Load Modulated Radio-frequency Amplifier with Extended Tuning Range

An electronic device may include wireless circuitry having an amplifier configured to receive a radio-frequency signal generated from a baseband signal, a first adjustable load component coupled to an output of the amplifier, a second adjustable load component coupled to the output of the amplifier, and a control signal generator configured to output one or more control signals for tuning the first and second adjustable load components based on an envelope of the baseband signal or the radio-frequency signal. The first adjustable load component can provide a first tuning range covering a first subrange of an instantaneous signal envelope of the baseband signal or the radio-frequency signal, whereas the second adjustable load can provide a second tuning range covering a second subrange of the instantaneous signal envelope of the baseband signal or the radio-frequency signal. The first and second tuning ranges are combined to provide an extended tuning range.

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 transceiver circuitry in the wireless communications circuitry uses the antennas to transmit and receive radio-frequency signals.

Radio-frequency signals transmitted by an antenna can be fed through one or more power amplifiers, which are configured to amplify low power analog signals to higher power signals more suitable for transmission through the air over long distances. It can be challenging to design a satisfactory power amplifier for an electronic device.

SUMMARY

An electronic device may include wireless communications circuitry. The wireless communications circuitry may include one or more processors or signal processing blocks for generating baseband signals, a transceiver for receiving the digital signals and for generating corresponding radio-frequency signals, and one or more radio-frequency power amplifiers configured to amplify the radio-frequency signals for transmission by one or more antennas in the electronic device. At least one of the radio-frequency power amplifiers can be implemented as a load-line modulated radio-frequency amplifier circuit. The load-line modulated radio-frequency amplifier circuit can include an amplifier core coupled to one or more adjustable load impedances.

As aspect of the disclosure provides wireless circuitry that includes a radio-frequency amplifier configured to receive a radio-frequency signal generated from a baseband signal, a first adjustable load component coupled to an output of the radio-frequency amplifier, a second adjustable load component coupled to the output of the radio-frequency amplifier, and a control signal generator configured to output one or more control signals for tuning the first and second adjustable load components based on an envelope of the baseband signal or the radio-frequency signal. The first adjustable load component can be configured to provide a first impedance tuning range for a first subrange of the envelope, whereas the second adjustable load component can be configured to provide a second impedance tuning range for a second subrange of the envelope. The first and second adjustable load components can be coupled to the output of the radio-frequency amplifier via first and second coupling circuits, respectively, or via a joint coupling circuit.

An aspect of the disclosure provides a method of operating wireless circuitry that includes receiving at an amplifier a radio-frequency signal that is generated based on a baseband signal, tuning a first adjustable load component at an output of the amplifier using a first load tuning control signal that is derived from an envelope of the baseband signal or the radio-frequency signal, and tuning a second adjustable load component at the output of the amplifier using a second load tuning control signal that is derived from the envelope of the baseband signal or the radio-frequency signal. The first adjustable load component can be used to provide a first impedance tuning range for a first subrange of the envelope, whereas the second adjustable load component can be used to provide a second impedance tuning range, different than the first impedance tuning range, for a second subrange of the envelope. A control signal generator can be used to generate a control signal based on the envelope of the baseband signal or the radio-frequency signal. A first conversion circuit can be used to output the first load tuning control signal based on a first range of the control signal, and a second conversion circuit can be used to output the second load tuning control signal based on a second range of the control signal. The second control signal can be shifted from the first control signal by a fixed or adjustable offset.

An aspect of the disclosure provides an electronic device that includes one or more processors configured to generate a baseband signal, an upconverter configured to convert the baseband signal into a radio-frequency signal, and a load-line modulated amplifier circuit configured to amplify the radio-frequency signal. The load-line modulated amplifier circuit can include an amplifier configured to receive the radio-frequency signal, a first adjustable load component coupled to an output of the amplifier and configured to provide a first tuning range covering a first subrange of an instantaneous signal envelope of the baseband signal or the radio-frequency signal, and a second adjustable load component coupled to the output of the amplifier and configured to provide a second tuning range covering a second subrange of the instantaneous signal envelope of the baseband signal or the radio-frequency signal. The first and second tuning ranges are combined to provide an extended tuning range for the load-line modulated amplifier circuit.

