US-12620943-B2 - Transmitter system with hybrid digital drift/trap compensation

US12620943B2US 12620943 B2US12620943 B2US 12620943B2US-12620943-B2

Abstract

The present disclosure relates to a transmitter system that includes a radio frequency (RF) power amplifier (PA) and a baseband processor. The RF PA is configured to amplify an RF input signal to an RF output signal and configured to receive an analog bias adjustment signal, which is applied to correct dynamic bias errors in the RF PA caused by amplification variations that have time constants. The baseband processor, in response to an input envelope and a feedback output envelope, is configured to generate a feedback envelope error signal. Herein, the input envelope is estimated based on a baseband input signal received by the baseband processor, and the feedback output envelope is estimated based on the RF output signal. The RF input signal and the analog bias adjustment signal fed to the RF PA are generated from the baseband input signal and the feedback envelope error signal, respectively.

Inventors

Paul Edward Gorday

Assignees

QORVO US, INC.

Dates

Publication Date: 20260505
Application Date: 20230109

Claims (20)

1 . A transmitter system comprising: a radio frequency (RF) power amplifier (PA) having an amplifier input terminal, an amplifier output terminal, and a bias input terminal, wherein: the RF PA is configured to receive an RF input signal at the amplifier input terminal and generate an RF output signal at the amplifier output terminal, wherein the RF output signal is an amplified version of the RF input signal; and the RF PA is configured to receive an analog bias adjustment signal at the bias input terminal, which is applied to correct dynamic bias errors in the RF PA caused by amplification variations that have time constants; and a baseband processor, in response to an input envelope and a feedback output envelope, configured to generate a feedback envelope error signal, wherein: the input envelope is estimated by detecting an input modulation signal, which corresponds to a baseband input signal received by the baseband processor, and the feedback output envelope is estimated by detecting a feedback modulation signal, which corresponds to the RF output signal and is received by the baseband processor, wherein the input modulation signal and the feedback modulation signal are baseband signals having lower frequencies than the RF input signal; the RF input signal fed to the amplifier input terminal is generated from the baseband input signal; and the analog bias adjustment signal fed to the bias input terminal is generated from the feedback envelope error signal.
2 . The transmitter system of claim 1 further comprises an RF-to-baseband converter, wherein: the RF-to-baseband converter is configured to convert the RF output signal from the amplifier output terminal of the RF PA down to the feedback modulation signal fed to the baseband processor; and the baseband processor is configured to receive the baseband input signal from an input port and the feedback modulation signal from the RF-to-baseband converter and configured to provide a pre-distorted modulation signal based on the received baseband input signal and the received feedback modulation signal.
3 . The transmitter system of claim 2 further comprises a baseband-to-RF converter, wherein: the pre-distorted modulation signal is provided from the baseband processor to the baseband-to-RF converter; and the baseband-to-RF converter is configured to convert the pre-distorted modulation signal up to the RF input signal fed to the amplifier input terminal of the RF PA.
4 . The transmitter system of claim 2 wherein the baseband processor includes a modulator, wherein the modulator is configured to modulate the baseband input signal to the input modulation signal.
5 . The transmitter system of claim 4 wherein the baseband processor further includes a digital pre-distorter (DPD), which is configured to compare the input modulation signal from the modulator with the feedback modulation signal from the RF-to-baseband converter to determine how much to distort the input modulation signal thereby distorting the RF input signal to correct nonlinearity of the RF PA, wherein the estimation of the input envelope is independent of the DPD.
6 . The transmitter system of claim 4 wherein the baseband processor further includes an input envelope detector, a feedback envelope detector, and a compensation block, wherein: the input envelope detector is configured to detect the input envelope of the input modulation signal, and the feedback envelope detector is configured to detect the feedback output envelope of the feedback modulation signal; and the compensation block is configured to compare the input envelope with the feedback output envelope to provide the feedback envelope error signal.
7 . The transmitter system of claim 6 wherein the compensation block includes a first configurable digital gain block, a first summation node, a second configurable digital gain block, and a digital loop filter, wherein: the first configurable digital gain block is configured to apply a first gain to the input envelope to provide a scaled input envelope; the first summation node is configured to provide an error signal, which indicates a difference between the scaled input envelope and the feedback output envelope; the second configurable digital gain block is configured to apply a second gain to the error signal to provide a scaled error signal; and the digital loop filter is configured to smooth the scaled error signal to provide the feedback envelope error signal.
8 . The transmitter system of claim 7 wherein the first gain is a gain of the RF PA.
9 . The transmitter system of claim 6 wherein the compensation block includes a first configurable digital gain block, a first summation node, a second configurable digital gain block, and a digital loop filter, wherein: the first configurable digital gain block is configured to apply a first gain to the feedback output envelope to provide a scaled feedback output envelope; the first summation node is configured to provide an error signal, which indicates a difference between the input envelope and the scaled feedback output envelope; the second configurable digital gain block is configured to apply a second gain to the error signal to provide a scaled error signal; and the digital loop filter is configured to smooth the scaled error signal to provide the feedback envelope error signal.
