PATENT DOCUMENT

Publication Number: US-11595069-B2
Application Number: US-202117375843-A
Country: US
Kind Code: B2

Title: Transimpedance amplifier (TIA) with tunable input resistance

Abstract:
An electronic device may include wireless circuitry with a baseband processor, a transceiver, and an antenna. The transceiver may include a mixer that outputs signals to a transimpedance amplifier. The mixer has an output impedance that varies depending on the frequency of operation. An adjustable resistance can be coupled to the input of the transimpedance amplifier. A control circuit can tune the adjustable resistance to compensate for changes in the output impedance of the mixer as the transceiver operates across a wide range of frequencies.

Claims:
What is claimed is: 
     
       1. Wireless circuitry operable in a plurality of radio-frequency bands, comprising:
 a first amplifier configured to receive a radio-frequency signal via an antenna; 
 a mixer having a first input coupled to an output of the first amplifier, a second input coupled to an oscillator circuit, and an output; 
 a second amplifier having first and second amplifier input terminals coupled to the output of the mixer; and 
 an adjustable resistance having a first terminal coupled at the first amplifier input terminal and having a second terminal coupled at the second amplifier input terminal, the adjustable resistance being configured to adjust an input impedance of the second amplifier as the wireless circuitry is operated across the plurality of radio-frequency bands. 
 
     
     
       2. The wireless circuitry of  claim 1 , further comprising:
 a control circuit configured to increase a resistance value of the adjustable resistance as an output impedance of the mixer is decreased and to decrease the resistance value of the adjustable resistance as the output impedance of the mixer is increased. 
 
     
     
       3. The wireless circuitry of  claim 1 , further comprising:
 a first shunt capacitor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to a ground line; and 
 a second shunt capacitor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to the ground line. 
 
     
     
       4. The wireless circuitry of  claim 3 , further comprising:
 a first feedback capacitor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to a first amplifier output terminal of the second amplifier; and 
 a second feedback capacitor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to a second amplifier output terminal of the second amplifier. 
 
     
     
       5. The wireless circuitry of  claim 4 , further comprising:
 a first feedback resistor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to the first amplifier output terminal; and 
 a second feedback resistor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to the second amplifier output terminal. 
 
     
     
       6. The wireless circuitry of  claim 1 , wherein the second amplifier comprises a transimpedance amplifier. 
     
     
       7. The wireless circuitry of  claim 1 , wherein:
 the adjustable resistance comprises a plurality of resistive strings; and 
 each resistive string in the plurality of resistive strings comprises a first resistor, a second resistor, and a switch coupled between the first and second resistors in that resistive string. 
 
     
     
       8. The wireless circuitry of  claim 1 , wherein:
 the adjustable resistance comprises a plurality of resistive strings; and 
 each resistive string in the plurality of resistive strings comprises a first switch, a second switch, and a resistor coupled between the first and second switches in that resistive string. 
 
     
     
       9. A method of operating wireless circuitry in a plurality of radio-frequency bands, comprising:
 receiving signals at a first amplifier via an antenna; 
 mixing signals from the first amplifier and signals from an oscillator at a mixer having an output impedance; 
 receiving signals at a second amplifier from the mixer; and 
 tuning an adjustable resistor coupled to an input of the second amplifier based on changes in the output impedance of the mixer as the wireless circuitry is operated across the plurality of radio-frequency bands to provide a first resistance value when the wireless circuitry is operating in a first radio-frequency band in the plurality of radio-frequency bands and to provide a second resistance value greater than the first resistance value when the wireless circuitry is operating in a second radio-frequency band in the plurality of radio-frequency bands greater than the first radio-frequency band. 
 
     
     
       10. The method of  claim 9 , wherein:
 the adjustable resistor comprises a plurality of resistive strings each having a first resistor, a second resistor, and a switch coupled between the first and second resistors in that resistive string; and 
 tuning the adjustable resistor comprises selectively activating and deactivating the switch in each of the plurality of resistive strings. 
 
     
     
       11. The method of  claim 9 , wherein:
 the adjustable resistor comprises a plurality of resistive strings each having a first switch, a second switch, and a resistor coupled between the first and second switches in that resistive string; and 
 tuning the adjustable resistor comprises selectively activating and deactivating the first and second switches in each of the plurality of resistive strings. 
 
     
     
       12. The method of  claim 9 , wherein the second amplifier comprises a transimpedance amplifier having a bandwidth that is greater than 100 MHz. 
     
     
       13. An electronic device comprising:
 a mixer having a first input coupled to an antenna, a second input coupled to an oscillator, and an output with a variable output impedance; 
 an amplifier having inputs coupled to the output of the mixer; 
 an adjustable resistance coupled across the inputs of the amplifier and configured to adjust an input impedance of the amplifier based on the variable output impedance of the mixer; and 
 processing circuitry configured to receive data generated based on signals output by the amplifier. 
 
