Dithered Waveform Averaging for ADC Nonlinearity Distortion
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Solution Overview
Problem
Existing techniques fail to effectively mitigate correlated noise and distortion in the digitization of repetitive waveforms, particularly due to analog-to-digital converter (ADC) differential and integral nonlinearity, which limits the high-fidelity characterization of repetitive waveforms in applications like optical pulse shaping and telecommunications.
Innovation Solution
The use of discrete offset dithered waveform averaging, where a signal under test is combined with a sequence of discrete time-varying offsets synchronized with the waveforms to decorrelate distortions, resulting in a higher fidelity measurement of the average waveform by reducing the impact of correlated distortions during analog-to-digital conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional waveform averaging is used to reduce noise, then uncorrelated noise is mitigated, but correlated noise and distortion from ADC nonlinearity cannot be effectively reduced
Solution Approach 1:
A dither signal is added to the input signal before ADC conversion. This preliminary action randomizes the quantization error and decorrelates the ADC nonlinearity distortion from the input signal, enabling effective noise and distortion reduction through subsequent waveform averaging while maintaining measurement precision
Solution Approach 2:
The dither signal acts as an intermediary between the input signal and the ADC nonlinearity. By introducing this intermediate signal, the direct correlation between input signal and quantization error is broken, allowing the averaging process to effectively reduce correlated distortion while preserving the original waveform characteristics
2Measurement precision
If dithering is applied to decorrelate ADC nonlinearity, then measurement fidelity improves, but performance tradeoffs occur with conventional dithering methods
Solution Approach 1:
The patent uses simple, easily generated dither signals (such as random noise or triangular waves) that can be produced with minimal circuitry. These simple dither signals achieve the desired decorrelation effect without requiring complex dithering systems, thereby improving measurement precision while avoiding performance tradeoffs associated with device complexity
Data Source
AI summary
Methods and devices for digitizing an analog repetitive signal using waveform averaging are described. An example method includes generating a discrete set of analog dither offset voltages, wherein at least two of the discrete set of analog dither offset voltages are different from each other, receiving the analog repetitive signal comprising multiple instances of a waveform, wherein the waveform has a waveform duration, generate a timing alignment to align each waveform of the analog repetitive signal and the corresponding analog dither offset voltage over the waveform duration, combining, based on the timing alignment, each waveform and the corresponding analog dither offset voltage over the waveform duration to produce an analog output signal, converting the analog output signal to a digital output signal, and producing, based on the timing alignment, a digital averaged signal based on averaging the multiple instances of the waveform in the analog output signal.