Trans-impedance amplifier (TIA) with tunable input resistance

Abstract

The present disclosure relates to a transimpedance amplifier (TIA) with tunable input resistance. An electronic device is disclosed that can include wireless circuitry with a baseband processor, a transceiver, and an antenna. The transceiver can include a mixer that outputs a signal to a transimpedance amplifier. The mixer has an output impedance that varies according to an operating frequency. A tunable resistance can be coupled to an input of the transimpedance amplifier. A control circuit can tune the tunable resistance to compensate for variations in the output impedance of the mixer when the transceiver operates over a wide range of frequencies.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 202210637930.2, filed on June 7, 2022, entitled "Transimpedance Amplifier (TIA) with Tunable Input Resistance".

[0002] This application claims priority to U.S. Patent Application No. 17 / 375,843, filed July 14, 2021, which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates in general to electronic devices, and more specifically to electronic devices having wireless communication circuitry. Background Technology

[0004] Electronic devices often possess wireless communication capabilities. Electronic devices with wireless communication capabilities have a wireless communication circuit, which includes one or more antennas. The wireless receiver circuit within this wireless communication circuit uses the antennas to receive radio frequency signals.

[0005] The signal received by the antenna is fed through a receiver, which typically includes a mixer coupled to a transimpedance amplifier. Designing a satisfactory receiver for electronic devices can be challenging. Summary of the Invention

[0006] Electronic devices may include wireless communication circuitry. Wireless communication circuitry may include: an antenna; a transceiver configured to receive radio frequency signals from the antenna and generate corresponding baseband signals; and a baseband processor configured to receive baseband signals from the transceiver.

[0007] One aspect of this disclosure provides a wireless circuit capable of operating across multiple radio frequency bands and multiple radio frequency standards. The wireless circuit may include: an antenna configured to receive radio frequency signals; a first amplifier having an input coupled to the antenna and an output; an oscillator circuit; a mixer having a first input coupled to the output of the first amplifier, a second input coupled to the oscillator circuit, and 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 variations in the output impedance of the mixer when the wireless circuit operates across the multiple radio frequency bands. One or more parallel capacitors may be coupled to the input of the second amplifier. One or more feedback capacitors and a feedback resistor may be coupled across the input and output of the second amplifier. The first amplifier may be a low-noise amplifier, and the second amplifier may be a wideband transimpedance amplifier. The adjustable resistor may include multiple resistor strings, each resistor string having at least one resistor and at least one switch, which are selectively enabled and disabled according to the operating frequency of the wireless circuit.

[0008] One aspect of this disclosure provides a method for operating a wireless circuit across multiple radio frequency bands. The method may include: receiving a radio frequency signal using an antenna; receiving a signal from the antenna using a first amplifier; receiving the signal from the first amplifier and a signal from an oscillator using a mixer having an output impedance; receiving the signal from the mixer using a second amplifier; and, when the wireless circuit operates across the multiple radio frequency bands, tuning an adjustable resistor coupled to the input of the second amplifier to compensate for variations in the output impedance of the mixer. When the wireless circuit operates in a first radio frequency band among the multiple radio frequency bands, the adjustable resistor may be tuned to provide a first resistance value, and when the wireless circuit operates in a second radio frequency band among the multiple radio frequency bands that is larger than the first radio frequency band, the adjustable resistor may be tuned to provide a second resistance value greater than the first resistance value.

[0009] One aspect of this disclosure provides an electronic device. The electronic device may include: an antenna configured to receive radio frequency (RF) signals; a baseband processor configured to receive baseband signals generated based on the RF signals; an oscillator; a mixer having a first input coupled to the antenna, a second input coupled to the oscillator, and 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 may further include control circuitry configured to tune the adjustable resistor according to the operating frequency of the amplifier. One or more parallel capacitors may be coupled to the input of the amplifier. One or more feedback capacitors and a feedback resistor may be coupled across the input and output of the amplifier. The amplifier may be a broadband transimpedance amplifier. Attached Figure Description

[0010] Figure 1 This is a diagram of an exemplary electronic device with wireless communication circuitry according to some implementation schemes.

[0011] Figure 2 This is a diagram illustrating an exemplary wireless communication circuit with transceiver circuitry according to some implementation schemes.

[0012] Figure 3 This is a diagram illustrating an exemplary multi-standard receiver circuit based on some implementation schemes.

[0013] Figure 4 This is a diagram illustrating an exemplary feedback receiver circuit based on some implementation schemes.

[0014] Figure 5 This is a diagram of an exemplary receiver circuit with an adjustable resistor coupled between a mixer and an amplifier, according to some implementation schemes.

[0015] Figure 6 It is a graph showing the change of mixer output impedance as a function of oscillator frequency, based on some implementation schemes.

[0016] Figure 7 This is a graph showing the resistance of an adjustable resistor configured to compensate for changes in the mixer output impedance as a function of the oscillator frequency, based on some implementation schemes.

[0017] Figure 8 This is a circuit diagram of an exemplary adjustable resistor according to some implementation schemes, which is configured to compensate for variations in the mixer output impedance when operating across different RF bands.

[0018] Figure 9This is a circuit diagram illustrating another embodiment of an exemplary adjustable resistor configured to compensate for variations in the mixer output impedance when operating across different radio frequency bands.

[0019] Figure 10 This illustrates the operational combination according to some implementation schemes. Figures 1 to 9 Illustrations of different modes of the receiver circuit of the type shown. Detailed Implementation

[0020] Electronic devices may include wireless receiver circuitry. This wireless receiver circuitry may include an antenna, a low-noise amplifier, a mixer, and a transimpedance amplifier. The low-noise amplifier is configured to receive radio frequency signals from the antenna, the mixer is configured to receive signals from the low-noise amplifier and an oscillator signal, and the transimpedance amplifier is configured to receive signals from the mixer. The wireless receiver circuitry can operate across multiple standards and multiple radio frequency bands. The mixer may have a variable output impedance across different radio frequency bands. An adjustable resistor may be placed at the input of the transimpedance amplifier to compensate for variations in the mixer's output impedance. Configuring and operating the receiver circuitry in this way allows the transimpedance amplifier's performance to be maintained across different radio frequency bands.