     
     
       14. The electronic device of  claim 13 , further comprising:
 a control circuit configured to tune the adjustable resistance as a function of the operating frequency of the amplifier. 
 
     
     
       15. The electronic device of  claim 13 , wherein:
 the input of the amplifier comprises a first amplifier input terminal and a second amplifier input terminal; and 
 the adjustable resistance has a first resistor terminal directly coupled to the first amplifier input terminal and a second resistor terminal directly coupled to the second amplifier input terminal. 
 
     
     
       16. The electronic device of  claim 15 , further comprising:
 a first shunt capacitor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to a ground line; and 
 a second shunt capacitor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to the ground line. 
 
     
     
       17. The electronic device of  claim 16 , wherein the amplifier comprises a first amplifier output terminal and a second amplifier output terminal and wherein the electronic device further comprises:
 a first feedback capacitor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to the first amplifier output terminal; 
 a second feedback capacitor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to the second amplifier output terminal; 
 a first feedback resistor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to the first amplifier output terminal; and 
 a second feedback resistor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to the second amplifier output terminal. 
 
     
     
       18. The electronic device of  claim 13 , wherein the adjustable resistance has a first resistance value when the mixer is operating at a first frequency and has a second resistance value greater than the first resistance value when the mixer is operating at a second frequency greater than the first frequency.

