Outphasing RF Transmitter Calibration for Gain and Phase Mismatch
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Solution Overview
Problem
Outphasing wireless systems face challenges due to gain and phase mismatches between decomposed signals, leading to reduced power amplifier linearity and increased error vector magnitude (EVM), which deteriorates signal quality.
Innovation Solution
An outphasing calibration method and system for RF transmitter devices that decompose variable-amplitude signals into constant-amplitude, phase-shifted signals, amplify them using differential power amplifiers, and combine them with a power combiner to reduce mismatches, utilizing phase and voltage detectors to adjust subsequent signals for improved alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If outphasing decomposition is used to achieve efficient linear power amplification, then power amplification efficiency is improved, but gain and phase mismatches occur between decomposed signals leading to reduced linearity and increased EVM
Solution Approach 1:
The patent implements a feedback mechanism where the received RF signal is fed back through the transmit chain to measure gain and phase mismatches. Phase detectors compare the feedback signal with reference signals to generate error signals that are used to adjust phase shifters and correct the mismatches in real-time, thereby maintaining signal linearity while preserving power amplification efficiency
Solution Approach 2:
The patent replaces manual or mechanical calibration methods with electronic feedback control systems. Digital signal processing and electronic phase shifters substitute for physical adjustment mechanisms, enabling automated correction of gain and phase mismatches through electronic control signals generated by the feedback loop
2Manufacturing precision
If gain and phase adjustments are made to correct mismatches, then signal quality is improved, but device complexity increases due to additional calibration components
Solution Approach 1:
The patent makes existing components perform multiple functions. The power amplifiers and phase shifters used for signal transmission also serve as part of the calibration system when processing feedback signals. The same RF chain hardware is utilized for both normal operation and self-calibration, eliminating the need for separate dedicated calibration hardware
Solution Approach 2:
The system performs self-calibration by using its own received signals as the calibration source. The feedback loop allows the transmitter to automatically measure and correct its own mismatches without requiring external calibration equipment or manual intervention, making the calibration process self-service and integrated into normal operation
Data Source
AI summary
An outphasing calibration method in an outphasing calibration RF transmitter comprises detection of differences of a first plurality of signal characteristics of a first plurality of amplified RF signals across at least a transmitter antenna and a plurality of load impedances. The first plurality of amplified RF signals corresponds to a first plurality of constant-envelope signals. Accordingly, at least a generation of a second plurality of constant-envelope signals and at least one signal characteristic of each of a second plurality of constant-envelope RF signals on a plurality of transmission paths are controlled. At least one of a first calibration or a second calibration of a second plurality of signal characteristics of the second plurality of constant-envelope signals is executed based on the controlled generation of the second plurality of constant-envelope signals and the at least one controlled signal characteristic of each of the second plurality of constant-envelope RF signals.