RF Amplifier Bias Modulation With DPD for Supply-Induced Distortion
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Solution Overview
Problem
Existing discrete supply modulation methods in power amplifiers (PAs) cause distortion due to abrupt changes in supply voltage, which existing systems fail to adequately address, leading to inefficiencies and linearity issues in radio frequency (RF) transmitters.
Innovation Solution
A radio frequency (RF) transceiver system with a digital pre-distorter (DPD) and a bias modulation circuit that generates a control signal to adjust the bias of the RF amplifier, combining it with the input signal to apply digital predistortion, taking into account various parameters like power, bandwidth, frequency, temperature, and voltage standing wave ratio (VSWR), to optimize PA efficiency and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If discrete supply modulation is used to improve PA efficiency, then power efficiency is improved, but distortion increases due to abrupt supply voltage changes
Solution Approach 1:
The patent applies preliminary action by pre-distorting the input signal to the power amplifier before the abrupt supply voltage changes occur. The digital pre-distorter modifies the input signal characteristics in advance, creating a predistorted signal that anticipates the distortion caused by discrete supply modulation. This allows the PA to produce the desired output signal despite the abrupt supply voltage transitions, thereby maintaining both efficiency and linearity.
2Measurement precision
If high-order nonlinearity basis functions are used to model PA distortion, then distortion modeling accuracy is improved, but system complexity increases
Solution Approach 1:
The patent applies parameter changes by adapting the pre-distortion model parameters based on the actual operating conditions of the power amplifier. Instead of using fixed high-order nonlinearity basis functions, the system dynamically adjusts model parameters to match the PA's behavior under different supply voltage levels and operating points. This reduces the need for complex high-order models while maintaining accurate distortion compensation across varying conditions.
3Measurement precision
If polynomial coefficients are indexed to PA supply voltage level, then pre-distortion accuracy is improved, but memory requirements and processing complexity increase
Solution Approach 1:
The patent applies local quality by using different pre-distortion model parameters specifically tailored to each discrete supply voltage level. Instead of using a single complex global model, the system maintains separate simplified models for each operating point. The digital pre-distorter selects and applies the appropriate local model based on the current supply voltage level, achieving accurate pre-distortion for each specific operating condition without requiring a single overly complex universal model.
Data Source
AI summary
In some embodiments, in a radio frequency (RF) transceiver system having an RF amplifier and a digital pre-distorter (DPD), a control unit includes: one or more inputs, one of which is connected to receive a first signal corresponding to a signal desired to be transmitted via the RF amplifier or a modified version thereof; circuitry configured to generate a control signal for controlling a bias of the RF amplifier; and an output connected to provide the control signal to the DPD and to a bias modulation circuit for varying the bias of the RF amplifier based in part the control signal, wherein the DPD is configured to apply digital predistortion to the signal to be transmitted based in part on combining the first signal with a second signal corresponding to the control signal or a translated version thereof, and to provide a resulting pre-distorted signal to the RF amplifier.