. For example, antennas  34  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, monopole antennas, dipoles, hybrids of these designs, etc. Parasitic elements may be included in antennas  34  to adjust antenna performance. 
     Filter circuitry, switching circuitry, impedance matching circuitry, and other circuitry may be interposed within radio-frequency transmission line path  32 , may be incorporated into front end circuitry  30 , and/or may be incorporated into antennas  34  (e.g., to support antenna tuning, to support operation in desired frequency bands, etc.). These components, sometimes referred to herein as antenna tuning components, may be adjusted (e.g., using control circuitry  14 ) to adjust the frequency response and wireless performance of antennas  34  over time. 
     In general, transceiver  28  may cover (handle) any suitable communications (frequency) bands of interest. The transceiver may convey radio-frequency signals using antennas  34  (e.g., antennas  34  may convey the radio-frequency signals for the transceiver circuitry). The term “convey radio-frequency signals” as used herein means the transmission and/or reception of the radio-frequency signals (e.g., for performing unidirectional and/or bidirectional wireless communications with external wireless communications equipment). Antennas  34  may transmit the radio-frequency signals by radiating the radio-frequency signals into free space (or to free space through intervening device structures such as a dielectric cover layer). Antennas  34  may additionally or alternatively receive the radio-frequency signals from free space (e.g., through intervening devices structures such as a dielectric cover layer). The transmission and reception of radio-frequency signals by antennas  34  each involve the excitation or resonance of antenna currents on an antenna resonating element in the antenna by the radio-frequency signals within the frequency band(s) of operation of the antennas. 
     In example where multiple antennas  34  are arranged in a phased antenna array, each antenna  34  may form a respective antenna element of the phased antenna array. Conveying radio-frequency signals using the phased antenna array may allow for greater peak signal gain relative to scenarios where individual antennas  34  are used to convey radio-frequency signals. In satellite navigation system links, cellular telephone links, and other long-range links, radio-frequency signals are typically used to convey data over thousands of feet or miles. In Wi-Fi®and Bluetooth® links at 2.4 and 5 GHz and other short-range wireless links, radio-frequency signals are typically used to convey data over tens or hundreds of feet. In scenarios where millimeter or centimeter wave frequencies are used to convey radio-frequency signals, a phased antenna array may convey radio-frequency signals over short distances that travel over a line-of-sight path. To enhance signal reception for millimeter and centimeter wave communications, the phased antenna array may convey radio-frequency signals using beam steering techniques (e.g., schemes in which antenna signal phase and/or magnitude for each antenna in an array are adjusted to perform beam steering). 
     For example, each antenna  34  in the phased antenna array may be coupled to a corresponding phase and magnitude controller in front end circuitry  30 . The phase and magnitude controllers may adjust the relative phases and/or magnitudes of the radio-frequency signals that are conveyed by each of the antennas  34  in the phased antenna array. The wireless signals that are transmitted or received by the phased antenna array in a particular direction may collectively form a corresponding signal beam. The signal beam may exhibit a peak gain that is oriented in a particular pointing direction at a corresponding pointing angle (e.g., based on constructive and destructive interference from the combination of signals from each antenna in the phased antenna array). Control circuitry  14  may adjust the phase and magnitude controllers to change the direction of the signal beam over time (e.g., to allow device  10  to continue to communicate with external equipment even if the external equipment moves relative to device  10  over time). This example is merely illustrative and, in general, antennas  34  need not be arranged in a phased antenna array. 
     High frequency bands such as 5G NR FR2 frequency bands have been deployed or are under development across the world. Several frequency bands have already been defined between around 24.25 GHz and 48.2 GHz that support channel bandwidths up to 400 MHz. Data rates can be further increased by aggregating multiple frequency blocks from one frequency band under an intra-band carrier aggregation (CA) scheme or by allocating two or more bands (e.g., using an inter-band CA scheme) to a single user. Front end circuitry  30  therefore needs to be sufficiently wideband to support these channel bandwidths and to allow for transmission and/or reception using intra-band CA or inter-band CA. It may also be desirable for front end circuitry  30  to support these operating modes while minimizing silicon area and complexity (e.g., without utilizing dedicated transmit/receive chains for each frequency band). 
     When operating at these frequency bands and supporting intra-band and inter-band CA, there may be situations where strong interference at other millimeter wave bands create intermodulation tones in the conveyed radio-frequency signals, which could degrade in-band signal sensitivity. It would therefore be desirable for front end circuitry  30  to be reconfigurable to support both wideband operations for inter-band CA and frequency selective filtering to reject interferences from other frequency bands. 
       FIG.  2    is a simplified schematic diagram showing one example of reconfigurable front end circuitry  30 . As shown in  FIG.  2   , wireless circuitry  24  may include front end circuitry  30  coupled to a corresponding antenna  34 . Front end circuitry  30  may include one or more low noise amplifiers such as low noise amplifier (LNA)  36 . The input of LNA  36  may be coupled to antenna  34 . The output of LNA  36  may be coupled to one or more receiver chains each with a corresponding phase and magnitude controller (e.g., for performing beam steering when antenna  34  is implemented in a phased antenna array). The phase and magnitude controllers may include phase shifters  38  and amplifiers (e.g., variable gain amplifiers)  40 . The output of the phase and magnitude controllers may be coupled to one or more signal combiners  42 . Signal combiners  42  may include one or more switches, filters, multiplexers, demultiplexers, couplers, etc. 
     Front end circuitry  30  may be adjustable (e.g., switchable or reconfigurable) between at least three different operating modes. Front end circuitry  30  may include an adjustable impedance matching network that is controlled to place front end circuitry  30  in a selected one of the three different operating modes at a given time. The adjustable impedance matching network may be a multi-coil transformer-based impedance matching network. In one implementation that is described herein as an example, the adjustable impedance matching network may be disposed within LNA  36 . This is merely illustrative and, in general, the adjustable impedance matching network may be disposed elsewhere in front end circuitry  30  (e.g., between LNA  36  and antenna  34 , between LNA  36  and phase shifter(s)  38 , within amplifier(s)  40 , etc.). The adjustable impedance matching network in LNA  36  may receive control signals CTRL (e.g., from control circuitry  14  of  FIG.  1   ). Control signals CTRL may adjust one or more components of the adjustable impedance matching network to place LNA  36  and thus front end circuitry  30  in a selected one of the three different operating modes (states). 
