Adaptive Predistortion Without Complex RF Down-Conversion
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Solution Overview
Problem
Existing radio frequency amplifier systems face inefficiencies in compensating for non-linear effects due to the need for complex and costly down-conversion chains in adaptive predistortion methods, which reduce the flexibility and efficiency of signal processing.
Innovation Solution
A signal processing arrangement that uses input and output signals to adaptively track non-linear parameters of the amplifier, eliminating the need for a down-conversion chain by performing complex multiplications and filtering to derive baseband information for predistortion, employing algorithms like mean-squared error or least mean-squares to adjust the predistortion characteristic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a down-conversion chain is used to down-convert the amplified signal for adaptive predistortion, then the non-linear parameters can be tracked adaptively, but the device complexity and cost increase significantly
Solution Approach 1:
The patent extracts only the necessary information from the amplified signal by using a simplified processing approach. Instead of fully down-converting the signal through a complex chain, the invention processes the amplified signal to extract baseband information directly, obtaining the required non-linear parameter information without the need for complete down-conversion infrastructure.
Solution Approach 2:
The patent uses a copy or model of the signal processing approach. Rather than implementing a full down-conversion chain, the invention creates a simplified processing path that replicates the essential function of extracting non-linear parameter information from the amplified signal, achieving the same adaptive tracking goal with reduced complexity.
2Adaptability or versatility
If a down-conversion chain with local oscillators and demodulators is implemented, then adaptive predistortion can be achieved, but the manufacturing cost and system expense increase
Solution Approach 1:
The patent replaces expensive, complex down-conversion components with simpler, more cost-effective processing elements. The invention uses affordable signal processing techniques that achieve adaptive predistortion without requiring costly local oscillators, demodulators, and associated hardware, making the system more economically viable for manufacturing.
Solution Approach 2:
The patent substitutes the mechanical/electrical down-conversion system with a signal processing approach. Instead of using physical down-conversion chains with multiple stages of mixing and demodulation, the invention employs digital or analog signal processing methods that achieve the same adaptive predistortion function with simpler, cheaper components.
3Measurement precision
If the amplified signal is down-converted and demodulated to obtain baseband components, then the non-linear characteristic can be estimated, but the processing time and computational effort increase
Solution Approach 1:
The patent performs preliminary processing of the amplified signal to prepare it for efficient analysis. By pre-processing the signal to extract relevant information in a simplified manner, the invention reduces the computational burden and processing time required to estimate non-linear characteristics, achieving accurate results more quickly than full down-conversion methods.
Solution Approach 2:
The patent skips the time-consuming steps of complete down-conversion and demodulation. The invention directly processes the amplified signal to extract the necessary non-linear parameter information, bypassing the intermediate stages of frequency conversion and demodulation that would consume additional time and computational resources.
Data Source
AI summary
A signal processing apparatus for processing an input signal (x) has an adaptive predistorter, an amplifier and a down-converter. The amplifier is configured to amplify a processed signal (y′) to obtain an amplified signal (y″). The down-converter is configured to multiply a version of the processed signal (y′) with a version of the amplified signal (y″), one of the signal versions being phase shifted, to obtain a first down-converted signal (z1, z1′), and to multiply the processed signal (y′) with the amplified signal (y″) to obtain a second down-converted signal (z2, z2′). The predistorter is configured to predistort the input signal (x) according to a predistortion characteristic to obtain the processed signal (y′), the predistorter being further configured to adapt the predistortion characteristic based on the first down-converted signal (z1, z1′) and the second down-converted signal (z2, z2′).