DETAILED DESCRIPTION

An electronic device such as device10ofFIG.1may be provided with wireless circuitry. The wireless circuitry may include a processor for generating baseband signals, an upconversion circuit for upconverting (mixing) the baseband signals into radio-frequency signals, an amplifier for amplifying the radio-frequency signals, and an antenna for radiating the amplified radio-frequency signals.

The amplifier may be a load modulated radio-frequency power amplifier having multiple adjustable load components each configured to cover a different modulation range. The load modulated radio-frequency amplifier is sometimes referred to as a load-line modulated (LLM) power amplifier. A first of the adjustable load components can be used to provide impedance tuning that covers a first subrange of an instantaneous signal envelope of the baseband signals, whereas a second of the adjustable load components can be used to provide impedance tuning covering a second subrange of the instantaneous signal envelope of the baseband signals. The use of multiple adjustable load components can collectively provide a wider effective load (impedance) tuning range for the load modulated radio-frequency amplifier.

Electronic device10ofFIG.1may 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'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 functional block diagram ofFIG.1, device10may include components located on or within an electronic device housing such as housing12. Housing12, which may sometimes be referred to as a case, may be formed from 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 embodiments, parts or all of housing12may be formed from dielectric or other low-conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other embodiments, housing12or at least some of the structures that make up housing12may be formed from metal elements.

Device10may include control circuitry14. Control circuitry14may include storage such as storage circuitry16. Storage circuitry16may 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 circuitry16may include storage that is integrated within device10and/or removable storage media.

Control circuitry14may include processing circuitry such as processing circuitry18. Processing circuitry18may be used to control the operation of device10. Processing circuitry18may 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 circuitry14may be configured to perform operations in device10using hardware (e.g., dedicated hardware or circuitry), firmware, and/or software. Software code for performing operations in device10may be stored on storage circuitry16(e.g., storage circuitry16may 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 circuitry16may be executed by processing circuitry18.

Control circuitry14may be used to run software on device10such 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 circuitry14may be used in implementing communications protocols. Communications protocols that may be implemented using control circuitry14include 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 protocols, etc.), antenna diversity protocols, satellite navigation system protocols (e.g., global positioning system (GPS) protocols, global navigation satellite system (GLONASS) protocols, etc.), antenna-based spatial ranging protocols (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.

Device10may include input-output circuitry20. Input-output circuitry20may include input-output devices22. Input-output devices22may be used to allow data to be supplied to device10and to allow data to be provided from device10to external devices. Input-output devices22may include user interface devices, data port devices, and other input-output components. For example, input-output devices22may include touch sensors, displays (e.g., touch-sensitive and/or force-sensitive displays), light-emitting components such as displays without touch sensor capabilities, buttons (mechanical, capacitive, optical, etc.), scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, buttons, speakers, status indicators, audio jacks and other audio port components, digital data port devices, motion sensors (accelerometers, gyroscopes, and/or compasses that detect motion), capacitance sensors, proximity sensors, magnetic sensors, force sensors (e.g., force sensors coupled to a display to detect pressure applied to the display), etc. In some configurations, keyboards, headphones, displays, pointing devices such as trackpads, mice, and joysticks, and other input-output devices may be coupled to device10using wired or wireless connections (e.g., some of input-output devices22may be peripherals that are coupled to a main processing unit or other portion of device10via a wired or wireless link).

Input-output circuitry20may include wireless circuitry24to support wireless communications. Wireless circuitry24(sometimes referred to herein as wireless communications circuitry24) may include one or more antennas. Wireless circuitry24may also include baseband processor circuitry, transceiver circuitry, amplifier circuitry, filter circuitry, switching circuitry, radio-frequency transmission lines, and/or any other circuitry for transmitting and/or receiving radio-frequency signals using the antenna(s).