     The operating modes (states) of LNA  36  and front end circuitry  30  may include a wideband operating mode, a first band rejection operating mode, and a second band rejection operating mode. In the wideband operating mode, control signals CTRL may control one or more components in the adjustable impedance matching network to configure the adjustable impedance matching network (and thus LNA  36 ) to exhibit a wideband transfer function  50 A, as shown by plot  44  (plotting voltage as a function of frequency F). Wideband transfer function  50 A may have a passband that encompasses both a first frequency band B 1  and a second frequency band B 2  at higher frequencies than the first frequency band. While in the wideband operating mode, the wideband transfer function  50 A of the adjustable impedance matching network may allow front end circuitry  30  to concurrently convey radio-frequency signals in both first frequency band B 1  and in second frequency band B 2  (e.g., using an inter-band CA scheme). However, the presence of interference signals within the passband may degrade reception of the signal of interest. 
     In the first band rejection operating mode, control signals CTRL may control one or more components in the adjustable impedance matching network to configure the adjustable impedance matching network (and thus LNA  36 ) to exhibit a first band rejection transfer function  50 B, as shown by plot  46 . Transfer function  50 B may have a passband that encompasses or overlaps second frequency band B 2  and a stop band that encompasses or overlaps first frequency band B 1 . While in the first band rejection operating mode, the transfer function  50 B of the adjustable impedance matching network may allow front end circuitry  30  to convey radio-frequency signals in second frequency band B 2  while blocking (rejecting) undesirable interference signals in first frequency band B 1 . This may prevent the interference signals from leaking onto the radio-frequency signals in second frequency band B 2  and degrading in-band signal sensitivity in second frequency band B 2 . 
     In the second band rejection operating mode, control signals CTRL may control one or more components in the adjustable impedance matching network to configure the adjustable impedance matching network (and thus LNA  36 ) to exhibit a second band rejection transfer function  50 C, as shown by plot  48 . Transfer function  50 C may have a passband that encompasses or overlaps first frequency band B 1  and a stop band that encompasses or overlaps second frequency band B 2 . While in the second band rejection operating mode, the transfer function  50 C of the adjustable impedance matching network may allow front end circuitry  30  to convey radio-frequency signals in first frequency band B 1  while blocking (rejecting) undesirable interference signals in first frequency band B 2 . This may prevent the interference signals from leaking onto the radio-frequency signals in first frequency band B 1  and degrading in-band signal sensitivity in first frequency band B 1 . Control circuitry  14  may use control signals CTRL to switch front end circuitry  30  between the wideband operating mode, the first band rejection operating mode, and the second band rejection operating mode in real time as needed (e.g., based on the frequency bands of operation of wireless circuitry  24  and/or based on where interference signals are present in frequency at any given time). 
       FIG.  3    is a schematic diagram showing one example of how LNA  36  may include an adjustable impedance matching network. As shown in  FIG.  3   , LNA  36  may include one or more amplifier stages  52 . For example, LNA  36  may include at least a jth stage  52 - j  having an output communicably coupled to the input of a subsequent kth stage  52 - k . One or more signal paths (e.g., a differential signal path) such as signal paths  54 - 1  and  54 - 2  may couple the output of stage  52 - j  to the input of stage  52 - k.    
     LNA  36  may include an adjustable impedance matching network such as adjustable impedance matching network  56 . Adjustable impedance matching network  56  may include an input port  58  coupled to the output of stage  52 - j  (e.g., via a portion of signal paths  54 - 1  and  54 - 2 ) and may include an output port  60  coupled to the input of stage  52 - k  (e.g., via a portion of signal paths  54 - 1  and  54 - 2 ). Adjustable impedance matching network  56  may include one or more resistors, one or more capacitors, and/or one or more inductors operatively coupled to signal paths  54 - 1  and/or  54 - 2 . Adjustable impedance matching network  56  may include one or more transformers formed from two or more of the inductors (coils). Adjustable impedance matching network  56  may, for example, include a multi-coil transformer having four inductors (coils). Adjustable impedance matching network  56  may therefore sometimes be referred to herein as transformer-based adjustable impedance matching network  56 , transformer-based impedance matching network  56 , multi-coil transformer-based adjustable impedance matching network  56 , multi-coil transformer-based impedance matching network  56 , adjustable impedance matching circuitry  56 , impedance matching circuitry  56 , transformer-based impedance matching circuitry  56 , transformer-based adjustable impedance matching circuitry  56 , or multi-coil transformer-based adjustable impedance matching circuitry  56 . 
     The example of  FIG.  3    in which adjustable impedance matching network  56  is interposed between amplifier stages  52 - j  and  52 - k  is merely illustrative. If desired, there may be no amplifier stage coupled to input port  58  and/or output port  60  (e.g., adjustable impedance matching network  56  may be coupled to the input of the first stage in LNA  36  or to the output of the last stage in LNA  36 ) or adjustable impedance matching network  56  may be disposed elsewhere in front end circuitry  30  ( FIG.  2   ) (e.g., input port  58  and/or output port  60  may be coupled to radio-frequency transmission line path  32  ( FIG.  1   ), input port  58  may be coupled to antenna  34 , output port  60  may be coupled to LNA  36 , input port  58  and/or output port  60  may be coupled to phase shifter  38  ( FIG.  2   ), etc.). 
     In some implementations, the adjustable impedance matching network includes a switched capacitor and an inductor coupled in parallel between signal paths  54 - 1  and  54 - 2 , with equivalent parallel resistances on either side of the switched capacitor and the inductor. In these implementations, the switched capacitor is adjusted to tune the resonance of the inductor and thus the frequency of interest to allow the adjustable impedance matching network to exhibit satisfactory rejection to interferences outside of the corresponding resonant band. However, such implementations do not allow for reception of signals in both frequency bands B 1  and B 2  simultaneously (e.g., does not allow for inter-band CA) due to its narrow bandwidth. In addition, the center frequency is sensitive to capacitor process variations and may require calibration or trimming. Further, the frequency tuning range exhibits a severe trade off with the Q factor of the switched capacitor, especially for millimeter wave frequencies. 