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 one or more antennas. Wireless receiver circuitry in the wireless communications circuitry uses the antennas to receive radio-frequency signals. 
     Signals received by the antennas are fed through a receiver, which often includes a mixer coupled to a transimpedance amplifier. It can be challenging to design a satisfactory receiver for an electronic device. 
     SUMMARY 
     An electronic device may include wireless communications circuitry. The wireless communications circuitry may include an antenna, a transceiver configured to receive radio-frequency signals from the antenna and to generate corresponding baseband signals, and a baseband processor configured to receive the baseband signals from the transceiver. 
     An aspect of the disclosure provides wireless circuitry operable in multiple radio-frequency bands and multiple radio-frequency standards. The wireless circuitry can include: an antenna configured to receive a radio-frequency signal; a first amplifier having an input coupled to the antenna and having an output; an oscillator circuit; a mixer having a first input coupled to the output of the first amplifier, having a second input coupled to the oscillator circuit, and having an output with an output impedance; a second amplifier having an input coupled to the output of the mixer; and an adjustable resistor coupled to the input of the second amplifier and configured to compensate for changes in the output impedance of the mixer as the wireless circuitry is operated across the plurality of radio-frequency bands. One or more shunt capacitors can be coupled to the input of the second amplifier. One or more feedback capacitors and feedback resistors can be coupled across the input and output of the second amplifier. The first amplifier can be a low noise amplifier, whereas the second amplifier can be a wideband transimpedance amplifier. The adjustable resistor can include multiple resistive strings each having at least one resistor and at least one switch selectively activated and deactivated depending on the operating frequency of the wireless circuitry. 
     An aspect of the disclosure provides a method of operating wireless circuitry in a plurality of radio-frequency bands. The method can include: using an antenna to receive a radio-frequency signal; using a first amplifier to receive signals from the antenna; using a mixer to receive signals from the first amplifier and to receive signals from an oscillator, the mixer having an output impedance; using a second amplifier to receive signals from the mixer; and tuning an adjustable resistor coupled to an input of the second amplifier to compensate for changes in the output impedance of the mixer as the wireless circuitry is operated across the plurality of radio-frequency bands. The adjustable resistor can be tuned to provide a first resistance value when the wireless circuitry is operating in a first radio-frequency band in the plurality of radio-frequency bands and can be tuned to provide a second resistance value greater than the first resistance value when the wireless circuitry is operating in a second radio-frequency band in the plurality of radio-frequency bands greater than the first radio-frequency band. 
     An aspect of the disclosure provides an electronic device. The electronic device can include: an antenna configured to receive radio-frequency signals; a baseband processor configured to receive baseband signals generated based on the radio-frequency signals; an oscillator; a mixer having a first input coupled to the antenna, having a second input coupled to the oscillator, and having an output; an amplifier having an input coupled to the output of the mixer; and an adjustable resistor coupled to the input of the amplifier. The electronic device can also include a control circuit configured to tune the adjustable resistor as a function of the operating frequency of the amplifier. One or more shunt capacitors can be coupled to the input of the amplifier. One or more feedback capacitors and feedback resistors can be coupled across the input and output of the amplifier. The amplifier can be a wideband transimpedance amplifier. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram of an illustrative electronic device having wireless communications circuitry in accordance with some embodiments. 
         FIG.  2    is a diagram of illustrative wireless communications circuitry having transceiver circuitry in accordance with some embodiments. 
         FIG.  3    is a diagram of illustrative multi-standard receiver circuitry in accordance with some embodiments. 
         FIG.  4    is a diagram of illustrative feedback receiver circuitry in accordance with some embodiments. 
         FIG.  5    is a diagram of illustrative receiver circuitry having an adjustable resistor coupled between a mixer and an amplifier in accordance with some embodiments. 
         FIG.  6    is a diagram plotting a mixer output impedance as a function of oscillator frequency in accordance with some embodiments. 
         FIG.  7    is a diagram plotting the resistance of an adjustable resistor configured to compensate for changes in the mixer output impedance as a function of oscillator frequency in accordance with some embodiments. 
         FIG.  8    is a circuit diagram of an illustrative adjustable resistor configured to compensate for changes in the mixer output impedance when operated across different radio-frequency bands in accordance with some embodiments. 
         FIG.  9    is a circuit diagram showing another embodiment of an illustrative adjustable resistor configured to compensate for changes in the mixer output impedance when operated across different radio-frequency bands. 
         FIG.  10    is a diagram showing different modes for operating receiver circuitry of the type shown in connection with  FIGS.  1 - 9    in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device may be provided with wireless receiver circuitry. The wireless receiver circuitry may include an antenna, a low noise amplifier configured to receive radio-frequency signals from the antenna, a mixer configured to receive signals from the low noise amplifier and to receive an oscillator signal, and a transimpedance amplifier configured to receive signals from the mixer. The wireless receiver circuitry may be operated in multiple radio-frequency bands across multiple standards. The mixer can have an output impedance that varies across the different radio-frequency bands. An adjustable resistor can be provided at the input of the transimpedance amplifier to compensate for the variation in the mixer output impedance. Configuring and operating the receiver circuitry in this way allows the performance of the transimpedance amplifier to be maintained across the different radio-frequency bands. 