10 . The transmitter system of claim 9 wherein the first gain is an inverse of a gain of the RF PA.
11 . The transmitter system of claim 1 further comprising a bias processor coupled between the baseband processor and the bias input terminal of the RF PA, wherein the bias processor is configured to receive the feedback envelope error signal from the baseband processor and to provide the analog bias adjustment signal to the bias input terminal of the RF PA.
12 . The transmitter system of claim 11 wherein the bias processor includes a digital-to-analog converter (DAC) and a DAC conditioning block, wherein: the DAC conditioning block is an interface between the baseband processor and the DAC, and is configured to modify the feedback envelope error signal with at least one of gaining and filtering; and the DAC is configured to convert the modified feedback envelope error signal to the analog bias adjustment signal, which is fed to the bias input terminal of the RF PA.
13 . A transmitter system comprising: a radio frequency (RF) power amplifier (PA) having an amplifier input terminal, an amplifier output terminal, and a bias input terminal, wherein: the RF PA is configured to receive an RF input signal at the amplifier input terminal and generate an RF output signal at the amplifier output terminal, wherein the RF output signal is an amplified version of the RF input signal; and the RF PA is configured to receive an analog bias adjustment signal at the bias input terminal, which is applied to correct dynamic bias errors in the RF PA caused by amplification variations that have time constants; a baseband processor comprising a modulator, an input envelope detector, and a digital pre-distorter (DPD), wherein: the modulator is configured to receive a baseband input signal and provide an input modulation signal based on the baseband input signal; wherein the input modulation signal is fed to both the input envelope detector and the DPD; the input envelope detector is configured to detect an input envelope of the input modulation signal, wherein the input modulation signal is a baseband signal having a lower frequency than the RF input signal; and the RF input signal fed to the amplifier input terminal is generated from the baseband input signal; and a bias processor configured to compare the input envelope from the baseband processor and a feedback output envelope estimated from the RF output signal, and to provide the analog bias adjustment signal to the bias input terminal of the RF PA based on the comparison, wherein the input envelope received by the bias processor does not undergo the DPD.
14 . The transmitter system of claim 13 wherein the bias processor comprises: an output envelope detector having a detector input coupled to the amplifier output terminal of the RF PA and a detector output, wherein the output envelope detector is configured to rectify and filter the RF output signal to generate an average signal envelope; an output analog-to-digital converter (ADC) configured to sample the average signal envelope to provide the feedback output envelope; and a compensation block having a first compensation input coupled to the baseband processor, a second compensation input coupled to the output ADC, and a compensation output, wherein the compensation block is configured to compare the input envelope from the baseband processor with the feedback output envelope from the output ADC, and to provide a feedback envelope error signal based on the comparison.
15 . The transmitter system of claim 14 wherein the bias processor further comprises a digital-to-analog converter (DAC) coupled between the compensation output of the compensation block and the bias input terminal of the RF PA, wherein the DAC is configured to receive the feedback envelope error signal from the compensation block and to convert the feedback envelope error signal into the analog bias signal at the bias input terminal of the RF PA.
16 . The transmitter system of claim 14 further comprising an output coupler, wherein: the detector input of the output envelope detector is coupled to the amplifier output terminal of the RF PA via the output coupler; and the output coupler is configured to divert a portion of the RF output signal to the output envelope detector.
17 . The transmitter system of claim 14 wherein the compensation block includes a first configurable digital gain block, a first summation node, a second configurable digital gain block, and a digital loop filter, wherein: the first configurable digital gain block is configured to apply a first gain to the input envelope to provide a scaled input envelope; the first summation node is configured to provide an error signal, which indicates a difference between the scaled input envelope and the feedback output envelope; the second configurable digital gain block is configured to apply a second gain to the error signal to provide a scaled error signal; and the digital loop filter is configured to smooth the scaled error signal to provide the feedback envelope error signal.
18 . The transmitter system of claim 17 wherein the first gain is a gain of the RF PA.
19 . The transmitter system of claim 14 wherein the compensation block includes a first configurable digital gain block, a first summation node, a second configurable digital gain block, and a digital loop filter, wherein: the first configurable digital gain block is configured to apply a first gain to the feedback output envelope to provide a scaled feedback output envelope; the first summation node is configured to provide an error signal, which indicates a difference between the input envelope and the scaled feedback output envelope; the second configurable digital gain block is configured to apply a second gain to the error signal to provide a scaled error signal; and the digital loop filter is configured to smooth the scaled error signal to provide the feedback envelope error signal.
20 . The transmitter system of claim 19 wherein the first gain is an inverse of a gain of the RF PA.

