Receiver-Side PA Linearization for Low-PAPR Wireless Transmission
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Solution Overview
Problem
Existing linearization techniques in wireless radio transmission suffer from efficiency degradation due to the increase in peak-to-average power ratio (PAPR) caused by predistortion at the transmitter side, leading to decreased power efficiency and increased heat dissipation in power amplifiers.
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, combined with transmitter-phase predistortion for improved efficiency and Bit Error Rate (BER) performance, allowing the power amplifier to operate closer to the compression region without power back-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If predistortion is applied at the transmitter side 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 inverts the location of the linearization function from the transmitter side to the receiver side. Instead of applying predistortion before the power amplifier, the system applies post-compensation after reception, using the inverse of the estimated PA nonlinearity characteristics. This eliminates the need for power back-off while achieving the same linearity improvement.
Solution Approach 2:
The patent introduces training sequences as an intermediary element that enables the receiver to estimate the PA's nonlinearity characteristics. These training sequences are transmitted through the channel, and their known properties at the receiver allow calculation of the PA's amplitude-to-amplitude and amplitude-to-phase distortion, which is then used for compensation without affecting the main data signal's power efficiency.
2Manufacturing precision
If power back-off is applied to maintain PA linearity, then signal distortion is reduced, but power efficiency decreases
Solution Approach 1:
The system performs preliminary characterization of the power amplifier's nonlinearity using training sequences before processing the main data signal. By estimating the PA's amplitude-to-amplitude and amplitude-to-phase characteristics in advance, the receiver can apply appropriate compensation to the received signal, eliminating the need for continuous power back-off during data transmission.
Solution Approach 2:
The patent implements a feedback mechanism where the receiver estimates the PA's nonlinearity characteristics from transmitted training sequences and uses this information to compensate for distortions. The estimated characteristics are effectively fed back to correct the signal, allowing the transmitter to operate at maximum power without sacrificing signal quality.
3Object-generated harmful factors
If digital predistortion is used to compensate for PA nonlinearity, then adjacent channel power ratio is improved, but device complexity increases
Solution Approach 1:
The patent extracts the complex linearization function from the transmitter and relocates it to the receiver. The transmitter's role is simplified to only transmitting the signal and training sequences, while the receiver performs the computationally intensive task of estimating PA characteristics and applying compensation. This reduces transmitter circuit complexity while maintaining spectral regrowth suppression.
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.