Power Amplifier Linearization Using Receiver-Side AM/AM Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing linearization techniques for power amplifiers in wireless radio transmission suffer from efficiency degradation due to increased peak-to-average power ratio (PAPR) and are affected by impairments in up and down-conversion circuits, requiring power back-off to maintain acceptable Bit Error Rate (BER).
Innovation Solution
A method and system that compensates for transmitter nonlinearity at the receiver side using a cumulative distribution function (CDF) based algorithm to estimate amplitude-to-amplitude (AM/AM) nonlinearity, allowing for phase predistortion at the transmitter and amplitude post-compensation at the receiver to improve power efficiency and BER performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If digital predistortion is applied to compensate for PA nonlinearity, then signal linearity is improved, but peak-to-average power ratio increases causing power efficiency degradation
Solution Approach 1:
The patent segments the linearization function into two parts: phase predistortion applied at the transmitter and amplitude post-compensation applied at the receiver. This segmentation allows each part to be optimized independently, with the receiver performing the computationally intensive amplitude compensation after reception, thereby avoiding the power efficiency penalty at the transmitter while still achieving full linearization performance.
Solution Approach 2:
Instead of applying the complete inverse nonlinearity function at the transmitter as in conventional DPD, the patent inverts the approach by applying only the phase component at the transmitter and reserving the amplitude component for post-processing at the receiver. This inversion of where the compensation is applied resolves the contradiction between linearity and power efficiency.
2Reliability
If power back-off is applied to maintain acceptable BER without linearization, then signal quality is maintained, but power efficiency decreases
Solution Approach 1:
The patent applies phase predistortion as a preliminary action at the transmitter to pre-compensate for nonlinear phase effects. This preliminary compensation reduces the overall distortion burden, allowing the system to operate closer to saturation while maintaining acceptable BER when combined with the amplitude post-compensation at the receiver.
Solution Approach 2:
The patent employs feedback mechanisms at the receiver to estimate the PA characteristics and compute the amplitude post-compensation. The receiver measures the received signal, estimates the nonlinear distortion, and applies the appropriate compensation, creating a closed-loop system that maintains BER performance while enabling high power efficiency operation.
3Loss of energy
If PA is operated in compression region to maintain high power efficiency, then power efficiency is improved, but signal distortions increase
Solution Approach 1:
The patent segments the linearization task so that the transmitter can operate in the efficient compression region while applying only phase predistortion, and the receiver handles the amplitude distortion compensation. This segmentation enables the PA to operate at high efficiency points while still achieving low distortion through the combined predistortion and post-compensation approach.
Solution Approach 2:
The patent introduces an intermediary processing step at the receiver that acts as a mediator between the distorted PA output and the final decoded signal. The amplitude post-compensation at the receiver serves as this intermediary, correcting the amplitude distortions introduced by compression-region operation without requiring the transmitter to operate in the linear region.
Data Source
AI summary
A method for distortion compensation in a transmission link comprising obtaining information of an amplitude distribution of a signal prior to being transmitted by a transmitter, receiving the transmitted signal at a receiver and determining a received signal amplitude distribution, comparing the received signal amplitude distribution to the amplitude distribution of the signal prior to transmission and using results of the comparison to estimate the AM/AM non-linearity in the transmitter.