[0021] Figure 1 This is an illustration of an electronic device, such as electronic device 10, which may be equipped with such wireless receiver circuitry. Electronic device 10 may be: a computing device, such as a laptop computer, desktop computer, computer monitor containing an embedded computer, tablet computer, cellular phone, media player, or other handheld or portable electronic device; a smaller device, such as a wristwatch, a wristband, a headset or handset, a device embedded in glasses; or other equipment worn on a user's head; or other wearable or micro-devices, televisions, computer monitors without embedded computers, gaming devices, navigation devices, embedded systems (such as systems in which electronic equipment with a display is installed in a kiosk or car), voice-controlled speakers connected to the wireless internet, home entertainment devices, remote control devices, game controllers, peripheral user input devices, wireless base stations or access points, equipment that enables the functionality of two or more of these devices; or other electronic equipment.

[0022] like Figure 1As illustrated in the schematic diagram, device 10 may include components located on or within an electronic device housing, such as housing 12. Housing 12 (sometimes referred to as a shell) may be formed of plastic, glass, ceramic, fiber composite material, metal (e.g., stainless steel, aluminum, metal alloys, etc.), other suitable materials, or combinations thereof. In some cases, part or all of housing 12 may be formed of dielectric or other low-conductivity materials (e.g., glass, ceramic, plastic, sapphire, etc.). In other cases, housing 12, or at least some of the structures constituting housing 12, may be formed of metallic elements.

[0023] Device 10 may include control circuitry 14. Control circuitry 14 may include storage devices, such as storage circuitry 16. Storage circuitry 16 may include hard disk drive storage devices, non-volatile memory (e.g., flash memory configured to form a solid-state drive or other electrically programmable read-only memory), volatile memory (e.g., static random access memory or dynamic random access memory), etc. Storage circuitry 16 may include storage devices and / or removable storage media integrated within device 10.

[0024] 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 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 a non-transitory (tangible) computer-readable storage medium storing software code). This software code may sometimes be referred to as program instructions, software, data, commands, or code. The software code stored on storage circuitry 16 may be executed by processing circuitry 18.

[0025] Control circuitry 14 can be used to run software on device 10, such as satellite navigation applications, internet browsing applications, Voice over Internet Protocol (VoIP) telephone calling applications, email applications, media playback applications, operating system functions, etc. To support interaction with external equipment, control circuitry 14 can be used to implement communication protocols. Communication protocols that can be implemented using control circuitry 14 include: Internet Protocol, Wireless Local Area Network (WLAN) protocols (e.g., IEEE 802.11 protocol—sometimes referred to as...). Protocols for other short-range wireless communication links, such as This protocol may be any of the following: wireless personal area network (WPAN) protocols, IEEE 802.11ad protocols (e.g., ultra-wideband protocols), cellular phone 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 for signals transmitted at millimeter and centimeter wave frequencies or other desired distance detection protocols), or any other desired communication protocol. Each communication protocol may be associated with a corresponding radio access technology (RAT), which specifies the physical connection method used to implement the protocol.

[0026] Device 10 may include input-output circuitry 20. Input-output circuitry 20 may include input-output device 22. Input-output device 22 may be used to allow data to be supplied to device 10 and to allow data to be supplied from device 10 to external devices. Input-output device 22 may include user interface devices, data port devices, and other input-output components. For example, input-output device 22 may include touch sensors, displays, light-emitting components such as displays without touch sensor capability, buttons (mechanical, capacitive, optical, etc.), scroll wheels, touchpads, keypads, 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), capacitive 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 touchpads, mice, electronic pens (e.g., styluses), joysticks, and other input-output devices may be coupled to device 10 using wired or wireless connections (e.g., some of the input-output devices 22 may be peripherals of the main processing unit or other parts of device 10 coupled via wired or wireless links).

[0027] Input-output circuitry 24 may include wireless communication circuitry for wirelessly transmitting radio frequency signals, such as wireless communication circuitry 34 (sometimes referred to herein as wireless circuitry 24). Although control circuitry 14 is shown separately from wireless communication circuitry 24 for clarity, wireless communication circuitry 24 may include processing circuitry and / or storage circuitry, the processing circuitry forming part of processing circuitry 18 and the storage circuitry forming part of storage circuitry 16 of control circuitry 14 (e.g., portions of control circuitry 14 may be implemented on wireless communication circuitry 24). For example, control circuitry 14 (e.g., processing circuitry 18) may include baseband processor circuitry or other control components forming part of wireless communication circuitry 24.

[0028] The wireless communication circuit 24 may include a radio frequency (RF) transceiver circuit formed by one or more integrated circuits, a power amplifier circuit configured to amplify uplink RF signals (e.g., RF signals transmitted by device 10 to an external device), a low-noise amplifier configured to amplify downlink RF signals (e.g., RF signals received by device 10 from an external device), passive RF components, one or more antennas, transmission lines, and other circuitry for processing the RF wireless signals. Light (e.g., infrared communication) may also be used to transmit the wireless signals.

