Load modulated radio-frequency amplifier with digital predistortion

Patent metadata

Field	Value
Publication number	US-12537548-B2
Application number	US-202318321454-A
Country	US
Kind code	B2
Filing date	May 22, 2023
Priority date	Jul 7, 2022
Publication date	Jan 27, 2026
Grant date	Jan 27, 2026

Abstract

An electronic device may include wireless circuitry. The wireless circuitry may include at least a digital predistortion circuit, an upconversion circuit, and a load-line modulated amplifier circuit. The digital predistortion circuit can be configured to receive a reference baseband signal from one or more processors and to selectively output a predistorted version of the reference baseband signal. The upconversion circuit can be configured to receive a signal from the digital predistortion circuit and to output a radio-frequency signal. The load-line modulated amplifier circuit can be configured to amplify the radio-frequency signal. The load-line modulated amplifier circuit can include an adjustable load component. The adjustable load component can have a constant impedance when an instantaneous signal amplitude of the reference baseband signal is within a first range and can be tuned to have a varying impedance when the instantaneous signal amplitude of the reference baseband signal is within a second range.

First claim

What is claimed is:

1 . Wireless circuitry comprising:
a digital predistortion circuit configured to receive a baseband reference signal and to selectively predistort the baseband reference signal to output either the baseband reference signal or a predistorted signal; an upconversion circuit configured to receive the baseband reference signal or the predistorted signal and configured to output a corresponding radio-frequency signal; a load modulated amplifier circuit configured to receive the radio-frequency signal and to output a corresponding amplified radio-frequency signal, the load modulated amplifier circuit including an adjustable load component having a constant impedance when an instantaneous signal amplitude of the baseband reference signal or the predistorted signal is within a first range and having a varying impedance when the instantaneous signal amplitude of the baseband reference signal or the predistorted signal is within a second range different than the first range; and a gain shaping circuit configured to receive the baseband reference signal or the predistorted signal and to output a control signal for tuning the adjustable load component, wherein the load modulated amplifier circuit has a gain and wherein the gain shaping circuit is configured to adjust the control signal such that a derivative of the gain is continuous.

2 . The wireless circuitry of claim 1 , the gain shaping circuit being further configured to:
keep the control signal constant when the instantaneous signal amplitude of the baseband reference signal or the predistorted signal is within the first range; and vary the control signal when the instantaneous signal amplitude of the baseband reference signal or the predistorted signal is within the second range.

3 . The wireless circuitry of claim 2 , wherein the gain shaping circuit is configured to vary the control signal as a function of the instantaneous signal amplitude of the baseband reference signal or the predistorted signal.

4 . The wireless circuitry of claim 1 , wherein the digital predistortion circuit is configured to linearize the gain of the load modulated amplifier circuit.

5 . The wireless circuitry of claim 1 , wherein the gain varies when the instantaneous signal amplitude of the baseband reference signal is within the first range and varies when the instantaneous signal amplitude of the baseband reference signal is within the second range.

6 . The wireless circuitry of claim 2 , further comprising:
a radio-frequency coupler coupled between the load modulated amplifier circuit and an antenna; a downconversion circuit configured to demodulate a radio-frequency signal coupled from the radio-frequency coupler to generate a corresponding demodulated signal; and an analog-to-digital converter configured to convert the demodulated signal from an analog domain to a digital domain to generate a corresponding measured signal.

7 . The wireless circuitry of claim 6 , further comprising an alignment circuit configured to phase and time align the baseband reference signal and the measured signal or to phase and time align the predistorted signal and the measured signal.

8 . The wireless circuitry of claim 7 , further comprising a gain calculation circuit configured to receive the baseband reference signal and the measured signal and further configured to compute an instantaneous gain value based on the received baseband reference signal and the received measured signal.

9 . The wireless circuitry of claim 8 , further comprising a gain shape analyzer circuit configured to receive the computed instantaneous gain value, to monitor recently computed gain values output from the gain calculation circuit, and to output information to the gain shaping circuit.

10 . The wireless circuitry of claim 7 , further comprising a gain calculation circuit configured to receive the predistorted signal and the measured signal and further configured to compute an instantaneous gain value based on the received predistorted signal and the received measured signal.

11 . A method of operating wireless circuitry, comprising: receiving a baseband signal from one or more processors; upconverting the baseband signal to a radio-frequency signal;
with a load modulated amplifier circuit, amplifying the radio-frequency signal; downconverting a portion of the amplified radio-frequency signal to produce a demodulated signal; converting the demodulated signal from an analog domain to a digital domain to produce a measured signal; aligning the measured signal and the baseband signal in phase and time; with a gain shaping circuit, outputting a control signal based on at least the measured signal to an adjustable load component in the load modulated amplifier circuit; keeping the control signal constant when an instantaneous amplitude of the baseband signal is within a first range; and varying the control signal when the instantaneous amplitude of the baseband signal is within a second range non-overlapping with the first range.

12 . The method of claim 11 , further comprising predistorting the baseband signal to linearize a gain of the load modulated amplifier circuit.

13 . The method of claim 12 , wherein the gain shaping circuit is configured to adjust the control signal such that a derivative of the gain is continuous.

14 . The method of claim 11 , further comprising
computing an instantaneous gain value based on the baseband signal and the measured signal; analyzing the instantaneous gain value to determine whether a derivative of the gain of the load modulated amplifier circuit is continuous; and in response to determining that the derivative of the gain of the load modulated amplifier circuit is not continuous, adjusting the gain shaping circuit.

15 . The method of claim 12 , further comprising aligning the measured signal and the predistorted baseband signal in phase and time.

16 . An electronic device comprising:
one or more processors configured to generate a baseband signal; a predistortion circuit configured to selectively predistort the baseband signal to output either the baseband signal or a predistorted signal; a modulator configured to convert the baseband signal or the predistorted signal to a radio-frequency signal; a load-line modulated amplifier circuit configured to amplify the radio-frequency signal; and gain shaping circuitry having a first input configured to receive the baseband signal from the one or more processors, a second input configured to receive a portion of the amplified radio-frequency signal via a radio-frequency coupler, a third input configured to receive the baseband signal or the predistorted signal from the predistortion circuit, and an output coupled to an adjustable impedance in the load-line modulated amplifier circuit.

17 . The electronic device of claim 16 , wherein the gain shaping circuitry comprises:
a gain shaping circuit configured to generate a control signal for tuning the adjustable impedance based on an instantaneous signal amplitude of the baseband signal or the predistorted signal, the control signal having a constant value when the instantaneous signal amplitude of the baseband signal or the predistorted signal is within a first signal range and having a varying value when the instantaneous signal amplitude of the baseband signal or the predistorted signal is within a second signal range greater than the first signal range.

18 . The electronic device of claim 17 , wherein the gain shaping circuitry comprises:
a demodulator configured

Assignees

• Apple Inc

Inventors

• Henzler Stephan
• Mirassol Tomé Pedro
• Langer Andreas
• Klinkan Alexander

Classifications

• H04B2001/0416

  having gain or transmission power control · CPC title

• H04B1/0475

  with means for limiting noise, interference or distortion (H04B1/0483 takes precedence) · CPC title

• H04B1/0089

  using a first intermediate frequency higher that the highest of any band received · CPC title

• H04B1/0096 Primary

  where a full band is frequency converted into another full band · CPC title

• H03F2200/102

  A non-specified detector of a signal envelope being used in an amplifying circuit · CPC title