Wireless circuitry24may transmit and/or receive radio-frequency signals within a corresponding frequency band at radio frequencies (sometimes referred to herein as a communications band or simply as a “band”). The frequency bands handled by wireless circuitry24may include wireless local area network (WLAN) frequency bands (e.g., Wi-Fi® (IEEE 802.11) or other WLAN communications bands) such as a 2.4 GHz WLAN band (e.g., from 2400 to 2480 MHz), a 5 GHz WLAN band (e.g., from 5180 to 5825 MHz), a Wi-Fi® 6E band (e.g., from 5925-7125 MHz), and/or other Wi-Fi® bands (e.g., from 1875-5160 MHz), wireless personal area network (WPAN) frequency bands such as the 2.4 GHz Bluetooth® band or other WPAN communications bands, cellular telephone frequency bands (e.g., bands from about 600 MHz to about 5 GHz, 3G bands, 4G LTE bands, 5G New Radio Frequency Range1(FR1) bands below 10 GHz, 5G New Radio Frequency Range2(FR2) bands between 20 and 60 GHz, etc.), other centimeter or millimeter wave frequency bands between 10-300 GHz, near-field communications frequency bands (e.g., at 13.56 MHz), satellite navigation frequency bands (e.g., a GPS band from 1565 to 1610 MHz, a Global Navigation Satellite System (GLONASS) band, a BeiDou Navigation Satellite System (BDS) band, etc.), ultra-wideband (UWB) frequency bands that operate under the IEEE 802.15.4 protocol and/or other ultra-wideband communications protocols, communications bands under the family of 3GPP wireless communications standards, communications bands under the IEEE 802.XX family of standards, and/or any other desired frequency bands of interest.

FIG.2is a diagram showing illustrative components within wireless circuitry24. As shown inFIG.2, wireless circuitry24may include a processor such as processor26, radio-frequency (RF) transceiver circuitry such as radio-frequency transceiver28, radio-frequency front end circuitry such as radio-frequency front end module (FEM)40, and antenna(s)42. Processor26may be a baseband processor, application processor, general purpose processor, microprocessor, microcontroller, digital signal processor, host processor, application specific signal processing hardware, power management unit, or other type of processor. Processor26may be coupled to transceiver28over path34. Transceiver28may be coupled to antenna42via radio-frequency transmission line path36. Radio-frequency front end module40may be disposed on radio-frequency transmission line path36between transceiver28and antenna42.

In the example ofFIG.2, wireless circuitry24is illustrated as including only a single processor26, a single transceiver28, a single front end module40, and a single antenna42for the sake of clarity. In general, wireless circuitry24may include any desired number of processors26, any desired number of transceivers36, any desired number of front end modules40, and any desired number of antennas42. Each processor26may be coupled to one or more transceiver28over respective paths34. Each transceiver28may include a transmitter circuit30configured to output uplink signals to antenna42, may include a receiver circuit32configured to receive downlink signals from antenna42, and may be coupled to one or more antennas42over respective radio-frequency transmission line paths36. Each radio-frequency transmission line path36may have a respective front end module40disposed thereon. If desired, two or more front end modules40may be disposed on the same radio-frequency transmission line path36. If desired, one or more of the radio-frequency transmission line paths36in wireless circuitry24may be implemented without any front end module disposed thereon.

Radio-frequency transmission line path36may be coupled to an antenna feed on antenna42. The antenna feed may, for example, include a positive antenna feed terminal and a ground antenna feed terminal. Radio-frequency transmission line path36may have a positive transmission line signal path such that is coupled to the positive antenna feed terminal on antenna42. Radio-frequency transmission line path36may have a ground transmission line signal path that is coupled to the ground antenna feed terminal on antenna42. This example is illustrative and, in general, antennas42may be fed using any desired antenna feeding scheme. If desired, antenna42may have multiple antenna feeds that are coupled to one or more radio-frequency transmission line paths36.

Radio-frequency transmission line path36may include transmission lines that are used to route radio-frequency antenna signals within device10(FIG.1). Transmission lines in device10may 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 device10such as transmission lines in radio-frequency transmission line path36may be integrated into rigid and/or flexible printed circuit boards.

In performing wireless transmission, processor26may provide transmit signals (e.g., digital or baseband signals) to transceiver28over path34. Transceiver28may further include circuitry for converting the transmit (baseband) signals received from processor26into corresponding radio-frequency signals. For example, transceiver circuitry28may include mixer circuitry for up-converting (or modulating) the transmit (baseband) signals to radio frequencies prior to transmission over antenna42. The example ofFIG.2in which processor26communicates with transceiver28is illustrative. In general, transceiver28may communicate with a baseband processor, an application processor, general purpose processor, a microcontroller, a microprocessor, or one or more processors within circuitry18. Transceiver circuitry28may also include digital-to-analog converter (DAC) and/or analog-to-digital converter (ADC) circuitry for converting signals between digital and analog domains. Transceiver28may use transmitter (TX)30to transmit the radio-frequency signals over antenna42via radio-frequency transmission line path36and front end module40. Antenna42may transmit the radio-frequency signals to external wireless equipment by radiating the radio-frequency signals into free space.