     In other implementations, the adjustable impedance matching network includes a transformer having only first and second magnetically-coupled inductors that are coupled between signal paths  54 - 1  and  54 - 2 . A shunt LC notch filter (e.g., a series-coupled capacitor and inductor) is then coupled between signal paths  54 - 1  and  54 - 2 , with equivalent parallel resistances and capacitances coupled between signal paths  54 - 1  and  54 - 2  on either side of the LC notch filter and transformer. This transformer exhibits a low magnetic coupling constant (factor) k as a fourth order network that provides wideband matching, where the LC notch filter is tuned to the frequency where interference presents. Such implementations may therefore allow for simultaneous signal reception in both frequency bands B 1  and B 2 . However, the LC notch filter can load the transformer at the signal of interest if the notch frequency is not far away from in-band, the LC notch filter may lead to an undesirable increase in chip area consumed by the adjustable impedance matching network, and the LC notch filter covers an excessively narrow frequency range. 
     To mitigate these issues (e.g., allowing adjustable impedance matching network  56  to cover both frequency bands B 1  and B 2  while allowing the adjustable impedance matching network to dynamically filter out interference in either frequency band as needed, minimizing chip area, minimizing cost, minimizing complexity, and/or minimizing process variation), adjustable impedance matching network  56  may include a multi-coil transformer that is controlled to switch adjustable impedance matching network  56  between the wideband operating mode, the first band rejection operating mode, and the second band rejection operating mode. 
       FIG.  4    is a circuit diagram showing how adjustable impedance matching network  56  may include a multi-coil transformer that is controlled to switch adjustable impedance matching network  56  between the wideband operating mode, the first band rejection operating mode, and the second band rejection operating mode. As shown in  FIG.  4   , adjustable impedance matching network  56  may have a multi-coil transformer  68  disposed along signal paths  54 - 1  and  54 - 2  between input port  58  and output port  60 . Multi-coil transformer  68  may include more than two inductors. 
     For example, multi-coil transformer  68  may include a first inductor (coil) L 1  having terminals  64  coupled to signal paths  54 - 1  and  54 - 2 . Multi-coil transformer  68  may include a second inductor (coil) L 2  having terminals  66  coupled to signal paths  54 - 1  and  54 - 2 . First inductor L 1  may be magnetically coupled to second inductor L 2  via a magnetic coupling characterized by magnetic coupling constant (factor) k 12 . Equivalent parallel resistance R 1  and capacitance C 1  may be coupled between signal paths  54 - 1  and  54 - 2  between input port  58  and first inductor L 1 . Equivalent parallel resistance R 2  and capacitance C 2  may be coupled between signal paths  54 - 1  and  54 - 2  between output port  60  and second inductor L 2 . 
     Multi-coil transformer  68  may include a third inductor (coil) L 3 . Third inductor L 3  may have no electrical connection to signal paths  54 - 1  and  54 - 2 . However, the terminals of third inductor L 3  may be coupled to respective terminals (electrodes) of adjustable capacitor C 3 . Third inductor L 3  and adjustable capacitor C 3  may therefore be floating with respect to the signal path. Third inductor L 3  may be magnetically coupled to first inductor L 1  via a magnetic coupling characterized by magnetic coupling constant (factor) k 13 . Third inductor L 3  may also be magnetically coupled to second inductor L 2  via a magnetic coupling characterized by magnetic coupling constant (factor) k 23 . 
     Multi-coil transformer  68  may also include a fourth inductor (coil) L 4 . Fourth inductor L 4  may have no electrical connection to signal paths  54 - 1  and  54 - 2 . However, the terminals of fourth inductor L 4  may be coupled to respective terminals (electrodes) of adjustable capacitor C 4 . Fourth inductor L 4  and adjustable capacitor C 4  may therefore be floating with respect to the signal path. Fourth inductor L 4  may be magnetically coupled to first inductor L 1  via a magnetic coupling characterized by magnetic coupling constant (factor) k 14 . Fourth inductor L 4  may also be magnetically coupled to second inductor L 2  via a magnetic coupling characterized by magnetic coupling constant (factor) k 24 . 
     Adjustable capacitors C 3  and C 4  may receive control signals CTRL (e.g., at control terminals or inputs of the adjustable capacitors). Adjustable capacitors C 3  and C 4  may, for example, be programmable/adjustable capacitors having capacitances that are adjusted using control signals CTRL. Control signals CTRL may be used to switch the operating mode of adjustable impedance matching network  56  by changing the capacitances of adjustable capacitors C 3  and/or C 4 . In general, coupling constant k 12  between inductors L 1  and L 2  may allow multi-coil transformer  68  and thus adjustable impedance matching network  56  to exhibit wideband transfer function  50 A ( FIG.  2   ) when operated in the wideband operating mode. Magnetic coupling constants k 13 , k 23 , k 14 , and k 24  may introduce zeroes at output  60  in the first and second band rejection operating modes. 
     For example, inductors L 1 , L 3 , and L 2  may be configured such that the magnetic coupling constant k 13  between inductors L 1  and L 3  is equal to the magnetic coupling constant k 23  between inductors L 2  and L 3 . Magnetic coupling constants k 13  and k 23  may therefore sometimes each be referred to herein as a first magnetic coupling constant k 1  (e.g., where k 1 =k 13 =k 23 ). At the same time, inductors L 1 , L 4 , and L 2  may be configured such that the magnetic coupling constant k 14  between inductors L 1  and L 4  is equal to the negative (inverse) of magnetic coupling constant k 24  between inductors L 2  and L 4  (e.g., where k 24 =−k 14  or k 14 =−k 24 ). Magnetic coupling constant k 14  may sometimes be referred to herein more simply as a second magnetic coupling constant k 2 , where the magnetic coupling constant k 24  between inductors L 2  and L 4  is sometimes referred to herein as the negative/inverse of second magnetic coupling constant k 2  (e.g., where k 24 =−k 2 ). Configuring magnetic coupling constants k 13 , k 23 , k 14 , and k 24  in this way may allow adjustable impedance matching network  56  to achieve notch filtering in one frequency band (e.g., frequency band B 1  or B 2 ) without impacting the in-band signal in the other frequency band (e.g., frequency band B 2  or B 1 ) while operating in the first or second band rejection operating modes. Inductors L 3 , L 4 , L 1  , and/or L 2  may be shaped and/or placed at locations relative to each other that are selected in such a way so as to configure the magnetic coupling constants to exhibit these values (e.g., to configure k 13  to be equal to magnetic coupling constant k 23  and to configure magnetic coupling constant k 14  to be equal to −k 24 ). Control signals CTRL may reconfigure adjustable capacitors C 3  and C 4  to switch adjustable impedance matching network  56  between operating modes and to tune the notch filtering frequency exhibited by the transfer function of adjustable impedance matching network  56 . 