       FIG.  1    is a diagram of an electronic device such as electronic device  10  that can be provided with such wireless receiver circuitry. Electronic device  10  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), 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, 5G New Radio (NR) protocols, etc.), MIMO protocols, 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 (e.g., radio detection and ranging (RADAR) protocols or other desired range detection protocols for signals conveyed at millimeter and centimeter wave frequencies), 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, electronic pencil (e.g., a stylus), 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  24  may include wireless communications circuitry such as wireless communications circuitry  34  (sometimes referred to herein as wireless circuitry  24 ) for wirelessly conveying radio-frequency signals. While control circuitry  14  is shown separately from wireless communications circuitry  24  for the sake of clarity, wireless communications 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 communications circuitry  24 ). As an example, control circuitry  14  (e.g., processing circuitry  18 ) may include baseband processor circuitry or other control components that form a part of wireless communications circuitry  24 . 
     Wireless communications circuitry  24  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry configured to amplify uplink radio-frequency signals (e.g., radio-frequency signals transmitted by device  10  to an external device), low-noise amplifiers configured to amplify downlink radio-frequency signals (e.g., radio-frequency signals received by device  10  from an external device), passive radio-frequency components, one or more antennas, transmission lines, and other circuitry for handling radio-frequency wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless circuitry  24  may include radio-frequency transceiver circuitry for handling transmission and/or reception of radio-frequency signals in various radio-frequency communications bands. For example, the radio-frequency transceiver circuitry may handle wireless local area network (WLAN) communications bands such as the 2.4 GHz and 5 GHz Wi-Fi® (IEEE 802.11) bands, wireless personal area network (WPAN) communications bands such as the 2.4 GHz Bluetooth® communications band, cellular telephone communications bands such as a cellular low band (LB) (e.g., 600 to 960 MHz), a cellular low-midband (LMB) (e.g., 1400 to 1550 MHz), a cellular midband (MB) (e.g., from 1700 to 2200 MHz), a cellular high band (HB) (e.g., from 2300 to 2700 MHz), a cellular ultra-high band (UHB) (e.g., from 3300 to 5000 MHz), or other cellular communications bands between about 600 MHz and about 5000 MHz (e.g., 3G bands, 4G LTE bands, 5G New Radio Frequency Range 1 (FR1) bands below 10 GHz, 5G New Radio Frequency Range 2 (FR2) bands at millimeter and centimeter wavelengths between 20 and 60 GHz, etc.), a near-field communications (NFC) band (e.g., at 13.56 MHz), satellite navigations bands (e.g., an L1 global positioning system (GPS) band at 1575 MHz, an L5 GPS band at 1176 MHz, a Global Navigation Satellite System (GLONASS) band, a BeiDou Navigation Satellite System (BDS) band, etc.), an ultra-wideband (UWB) communications band supported by the IEEE 802.15.4 protocol and/or other UWB communications protocols (e.g., a first UWB communications band at 6.5 GHz and/or a second UWB communications band at 8.0 GHz), and/or any other desired communications bands. The communications bands handled by such radio-frequency transceiver circuitry may sometimes be referred to herein as frequency bands or simply as “bands,” and may span corresponding ranges of frequencies. In general, the radio-frequency transceiver circuitry within wireless circuitry  24  may cover (handle) any desired frequency bands of interest. 
       FIG.  2    is a diagram showing illustrative components within wireless circuitry  24 . As shown in  FIG.  2   , wireless circuitry  24  may include a baseband processor such as baseband processor  26 , radio-frequency (RF) transceiver circuitry such as radio-frequency transceiver  28 , radio-frequency front end circuitry such as radio-frequency front end module (FEM)  40 , and antenna(s)  42 . Baseband processor  26  may be coupled to transceiver  28  over baseband path  34 . Transceiver  28  may be coupled to antenna  42  via radio-frequency transmission line path  36 . Radio-frequency front end module  40  may be interposed on radio-frequency transmission line path  36  between transceiver  28  and antenna  42 . 
     In the example of  FIG.  2   , wireless circuitry  24  is illustrated as including only a single baseband processor  26 , a single transceiver  28 , a single front end module  40 , and a single antenna  42  for the sake of clarity. In general, wireless circuitry  24  may include any desired number of baseband processors  26 , any desired number of transceivers  36 , any desired number of front end modules  40 , and any desired number of antennas  42 . Each baseband processor  26  may be coupled to one or more transceiver  28  over respective baseband paths  34 . Each transceiver  28  may include one or more transmitters configured to output uplink signals to antenna  42 , may include one or more receivers configured to receive downlink signals from antenna  42 , and may be coupled to one or more antennas  42  over respective radio-frequency transmission line paths  36 . Each radio-frequency transmission line path  36  may have a respective front end module  40  interposed thereon. If desired, two or more front end modules  40  may be interposed on the same radio-frequency transmission line path  36 . If desired, one or more of the radio-frequency transmission line paths  36  in wireless circuitry  24  may be implemented without any front end module interposed thereon. 
     Radio-frequency transmission line path  36  may be coupled to an antenna feed on antenna  42 . The antenna feed may, for example, include a positive antenna feed terminal and a ground antenna feed terminal. Radio-frequency transmission line path  36  may have a positive transmission line signal path such that is coupled to the positive antenna feed terminal on antenna  42 . Radio-frequency transmission line path  36  may have a ground transmission line signal path that is coupled to the ground antenna feed terminal on antenna  42 . This example is merely illustrative and, in general, antennas  42  may be fed using any desired antenna feeding scheme. If desired, antenna  42  may have multiple antenna feeds that are coupled to one or more radio-frequency transmission line paths  36 . 