Front end module (FEM)40may include radio-frequency front end circuitry that operates on the radio-frequency signals conveyed (transmitted and/or received) over radio-frequency transmission line path36. FEM40may, for example, include front end module (FEM) components such as radio-frequency filter circuitry44(e.g., low pass filters, high pass filters, notch filters, band pass filters, multiplexing circuitry, duplexer circuitry, diplexer circuitry, triplexer circuitry, etc.), switching circuitry46(e.g., one or more radio-frequency switches), radio-frequency amplifier circuitry48(e.g., one or more power amplifier circuits50and/or one or more low-noise amplifier circuits52), impedance matching circuitry (e.g., circuitry that helps to match the impedance of antenna42to the impedance of radio-frequency transmission line36), antenna tuning circuitry (e.g., networks of capacitors, resistors, inductors, and/or switches that adjust the frequency response of antenna42), radio-frequency coupler circuitry, charge pump circuitry, power management circuitry, digital control and interface circuitry, and/or any other desired circuitry that operates on the radio-frequency signals transmitted and/or received by antenna42. 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. If desired, amplifier circuitry48and/or other components in front end40such as filter circuitry44may also be implemented as part of transceiver circuitry28.

Filter circuitry44, switching circuitry46, amplifier circuitry48, and other circuitry may be disposed along radio-frequency transmission line path36, may be incorporated into FEM40, and/or may be incorporated into antenna42(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 circuitry14) to adjust the frequency response and wireless performance of antenna42over time.

Transceiver28may be separate from front end module40. For example, transceiver28may be formed on another substrate such as the main logic board of device10, a rigid printed circuit board, or flexible printed circuit that is not a part of front end module40. While control circuitry14is shown separately from wireless circuitry24in the example ofFIG.1for the sake of clarity, wireless circuitry24may include processing circuitry that forms a part of processing circuitry18and/or storage circuitry that forms a part of storage circuitry16of control circuitry14(e.g., portions of control circuitry14may be implemented on wireless circuitry24). As an example, processor26and/or portions of transceiver28(e.g., a host processor on transceiver28) may form a part of control circuitry14. Control circuitry14(e.g., portions of control circuitry14formed on processor26, portions of control circuitry14formed on transceiver28, and/or portions of control circuitry14that are separate from wireless circuitry24) may provide control signals (e.g., over one or more control paths in device10) that control the operation of front end module40.

Transceiver circuitry28may 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 Range1(FR1) bands below 10 GHz, 5G New Radio Frequency Range2(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 circuitry24may include one or more antennas such as antenna42. Antenna42may be formed using any desired antenna structures. For example, antenna42may 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 antennas42may 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 antenna42to adjust antenna performance. Antenna42may be provided with a conductive cavity that backs the antenna resonating element of antenna42(e.g., antenna42may be a cavity-backed antenna such as a cavity-backed slot antenna).

As described above, front end module40may include one or more power amplifiers (PA) circuits50in the transmit (uplink) path. A power amplifier50(sometimes referred to as radio-frequency power amplifier, transmit amplifier, or amplifier) may be configured to amplify a radio-frequency signal without changing the signal shape, format, or modulation. Amplifier50may, for example, be used to provide 10 dB of gain, 20 dB of gain, 10-20 dB of gain, less than 20 dB of gain, more than 20 dB of gain, or other suitable amounts of gain.

It can be challenging to design a satisfactory radio-frequency power amplifier for an electronic device. In certain applications, the radio-frequency power amplifier can be implemented as a load-line modulated (LLM) radio-frequency power amplifier. A load-line modulated radio-frequency power amplifier (sometimes referred to herein as a load modulated radio-frequency amplifier) can have an adjustable load component, including an adjustable load line, that is tuned to provide different gain profiles. The adjustable load component, however, has a limited modulation (tuning) range. In other words, tuning of the adjustable load component may provide load line adaptation for only a subrange of an instantaneous signal envelope of the baseband signals generated at the output of processor26.

