RF Power Amplifier DPD Using Digital Supply Modulation Signals
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Solution Overview
Problem
Existing discrete supply modulation methods in radio frequency (RF) transceivers cause distortion due to abrupt changes in power amplifier (PA) supply voltage, which existing systems fail to adequately address through polynomial coefficients or look-up-tables.
Innovation Solution
A control unit in an RF transceiver system generates a control signal to manage the supply voltage of the PA, combining it with the signal to be transmitted using digital pre-distortion (DPD) to mitigate distortion, employing preprocessing blocks and a nonlinear combiner to algebraically combine signals and adjust coefficients based on operating conditions.
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 signal characteristics in advance to compensate for the expected distortion caused by discrete supply modulation, ensuring that the output signal remains accurate despite the efficiency-optimizing voltage switches.
Solution Approach 2:
The patent converts the harmful effect of abrupt supply voltage changes into a beneficial outcome by using these same voltage transitions as reference signals to dynamically adjust pre-distortion coefficients. The distortion-causing events are transformed into calibration opportunities, where the actual voltage transitions are measured and used to optimize the compensation parameters in real-time.
2Manufacturing precision
If polynomial coefficients or look-up-tables are used to compensate for distortion, then linearity is improved, but memory effects in the PA are not adequately addressed
Solution Approach 1:
The patent applies dynamics by transitioning from static polynomial coefficients or look-up-tables to dynamic pre-distortion coefficients that are continuously updated based on real-time measurements of supply voltage transitions. The system adapts the compensation parameters dynamically to match the actual operating conditions, including memory effects, rather than relying on fixed pre-determined values.
Solution Approach 2:
The patent implements feedback by using the actual supply voltage transitions as reference signals to update the pre-distortion coefficients. The system measures the real voltage changes, compares them with the expected transitions, and adjusts the compensation parameters accordingly, creating a closed-loop system that continuously optimizes linearity compensation under dynamic operating conditions.
3Measurement precision
If high-order nonlinearity basis functions or neural networks are used for DPD, then distortion modeling accuracy is improved, but system complexity increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the pre-distortion coefficients based on the actual supply voltage transition characteristics rather than using fixed high-order nonlinearity models. The system changes the parameters (coefficients) in response to varying operating conditions, providing accurate distortion compensation for each specific voltage transition scenario without requiring complex universal models.
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, at least 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 supply voltage level of the RF amplifier; and an output connected to provide the control signal to the DPD and to a circuit to alter the supply voltage level of the RF amplifier, wherein the DPD is configured to apply digital predistortion to the signal to be transmitted based at least 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.