Power Amplifier Predistortion for Adjacent-Band Interference
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Solution Overview
Problem
Non-linear power amplifiers in systems like cellular base stations, when operating outside their linear range, cause energy to leak into adjacent frequency bands, leading to interference, making it inefficient to transmit data within their non-linear operating range.
Innovation Solution
A method and system for linearizing non-linear power amplifiers by acquiring input and output data, estimating model parameters using sparse regression or other iterative procedures, and processing input signals to form modified signals that compensate for the non-linear characteristics, allowing for accurate linearization and efficient data transmission across the entire operating range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If power amplifiers operate in the non-linear portion of their operating range, then transmission efficiency is improved, but interference in adjacent frequency bands increases
Solution Approach 1:
The system applies preliminary anti-action by using a predistorter to pre-compensate the input signal with inverse non-linear characteristics before the signal enters the power amplifier. This predistortion cancels out the expected non-linear distortion, allowing the amplifier to operate in its non-linear region while maintaining linear output characteristics and preventing adjacent band interference.
Solution Approach 2:
The predistorter acts as an intermediary component between the signal source and the power amplifier. It processes the input signal to introduce pre-distortion that compensates for the amplifier's non-linearities, enabling the amplifier to operate efficiently in its non-linear region without generating harmful interference.
2Object-generated harmful factors
If power amplifiers operate in the linear portion of their operating range, then interference in adjacent frequency bands is reduced, but transmission efficiency decreases
Solution Approach 1:
Instead of restricting operation to the linear range, the system applies preliminary anti-action through predistortion, which allows the amplifier to operate in its non-linear region while the predistorter pre-compensates the signal to cancel out expected distortions, thereby maintaining both efficiency and low interference.
Solution Approach 2:
The system changes the parameter of the input signal by applying non-linear transformation through the predistorter. This parameter change pre-distorts the signal in a controlled manner that compensates for the amplifier's non-linearities, enabling efficient operation without harmful interference.
3Measurement precision
If complex predistortion methods are used to linearize power amplifiers, then linearization accuracy is improved, but device complexity increases
Solution Approach 1:
The system uses feedback from the power amplifier's output to the predistorter, enabling adaptive adjustment of predistortion parameters. This feedback mechanism allows the system to maintain high linearization accuracy across varying operating conditions while using a relatively simple predistorter structure.
Solution Approach 2:
The predistorter implements dynamic adaptation by adjusting its predistortion characteristics based on real-time feedback from the power amplifier. This dynamic behavior allows the system to maintain high linearization accuracy across different operating points without requiring an overly complex fixed structure.
Data Source
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AI summary
A method for linearizing a non-linear system element includes acquiring data representing inputs and corresponding outputs of the non-linear system element. A model parameter estimation procedure is applied to the acquired data to determine model parameters of a model characterizing input-output characteristics of the non-linear element. An input signal representing a desired output signal of the non-linear element is accepted and processed to form a modified input signal according to the determined model parameters. The processing includes, for each of a series of successive samples of the input signal, applying an iterative procedure to determining a sample of the modified input signal according to a predicted output of the model of the non-linear element. The modified input signal is provided for application to the input of the non-linear element.