     Radio-frequency transmission line path  36  may include transmission lines that are used to route radio-frequency antenna signals within device  10  ( FIG.  1   ). 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  10  such as transmission lines in radio-frequency transmission line path  36  may be integrated into rigid and/or flexible printed circuit boards. 
     In performing wireless transmission, baseband processor  26  may provide baseband signals to transceiver  28  over baseband path  34 . Transceiver  28  may further include circuitry for converting the baseband signals received from baseband processor  26  into corresponding radio-frequency signals. For example, transceiver circuitry  28  may include mixer circuitry  50  for up-converting (or modulating) the baseband signals to radio-frequencies prior to transmission over antenna  42 . Transceiver circuitry  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 include a transmitter component to transmit the radio-frequency signals over antenna  42  via radio-frequency transmission line path  36  and front end module  40 . Antenna  42  may transmit the radio-frequency signals to external wireless equipment by radiating the radio-frequency signals into free space. 
     In performing wireless reception, antenna  42  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  36  and front end module  40 . Transceiver  28  may include circuitry for converting the received radio-frequency signals into corresponding baseband signals. For example, transceiver  28  may use mixer circuitry  50  for down-converting (or demodulating) the received radio-frequency signals to baseband frequencies prior to conveying the received signals to baseband processor  26  over baseband path  34 . Mixer circuitry  50  can include oscillator circuitry such as a local oscillator  52 . Local oscillator  52  can generate oscillator signals that mixer circuitry  50  uses to modulate transmitting signals from baseband frequencies to radio frequencies and/or to demodulate the received signals from radio frequencies to baseband or intermediate frequencies. Transceiver  28  may further include an amplifier such as amplifier  54  configured to filter signals output from mixer circuitry  50 . 
     Front end module (FEM)  40  may include radio-frequency front end circuitry that operates on the radio-frequency signals conveyed (transmitted and/or received) over radio-frequency transmission line path  36 . Front end module may, for example, include front end module (FEM) components such as filter circuitry (e.g., low pass filters, high pass filters, notch filters, band pass filters, radio-frequency coupling/switching circuitry  44  (e.g., radio-frequency coupler, multiplexing circuitry, duplexer circuitry, diplexer circuitry, triplexer circuitry, one or more radio-frequency switches, etc.), radio-frequency amplifier circuitry such as one or more power amplifiers  46  and one or more low noise amplifiers  48 , impedance matching circuitry (e.g., circuitry that helps to match the impedance of antenna  42  to the impedance of radio-frequency transmission line  36 ), antenna tuning circuitry (e.g., networks of capacitors, resistors, inductors, and/or switches that adjust the frequency response of antenna  42 ), 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 antenna  42 . Each of the front end module components may be mounted to a common (shared) substrate such as a rigid printed circuit board substrate or flexible printed circuit substrate. If desired, the various front end module components may also be integrated into a single integrated circuit chip. 
     Circuitry  44 , amplifiers  46  and  48 , and other circuitry may be interposed within radio-frequency transmission line path  36 , may be incorporated into FEM  40 , and/or may be incorporated into antenna  42  (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 antenna  42  over time. 
     Transceiver  28  may be separate from front end module  40 . For example, transceiver  28  may be formed on another substrate such as the main logic board of device  10 , a rigid printed circuit board, or flexible printed circuit that is not a part of front end module  40 . 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 processor  26  and/or portions of transceiver  28  (e.g., a host processor on transceiver  28 ) may form a part of control circuitry  14 . Control circuitry  14  (e.g., portions of control circuitry  14  formed on baseband processor  26 , portions of control circuitry  14  formed on transceiver  28 , and/or portions of control circuitry  14  that are separate from wireless circuitry  24 ) may provide control signals (e.g., over one or more control paths in device  10 ) that control the operation of front end module  40 . 
     Transceiver circuitry  28  may include wireless local area network transceiver circuitry that handles WLAN communications 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 transceiver circuitry that handles the 2.4 GHz Bluetooth® band or other WPAN communications bands, cellular telephone transceiver circuitry that handles cellular telephone 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.), near-field communications (NFC) transceiver circuitry that handles near-field communications bands (e.g., at 13.56 MHz), satellite navigation receiver circuitry that handles satellite navigation 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) transceiver circuitry that handles communications using the IEEE 802.15.4 protocol and/or other ultra-wideband communications protocols, and/or any other desired radio-frequency transceiver circuitry for covering any other desired communications bands of interest. 
     Wireless circuitry  24  may include one or more antennas such as antenna  42 . Antenna  42  may be formed using any desired antenna structures. For example, antenna  42  may be an antenna with a resonating element that is 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. Two or more antennas  42  may be arranged into one or more phased antenna arrays (e.g., for conveying radio-frequency signals at millimeter wave frequencies). Parasitic elements may be included in antenna  42  to adjust antenna performance. Antenna  42  may be provided with a conductive cavity that backs the antenna resonating element of antenna  42  (e.g., antenna  42  may be a cavity-backed antenna such as a cavity-backed slot antenna). 