[0029] Wireless circuit 24 may include radio frequency transceiver circuitry for transmitting and / or receiving radio frequency signals in various radio frequency communication bands. For example, the radio frequency transceiver circuitry may handle wireless local area network (WLAN) communication bands such as 2.4 GHz and 5 GHz. (IEEE 802.11) bands, Wireless Personal Area Network (WPAN) communication bands such as 2.4 GHz Communication frequency bands, cellular telephone communication frequency bands such as the cellular low frequency band (LB) (e.g., 600MHz to 960MHz), the cellular low intermediate frequency band (LMB) (e.g., 1400MHz to 1550MHz), the cellular intermediate frequency band (MB) (e.g., 1700MHz to 2200MHz), the cellular high frequency band (HB) (e.g., 2300MHz to 2700MHz), the cellular ultra-high frequency band (UHB) (e.g., 3300MHz to 5000MHz), or other cellular communication frequency bands between approximately 600MHz and approximately 5000MHz (e.g., 3G bands, 4G bands). This includes LTE bands, 5G NR frequency range 1 (FR1) bands below 10 GHz, 5G NR frequency range 2 (FR2) bands with millimeter and centimeter wavelengths between 20 GHz and 60 GHz, etc., near field communication (NFC) bands (e.g., 13.56 MHz), satellite navigation bands (e.g., the 1575 MHz L1 Global Positioning System (GPS) band, the 1176 MHz L5 GPS band, the GLONASS band, the BeiDou Navigation Satellite System (BDS) band, etc.), ultra-wideband (UWB) communication bands supported by the IEEE 802.15.4 protocol and / or other UWB communication protocols (e.g., a first UWB communication band of 6.5 GHz and / or a second UWB communication band of 8.0 GHz), and / or any other desired communication bands. The communication bands processed by such RF transceiver circuits are sometimes referred to herein as frequency bands or simply "bands," and may span corresponding frequency ranges. Generally speaking, the radio frequency transceiver circuit in wireless circuit 24 can cover (process) any desired frequency band of interest.

[0030] Figure 2 This is a schematic diagram showing exemplary components within wireless circuit 24. For example... Figure 2 As shown, wireless circuitry 24 may include a baseband processor such as baseband processor 26, radio frequency (RF) transceiver circuitry such as RF transceiver 28, RF front-end circuitry such as RF front-end module (FEM) 40, and antenna 42. Baseband processor 26 may be coupled to transceiver 28 via baseband path 34. Transceiver 28 may be coupled to antenna 42 via RF transmission line path 36. RF front-end module 40 may be inserted into RF transmission line path 36 between transceiver 28 and antenna 42.

[0031] exist Figure 2In the example, for clarity, wireless circuit 24 is shown as including only a single baseband processor 26, a single transceiver 28, a single front-end module 40, and a single antenna 42. Generally, wireless circuit 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 transceivers 28 via a corresponding baseband path 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 via a corresponding RF transmission line path 36. Each RF transmission line path 36 may have a corresponding front-end module 40 inserted thereon. If desired, two or more front-end modules 40 may be inserted on the same RF transmission line path 36. If desired, one or more RF transmission lines 36 in wireless circuit 24 may be implemented without any front-end modules inserted thereon.

[0032] The RF transmission line path 36 may be coupled to an antenna feed section on the antenna 42. The antenna feed section may, for example, include a positive antenna feed terminal and a ground antenna feed terminal. The RF transmission line path 36 may have a positive transmission line signal path coupled to the positive antenna feed terminal on the antenna 42. The RF transmission line path 36 may also have a ground transmission line signal path coupled to the ground antenna feed terminal on the antenna 42. This example is merely illustrative, and in general, the antenna 42 may be fed using any desired antenna feeding scheme. If desired, the antenna 42 may have multiple antenna feed sections coupled to one or more RF transmission line paths 36.

[0033] RF transmission line path 36 may include routing device 10 ( Figure 1 The transmission lines in device 10 are for transmitting radio frequency antenna signals. These transmission lines may include coaxial cables, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, and combinations thereof. Transmission lines in device 10, such as those in radio frequency transmission line path 36, may be integrated into rigid and / or flexible printed circuit boards.

[0034] During wireless transmission, baseband processor 26 provides baseband signals to transceiver 28 via baseband path 34. Transceiver 28 may also include circuitry for converting the baseband signals received from baseband processor 26 into corresponding radio frequency (RF) signals. For example, transceiver circuitry 28 may include mixer circuitry 50 for up-converting (or modulating) the baseband signals to RF before transmission via antenna 42. Transceiver circuitry 28 may also include digital-to-analog converter (DAC) circuitry and / or analog-to-digital converter (ADC) circuitry for converting signals between the digital and analog domains. Transceiver 28 may include transmitter components for transmitting RF signals via antenna 42 through RF transmission line path 36 and front-end module 40. Antenna 42 transmits RF signals to external wireless equipment by radiating the RF signals into free space.

[0035] During wireless reception, antenna 42 can receive radio frequency (RF) signals from external wireless equipment. The received RF signals can be transmitted to transceiver 28 via RF transmission line path 36 and front-end module 40. Transceiver 28 may include circuitry for converting the received RF signals into corresponding baseband signals. For example, transceiver 28 may use mixer circuitry 50 to downconvert (or demodulate) the received RF signals to baseband frequencies before transmitting the received signals via baseband path 34 to baseband processor 26. Mixer circuitry 50 may include oscillator circuitry, such as local oscillator 52. Local oscillator 52 can generate oscillator signals that mixer circuitry 50 uses to modulate the transmitted signals from baseband frequency to RF and / or demodulate the received signals from RF to baseband or intermediate frequency. Transceiver 28 may also include amplifiers, such as amplifier 54 configured to filter the signals output from mixer circuitry 50.

[0036] The front-end module (FEM) 40 may include radio frequency front-end circuitry that operates on radio frequency signals transmitted (transmitted and / or received) through radio frequency transmission line path 36. The front-end module may include, for example, 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 couplers, multiplexing circuitry, duplexer circuitry, triplexer circuitry, one or more radio frequency switches, etc.), radio frequency amplifier circuitry (e.g., one or more power amplifiers 46 and one or more low-noise amplifiers 48), impedance matching circuitry (e.g., circuitry that helps match the impedance of antenna 42 to the impedance of radio frequency transmission line 36), antenna tuning circuitry (e.g., a network 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 on a common (shared) substrate, such as a rigid printed circuit board substrate or a flexible printed circuit board substrate. If needed, various front-end module components can also be integrated into a single integrated circuit chip.