In accordance with an embodiment, wireless circuitry24can be provided with load-line modulated amplifier circuitry that includes a plurality of adjustable load components each providing coverage for a different subrange of the instantaneous signal envelope. The plurality of adjustable load components can be tuned using different control signals. The control signals can be chosen such that the various tuning ranges of the adjustable load components can be stitched together to provide a broader (wider) tuning range.

FIG.3is a diagram of illustrative wireless circuitry24having a load-line modulated amplifier circuit50having multiple adjustable load components each providing a different tuning (modulation) range. As shown inFIG.3, wireless circuitry24may include processor26configured to generate baseband signals, a data converter such as digital-to-analog converter (DAC)66, an upconversion circuit such as upconverter68, a load-line modulated radio-frequency power amplifier circuit such as amplifier circuit50, and an antenna42configured to radiate radio-frequency signals output from amplifier circuit50.

Processor26may represent one or more processors such as a baseband processor, an application processor, a digital signal processor, a microcontroller, a microprocessor, a central processing unit (CPU), a programmable device, a combination of these circuits, and/or one or more processors within circuitry18. Processor26may be configured to generate digital (baseband) signals BB. Signals BB generated at the output of processor26are sometimes referred to as baseband signals, digital signals, or transmit signals. As examples, the digital signals generated by processor26may include in-phase (I) and quadrature-phase (Q) signals, radius and phase signals, or other digitally-coded signals.

The digital baseband signals output from processor26may be converted from the digital domain into the analog domain using digital-to-analog converter66and then upconverted (modulated) to radio frequencies, using upconverter68, from the baseband frequency range (which is typically in the range of a couple hundred kHz to a couple hundred MHz) to radio frequencies in the range of hundreds of MHz or in the GHz range. Upconverter68is sometimes referred to as a radio-frequency modulator or a radio-frequency mixer.

The upconverted radio-frequency signals may be fed as an input to radio-frequency (RF) amplifier circuit50. Amplifier circuit50may include an amplifier60having an input configured to receive the upconverted radio-frequency signals from modulator68and having an output coupled to a plurality of adjustable load components including but not limited to a first adjustable load component Z1and a second adjustable load component Z1. Adjustable load component Z1may have a first terminal coupled to the output of amplifier60via at least a first coupling circuit62-1and a second terminal coupled to a ground power supply line64(e.g., a ground line on which a ground power supply voltage is provided). Adjustable load component Z2may have a first terminal coupled to the output of amplifier60via at least a second coupling circuit62-2and a second terminal coupled to ground64.

Adjustable load components Z1and Z2can each be a tunable resistance (e.g., an adjustable resistor), a tunable capacitance (e.g., an adjustable capacitor), a tunable inductance (e.g., an adjustable inductor), other reactive or lossless electrical component, a combination of these components, or other adjustable impedance component(s). The example ofFIG.3in which load-line modulated amplifier circuit50includes at least two adjustable impedance components Z1and Z2is illustrative. In general, amplifier circuit50may include three or more adjustable impedance components, four or more adjustable impedance components, 5-10 adjustable impedance components, or more than 10 adjustable impedance components each providing a different tuning/modulation range.

Adjusting load components Z1and Z2can tune the load impedance seen by amplifier60from its output (see, e.g., load impedance ZLseen by the amplifier core), which can shift the gain curve response of amplifier circuit50. Adjustable load component Z1can be controlled using a first control voltage signal Vc1(sometimes referred to as a first load tuning control signal), whereas adjustable load component Z2can be controlled using a second control voltage signal Vc2(sometimes referred to as a second load tuning control signal). First control signal Vc1can be output from a first buffer or voltage driver72-1based on a first envelope signal. Second control signal Vc2can be output from a second buffer or voltage driver72-2based on a second envelope signal that is shifted from the first envelope signal by an offset. In the example ofFIG.3, control signals Vc1and Vc2are both generated based on an envelope signal Vctr output from control signal generator70. Control signal (voltage) Vctr may be fed directly to the input of buffer72-1. On the other hand, control voltage Vctr can be fed via a voltage offset component74to the input of buffer72-2. Operated in this way, the control signal Vc2output from buffer72-2may deviate from control signal Vc1by a voltage offset Vos (e.g., second buffer72-2is configured to receive a shifted version of the control voltage Vctr). Voltage offset Vos can be a predetermined voltage, a fixed voltage, or an adjustable voltage. The offset between the two load tuning control signals being shown as a voltage is exemplary. In general, the offset can be implemented in a non-voltage domain such as in a digital domain prior to digital-to-analog conversion. In such scenarios, buffer72-1can be a first digital-to-analog (D/A) conversion circuit and buffer72-2can be a second digital-to-analog (D/A) conversion circuit.