     If desired, an optional signal peak detector  62  may be disposed at one or more locations within adjustable impedance matching network  56  for detecting interference signals conveyed over signal paths  54 - 1  and  54 - 2 . Peak detector  62  may, for example, be interposed on or coupled to locations within inductor L 4  and/or may be interposed on or coupled to locations within third inductor L 3  (e.g., via path  64 ). Peak detector  62  may process signals conveyed over signal paths  54 - 1  and  54 - 2  to detect the presence of interference signals in one or more frequency bands. For example, peak detector  62  may detect the presence and frequency of an interference signal on first frequency band B 1  and/or on second frequency band B 2 . Control circuitry  14  ( FIG.  1   ) may use information about the interference signal gathered by peak detector  62  to know when and how to adjust the operating mode of adjustable impedance matching network  56 . For example, when no interference signal is detected, control circuitry  14  may place adjustable impedance matching network  56  in the wideband operating mode. When peak detector  62  detects an interference signal in first frequency band B 1 , control circuitry  14  may place adjustable impedance matching network  56  in the first band rejection mode and may optionally tune one of the adjustable capacitors so the transfer function rejects the interference signal in first frequency band B 1 . When peak detector  62  detects an interference signal in second frequency band B 2 , control circuitry  14  may place adjustable impedance matching network  56  in the second band rejection mode and may optionally tune one of the adjustable capacitors so the transfer function rejects the interference signal in second frequency band B 2 . This may allow wireless circuitry  24  to dynamically filter out interference signals while otherwise exhibiting as wide a bandwidth as possible (e.g., for performing inter-band CA). 
       FIGS.  5 A-C  are top-down layout diagrams of multi-coil transformer  68 . As shown in  FIGS.  5 A-C , multi-coil transformer  68  may be formed on a dielectric substrate such as dielectric substrate  70 . Dielectric substrate  70  may, for example, include multiple vertically-stacked dielectric layers (e.g., dielectric layers that are stacked in the direction of the Z-axis of  FIGS.  5 A- C ). First inductor L 1  may be formed from first conductive traces  74  on dielectric substrate  70 . Second inductor L 2  may be formed from second conductive traces  76  on dielectric substrate  70 . Third inductor L 3  may be formed from third conductive traces  78  on dielectric substrate  70 . Fourth inductor L 4  may be formed from fourth conductive traces  80  on dielectric substrate  70 . 
     As one example, third conductive traces  78  and fourth conductive traces  80  may be patterned onto a first layer of dielectric substrate  70  (e.g., within a first metallization layer), first conductive traces  74  may be patterned onto a second layer of dielectric substrate  70  (e.g., within a second metallization layer), and second conductive traces  76  may be patterned onto a third layer of dielectric substrate  70  (e.g., within a third metallization layer, where the second metallization layer is interposed between the first and third metallization layers). In this example, first inductor L 1  may also include conductive vias and conductive traces on the second and/or third metallization layers that allow first inductor L 1  to overlap one or more of inductors L 2 -L 4  without contacting the conductive material in inductors L 2 -L 4  and/or to allow any one of inductors L 1 -L 4  to coil more than once around its respective opening (e.g., at cross-over points  75 ). This example is merely illustrative and, in general, inductors L 1 -L 4  may be disposed on any desired number of two or more layers in dielectric substrate  70 , one or more of the inductors may be distributed across two or more of the layers in dielectric substrate  70 , and the layers may be disposed in any order in dielectric substrate  70  (e.g., different relative positioning between inductors L 1 -L 4  along the Z-axis may be used). 
     Conductive ground traces such as ground traces  72  may be patterned onto dielectric substrate  70 . Ground traces  72  may laterally surround multi-coil transformer  68 . If desired, ground traces  72  may be patterned on two or more layers of dielectric substrate  70 . In these examples, conductive vias may couple the ground traces on each of the layers together. Ground traces  72  may be held at a reference potential and may help to electromagnetically shield multi-coil transformer  68 . 
     First conductive traces  74  in first inductor L 1  may follow a loop or coil (e.g., spiral) path that wraps, runs, extends, or coils at least once around a first opening  84 . Second conductive traces  76  in second inductor L 2  may follow a loop or coil (e.g., spiral) path that wraps, runs, extends, or coils at least once around a second opening  86 . Third conductive traces  78  in third inductor L 3  may follow a loop or coil (e.g., spiral) path that wraps, runs, extends, or coils at least once around a third opening  90 . Fourth conductive traces  70  in fourth inductor L 4  may follow a loop or coil (e.g., spiral) path that wraps, runs, extends, or coils at least once around a fourth opening  88 . 
     The layout and relative placement of conductive traces  74 - 80  may be selected to configure the magnetic coupling constant k 13  between conductive traces  74  and  78  (e.g., between inductors L 1  and L 3 ) to be equal to the magnetic coupling constant k 23  between conductive traces  76  and  78  (e.g., between inductors L 2  and L 3 ). At the same time, the layout and relative placement of conductive traces  74 - 80  may be selected to configure the magnetic coupling constant k 14  between conductive traces  74  and  80  (e.g., between inductors L 1  and L 4 ) to be equal to the negative of the magnetic coupling constant k 24  between conductive traces  76  and  80  (e.g., between inductors L 2  and L 4 ). 
     For example, as shown in  FIGS.  5 A-C , first conductive traces  74  of first inductor L 1  may at least partially overlap second conductive traces  76  of second inductor L 2  (e.g., opening  84  of first inductor L 1  may at least partially overlap opening  86  of second inductor L 2 ). At the same time, fourth conductive traces  80  in fourth inductor L 4  may at least partially overlap second conductive traces  76  in second inductor L 2  without overlapping first conductive traces  74  in first inductor L 1  (e.g., opening  88  of fourth inductor L 4  may overlap opening  86  of second inductor L 2  without overlapping opening  84  of first inductor L 1 ). In addition, third conductive traces  78  in third inductor L 3  may at least partially overlap first conductive traces  74  in first inductor L 1 , second conductive traces  76  in second inductor L 2 , and fourth conductive traces  80  in fourth inductor L 4  (e.g., opening  90  of third inductor L 3  may at least partially overlap opening  84  of first inductor L 1 , may at least partially overlap opening  86  of second inductor L 2 , and may overlap an entirety of fourth inductor  14  and/or opening  88  in fourth inductor L 4 ). 