[0037] Circuit 44, amplifier circuits 46 and 48, and other circuits may be inserted within the RF transmission line path 36, may be integrated into the FEM 40, and / or may be integrated into the antenna 42 (e.g., to support antenna tuning, to support operation in a desired frequency band, etc.). These components (sometimes referred to herein as antenna tuning components) may be adjusted (e.g., using control circuit 14) to adjust the frequency response and wireless performance of the antenna 42 over time.

[0038] 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 a flexible printed circuit that is not part of front-end module 40. Although for clarity, in Figure 1 In the example, control circuitry 14 is shown separate from wireless circuitry 24, but wireless circuitry 24 may include processing circuitry and / or storage circuitry, the processing circuitry forming part of processing circuitry 18, and the storage circuitry forming 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, portions of baseband processor 26 and / or transceiver 28 (e.g., a host processor on transceiver 28) may form 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 separate from wireless circuitry 24) may provide control signals (e.g., via one or more control paths in device 10) to control the operation of front-end module 40.

[0039] Transceiver circuitry 28 may include processing WLAN communication bands (e.g., (IEEE 802.11) or other WLAN communication bands, such as the 2.4 GHz WLAN band (e.g., 2400 MHz to 2480 MHz), the 5 GHz WLAN band (e.g., 5180 MHz to 5825 MHz), 6E band (e.g., 5925MHz to 7125MHz) and / or others Wireless LAN transceiver circuitry covering a frequency band (e.g., 1875MHz to 5160MHz); handling 2.4GHz. Wireless personal area network transceiver circuits for frequency bands or other WPAN communication bands; cellular phone transceiver circuits for processing cellular phone frequency bands (e.g., bands from about 600 MHz to about 5 GHz, 3G bands, 4G LTE bands, 5G NR frequency range 1 (FR1) band below 10 GHz, 5G NR frequency range 2 (FR2) band between 20 GHz and 60 GHz, etc.); near field communication (NFC) transceiver circuits for processing near field communication bands (e.g., 13.56 MHz); satellite navigation receiver circuits for processing satellite navigation bands (e.g., GPS band from 1565 MHz to 1610 MHz, GLONASS band, BeiDou Navigation Satellite System (BDS) band, etc.); ultra-wideband (UWB) transceiver circuits for processing communications using the IEEE 802.15.4 protocol and / or other ultra-wideband communication protocols; and / or any other desired radio frequency transceiver circuits for covering any other desired communication bands of interest.

[0040] Wireless circuit 24 may include one or more antennas, such as antenna 42. Antenna 42 can be formed using any desired antenna structure. For example, antenna 42 may be an antenna with a resonant element, formed from a loop antenna structure, patch antenna structure, inverted F-shaped antenna structure, slot antenna structure, planar inverted F-shaped antenna structure, helical antenna structure, monopole antenna, dipole, a combination of these designs, etc. Two or more antennas 42 may be arranged in one or more phased antenna arrays (e.g., for transmitting 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 supports the antenna resonant element of antenna 42 (e.g., antenna 42 may be a cavity-backed antenna, such as a cavity-backed slot antenna).

[0041] Wireless circuit 24 can operate in multiple radio frequency bands. Figure 3 This is a diagram illustrating a wireless circuit 24 having multiple receiver blocks for processing (receiving) signals from various radio frequency bands. (See diagram for reference.) Figure 3 As shown, wireless circuit 24 may include a first receiver block RX1 configured to receive signals from a first radio frequency band group BG1 via antenna 42, a second receiver block RX2 configured to receive signals from a second radio frequency band group BG2 via antenna 42, and a third receiver block RX3 configured to receive signals from a third radio frequency band group BG3 via antenna 42, and so on. Each radio frequency band group typically includes multiple radio frequency bands. During normal operation, only one selected receiver block is activated, depending on the desired radio frequency band for operation. As an example, BG1 may cover communication in the range of 0.6 GHz to 1 GHz, BG2 may cover communication in the range of 1 GHz to 1.8 GHz, and BG3 may cover communication in the range of 1.8 GHz to 2.3 GHz. These radio frequency band ranges are merely illustrative. Typically, each radio frequency band may cover 400 MHz, less than 400 MHz, greater than 400 MHz, 500 MHz, 600 MHz, 700 MHz, or other frequency ranges. A local oscillator 52 may be used to provide an oscillator signal to one or more receiver blocks. For example, the first local oscillator 52 can be used to cover frequency band groups BG1 and BG2. The second local oscillator 52 can be used to cover only a single frequency band group BG3 (as an example). The third local oscillator 52 can be used to cover three or more frequency band groups.

[0042] Figure 3 The example of wireless circuit 24 including three independent receiver blocks for handling different radio frequency bands is merely illustrative. This type of wireless receiver circuit is sometimes referred to as a multi-band or multi-standard receiver. Receiver circuitry may include more or fewer than three independent receiver blocks if desired. The amplifier 54 used in such multi-standard receivers is sometimes referred to herein as a “wideband” amplifier.

[0043] Each of the receiver blocks RX1, RX2, and RX3 may include switching circuitry such as a RF switch 44 coupled to antenna 42 (or coupled to an RF duplexer), matching circuitry such as matching circuitry 47, RF amplifiers such as a low-noise amplifier (LAN) 48 configured to receive signals from switch 44, and mixer circuitry such as an RF mixer 51 configured to receive amplified signals from LAN and oscillator signals from local oscillator 52. Wireless circuitry 24 may include a single amplifier circuit, such as an amplifier 54 coupled to mixer 51 in each of the receiver blocks. Amplifier 54 may be, for example, a transimpedance amplifier (TIA). Amplifier 54 may be a broadband amplifier capable of handling communication across all various RF band groups (e.g., BG1, BG2, BG3, etc.). This type of amplifier 54, with its wide bandwidth and ability to handle communication across multiple RF bands (standards), is sometimes referred to as a multi-band (multi-standard) broadband amplifier.