     Wireless circuitry  24  may be operable in multiple radio-frequency bands.  FIG.  3    is a diagram showing wireless circuitry  24  having multiple receiver blocks for handling (receiving) signals from the various radio-frequency bands. As shown in  FIG.  3   , wireless circuitry  24  may include a first receiver block RX 1  configured to receive from antenna  42  signals in a first radio-frequency band group BG 1 , a second receiver block RX 2  configured to receive from antenna  42  signals in a second radio-frequency band group BG 2 , a third receiver block RX 3  configured to receive from antenna  42  signals in a third radio-frequency band group BG 3 , and so on. Each radio-frequency band group may generally include multiple radio-frequency bands. During normal operation, only a selected one of the receiver blocks is activated depending on the desired radio-frequency band of operation. As an example, BG 1  may cover communications in the 0.6 to 1 GHz range, BG 2  may cover communications in the 1 to 1.8 GHz range, and BG 3  may cover communications in the 1.8 to 2.3 GHz range. These radio-frequency band ranges are merely illustrative. In general, each radio-frequency band can cover 400 MHz, less than 400 MHz, greater than 400 MHz, 500 MHz, 600 MHz, 700 MHz, or other frequency ranges. Local oscillator  52  can be used to supply oscillator signals to one or more receiver blocks. For example, a first local oscillator  52  might be used to cover both band groups BG 1  and BG 2 . A second local oscillator  52  might be used to cover only a single band group BG 3  (as an example). A third local oscillator  52  might be used to cover three or more band groups. 
     The example of  FIG.  3    in which wireless circuitry  24  includes three separate receiver blocks for handling different radio-frequency bands is merely illustrative. Such type of wireless receiver circuitry is sometimes referred to as a multi-band or multi-standard receiver. If desired, the receiver circuitry may include more or less than three separate receiver blocks. Amplifier  54  used within such multi-standard receiver is sometimes referred to herein as a “wideband” amplifier. 
     Each of receiver blocks RX 1 , RX 2 , and RX 3  may include a switching circuit such as radio-frequency switch  44  coupled to antenna  42  (or to a radio-frequency duplexer), a matching circuit such as matching circuit  47 , a radio-frequency amplifier such as low noise amplifier (LNA)  48  configured to receive signals from switch  44 , and a mixer circuit such as radio-frequency mixer  51  configured to receive amplified signals from low noise amplifier  48  and to receive an oscillator signal from a local oscillator  52 . Wireless circuitry  24  may include a single amplifier circuit such as amplifier  54  coupled to mixer  51  in each of the multiple receiver blocks. Amplifier  54  may, for example, be a transimpedance amplifier (TIA). Amplifier  54  may be a wideband amplifier that is capable of handling communications across all of the various radio-frequency band groups (e.g., BG 1 , BG 2 , BG 3 , etc.). Amplifier  54  of this type having a wide bandwidth while being capable of handling communications across multiple radio-frequency bands (standards) is sometimes referred to as a multi-band (multi-standard), wideband amplifier. 
     The example of  FIG.  3    in which wireless circuitry  24  includes multiple receiver blocks is merely illustrative.  FIG.  4    shows another embodiment in which wireless circuitry  24  is a feedback receiver capable of handling wireless communications in the various radio-frequency bands. The feedback receiver of  FIG.  4    can be used for power control and calibrating the transmit signal. As shown in  FIG.  4   , antenna  42  may be coupled to a transmit amplifier such as power amplifier  46  and may be coupled to receiver block RX via a radio-frequency coupler such as directional coupler  44 . Receiver block RX may further include a radio-frequency attenuating circuit such as attenuator  45  connected to coupler  44 , a low noise amplifier (LNA)  48  configured to receive signals from coupler  44  via attenuator  45 , and a radio-frequency mixer circuit such as mixer  51  configured to receive signals from low noise amplifier  48  and to receive an oscillator signal from local oscillator  52 . Mixer  51  may output demodulated signals to amplifier  54 . Amplifier  54  may be a multi-band, wideband transimpedance amplifier (as an example). 
     Receiver block RX may be configured to handle a wide range of radio-frequency bands. For example, receiver block RX may be operated in a first mode to handle wireless communications in a first radio-frequency band group from about 0.6 to 1 GHz, in a second mode to handle wireless communications in a second radio-frequency band group from about 1 to 1.8 GHz, in a third mode to handle wireless communications in a third radio-frequency band group from about 1.8 to 2.3 GHz, in a fourth mode to handle wireless communications in a fourth radio-frequency band group from about 2.3 to 2.9 GHz, and so on up to 7 GHz or greater. These radio-frequency bands are merely illustrative. The arrangement of  FIG.  4    in which a single receiver block RX is coupled to transmit amplifier  46  via a directional coupler  44  is sometimes referred to as a feedback receiver architecture. Compared to the multi-standard receiver of  FIG.  3   , the feedback receiver of  FIG.  4    generally exhibits a more relaxed noise sensitivity requirement. 
       FIG.  5    is a diagram showing additional details at the interface between mixer  51  and transimpedance amplifier  54 , which are applicable to the multi-standard receiver of the type described in connection with  FIG.  3   , the feedback receiver of the type described in connection with  FIG.  4   , and/or other wireless receiver architectures utilizing a wideband amplifier. As shown in  FIG.  5   , low noise amplifier  48 , mixer  51 , and transimpedance amplifier  54  may be differential circuits having differential input terminals and differential output terminals. 
     A set of shunt capacitors Cmix can be coupled to the output of mixer  51 , which is also coupled to the input of amplifier  54 . For instance, a first capacitor Cmix in the set of shunt capacitors has a first terminal coupled to a first input of amplifier  54  and a has a second terminal coupled to a ground power supply line (sometimes referred to as a ground line or ground), whereas a second capacitor Cmix in the set of shunt capacitors has a first terminal coupled to a second input of amplifier  54  and has a second terminal coupled to the ground line. 