     When arranged in this way, inductors L 1  and L 2  form weakly coupled transformers having magnetic coupling constant k 12 . Third inductor L 3  shares a common magnetic flux with inductors L 1  and L 2 , thereby achieving the same coupling polarity (e.g., configuring magnetic coupling constant k 13  between inductors L 1  and L 3  to have the same polarity as magnetic coupling constant k 23  between inductors L 2  and L 3 ). The amount of overlap between opening  90  of third inductor L 3  and opening  84  of first inductor L 1  and the amount of overlap between opening  90  of third inductor L 3  and opening  86  of second inductor L 2  then configures the magnetic coupling constant k 13  between inductors L 1  and L 3  to be equal to the magnetic coupling constant k 23  between inductors L 2  and L 3  (e.g., equalizing the desired coupling strength). On the other hand, fourth inductor L 4  is wound once inside second inductor L 2  (e.g., overlapping opening  86  of second inductor L 2 ) and outside first inductor L 1  (e.g., without overlapping opening  84  of first inductor L 1 ), thereby achieving opposite coupling polarity with the same coupling strength (e.g., configuring magnetic coupling constant k 14  between inductors L 1  and L 4  to have opposite polarity but the same strength/magnitude as the magnetic coupling constant k 24  between inductors L 2  and L 4 ). 
     The layout shown in  FIGS.  5 A-C  is merely illustrative. In general, conductive traces  74 - 80  may have any desired shapes (e.g., having any desired number of straight and/or curved segments) and any desired relative positioning (e.g., where the opening of each of inductors L 1 -L 4  at least partially overlaps the opening of one or more of the other inductors and/or does not overlap the opening of any of the other inductors in multi-coil transformer  68 ). As just one example, fourth conductive traces  80  and thus fourth inductor L 4  may overlap first inductor L 1  but not second inductor L 2  (e.g., fourth inductor L 4  may be disposed at location  82  such that opening  88  in fourth inductor  14  overlaps opening  84  in first inductor L 1 , an entirety of opening  88  in fourth inductor L 4  overlaps opening  90  in third inductor L 3 , and opening  88  in fourth inductor L 4  does not overlap any of opening  86  in second inductor L 2 ). 
     Terminals  64  of first inductor L 1  may be coupled to input port  58  and terminals  66  of second inductor L 2  may be coupled to output port  60  of adjustable impedance matching network  56  ( FIG.  4   ). First conductive traces  74  in first inductor L 1  may extend between terminals  64 . Second conductive traces  76  in second inductor L 2  may extend between terminals  66 . Adjustable capacitor C 3  may be coupled between opposing ends of third conductive traces  78 . Adjustable capacitor C 4  may be coupled between opposing ends of fourth conductive traces  80 . Adjustable capacitors C 3  and C 4  may be varactors, surface-mount capacitors that are soldered to substrate  70 , distributed adjustable capacitors, or any other desired adjustable/programmable capacitances. Adjustable capacitors C 3  and C 4  may receive control signals CTRL ( FIG.  4   ) to switch adjustable impedance matching network  56  between the wideband, first band rejection, and second band rejection operating modes. 
     Multi-stage amplifier design generally involves progressively increasing device size towards the last stage to maximize output power and linearity. This assumption may allow multi-coil transformer  68  to be equivalently represented as a balanced input/output impedance network followed by an ideal impedance transformer.  FIG.  6    is a diagram of multi-coil transformer  68  when represented as a balanced input/output impedance network followed by an ideal impedance transformer for the sake of simplicity. 
     As shown in  FIG.  6   , when assuming that LNA  36  includes progressively increasing device size towards its last stage  52 , a scaling factor m can be defined such that C 2  ( FIG.  4   ) can be written as C 2 =m*C 1 , such that R 2  ( FIG.  4   ) can be written as R 2 =R 1 /m, and such that L 2  ( FIG.  4   ) can be written as L 2 =L 1 /m. The inductors, resistors, and capacitors in  FIG.  3    have been rewritten in the simplified representation of  FIG.  6    to account for this assumption, modeling multi-coil impedance transformer  68  as including two inductors L 1  that exhibit magnetic coupling coefficient k 12  (instead of a first inductor L 1  and a second inductor L 2 ), followed by capacitance C 1  and R 1  between signal paths  54 - 1  and  54 - 2  and then an ideal impedance transformer  106  at output port  60 . This simplification will be applied to illustrate the operation of adjustable impedance matching network  56  below for the sake of simplicity. 
       FIG.  7    shows simplified equivalent circuit diagrams illustrating the effective electrical operation of multi-coil transformer  68  in the wideband operating mode. In the wideband operating mode, control circuitry  14  ( FIG.  1   ) may use control signal CTRL to turn (switch) off adjustable capacitor C 3  ( FIG.  5 A , which illustrates the wideband operating mode). This forms an open circuit in third inductor L 3  at the location of adjustable capacitor C 3 , configuring third inductor L 3  to form an open loop such that no current is induced on third inductor L 3  by inductors L 1  and L 2 . Control circuitry  14  may also use control signal CTRL to turn (switch) off adjustable capacitor C 4 . This forms an open circuit in fourth inductor L 4  at the location of adjustable capacitor C 4 , configuring fourth inductor L 4  to form an open loop such that no current is induced on fourth inductor L 4  by inductors L 1  and L 2 . 
     Current from signal paths  54 - 1  and  54 - 2  may flow through first inductor L 1  between terminals  64  in a first (e.g., clockwise) direction, as shown by arrows  92  of  FIG.  5   . The operation of multi-coil transformer  68  may be decomposed into an even mode and an odd mode (e.g., an even mode excitation and an odd mode excitation). In the even mode, current flows through second inductor L 2  between terminals  66  in the first (e.g., clockwise) direction, as shown by arrows  94  of  FIG.  5 A . At the same time, in the odd mode, current flows through second inductor L 2  between terminals  66  in a second (e.g., counterclockwise) direction opposite the first direction, as shown by arrows  96  of  FIG.  5 A . 