[0044] Figure 3 The example of wireless circuit 24 including multiple receiver blocks is merely illustrative. Figure 4 Another embodiment is shown, in which the wireless circuit 24 is a feedback receiver capable of handling wireless communications in various radio frequency bands. Figure 4 The feedback receiver can be used for power control and calibration of transmitted signals. For example... Figure 4 As shown, antenna 42 can be coupled to a transmission amplifier such as power amplifier 46, and can be coupled to receiver block RX via an RF coupler such as directional coupler 44. Receiver block RX may also include RF attenuation circuitry 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 RF mixer circuitry such as mixer 51 configured to receive signals from low-noise amplifier 48 and oscillator signals from local oscillator 52. Mixer 51 can output a demodulated signal to amplifier 54. Amplifier 54 may be a multi-band, wideband transimpedance amplifier (as an example).

[0045] The receiver block RX can be configured to handle a wide range of radio frequency bands. For example, the receiver block RX can operate in a first mode to handle wireless communications in a first radio frequency band group from about 0.6 GHz to 1 GHz, in a second mode to handle wireless communications in a second radio frequency band group from about 1 GHz to 1.8 GHz, in a third mode to handle wireless communications in a third radio frequency band group from about 1.8 GHz to 2.3 GHz, in a fourth mode to handle wireless communications in a fourth radio frequency band group from about 2.3 GHz to 2.9 GHz, and so on, up to handling wireless communications in radio frequency band groups of 7 GHz or greater. These radio frequency bands are merely illustrative. Figure 4 The arrangement of a single receiver block RX coupled to a transmission amplifier 46 via a directional coupler 44 is sometimes referred to as a feedback receiver architecture. Figure 3 Compared to multi-standard receivers Figure 4 Feedback receivers typically exhibit more lenient noise sensitivity requirements.

[0046] Figure 5 This is an illustration showing additional details at the interface between mixer 51 and transimpedance amplifier 54, which are adapted to be combined... Figure 3 The type of multi-standard receiver, combined Figure 4 Feedback receivers of this type, and / or other wireless receiver architectures utilizing broadband amplifiers. For example... Figure 5 As shown, the low-noise amplifier 48, mixer 51, and transimpedance amplifier 54 can be differential circuits with differential input terminals and differential output terminals.

[0047] A set of parallel capacitors Cmix can be coupled to the output of mixer 51, which is also coupled to the input of amplifier 54. For example, the first capacitor Cmix in the set of parallel capacitors has a first terminal coupled to the first input of amplifier 54 and a second terminal coupled to a ground power supply line (sometimes referred to as ground line or ground), while the second capacitor Cmix in the set of parallel capacitors has a first terminal coupled to the second input of amplifier 54 and a second terminal coupled to the ground line.

[0048] A set of feedback capacitors Cf can also be coupled across the input and output terminals of amplifier 54. For example, the first feedback capacitor Cf in this set of feedback capacitors has a first terminal coupled to a first input terminal of amplifier 54 and a second terminal coupled to a first output terminal of amplifier 54. The second feedback capacitor Cf in this set of feedback capacitors has a first terminal coupled to a second input terminal of amplifier 54 and a second terminal coupled to a second output terminal of amplifier 54.

[0049] A set of feedback resistors Rf can also be coupled across the input and output terminals of amplifier 54. For example, the first feedback resistor Rf in this set of feedback resistors has a first terminal coupled to the first input terminal of amplifier 54 and a second terminal coupled to the first output terminal of amplifier 54 (i.e., the first feedback resistor Rf can be coupled in parallel with the first feedback capacitor Cf). The second feedback resistor Rf in this set of feedback resistors has a first terminal coupled to the second input terminal of amplifier 54 and a second terminal coupled to the second output terminal of amplifier 54 (i.e., the second feedback resistor Rf can be coupled in parallel with the second feedback capacitor Cf). Configured in this way, the transimpedance amplifier 54 and the associated components Cmix, Cf, and Rf can collectively serve as a low-pass filter circuit to provide low-pass filtering functionality, and may sometimes be referred to as a baseband filter or a baseband active filter. Figure 5 Each of the capacitors Cmix and / or Cf shown may include a set of switchable capacitors that can be adjusted by controller 64 to optionally tune the bandwidth of the baseband filter. Each feedback resistor Rf may also include a set 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, while resistor Rf can be adjusted to control the gain of the filter.

[0050] Mixer 51 can have an output impedance Rout. The mixer output impedance Rout can be related to Cpar and f. LO The product is inversely proportional, where Cpar represents the parasitic capacitance at the output of the LNA 48, and where f LO This indicates the frequency of the oscillator signal generated by the local oscillator 52. Figure 6 This involves plotting the mixer output impedance Rout as a function of the oscillator frequency f. LO A diagram illustrating the changes. (For example...) Figure 6 As shown, the oscillator frequency f LO When supporting wideband operation, it can vary across a wide frequency range (e.g., from 0.6 GHz to 7.2 GHz). This is because the mixer output impedance Rout is related to f... LO It is inversely proportional, therefore Rout changes with frequency f LO The value decreases as the oscillator increases (as shown in curve 60). Curve 60 illustrates how Rout can vary considerably over a wide operating frequency range of the oscillator (e.g., from greater than 9kΩ to less than 3kΩ). These Rout values ​​are merely illustrative. Mixer Rout values ​​can vary widely depending on the intended application of the receiver and the actual design.

[0051] The bandwidth and stability of amplifier 54 vary with the mixer output impedance Rout. Therefore, large variations in the mixer Rout can reduce the amplifier bandwidth when the receiver operates in different RF bands. One way to maintain the target bandwidth of amplifier 54 when the mixer Rout varies is to tune the parallel capacitor Cmix. However, tuning Cmix and / or Cf to compensate for variations in the mixer Rout can alter the quality factor and phase margin of amplifier 54, making it challenging to design a receiver that meets performance standards across all operating frequencies.

