Millimeter-Wave PA Linearity Optimization With Feedback Gain Control
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Solution Overview
Problem
Conventional RF transceivers face challenges in achieving optimal linearity and efficiency for power amplifiers, particularly in high-power operations, leading to nonlinear distortions and reduced modulation accuracy, which is exacerbated in millimeter-wave/5G technologies.
Innovation Solution
The implementation of a linearity optimizer circuit that adjusts either the drive signal or the bias signal for power amplifiers using a vector of complex gains computed by a linearity adaptation circuit, ensuring the power amplifier operates within linear parameters while maximizing power output, thereby minimizing or eliminating back-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power amplifiers operate at high power output, then productivity and power are improved, but linearity deteriorates causing nonlinear distortions
Solution Approach 1:
The system performs preliminary measurements of the power amplifier's output signal characteristics (amplitude and phase) before final transmission. Based on these measurements, it pre-adjusts the drive signal parameters to compensate for expected nonlinearities, ensuring the amplifier operates in a linear region while maintaining high power output capability
Solution Approach 2:
The system continuously measures the actual output signal from the power amplifier and uses this feedback to dynamically adjust the drive signal. The linearity optimization circuit modifies drive signal parameters based on measured output characteristics, creating a closed-loop control system that maintains linearity even at high power levels
2Productivity
If drive signal power is increased to maximize output, then productivity is improved, but linearity deteriorates due to amplifier saturation
Solution Approach 1:
The system dynamically adjusts the drive signal power level based on real-time measurements of the power amplifier's operating state. Instead of using a fixed high drive level, the system adapts the drive power to maintain optimal linearity while maximizing output efficiency under different operating conditions
Solution Approach 2:
The system changes key parameters of the drive signal (amplitude, phase, timing) based on measured output characteristics. By adjusting these parameters, the system optimizes the operating point of the power amplifier to achieve both high productivity and maintained linearity
Data Source
AI summary
An example apparatus includes a power amplifier (PA) and a linearity optimizer. The optimizer includes a PA actuator and a linearity adaptation circuit. The actuator is configured to generate an actuator output based on an actuator input and a vector of complex gains computed by the linearity adaptation circuit based on a feedback signal indicative of PA's output. The adaptation circuit is configured to compute the vector of complex gains in a manner that maximizes the power of the actuator output while ensuring that the deviation of PA's behavior from a linear behavior (e.g., in terms of one or more linearity parameters) is below a threshold. Controlling actuator output in a manner that maximizes its power while taking into consideration one or more linearity parameters to ensure that target linearity is achieved controls drive signals for the PA and, thus, may help in terms of PA linearity and efficiency.