     Equivalent circuit diagram  108  of  FIG.  7    illustrates the even mode excitation of multi-coil transformer  68  when placed in the wideband operating mode (e.g., using the simplification assumptions of  FIG.  6   ). Equivalent circuit diagram  112  illustrates the odd mode excitation of multi-coil transformer  68  when placed in the wideband operating mode (e.g., having a current source coupled to the second inductor with opposite polarity relative to the even mode). The multi-coil transformer may form a fourth order matching network having a first pole produced by the even mode excitation at a first angular frequency ωp1 and having a second pole produced by the odd mode excitation at a second angular frequency ωp2. Equation  110  of  FIG.  7    defines first angular frequency ωp1 as a function of L 1  (e.g., the inductance of first inductor L 1 ) and C 1  (e.g., the capacitance of capacitor C 1 ). Equation  116  of  FIG.  7    defines second angular frequency ωp2 as a function of L 1  and C 1 . 
       FIG.  8    is a plot of the transfer function  50 A of adjustable impedance matching network  56  while in the wideband operating mode (in voltage V as a function of frequency). As shown in  FIG.  8   , transfer function  50 A may exhibit a first peak (pole) P 1  at a frequency corresponding to first angular frequency ωp1. Transfer function  50 A may also exhibit a second peak (pole) P 2  at a frequency corresponding to second angular frequency ωp2. As angular frequencies owl and ωp2 are a function of L 1  and C 1  (e.g., as shown by equations  110  and  116  of  FIG.  7   ), the magnitude of L 1  (e.g., the inductance of first inductor L 1 ) and C 1  (e.g., the capacitance of capacitor C 1 ) may be selected to tune the frequency of pole P 1  to align with a frequency F 1  in first frequency band B 1  and to tune the frequency of pole P 2  to align with a frequency F 2  in second frequency band B 2 . This may allow adjustable impedance matching network  56  to receive or transmit in both bands B 1  and B 2  simultaneously (e.g., using inter-band CA). 
       FIG.  9    shows simplified equivalent circuit diagrams illustrating the effective electrical operation of multi-coil transformer  68  in the first band rejection mode. In the first band rejection mode, control circuitry  14  ( FIG.  1   ) may use control signal CTRL to turn (switch) off adjustable capacitor C 4  ( FIG.  5 B , which illustrates the first band rejection mode). This forms an open circuit in fourth inductor L 4  at the location of adjustable capacitor C 4  (e.g., C 4 =0), configuring fourth inductor L 4  to form an open loop such that no current is induced on fourth inductor L 4  by inductors L 1  and L 2 . As such, fourth inductor L 4  does not affect the transfer function of adjustable impedance matching network  56  in the first band rejection mode. 
     At the same time, control circuitry  14  may use control signal CTRL to configure adjustable capacitor C 3  to exhibit a first capacitance value (e.g., a capacitance value that does not form an open circuit). In the even mode, current flows through first inductor L 1  between terminals  64  in the first (e.g., clockwise) direction, as shown by arrows  92  of  FIG.  5 B . Current also flows through second inductor L 2  between terminals  66  in the first direction, as shown by arrows  94  of  FIG.  5 B . First inductor L 1  and second inductor L 2  may both induce current on third inductor L 3  with the same polarity. For example, first inductor L 1  and second inductor L 2  may both induce current on third inductor L 3  in the second (e.g., counterclockwise) direction, as shown by arrow  98  of  FIG.  5 B . The first capacitance value of adjustable capacitor C 3  may tune the response of multi-coil transformer  68  to introduce a zero at output port  60  at a frequency that is selected to reject an interference signal present in the first frequency band Bl. 
     In the odd mode, current flows through first inductor L 1  in the first (e.g., clockwise) direction, as shown by arrows  92  of  FIG.  5 B . Current flows through second inductor L 2  in the second (e.g., counterclockwise) direction, as shown by arrows  96  of  FIG.  5 B . Inductors L 1  and L 2  may thereby induce the same magnitude of current on third inductor L 3  but with opposite polarity. For example, the current on first inductor L 1  may induce current on third inductor L 3  that flows in the second (e.g., counterclockwise) direction, as shown by arrow  98 , whereas the current on second inductor L 2  induces current of equal magnitude on third inductor L 3  but that flows in the first (e.g., clockwise) direction, as shown by arrow  100 . The current induced on third inductor L 3  by first inductor L 1  will thereby cancel out the current induced on third inductor L 3  by second inductor L 2 , causing adjustable capacitor C 3  to form a virtual open circuit in the odd mode. This may cause third inductor L 3  to be transparent to current induced by inductors L 1  and L 2  in the second frequency band B 2 . In this way, any interference signal in first frequency band B 1  can be nulled or rejected without affecting the gain of the signal of interest in second frequency band B 2 . 
     Equivalent circuit diagram  118  of  FIG.  9    illustrates the operation of multi-coil transformer  68  in the first band rejection mode. As shown by equivalent circuit diagram  118 , fourth inductor L 4  does not affect the response of the transformer because an open circuit is formed in fourth inductor L 4  by adjustable capacitor C 4 . As shown by arrows  120  of  FIG.  9   , the circuit may be decomposed into an even mode, shown by equivalent circuit diagram  122 , and an odd mode, shown by equivalent circuit diagram  124 . The even mode may produce a first peak (pole) at a first angular frequency ωp1 and a second peak (pole) at a second angular frequency ωp2, which are defined by equations  128 . The even mode may also produce a zero or null at a zero angular frequency coz, which is defined by equation  130 . Note that the zero angular frequency is only a function of magnetic coupling constant k 13 , magnetic coupling constant k 12 , the inductance of third inductor L 3 , and the capacitance of adjustable capacitor C 3 , and is independent of L 1  and C 1 . At the same time, the odd mode may produce a third peak (pole) at a third angular frequency ωp3, which is defined by equation  126 . This pole is at a relatively high frequency and has a gain not affected by the notch filter. 