[0052] According to some implementations, an adjustable resistor circuit, such as an adjustable resistor Rin, is coupled to the input of amplifier 54 to adjust the input impedance of amplifier 54, thereby helping to compensate for variations in the mixer output impedance Rout (see, for example...). Figure 5 The adjustable resistor Rin may have a first terminal coupled to a first input terminal of amplifier 54 and a second terminal coupled to a second input terminal of amplifier 54 (e.g., resistor Rin may be coupled across the differential input terminals of amplifier 54). Connected in this way, the adjustable resistor Rin is effectively coupled in parallel with the mixer output impedance Rout.

[0053] Figure 7 This plots the resistance of the adjustable resistor Rin as a function of the oscillator frequency f. LO A diagram illustrating the changes. (For example...) Figure 7 As shown in curve 62, with the oscillator frequency f LO By increasing the resistance, resistor Rin can be tuned to represent an increased resistance (i.e., an increased true impedance value). Resistor Rin should be tuned so that the total parallel resistance of Rout and Rin remains constant across all RF bands of interest. Operating in this way, the adjustable resistor Rin can be used to maintain the bandwidth of amplifier 54 by compensating for variations in mixer Rout across the entire operating frequency range (e.g., increasing Rin when mixer Rout decreases, and vice versa). Using an adjustable (tunable) resistor Rin to compensate for variations in mixer Rout avoids the need to tune the parallel capacitor Cmix when transitioning from one operating band to another, which helps ensure that amplifier 54's Q factor and phase margin meet performance standards across the entire operating frequency range.

[0054] Figure 8 A suitable implementation of the adjustable resistor Rin is shown. For example... Figure 8 As shown, resistor Rin can have multiple resistor strings coupled together in parallel between terminals 70 and 72. Terminal 70 can be coupled to the first input terminal of amplifier 54, while terminal 72 can be coupled to the second input terminal of amplifier 54.

[0055] An adjustable resistor Rin (sometimes called an adjustable resistor, adjustable resistor circuit, or adjustable resistor circuit with a true impedance value) may include multiple resistor strings, such as a first resistor string with resistors R1a and R1b selectively enabled by switch S1 (e.g., switch S1 may be coupled in series between resistors R1a and R1b), a second resistor string with resistors R2a and R2b selectively enabled by switch S2 (e.g., switch S2 may be coupled in series between resistors R2a and R2b), a third resistor string with resistors R3a and R3b selectively enabled by switch S3 (e.g., switch S3 may be coupled in series between resistors R3a and R3b), and so on. Switches S1-S6 may be composed of, for example, Figure 5 The switch control circuit 64 is controlled by the switch control circuit of the control circuit 14. The switch control circuit 64 may be part of the control circuit 14 (see example). Figure 1 ).

[0056] Figure 8 The example of a resistor Rin having six switchable resistor strings is merely illustrative. Typically, a 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 the adjustable resistor Rin can be selected to provide a desired resistance range, thereby compensating for variations in the mixer Rout (e.g., allowing different switching configurations to provide a range of resistances depending on the operating frequency of the wireless receiver). Figure 7 The corresponding compensation value for Rin is shown in curve 62. For example, when operating in the highest RF band, all Rin switches can be turned off (disabled). On the other hand, when operating in the lowest RF band, all Rin switches can be turned on (enabled) to provide the lowest total resistance. For the operating frequency between the two extremes, different subsets of switches can be selectively enabled. Control circuit 64 (see...) Figure 5 It can store a lookup table (as an example) that determines which switch group to enable based on the current operating frequency. The amplifier 54's gain, bandwidth, linearity, noise, and phase margin can be maintained for all resistor values ​​of Rin.

[0057] Figure 8 The example of each resistor string in Rin having two resistors and one switch is merely illustrative. Figure 9 Another suitable implementation of an adjustable resistor Rin with resistor strings is shown, where each resistor string has a single resistor and two switches. (e.g.) Figure 9As shown, an adjustable resistor Rin (sometimes called a resistor circuit or a resistor circuit with a true impedance value) may include: a first resistor string having a resistor R1 selectively activated by switches S1a and S1b (e.g., resistor R1 may be coupled in series between switches S1a and S1b); a second resistor string having a resistor R2 selectively activated by switches S2a and S2b (e.g., resistor R2 may be coupled in series between switches S2a and S2b); a third resistor string having a resistor R3 selectively activated by switches S3a and S2b (e.g., resistor R3 may be coupled in series between switches S3a and S3b), and so on. These switches may be made of, for example, Figure 5 The control circuit 64 is controlled by the switch control circuit.

[0058] Figure 9 The example of a resistor Rin having six switchable resistor strings is merely illustrative. Typically, a 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 the adjustable resistor Rin can be selected to provide a desired resistance range, thereby compensating for variations in the mixer Rout (e.g., allowing different switching configurations to provide a range of resistances depending on the operating frequency of the wireless receiver). Figure 7 The corresponding compensation value for Rin is shown in curve 62. The gain, bandwidth, linearity, noise, and phase margin of amplifier 54 can be maintained for all resistance values ​​of Rin. If needed, each resistor string may have only one resistor and one switch (e.g., the first resistor string may have only resistor R1 coupled in series with S1a, omitting S1b; the second resistor string may have only resistor T2 coupled in series with S2a, omitting S2b; etc.).

[0059] Figure 10 It shows the combination Figures 1 to 9 Illustrations of different operating modes of the receiver circuit of the type shown. Figure 10 As shown, the receiver circuit can operate in a first mode such as mode 80, during which the receiver receives signals in the first radio frequency band group BG1; it can operate in a second mode such as mode 82, during which the receiver receives signals in the second radio frequency band group BG2; it can operate in a third mode such as mode 84, during which the receiver receives signals in the third radio frequency band group BG3, and so on.