Control signal generator70may receive baseband signal BB from processor26and output corresponding control voltage Vctr. Control voltage Vctr may be an envelope signal of the baseband signal BB or the radio-frequency signal input to amplifier circuit50. Control signal generator70may include an absolute value function generator, a signal shaping function, a linear or non-linear transformation function, a combination of these functions, or other signal conditioning function for outputting control voltage Vctr. If desired, control signal generator70may also include a non-linearity estimator (e.g., an amplifier non-linearity estimator that models a non-linear behavior of amplifier50), an amplifier load response estimator (e.g., an amplifier load response estimator that implements a baseband model of a frequency-dependent response of a load at the output of amplifier50), and/or other circuitry that can otherwise help tune components Z1and Z2for optimum performance and efficiency. Control voltage Vctr may be a function of or is derived from an instantaneous signal envelope of baseband signal BB or an instantaneous signal envelope of the radio-frequency signal at the input of amplifier circuit50. Control voltage Vctr can therefore sometime be referred to as an envelope signal. For example, the first control signal Vc1can be generated based on a first subrange of envelope signal Vctr, whereas the second control signal Vc2can be generated based on a second subrange of envelope signal Vctr, where Vc1and Vc2are shifted by a fixed or adjustable offset. By shifting control signal Vc2relative to control signal Vc1by an offset amount, adjustable load components Z1and Z2can separately react to different regions or subranges of the overall voltage range of the instantaneous signal envelope of the baseband or RF signal.

Wireless circuitry24can optionally include an adaptive power tracking (APT) circuit76. Adaptive power tracking circuit76can receive baseband signal BB from processor26and output a control signal to amplifier60via control path78. Unlike envelope tracking (ET) techniques that constantly varies the power supply voltage of amplifier60, adaptive power tracking circuit76can be used to provide a relatively constant power supply voltage to amplifier60. Adaptive power tracking circuit76can adjust amplifier60to operate in different power modes. When the overall power level of the radio-frequency signals arriving at the input of amplifier circuit50is low, adaptive power tracking circuit76can provide a relatively high power supply voltage to amplifier60so that amplifier60can operate in a high power mode. Conversely, when the overall power level of the radio-frequency signals arriving at the input of amplifier circuit50is low, adaptive power tracking circuit76can provide a relatively low power supply voltage to amplifier60so that amplifier60can operate in a low power mode. In general, adaptive power tracking circuit76can provide amplifier circuit50with fine power mode tuning capabilities, coarse power mode tuning capabilities, and/or can direct amplifier60to operate in any suitable number of power modes.

FIG.4is a circuit diagram showing one suitable implementation of a portion of wireless circuitry24. In the example ofFIG.4, coupling circuits62-1and62-2can be implemented as transformers. First coupling circuit62-1can include a primary coil (winding) L1acoupled to the output of amplifier60and a secondary coil (winding) L1bcoupled to antenna42. In particular, secondary coil L1bmay have a first terminal coupled to antenna42and the second terminal coupled in series with first adjustable load component Z1. Second coupling circuit6202can include a primary coil (winding) L2aand a secondary coil (winding) L2b. Primary coil L2amay have a first terminal coupled to first coupling circuit62-1and a second terminal coupled to first adjustable load component Z1. Secondary coil L2bmay have a first terminal coupled to a power supply line (e.g., a ground line as shown inFIG.4or alternatively a positive power supply line) and a second terminal coupled to second adjustable load component Z2. The use of transformers as coupling circuits62-1and62-2is exemplary. If desired, other types of radio-frequency coupling structures can be employed.