       FIG.  10    is a plot of the transfer function  50 B of adjustable impedance matching network  56  while in the first band rejection operating mode (in voltage V as a function of frequency). As shown in  FIG.  10   , transfer function  50 B may exhibit a first peak (pole) P 1 , a second peak (pole) P 2 , and a third peak (pole) P 3 . The frequency of first pole P 1  corresponds to first angular frequency owl and the frequency of second pole P 2  corresponds to second angular frequency ωp2, as defined by equations  128  of  FIG.  9   . The frequency of third pole P 3  corresponds to third angular frequency ωp3, as defined by equation  126  of  FIG.  9   . Transfer function  50 B may also exhibit a zero Z. The frequency of zero Z corresponds to zero angular frequency ωz, as defined by equation  130  of  FIG.  9   . 
     Poles P 1  and P 2  may be shaped by selecting corresponding inductances and capacitances for inductors L 1  and L 3  and capacitors C 1  and C 3  (e.g., as shown by equations  128 ). Pole P 3  may be shaped by selecting a corresponding inductance and capacitance for first inductor L 1  and capacitor Cl (e.g., as shown by equation  126 ). Zero Z may be shaped by selecting a corresponding inductance and capacitance for third inductor L 3  and adjustable capacitor C 3 . Poles P 1 , P 2 , and P 3  and zero Z may be shaped to align zero Z with a frequency F 1  in first frequency band B 1  and to align poles P 2  and P 3  with second frequency band B 2 . This may configure adjustable impedance matching network  56  to receive or transmit in second frequency band B 2  while blocking interference signals in first frequency band B 1 . 
       FIG.  11    shows simplified equivalent circuit diagrams illustrating the effective electrical operation of multi-coil transformer  68  in the second band rejection mode. In the second band rejection mode, control circuitry  14  ( FIG.  1   ) may use control signal CTRL to turn (switch) off adjustable capacitor C 3  ( FIG.  5 C , which illustrates the second band rejection mode). This forms an open circuit in third inductor L 3  at the location of adjustable capacitor C 3  (e.g., C 3 =0), configuring third inductor L 3  to form an open loop such that no current is induced on third inductor L 3  by inductors L 1  and L 2 . As such, third inductor L 3  does not affect the transfer function of adjustable impedance matching network  56  in the second band rejection mode. At the same time, control circuitry  14  may use control signal CTRL to configure adjustable capacitor C 4  to exhibit a second capacitance value (e.g., a capacitance value that does not form an open circuit). 
     In the odd mode, current flows through first inductor L 1  in the first (e.g., clockwise) direction, as shown by arrows  92  of  FIG.  5 C . Current flows through second inductor L 2  in the second (e.g., counterclockwise) direction, as shown by arrows  96  of  FIG.  5 C . First inductor L 1  and second inductor L 2  may both induce current on fourth inductor L 4 , which overlaps second inductor L 2  but not first inductor L 1 , with the same polarity. For example, first inductor L 1  and second inductor L 2  may both induce current on fourth inductor L 4  in the first (e.g., clockwise) direction, as shown by arrow  102  of  FIG.  5 C . The second capacitance value of adjustable capacitor C 4  may be selected to tune the response of multi-coil transformer  68  to introduce a zero at output port  60  at a frequency that is selected to reject an interference signal present in the second frequency band B 2 . 
     In the even mode, current flows through first inductor L 1  between terminals  64  in the first (e.g., clockwise) direction, as shown by arrows  92  of  FIG.  5 C . Current also flows through second inductor L 2  between terminals  66  in the first direction, as shown by arrows  94  of FIG. Inductors L 1  and L 2  may thereby induce the same magnitude of current on fourth inductor L 4  but with opposite polarity. For example, the current on first inductor L 1  may induce current on fourth inductor L 4  that flows in the first (e.g., clockwise) direction, as shown by arrow  102  of  FIG.  5 C , whereas the current on second inductor L 2  induces current of equal magnitude on fourth inductor L 4  but that flows in the second (e.g., counterclockwise) direction, as shown by arrow  104  of  FIG.  5 C . The current induced on fourth inductor L 4  by first inductor L 1  will thereby cancel out the current induced on fourth inductor IA by second inductor L 2 , causing adjustable capacitor C 4  to form a virtual open circuit in the even mode. This may cause fourth inductor L 4  to be transparent to current induced by inductors L 1  and L 2  in the first frequency band B 1 . In this way, any interference signal in second frequency band B 2  can be nulled or rejected without affecting the gain of the signal of interest in first frequency band B 1 . 
     Equivalent circuit diagram  132  of  FIG.  11    illustrates the operation of multi-coil transformer  68  in the second band rejection mode. As shown by equivalent circuit diagram  132 , third inductor L 3  does not affect the response of the transformer because an open circuit is formed in third inductor L 3  by adjustable capacitor C 3 . As shown by arrows  134  of  FIG.  11   , the circuit may be decomposed into an even mode, shown by equivalent circuit diagram  136 , and an odd mode, shown by equivalent circuit diagram  138 . The even mode may produce a first peak (pole) at a first angular frequency ωp1, which is defined by equation  140 . This pole is at a relatively low frequency and has a gain not affected by the notch filter. The even mode may also produce a zero or null at a zero angular frequency ωz, which is defined by equation  142 . Note that the zero angular frequency is only a function of magnetic coupling constant k 14 , magnetic coupling constant k 12 , the inductance of fourth inductor L 4 , and the capacitance of adjustable capacitor C 4 , and is independent of L 1  and C 1 . At the same time, the odd mode may produce a second peak (pole) at a second angular frequency ωp2 and a third peak (pole) at a third angular frequency ωp3, which are defined by equations  144 . 
       FIG.  12    is a plot of the transfer function  50 C of adjustable impedance matching network  56  while in the second band rejection operating mode (in voltage V as a function of frequency). As shown in  FIG.  12   , transfer function  50 C may exhibit a first peak (pole) P 1 , a second peak (pole) P 2 , and a third peak (pole) P 3 . The frequency of first pole P 1  corresponds to first angular frequency ωp1 (as defined by equation  140  of  FIG.  11   ). The frequency of second pole P 2  corresponds to second angular frequency ωp2 and the frequency of third pole P 3  corresponds to third angular frequency ωp3, as defined by equations  144  of  FIG.  11   . Transfer function  50 C may also exhibit a zero Z. The frequency of zero Z corresponds to zero angular frequency ωz, as defined by equation  142  of  FIG.  11   . 