[0060] During mode 80, when operating in BG1 (e.g., the lowest frequency operating band group), the adjustable resistor Rin can be set to its minimum value Rlow by enabling all or almost all of its resistor strings. During mode 82, when operating in BG2 (e.g., the next operating band group above BG1), the adjustable resistor Rin can be adjusted to a different value to compensate for the change in mixer Rout caused by switching from another mode to mode 82. During mode 84, when operating in BG3 (e.g., the next operating band group above BG2), the adjustable resistor Rin can be adjusted to a different value to compensate for the change in mixer Rout caused by switching from another mode to mode 84. Typically, the receiver circuitry can operate in n different operating modes, where n can be equal to 5 or greater, 6-10, 11-15, greater than 10, or other suitable values.

[0061] The above combination Figures 1 to 10 The described methods and operations can be performed by components of device 10 using software, firmware, and / or hardware (e.g., dedicated circuitry or hardware). The software code for performing these operations can be stored on a non-transitory computer-readable storage medium (e.g., a tangible computer-readable storage medium) stored on one or more components of device 10 (e.g., ...). Figure 1 The storage circuit 16 and / or wireless communication circuit 24). This software code may sometimes be referred to as software, data, instructions, program instructions, or code. 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. The software stored on the non-transitory computer-readable storage medium may be processed by processing circuitry on one or more components of device 10 (e.g., processing circuitry in wireless communication circuitry 24, etc.). Figure 1 The processing circuitry (e.g., 18) executes the operation. This processing circuitry may include a microprocessor, application processor, digital signal processor, central processing unit (CPU), application-specific integrated circuit (ASIC) with processing circuitry, or other processing circuitry.

[0062] According to an embodiment, a wireless circuit capable of operating across multiple radio frequency bands is provided, the wireless circuit comprising: a first amplifier configured to receive radio frequency signals 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 an input coupled to the output of the mixer; and an adjustable resistor coupled to an input of the second amplifier and configured to adjust the input impedance of the second amplifier when the wireless circuit operates across multiple radio frequency bands.

[0063] According to another embodiment, the wireless circuit includes a control circuit configured to increase the resistance value of the adjustable resistor when the output impedance of the mixer decreases and decrease the resistance value of the adjustable resistor when the output impedance of the mixer increases.

[0064] According to another embodiment, the input terminals of the second amplifier include a first amplifier input terminal and a second amplifier input terminal, and the adjustable resistor has a first terminal coupled to the first amplifier input terminal and a second terminal coupled to the second amplifier input terminal.

[0065] According to another embodiment, the wireless circuit includes: a first parallel capacitor having a first terminal coupled to an input terminal of a first amplifier and a second terminal coupled to a ground wire; and a second parallel capacitor having a first terminal coupled to an input terminal of a second amplifier and a second terminal coupled to a ground wire.

[0066] According to another embodiment, the wireless circuit includes: a first feedback capacitor having a first terminal coupled to a first amplifier input terminal of a second amplifier and a second terminal coupled to a first amplifier output terminal; and a second feedback capacitor having a first terminal coupled to a second amplifier input terminal of a second amplifier and a second terminal coupled to a second amplifier output terminal.

[0067] According to another embodiment, the wireless circuit includes: a first feedback resistor having a first terminal coupled to an input terminal of a first amplifier and a second terminal coupled to an output terminal of a first amplifier; and a second feedback resistor having a first terminal coupled to an input terminal of a second amplifier and a second terminal coupled to an output terminal of a second amplifier.

[0068] According to another embodiment, the second amplifier includes a transimpedance amplifier.

[0069] According to another embodiment, the adjustable resistor includes a plurality of resistor strings, and each of the plurality of resistor strings includes a first resistor, a second resistor, and a switch coupled between the first resistor and the second resistor in the resistor string.

[0070] According to another embodiment, the adjustable resistor includes a plurality of resistor strings, and each of the plurality of resistor strings includes a first switch, a second switch, and a resistor coupled between the first switch and the second switch in the resistor string.

[0071] According to one embodiment, a method for operating a wireless circuit across multiple radio frequency bands is provided, the method comprising: receiving a signal at a first amplifier via an antenna; mixing the signal from the first amplifier with a signal from an oscillator at a mixer having an output impedance; receiving a signal from the mixer at a second amplifier; and, when the wireless circuit operates across multiple radio frequency bands, tuning an adjustable resistor coupled to the input of the second amplifier based on a change in the output impedance of the mixer.

[0072] According to another embodiment, the adjustable resistor includes a plurality of resistor strings, each resistor string having a first resistor, a second resistor and a switch coupled between the first resistor and the second resistor in the resistor string, and tuning the adjustable resistor includes selectively enabling and disabling the switch in each of the plurality of resistor strings.

[0073] According to another embodiment, the adjustable resistor includes a plurality of resistor strings, each resistor string having a first switch, a second switch and a resistor coupled between the first switch and the second switch in the resistor string, and the tuning adjustable resistor includes selectively enabling and disabling the first switch and the second switch in each of the plurality of resistor strings.

[0074] According to another embodiment, the tuned adjustable resistor includes tuning the adjustable resistor to provide a first resistance value when the wireless circuit operates in a first radio frequency band among a plurality of radio frequency bands, and tuning the adjustable resistor to provide a second resistance value different from the first resistance value when the wireless circuit operates in a second radio frequency band among a plurality of radio frequency bands.

[0075] According to another embodiment, the tuned adjustable resistor includes tuning the adjustable resistor to provide a first resistance value when the wireless circuit operates in a first radio frequency band among a plurality of radio frequency bands, and tuning the adjustable resistor to provide a second resistance value greater than the first resistance value when the wireless circuit operates in a second radio frequency band among a plurality of radio frequency bands that is greater than the first radio frequency band.

[0076] According to another embodiment, the second amplifier includes a transimpedance amplifier with a bandwidth greater than 100 MHz.

