Load-Modulated Power Amplifier Calibration for Distortion Control
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Solution Overview
Problem
Existing RF power amplifiers suffer from phase and amplitude distortion due to impedance modulation, leading to inefficiencies and complexity in RF communication systems.
Innovation Solution
A load modulated power amplifier system with a controllable impedance modulated by a shaped envelope signal, utilizing an envelope shaping table with a smoothed response characteristic to compensate for phase distortion, and a power management circuit to control supply voltage, along with a gain shaping table to scale RF signals, achieving less than −120 dBm of phase distortion and −130 dBm of amplitude distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If impedance modulation is used to control power amplifier output, then power efficiency is improved, but phase and amplitude distortion increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing compensation values in lookup tables before operation. The envelope shaping table stores pre-computed impedance modulation signals that compensate for phase distortion, and the amplitude correction table stores pre-computed correction factors for amplitude variations. This preliminary preparation eliminates the need for real-time complex calculations during operation, achieving both high efficiency and low distortion.
Solution Approach 2:
The patent implements feedback by measuring the actual phase and amplitude distortion caused by impedance modulation and using this information to generate correction signals. The system continuously monitors the distortion and adjusts the modulation signals through the lookup tables to compensate for the distortion, creating a closed-loop control system that maintains low distortion while preserving efficiency benefits.
2Manufacturing precision
If complex distortion compensation algorithms are implemented in real-time, then phase and amplitude distortion is reduced, but computational complexity and processing time increase
Solution Approach 1:
The patent pre-computes complex distortion compensation values and stores them in lookup tables during system initialization or calibration. The envelope shaping table and amplitude correction table contain pre-calculated compensation signals for various operating conditions. During real-time operation, the system simply retrieves pre-computed values based on current operating parameters, avoiding time-consuming real-time calculations while maintaining high compensation accuracy.
Solution Approach 2:
The patent creates simplified copies of the complex distortion compensation function in the form of lookup tables. Instead of implementing the full complex algorithm in real-time, the system uses pre-computed tabular data that replicates the compensation effect. This copying approach trades memory storage for computational speed, enabling fast real-time operation with accurate distortion compensation.
3Measurement precision
If additional correction circuits and algorithms are added to compensate for distortion, then signal accuracy is improved, but device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by using a single impedance modulation mechanism to simultaneously control power amplifier output level and compensate for phase distortion. The envelope shaping table serves multiple purposes: it shapes the envelope signal for efficiency while embedded within it are the phase compensation corrections. This universal approach eliminates the need for separate correction circuits, reducing overall device complexity while maintaining high signal accuracy.
Solution Approach 2:
The patent merges the envelope shaping function and phase distortion compensation function into a single integrated lookup table (the envelope shaping table). Instead of having separate circuits for envelope control and phase correction, the patent combines both correction signals into one unified table that generates both simultaneously. This merging reduces the number of components and simplifies the overall system architecture while achieving both efficiency and accuracy goals.
Data Source
AI summary
Control and calibration for load modulation power amplifiers are disclosed. In certain embodiments, envelope shaping for a modulated power amplifier incorporates shifting of the envelope shaping table response characteristic with a signal power target (for instance, an average power target). Thus, as a voltage level of a power amplifier supply voltage changes for APT for a given power range, a replicated but shifted envelope shaping table response characteristic can be used for load modulation.