     A set of feedback capacitors Cf can also be coupled across the input and output terminals of amplifier  54 . For example, a first feedback capacitor Cf in the set of feedback capacitors has a first terminal coupled to the first input of amplifier  54  and has a second terminal coupled to a first output of amplifier  54 . A second feedback capacitor Cf in the set of feedback capacitors has a first terminal coupled to the second input of amplifier  54  and has a second terminal coupled to a second output of amplifier  54 . 
     A set of feedback resistors Rf can also be coupled across the input and output terminals of amplifier  54 . For example, a first feedback resistor Rf in the set of feedback resistors has a first terminal coupled to the first input of amplifier  54  and has a second terminal coupled to the first output of amplifier  54  (i.e., first feedback resistor Rf may be coupled in parallel with first feedback capacitor Cf). A second feedback resistor Rf in the set of feedback resistors has a first terminal coupled to the second input of amplifier  54  and has a second terminal coupled to the second output of amplifier  54  (i.e., second feedback resistor Rf may be coupled in parallel with second feedback capacitor Cf). Configured in this way, transimpedance amplifier  54  and associated components Cmix, Cf, and Rf may be used collectively as a low pass filter circuit to provide low pass filtering functions and may sometimes be referred to as a baseband filter or baseband active filter. Each of the capacitors Cmix and/or Cf shown in  FIG.  5    may include a bank of switchable capacitors that can be adjusted by controller  64  to optionally tune the bandwidth of the baseband filter. Each of the feedback resistors Rf may also include a bank of switchable resistors that can be adjusted by controller  64  to optionally tune the gain of the baseband filter. Components Cmix, Cf, and Rf can be adjusted to control the bandwidth of the filter, whereas resistor Rf can be adjusted to control the gain of the filter. 
     Mixer  51  may have an output impedance Rout. The mixer output impedance Rout may be inversely proportional to the product of Cpar and f LO , where Cpar represents the parasitic capacitance at the output of LNA  48  and where f LO  represents the frequency of the oscillator signal generated by local oscillator  52 .  FIG.  6    is a diagram plotting mixer output impedance Rout as a function of oscillator frequency fin. As shown in  FIG.  6   , oscillator frequency f LO  may be varied across a wide frequency range (e.g., from 0.6 to 7.2 GHz) when supporting wideband operation. Since mixer output impedance Rout is inversely proportional to f LO , Rout decreases as frequency f LO  increases (as indicated by curve  60 ). Curve  60  shows how Rout can vary greatly (e.g., from more than 9 kΩ to less than 3 kΩ) across the wide operating frequency range of the oscillator. These Rout values are merely illustrative. The mixer Rout values can vary widely depending on the intended application and actual design of the receiver. 
     The bandwidth and stability of amplifier  54  varies as a function of mixer output impedance Rout. Thus, large variations in the mixer Rout can potentially degrade the amplifier bandwidth as the receiver operates in the different radio-frequency bands. One way of maintaining the target bandwidth of amplifier  54  as the mixer Rout varies is to tune the shunt capacitor(s) Cmix. Tuning Cmix and/or Cf to compensate for changes in mixer Rout can, however, cause the quality factor and the phase margin of amplifier  54  to change, which makes it challenging to design a receiver that satisfies performance criteria across all operating frequencies. 
     In accordance with some embodiments, an adjustable resistive circuit such as adjustable resistor Rin is coupled to the input of amplifier  54  to adjust the input impedance of amplifier  54  to help compensate for variations in mixer output impedance Rout (see, e.g.,  FIG.  5   ). Adjustable resistor Rin may have a first terminal coupled to the first input of amplifier  54  and a second terminal coupled to the second input of amplifier  54  (e.g., resistor Rin may be coupled across the differential input terminals of amplifier  54 ). Connected in this way, adjustable resistor Rin is effectively coupled in parallel with the mixer output impedance Rout. 
       FIG.  7    is a diagram plotting the resistance of adjustable resistor Rin as a function of oscillator frequency f LO . As shown by curve  62  in  FIG.  7   , resistor Rin may be tuned to exhibit an increasing resistance (i.e., an increasing real impedance value) as oscillator frequency f LO  is increased. Resistor Rin should be tuned such that the total parallel resistance of Rout and Rin remains constant across all of the radio-frequency bands of interest. Operated in this way, adjustable resistor Rin can be used to maintain the bandwidth of amplifier  54  by compensating for changes in the mixer Rout across the entire range of operating frequencies (e.g., Rin is increased when the mixer Rout decreases, and vice versa). Using adjustable (tunable) resistor Rin to compensate for variations in mixer Rout obviates the need to tune shunt capacitor(s) Cmix when changing from one operating frequency band to another, which can help ensure that the Q factor and the phase margin of amplifier  54  meets performance criteria across the entire range of operating frequencies. 
       FIG.  8    shows one suitable implementation of adjustable resistor Rin. As shown in  FIG.  8   , resistor Rin can have multiple strings of resistors coupled together in parallel between terminals  70  and  72 . Terminal  70  may be coupled to the first input terminal of amplifier  54 , whereas terminal  72  may be coupled to the second input terminal of amplifier  54 . 
     Adjustable resistor Rin (sometimes referred to as an adjustable resistance, adjustable resistor circuit, or an adjustable resistive circuit having real impedance values) may include multiple resistive strings such as a first resistor string having resistors R 1   a  and R 1   b  selectively activated by switch S 1  (e.g., switch S 1  may be coupled in series between resistors R 1   a  and R 1   b ), a second resistor string having resistors R 2   a  and R 2   b  selectively activated by switch S 2  (e.g., switch S 2  may be coupled in series between resistors R 2   a  and R 2   b ), a third resistor string having resistors R 3   a  and R 3   b  selectively activated by switch S 3  (e.g., switch S 3  may be coupled in series between resistors R 3   a  and R 3   b ), and so on. Switches S 1 -S 6  can be controlled by a switch control circuit such as control circuit  64  of  FIG.  5   . Switch control circuit  64  may be part of control circuitry  14  (see, e.g.,  FIG.  1   ). 