     Poles P 2  and P 3  may be shaped by selecting corresponding inductances and capacitances for inductors L 1  and L 4  and capacitors C 1  and C 4  (e.g., as shown by equations  144 ). Pole P 1  may be shaped by selecting a corresponding inductance and capacitance for first inductor L 1  and capacitor C 1  (e.g., as shown by equation  140 ). Zero Z may be shaped by selecting a corresponding inductance and capacitance for fourth inductor L 4  and adjustable capacitor C 4 . Poles P 1 , P 2 , and P 3  and zero Z may be shaped to align zero Z with a frequency F 2  in second frequency band B 2  and to align poles P 1  and P 2  with first frequency band B 1 . This may configure adjustable impedance matching network  56  to receive or transmit in first frequency band B 1  while blocking interference signals in first frequency band B 2 . 
       FIG.  13    is a flow chart of illustrative operations that may be performed by wireless circuitry  24  to convey radio-frequency signals while switching adjustable impedance matching network  56  between the wideband, first band rejection, and second band rejection operating modes. 
     At optional operation  150 , peak detector  62  ( FIG.  2   ) may measure the signal flowing through signal paths  54 - 1  and  54 - 2  to detect one or more signal peaks produced by interference signal(s) at one or more frequencies. Peak detector  62  may be interposed on inductors L 3  and/or L 4  of  FIG.  4   , as an example. Peak detector  62  may detect (e.g., measure, determine, identify, generate, etc.) the one or more frequencies of the interference signal(s). This may allow peak detector  62  to assess the real-time spectral characteristics of adjustable impedance matching network  56 . 
     At operation  152 , control circuitry  14  may select an operating mode for adjustable impedance matching network  56 . For example, control circuitry  14  may select the wideband operating mode, the first band rejection operating mode, or the second band rejection operating mode. Control circuitry  14  may select the operating mode based on the frequency band(s) to be used by wireless circuitry  24  to transmit or receive radio-frequency signals (e.g., as assigned to device  10  by a wireless base station or access point, as determined by the wireless communications protocol governing wireless circuitry, etc.). Control circuitry  14  may additionally or alternatively select the operating mode based on the interference signals detected by the peak detector and/or any other desired sensor data gathered by device  10 . 
     As examples, when device  10  has been assigned to communicate using both first frequency band B 1  and second frequency band B 2  (e.g., using inter-band CA) and peak detector  62  does not detect any interference signals in frequency bands B 1  and B 2 , control circuitry  14  may select the wideband operating mode. When device  10  has been assigned to communicate using only a single frequency band (e.g., when device  10  has been configured to operate without inter-band CA), control circuitry  14  may select the wideband operating mode, the first band rejection mode, or the second band rejection mode. When device  10  has been assigned to communicate using first frequency band B 1  (e.g., without inter-band CA) or when device  10  has been assigned to communicate using first frequency band B 1  and second frequency band B 2  (e.g., with inter-band CA) but peak detector  62  detects an interference signal peak in second frequency band B 2 , control circuitry  14  may select the second band rejection mode. Conversely, when device  10  has been assigned to communicate using second frequency band B 2  (e.g., without inter-band CA) or when device  10  has been assigned to communicate using first frequency band B 1  and second frequency band B 2  (e.g., with inter-band CA) but peak detector  62  detects an interference signal peak in first frequency band B 1 , control circuitry  14  may select the first band rejection mode. These examples are merely illustrative and, in general, control circuitry  14  may select the operating mode based on any desired control inputs or triggers. 
     At operation  154 , control circuitry  14  may place adjustable impedance matching network  56  in the selected operating mode. For example, control circuitry  14  may use control signals CTRL provided to adjustable capacitors C 3  and C 4  in multi-coil impedance transformer  68  to place the adjustable impedance matching network in the selected operating mode. Control signals CTRL may control adjustable capacitors to form open circuits and/or to adjust the non-open circuit value of one of the adjustable capacitors. Control circuitry  14  may actively adjust the non-open circuit value of one of the adjustable capacitors to tune the zero frequency of adjustable impedance matching network  56  (e.g., to align the zero frequency with the detected frequency of the interference signal). This may allow adjustable impedance matching network  56  to be dynamically configured to reject the interference signal even as the frequency of the interference signal changes over time. 
     At operation  156 , adjustable impedance matching network  56  and one or more corresponding antennas  34  ( FIG.  1   ) may convey radio-frequency signals while adjustable impedance matching network  56  is in the selected operating mode. This may allow adjustable impedance matching network  56  to cover a relatively wide bandwidth when needed (e.g., during inter-band CA) while also dynamically rejecting interference signals that may arise over time (e.g., thereby maximizing signal sensitivity and radio-frequency performance) without undesirably increasing the chip area consumed by the matching circuitry. Processing may subsequently loop back to operation  150  (or operation  152  when operation  150  is omitted) via path  158 , allowing wireless circuitry  24  to continue communications while adapting to changing interference conditions over time. 
     Device  10  may gather and/or use personally identifiable information. It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     The methods and operations described above in connection with  FIGS.  1 - 13    may be performed by the components of device  10  using software, firmware, and/or hardware (e.g., dedicated circuitry or hardware). Software code for performing these operations may be stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media) stored on one or more of the components of device  10  (e.g., storage circuitry  16  of  FIG.  1   ). The software code may sometimes be referred to as software, data, instructions, program instructions, or code. The non-transitory computer readable storage media may include drives, non-volatile memory such as non-volatile random-access memory (NVRAM), removable flash drives or other removable media, other types of random-access memory, etc. Software stored on the non-transitory computer readable storage media may be executed by processing circuitry on one or more of the components of device  10  (e.g., processing circuitry  18  of  FIG.  1   , etc.). The processing circuitry may include microprocessors, central processing units (CPUs), application-specific integrated circuits with processing circuitry, or other processing circuitry. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20220523
Publication Date: 20240123
Grant Date: 20240123
Priority Date: 20220523
Inventors: WANG, Hongrui
KOMIJANI, ABBAS
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/005", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F27/027", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/2804", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F2027/2809", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03H7/0115", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/005", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03H2001/0078", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03H7/0123", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03H7/0153", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03H7/0161", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03H7/09", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03H7/383", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03H2210/015", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03H2210/025", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03H7/466", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03H2007/386", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01F21/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F1/565", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F2200/294", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F3/195", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F2200/537", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F2200/168", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F2200/451", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/027", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F27/2804", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F2027/2809", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B1/401", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/0057", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 86332356