InFIG.4, first voltage driver circuit72-1may be implemented as a first unity gain buffer73-1(e.g., an operational amplifier connected in the unity gain configuration), whereas second voltage driver circuit72-2may be implemented as a second unity gain buffer73-2. Configured in this way, voltage drivers72-1and72-2can pass through their respective control voltages with a gain of one. The use of unity gain buffers is exemplary. If desired, other types of buffer or driver circuits that provide a voltage gain of one, greater than one, or less than one can be employed for driving control signals Vc1and Vc2.

The embodiment ofFIG.4in which adjustable load components Z1and Z2are coupled to the output of amplifier60via first and second coupling circuits62-1and62-2is exemplary. In other embodiments, the various adjustable load components can be coupled to the output of amplifier60via a single (joint) coupling circuit. For example, adjustable load components Z1and Z2can be coupled to the output of amplifier60via a multi-winding inductor or transformer having a primary coil (winding) connected to the output port of amplifier60, a 1stsecondary coil (winding) connected to adjustable load component Z1, and a 2ndsecondary coil (winding) connected to adjustable load component Z2. In general, such multi-winding inductor or transformer can include any number of secondary coils (winding) for coupling to any desired number of adjustable load components.

FIG.5is a diagram plotting amplifier load impedance ZLas a function of the control voltage signals for tuning adjustable load components Z1and Z2ofFIG.4. As shown inFIG.5, control signal Vc1may start increasing first when Vctr exceeds a first voltage level Vctr_x. Adjusting load tuning control signal Vc1may tune first load component Z1to vary the amplifier load impedance between impedance values ZL0and ZL1. Due to the voltage offset, control signal Vc2may only start increasing when Vctr exceeds a second voltage level Vctr_y that is greater than Vctr_x. Voltage Vctr_y may be greater than voltage Vctr_x by offset amount Vos. By offsetting Vc2relative to Vc1, adjustable load components Z1and Z2can have shifted tuning ranges. Adjusting load tuning control signal Vc2may tune second load component Z2to effectively vary the amplifier load impedance between impedance values ZL1and ZL2(see, e.g., the total voltage tuning curve Vc_total).

Thus, the use to two separate adjustable load components controlled by different voltage signals can provide a wider effective overall tuning range than either of the adjustable load components by themselves. In other words, tuning the first load component Z1using control signal Vc1can provide a first tuning range for a first portion of the instantaneous signal envelope of the baseband or RF signal (e.g., for a first subrange covering small signal envelopes), whereas tuning the second load component Z2using control signal Vc2can provide a second tuning range for a second portion of the instantaneous signal envelope of the baseband or RF signal (e.g., for a second subrange covering large signal envelopes). The first and second tuning ranges can collectively provide an extended or broader effective modulation range covering all possible or most of the signal envelope values.

The example ofFIG.5illustrates a scenario in which the tuning ranges associated with Vc1and Vc2are non-overlapping. As shown inFIG.5, the amplifier load impedance is increased from ZL0to ZL1by solely increasing Vc1, and Vc2picks up right after Vc1to increase the amplifier load impedance from ZL1to ZL2with no discontinuity or kinks in the overall effective impedance curve corresponding to Vc_total. In practice, however, the tuning ranges associated with Vc1and Vc2can be at least partially overlapping (see, e.g.,FIG.6). This may be a result of curved transitions such as curving portion80in the Vc1profile and curving portion82in the Vc2profile. This can show up as slight deviations84in the overall effective impedance curve corresponding to Vc_total. Regardless, overlapping tuning ranges can provide a wider effective total modulation range for the load-line modulated amplifier.

The embodiment ofFIG.3in which amplifier circuit50is provided with at least two separate adjustable load components Z1and Z2is exemplary.FIG.7shows another embodiment in which amplifier circuit50is provided with more than two adjustable load components. As shown inFIG.7, amplifier60may be coupled to at least three adjustable load components Z1, Z2, and Z3with coupling circuitry62. Coupling circuitry62may be transformer based couplers, coupling structures based on closely coupled transmission lines, or other types of radio-frequency signal coupling circuits.

