Sigma-Delta Modulator Correction After Decimation for High-Frequency ADCs
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Solution Overview
Problem
Conventional Analog-Digital Converters (ADCs) face limitations in precision at high frequencies due to inadequate sample-and-hold unit speed and metastability issues, leading to errors in signal conversion and noise distortion, making them unsuitable for high-frequency applications like radars.
Innovation Solution
A method for improving resolution and correcting distortions in sigma-delta modulators involves re-sampling the feedback digital signal, applying demodulation and decimation, and using filtering operations based on open-loop analog response measurements to generate a secondary output with enhanced precision and noise correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ADCs operate at high sampling frequencies, then productivity increases, but measurement precision deteriorates due to sample-and-hold unit limitations and quantization noise
Solution Approach 1:
The patent segments the quantization noise affecting different frequency bands and applies separate correction filters for each band. The correction device divides the frequency spectrum into multiple bands and processes each band independently to remove quantization noise while preserving the original signal, thereby maintaining high sampling frequency operation without precision loss
Solution Approach 2:
The patent implements a feedback mechanism where the digital output signal is fed back through a correction device that analyzes and removes quantization noise. The corrected signal is then combined with the original signal to produce the final output, creating a closed-loop system that continuously improves precision while maintaining high sampling rates
2Measurement precision
If sigma-delta modulation is used to improve precision, then measurement precision improves, but device complexity increases due to multiple processing stages
Solution Approach 1:
The patent extracts and removes only the harmful quantization noise components from the sigma-delta modulator output through frequency-band-specific filtering. By taking out only the necessary correction operations rather than redesigning the entire modulator, the patent improves precision while minimizing additional complexity
Solution Approach 2:
The patent changes the parameters of existing filter stages by introducing frequency-dependent correction filters with specific impulse responses tailored to each frequency band. This allows precision improvement through parameter optimization rather than structural complexity increase
3Measurement precision
If over-sampling is applied to improve precision in a specific frequency band, then measurement precision improves, but quantization noise increases in other frequency bands
Solution Approach 1:
The patent applies local quality by designing correction filters with impulse responses specifically tailored to each frequency band. Each band receives customized filtering that removes quantization noise locally without affecting other bands, thereby improving precision in the desired band while controlling noise in other bands through targeted processing
Data Source
AI summary
In a method for improving resolution and for correcting distortions for a sigma-delta modulator, a modulator converts an analog input signal into a secondary output digital signal sampled at a frequency fe and coded on NB bits, a second main output digital signal s′(t) is represented on NMSB bits also being available at the output. At least three processings are applied successively to the outputs, a first processing carrying out a demodulation by a frequency f0 and a decimation of factor N in an independent manner, z second processing carrying out an improvement of the resolution and a third processing carrying out a correction of the distortions. These three processings are carried out after decimation. A sigma-delta modulator implements the method.