Load-Modulated Power Amplifier Phase Compensation for AM/PM Distortion
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Solution Overview
Problem
Existing RF power amplifiers in communication systems face inefficiencies, particularly with high peak-to-average power ratio waveforms, and suffer from amplitude-to-phase modulation (AM/PM) distortion, which complicates spectral performance.
Innovation Solution
Implementing a load modulated power amplifier system with digital pre-distortion and phase compensation, utilizing a controllable load impedance adjusted by an envelope signal, and incorporating a phase modulator to correct for AM/PM distortion, thereby enhancing efficiency and spectral performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If load modulation is used to improve efficiency, then power efficiency is improved, but AM/PM distortion increases
Solution Approach 1:
The patent applies preliminary anti-action by using digital pre-distortion to pre-compensate the input signal before it enters the load-modulated power amplifier. The pre-distorter applies an inverse of the expected AM/PM distortion characteristics, so that when the load modulation occurs, the net result is minimal phase distortion. This anticipatory correction allows the system to maintain both high efficiency through load modulation and low distortion through pre-compensation.
Solution Approach 2:
The patent implements feedback by measuring the actual output signal from the power amplifier and using that information to adjust the pre-distortion parameters. The system monitors the AM/PM characteristics in real-time and dynamically adjusts the pre-distortion filter coefficients to optimize compensation. This closed-loop feedback mechanism ensures that the system maintains low distortion while operating in the highly efficient load-modulated regime.
2Object-generated harmful factors
If digital pre-distortion is applied to reduce distortion, then spectral performance is improved, but system complexity increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the pre-distortion filter coefficients based on operating conditions such as input power level and modulation type. Rather than using a fixed complex algorithm, the system changes key parameters (filter coefficients, distortion model order) adaptively to match the current operating point. This reduces computational complexity while maintaining effective distortion cancellation across varying signal conditions.
Solution Approach 2:
The patent uses preliminary action by pre-calculating and storing distortion compensation characteristics in lookup tables before operation. The system characterizes the power amplifier's AM/PM behavior in advance and stores correction data that can be quickly applied during normal operation. This pre-computation approach avoids the need for complex real-time calculations, reducing processing complexity while maintaining effective spectral performance.
3Use of energy by moving object
If load impedance is dynamically adjusted to enhance efficiency, then power efficiency is improved, but phase stability deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by predicting the phase shifts that will result from load impedance changes and pre-compensating for them. The system uses a model of the power amplifier's phase characteristics under different load conditions to calculate and apply appropriate pre-distortion. This anticipatory phase compensation counteracts the destabilizing effect of dynamic load adjustment, maintaining phase stability while enabling efficiency improvements through load modulation.
Data Source
AI summary
A mobile device includes a baseband processor configured to provide a modulated digital signal and one or more processors configured to apply digital pre-distortion and phase compensation to the modulated digital signal to generate a compensated digital signal. A radio frequency modulator converts the compensated digital signal to a radio frequency signal, and a load modulated power amplifier amplifies the radio frequency signal.