     The example of  FIG.  8    in which resistor Rin has six switchable resistor strings is merely illustrative. In general, resistor Rin can have any desired number of resistor strings. The various resistor strings in Rin can have the same resistance value or different resistance values. The on resistance of each resistor string in adjustable resistor Rin can be selected to provide the desired range of resistance to compensate for changes in the mixer Rout (e.g., such that different switch configurations can provide the corresponding compensation value of Rin as shown in curve  62  of  FIG.  7    depending on the operating frequency of the wireless receiver). For example, when operating in the highest radio-frequency band, all of the Rin switches can be turned off (deactivated). On the other hand, when operating in the lowest radio-frequency band, all of the Rin switches can be turned on (activated) to provide the lowest total resistance. Different subsets of switches can be selectively activated for operating frequencies between the two extremes. Control circuit  64  (see  FIG.  5   ) may store a lookup table (as an example) that determines which group of switches to activate depending on the current operating frequency. The gain, bandwidth, linearity, noise, and phase margin of amplifier  54  can be maintained for all resistance values of Rin. 
     The example of  FIG.  8    in which each resistor string in Rin has two resistors and one switch is merely illustrative.  FIG.  9    shows another suitable implementation of adjustable resistor Rin having resistor strings each with a single resistor and two switches. As shown in  FIG.  9   , adjustable resistor Rin (sometimes referred to as a resistor circuit or a resistive circuit having real impedance values) may include: a first resistor string having resistor R 1  selectively activated by switches S 1   a  and S 1   b  (e.g., resistor R 1  may be coupled in series between switches S 1   a  and S 1   b ); a second resistor string having resistor R 2  selectively activated by switches S 2   a  and S 2   b  (e.g., resistor R 2  may be coupled in series between switches S 2   a  and S 2   b ); a third resistor string having resistor R 3  selectively activated by switches S 3   a  and S 2   b  (e.g., resistor R 3  may be coupled in series between switches S 3   a  and S 3   b ), and so on. These switches can be controlled by a switch control circuit such as control circuit  64  of  FIG.  5   . 
     The example of  FIG.  9    in which resistor Rin has six switchable resistor strings is merely illustrative. In general, resistor Rin can have any desired number of resistor strings. The various resistor strings in Rin can have the same resistance value or different resistance values. The on resistance of each resistor string in adjustable resistor Rin can be selected to provide the desired range of resistance to compensate for changes in the mixer Rout (e.g., such that different switch configurations can provide the corresponding compensation value of Rin as shown in curve  62  of  FIG.  7    depending on the operating frequency of the wireless receiver). The gain, bandwidth, linearity, noise, and phase margin of amplifier  54  can be maintained for all resistance values of Rin. If desired, each resistor string might only have one resistor and one switch (e.g., the first resistor string can have only resistor R 1  coupled in series with S 1   a  while omitting S 1   b ; the second resistor string can have only resistor T 2  coupled in series with S 2   a  while omitting S 2   b ; etc.) 
       FIG.  10    is a diagram showing different modes of operation for receiver circuitry of the type shown in connection with  FIGS.  1 - 9   . As shown in  FIG.  10   , the receiver circuitry can be operated in a first mode such as mode  80  during which the receiver receives signals in a first radio-frequency band group BG 1 , in a second mode such as mode  82  during which the receiver receives signals in a second radio-frequency band group BG 2 , in a third mode such as mode  84  during which the receiver receives signals in a third radio-frequency band group BG 3 , and so on. 
     During mode  80  when operating in BG 1  (e.g., the lowest frequency operating band group), adjustable resistor Rin may be set to its minimum value Rlow by activating all or almost all of its resistor strings. During mode  82  when operating in BG 2  (e.g., the next operating band group above BG 1 ), adjustable resistor Rin may be adjusted to a different value to compensate for changes in the mixer Rout that result from switching from another mode to mode  82 . During mode  84  when operating in BG 3  (e.g., the next operating band group above BG 2 ), adjustable resistor Rin may be adjusted to a different value to compensate for changes in the mixer Rout that result from switching from another mode to mode  84 . In general, the receiver circuitry can be operated inn different modes of operation, where n can be equal to 5 or more, 6-10, 11-15, more than 10, or other suitable values. 
     The methods and operations described above in connection with  FIGS.  1 - 10    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  and/or wireless communications circuitry  24  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 in wireless circuitry  24 , processing circuitry  18  of  FIG.  1   , etc.). The processing circuitry may include microprocessors, application processors, digital signal processors, 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: 20210714
Publication Date: 20230228
Grant Date: 20230228
Priority Date: 20210714
Inventors: WOO, SANG HYUN
MRUGALLA, FLORIAN
Assignee: APPLE INC
CPC Classifications: [{"code": "H03F2200/451", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F2200/294", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B1/1638", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F3/193", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F1/56", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F1/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03F1/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F2200/294", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B1/1638", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/005", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03F3/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F2200/451", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F2200/451", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03F3/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F1/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03F2200/294", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B1/40", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 82117360