Adjustable load component Z1may receive a first control signal Vc1from control signal generator70. Adjustable load component Z2may receive a second control signal Vc2from control signal generator70. Adjustable load component Z3may receive a third control signal Vc3from control signal generator70. Control signals Vc1, Vc2, and Vc3may each be a function of or can be derived from an instantaneous signal envelope of baseband signal BB received from processor26or an instantaneous signal envelope of the RF signal at the input of amplifier circuit50. Signals Vc1, Vc2, and Vc3may be optionally shifted with respect to one another by fixed or adjustable voltage offset amounts. In the example ofFIG.7, control signal generator70includes three separate generator sub-circuits for outputting Vc1, Vc2, and Vc3respectively. In other embodiments, a single generator can output Vctr, one of which is fed through as Vc1while additional voltage offsets can be introduced to successively generate Vc2and Vc3in a way similar to the embodiments ofFIGS.3and4.

Configured in this way, adjustable load component Z1can be tuned using Vc1to provide a first tuning range covering a first subrange of the instantaneous signal envelope of the baseband or RF signal; adjustable load component Z2can be tuned using Vc2to provide a second tuning range, non-overlapping or partially overlapping with the first tuning range, covering a second subrange of the instantaneous signal envelope; and adjustable load component Z3can be tuned using Vc3to provide a third tuning range, non-overlapping or partially overlapping with the second tuning range, covering a third subrange of the instantaneous signal envelope. Operated in this way, the load-line modulated amplifier circuit50can exhibit a broader (extended) total tuning range that is a sum of the first, second, and third tuning ranges.

The example ofFIG.7in which load-line modulated amplifier circuit50includes at least three adjustable load components Z1, Z2, and Z3is illustrative. In general, amplifier circuit50may include more than three adjustable load components, four or more adjustable load components, 5-10 adjustable load components, 10-20 adjustable load components, or more than 20 adjustable load components each providing a different tuning/modulation range corresponding to different subranges of the overall voltage range of the instantaneous signal envelope of the baseband or RF signal.

As described above in connection withFIG.3, wireless circuitry24can optionally include an adaptive power tracking circuit76that can be used to operate the load-line modulated amplifier in a plurality of different power modes.FIG.8is a state diagram showing how load-line modulated amplifier circuit50of the type described in connection withFIGS.2-7can be operable in at least a first power mode90, a second power mode92, and a third power mode94.

In the first power mode90, adaptive power tracking circuit76may provide a relatively low power supply voltage to amplifier60such that amplifier60operates in a low power mode. In this mode90, adjustable load components Z1and Z2(and optionally additional load components) can be separately tuned using Vc1an Vc2to provide a first total load tuning range when the amplifier is operating in the low power mode.

In the second power mode92, adaptive power tracking circuit76may provide an intermediate (medium) power supply voltage to amplifier60such that amplifier60operates in a medium (normal) power mode. In this mode92, adjustable load components Z1and Z2(and optionally additional load components) can be separately tuned using Vc1an Vc2to provide a second total load tuning range when the amplifier is operating in the medium power mode. The second total load tuning range may be non-overlapping or only partially overlapping with the first total load tuning range.

In the third power mode94, adaptive power tracking circuit76may provide an high (boosted) power supply voltage to amplifier60such that amplifier60operates in a high power mode. In this mode94, adjustable load components Z1and Z2(and optionally additional load components) can be separately tuned using Vc1an Vc2to provide a third total load tuning range when the amplifier is operating in the high power mode. The third total load tuning range may be non-overlapping or only partially overlapping with the first and second total load tuning ranges. By combining the flexible power modes provided by adaptive power tracking circuit76and the extended tuning ranges provided by the multiple adjustable load components, the LLM amplifier circuitry can exhibit a much broader tuning capability across a wide range of power modes.

The example ofFIG.8showing only three different power modes is illustrative. In general, adaptive power tracking circuit76can direct the LLM amplifier to operate in more than three different power modes, in 3-10 different power modes, in 10-20 different power modes, in 20-100 different power modes, or in more than 100 different power modes. In each of the various power modes, the overall effective tuning range can be expanded using two or more adjustable load components each covering a different subrange of an instantaneous signal envelope of a baseband or RF signal.

The methods and operations described above in connection withFIGS.1-8may be performed by the components of device10using 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 device10(e.g., storage circuitry16and/or wireless communications circuitry24ofFIG.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 device10(e.g., processing circuitry in wireless circuitry24, processing circuitry18ofFIG.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.