[0077] According to one embodiment, an electronic device is provided, comprising: a mixer having a first input coupled to an antenna, a second input coupled to an oscillator, and an output; an amplifier having an input coupled to the output of the mixer; an adjustable resistor coupled to the input of the amplifier; and processing circuitry configured to receive data generated based on a signal output from the amplifier.

[0078] According to another embodiment, the electronic device includes a control circuit configured to tune an adjustable resistor according to the operating frequency of the amplifier.

[0079] According to another embodiment, the amplifier's input terminals include a first amplifier input terminal and a second amplifier input terminal, and the adjustable resistor has a first resistor terminal coupled to the first amplifier input terminal and a second resistor terminal coupled to the second amplifier input terminal.

[0080] According to another embodiment, the electronic device includes: a first parallel capacitor having a first terminal coupled to an input terminal of a first amplifier and a second terminal coupled to a ground wire; and a second parallel capacitor having a first terminal coupled to an input terminal of a second amplifier and a second terminal coupled to a ground wire.

[0081] According to another embodiment, the amplifier includes a first amplifier output terminal and a second amplifier output terminal, and the electronic device includes: a first feedback capacitor having a first terminal coupled to the first amplifier input terminal and 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 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 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 a second terminal coupled to the second amplifier output terminal.

[0082] The foregoing description is merely illustrative and various modifications can be made to the described implementation scheme. The described implementation scheme can be implemented independently or in any combination.

Claims

1. A wireless circuit, comprising: A first amplifier, configured to receive a radio frequency signal and generate a corresponding amplified signal; A mixer configured to receive the amplified signal and generate a corresponding demodulated signal; A second amplifier, configured to receive the demodulated signal; as well as An adjustable resistor, coupled between the mixer and the second amplifier, wherein the adjustable resistor comprises: The first terminal is directly coupled to the first amplifier input terminal of the second amplifier. The second terminal is directly coupled to the second amplifier input terminal of the second amplifier. Multiple resistors, and Multiple switches are configured to selectively switch one or more of the multiple resistors into use.

2. The wireless circuit of claim 1, wherein the second amplifier comprises a transimpedance amplifier.

3. The wireless circuit according to claim 1, further comprising: A first capacitor, the first capacitor having a first terminal coupled to the input terminal of the first amplifier and a second terminal coupled to a ground wire; as well as The second capacitor has a first terminal coupled to the input terminal of the second amplifier and a second terminal coupled to the ground wire.

4. The wireless circuit according to claim 1, further comprising: A first feedback capacitor has a first terminal coupled to the input terminal of the first amplifier and a second terminal coupled to the output terminal of the first amplifier of the second amplifier. The second feedback capacitor has a first terminal coupled to the input terminal of the second amplifier and a second terminal coupled to the output terminal of the second amplifier. A first feedback resistor has a first terminal coupled to the input terminal of the first amplifier and a second terminal coupled to the output terminal of the first amplifier of the second amplifier; as well as The second feedback resistor has a first terminal coupled to the input terminal of the second amplifier and a second terminal coupled to the output terminal of the second amplifier.

5. The wireless circuit according to claim 1, further comprising: A first feedback capacitor has a first terminal coupled to the input terminal of the first amplifier and a second terminal coupled to the output terminal of the first amplifier of the second amplifier; as well as The second feedback capacitor has a first terminal coupled to the input terminal of the second amplifier and a second terminal coupled to the output terminal of the second amplifier.

6. The wireless circuit according to claim 1, further comprising: A first feedback resistor has a first terminal coupled to the input terminal of the first amplifier and a second terminal coupled to the output terminal of the first amplifier of the second amplifier. as well as The second feedback resistor has a first terminal coupled to the input terminal of the second amplifier and a second terminal coupled to the output terminal of the second amplifier.

7. The wireless circuit according to claim 1, further comprising: A control circuit configured to adjust the adjustable resistor based on the operating frequency associated with the mixer.

8. The wireless circuit according to claim 1, further comprising: A control circuit configured to adjust the adjustable resistor to compensate for changes in the output impedance of the mixer.

9. A method of operating a wireless circuit, comprising: It receives radio frequency signals and generates corresponding amplified signals; Receive the amplified signal and generate a corresponding demodulated signal based on the oscillation signal; The demodulated signal is received using an amplifier; as well as The resistor at the input of the amplifier is tuned by increasing the resistor when the frequency of the oscillation signal increases and decreasing the resistor when the frequency of the oscillation signal decreases.

10. The method of claim 9, wherein the amplifier comprises a transimpedance amplifier.

11. The method of claim 9, wherein: The resistor comprises multiple resistor strings, each resistor string having a first resistor, a second resistor, and a switch, the switch being coupled between the first resistor and the second resistor in the resistor string; and Tuning the resistors includes selectively enabling and disabling the switches in each of the plurality of resistor strings.

12. The method of claim 9, wherein: The resistor comprises multiple resistor strings, each resistor string having a first switch, a second switch, and a resistor, wherein the resistor is coupled between the first switch and the second switch in the resistor string; and Tuning the resistors includes selectively enabling and disabling the first and second switches in each of the plurality of resistor strings.

13. A circuit comprising: A first differential circuit has an output impedance that varies with frequency and is configured to receive radio frequency signals and oscillation signals. A second differential circuit is configured to receive a signal from the first differential circuit; An adjustable input resistor is coupled to the input terminal of the second differential circuit; as well as A control circuit configured to increase the adjustable input resistance when the frequency of the oscillation signal increases, and to decrease the adjustable input resistance when the frequency of the oscillation signal decreases.

14. The circuit of claim 13, wherein the first differential circuit comprises an RF mixer, and wherein the second differential circuit comprises a transimpedance amplifier.

15. The circuit of claim 13, wherein the second differential circuit further comprises: Multiple feedback capacitors; as well as Multiple feedback resistors.

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