Adaptive Pre-Distorter Bias Control for Multi-Mode Power Amplifiers
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Solution Overview
Problem
Conventional power amplifiers struggle to maintain linearity when switching between single carrier and multi-carrier signals, particularly in high output power systems, due to the limitations of analog pre-distorters using GaAs FETs, which degrade performance when input power changes.
Innovation Solution
A power amplifier system that includes a detection module to assess the power level of input or output signals and adjusts the gate bias of the GaAs FET to operate in class A or B regions, generating pre-distortion components to offset distortion, thereby supporting both single carrier and multi-carrier operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the quantity of current used by amplifier elements is increased to reduce distortion, then linearity is improved, but the quantity of used current becomes too large in high output power systems
Solution Approach 1:
The pre-distorter applies preliminary distortion to the input signal before it enters the power amplifier. By pre-distorting the signal in the opposite direction of the amplifier's non-linearity, the amplifier's inherent distortion is compensated, achieving better linearity without increasing the current through the amplifier elements.
Solution Approach 2:
The pre-distorter acts as an intermediary device between the input signal and the power amplifier. It modifies the input signal characteristics before amplification, enabling the amplifier to operate more linearly at its optimal current level, thus resolving the contradiction between linearity and current consumption.
2Reliability
If a pre-distorter using GaAs FET is used to reduce distortion, then linearity is improved, but performance degrades when input power changes between single carrier and multi-carrier modes
Solution Approach 1:
The patent implements dynamic switching between different pre-distorter configurations based on the input signal mode. A first pre-distorter is used for single carrier mode and a second pre-distorter is used for multi-carrier mode, allowing the system to adapt its distortion compensation characteristics to match the specific requirements of each operating mode, thereby maintaining consistent performance.
Solution Approach 2:
The system changes the pre-distortion parameters by switching between different pre-distorter circuits depending on the operating mode. This parameter change allows optimal distortion compensation for both single carrier and multi-carrier signals, resolving the performance degradation issue when input power changes between modes.
3Adaptability or versatility
If a single power amplifier is designed to support both single carrier and multi-carrier modes, then versatility is improved, but maintaining linearity across both modes becomes difficult
Solution Approach 1:
The pre-distortion function is segmented into multiple independent pre-distorter circuits, each optimized for a specific operating mode. The first pre-distorter handles single carrier mode while the second pre-distorter handles multi-carrier mode, allowing each segment to be independently optimized for its specific function while maintaining overall system linearity.
Solution Approach 2:
The power amplifier system achieves multi-functionality by incorporating multiple pre-distorter configurations that can be switched based on the operating mode. This universal design allows a single amplifier to maintain high linearity performance across both single carrier and multi-carrier modes through appropriate pre-distortion selection.
Data Source
AI summary
A method and an apparatus for amplifying power in a communication system is disclosed that includes a detection module which detects a power level of a predetermined signal selected from among an input signal and an output signal of a power amplifier and then transmits an operation mode control signal for the power amplifier; a gate bias controller which controls a gate bias of the power amplifier in accordance with the detected power level; and a power amplifier which operates as class B or class A in accordance with control by the gate bias controller to generate a pre-distortion component, offsets a distortion component generated during amplification of the predetermined signal by synthesizing the pre-distortion component with the distortion component, and outputs only the predetermined signal without a distortion component.