Description

RELATED APPLICATIONS This application claims the benefit of provisional patent application Ser. No. 63/301,772, filed Jan. 21, 2022, and provisional patent application Ser. No. 63/390,755, filed Jul. 20, 2022, the disclosures of which are hereby incorporated herein by reference in their entireties. FIELD OF THE DISCLOSURE The present disclosure is related to a transmitter system, within which hybrid digital drift/trap compensation is provided for a radio frequency power amplifier. BACKGROUND Present transmitter systems can include a gallium nitride (GaN) device that makes up a controlled radio frequency (RF) power amplifier, a drain-current sensor, circuitry for controlling drain current by manipulating gate voltage of the GaN device, and a baseband processor having a low-speed data bus coupling the baseband processor to a power amplifier module in which the GaN device is integrated. The circuitry for controlling drain current further comprises an analog-to-digital converter for converting the magnitude of the drain current to a digital representation, a digital-to-analog converter for converting the digital representation of a gate bias value to an analog voltage coupled to a gate of the GaN device, and a logic block for, among other things, setting the GaN device gate voltage. A codeplug (one-time programmable) provides settings for the power amplifier control logic block. A negative voltage generator provides a negative voltage to serve as a power supply to generate the gate bias voltage to the GaN device. The negative voltage generator provides a practical means of biasing the GaN device, which is typically depletion mode and requires a negative gate voltage to function correctly. In operation, these RF amplifier systems can perform pre-wired control functions such as gate-bias generation. However, because stored information is one-time programmable, all characterization must be accomplished during the manufacturing process. The current sense operates only at direct current and so cannot be used when an alternating current signal is present. The power amplifier control logic comprises registers that can be written from the baseband processor, so overrides of codeplug information are possible. All decision-making beyond some simple hard-wired functions must be implemented in the baseband controller. As such, there is a latency between the baseband controller and the power amplifier module. This latency makes mitigation of trapping and drift in transmit devices such as the GaN device unrealizable or at least impractical. Accordingly, there remains a need for digital drift/trap compensation within the transmitted systems, so as to provide low latency control of devices that comprise RF amplifiers to mitigate charge trapping and drift in the devices. SUMMARY The present disclosure relates to a transmitter system, within which hybrid digital drift/trap compensation is provided for a radio frequency power amplifier. The disclosed transmitter system includes a baseband processor and a radio frequency (RF) power amplifier having an amplifier input terminal, an amplifier output terminal, and a bias input terminal. The RF power amplifier is configured to receive an RF input signal at the amplifier input terminal and generate an RF output signal at the amplifier output terminal, the RF output signal being an amplified version of the RF input signal. The RF power amplifier is also configured to receive an analog bias adjustment signal at the bias input terminal, which is applied to correct dynamic bias errors in the RF power amplifier caused by amplification variations that have time constants. The baseband processor, in response to an input envelope and a feedback output envelope, is configured to generate a feedback envelope error signal. Herein, the input envelope is estimated based on a baseband input signal received by the baseband processor, and the feedback output envelope is estimated based on the RF output signal. The RF input signal fed to the amplifier input terminal is generated from the baseband input signal, and the analog bias adjustment signal fed to the bias input terminal is generated from the feedback envelope error signal. According to one embodiment, the transmitter system further includes an RF-to-baseband converter and a baseband-to-RF converter. Herein, the RF-to-baseband converter is configured to convert the RF output signal from the amplifier output terminal of the RF power amplifier into a feedback modulation signal fed to the baseband processor. The baseband processor is configured to receive the baseband input signal from an input port and the feedback modulation signal from the RF-to-baseband converter, and configured to provide a pre-distorted modulation signal to the baseband-to-RF converter based on the received baseband input signal and the received feedback modulation signal. The baseband-to-RF converter is configured to convert the pre-distorted modulation signal to the RF input