Signal Generator Predistortion for Nonlinear Distortion Correction
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Solution Overview
Problem
High frequency device testing is hindered by non-linear distortions introduced by signal generators, making it challenging to correct for these distortions effectively.
Innovation Solution
A system and method that iteratively updates a time domain input signal to a signal generator by measuring and comparing its frequency spectrum with a target signal, using different computational schemes for in-band and out-of-band regions, and applying predistortion tones to correct for distortions, with the aid of a vector network analyzer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a signal generator is used to generate high frequency test signals, then the desired digital signal can be up-converted to an analog test signal, but non-linear distortions are introduced into the output signal
Solution Approach 1:
The patent applies predistortion by pre-modifying the input signal to counteract the non-linear distortions that will be introduced by the signal generator. The predistortion signal is calculated based on the measured distortion characteristics, and when combined with the original signal, it creates a pre-compensated input that results in a cleaner output signal after passing through the generator.
Solution Approach 2:
The patent employs an iterative feedback process where the output signal is measured, distortion characteristics are extracted, and the input signal is updated based on this information. This closed-loop approach continues until the distortion is sufficiently reduced, allowing the system to adaptively correct for non-linearities.
2Measurement precision
If the frequency spectrum is divided into in-band and out-of-band regions with different computational schemes, then out-of-band distortions can be more effectively corrected, but the device complexity increases
Solution Approach 1:
The patent divides the frequency spectrum into distinct in-band and out-of-band regions, applying different computational schemes to each. This segmentation allows for targeted correction strategies: in-band regions use standard predistortion techniques while out-of-band regions use specialized probe signal methods, optimizing correction accuracy for each frequency region independently.
Solution Approach 2:
Different computational approaches are applied to different frequency regions based on their specific characteristics. The in-band regions receive one type of processing while out-of-band regions receive another, tailoring the correction method to the local requirements of each frequency region rather than applying a uniform approach.
3Manufacturing precision
If an iterative process is used to update the input signal by comparing measured and target frequency spectra, then the output signal accuracy is improved, but the time required for signal generation increases
Solution Approach 1:
The patent performs predistortion calculations and signal modifications in advance, before actual signal generation begins. By pre-computing the necessary corrections based on measured distortion characteristics, the system reduces the time required during actual operation, as the iterative refinement is completed during the calibration phase.
Solution Approach 2:
The iterative update process is performed periodically during calibration rather than continuously during operation. The system establishes the predistortion parameters through repeated measurement and adjustment cycles, then applies these fixed parameters during actual signal generation, reducing the time overhead to periodic calibration intervals.
Data Source
AI summary
A system and method for operating a data processing system to modify a time domain input signal to a signal generator to correct for distortions introduced by the signal generator are disclosed. The method includes receiving a target signal specifying a signal to be generated by the signal generator and initializing an input signal with the target signal, the method includesa) inputting the input signal to the signal generator to arrive at a signal generator output signal;b) measuring a frequency spectrum of the signal generator output signal with a test instrument;c) updating the input signal based on a comparison of said measured frequency spectrum and a frequency spectrum of target input signal; andd) repeating steps a)-c) until an exit condition is satisfied.