Sample-Rate Conversion Branches for ADC Jitter Mitigation
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Solution Overview
Problem
Conventional analog-to-digital converters face significant degradation due to sampling jitter, particularly when processing high-frequency signals, leading to reduced conversion accuracy and limited processing speed, with existing methods failing to effectively mitigate low-frequency jitter and drift.
Innovation Solution
The implementation of a system that includes multiple processing branches with analog bandpass filters, digital bandlimiting circuits, and sample-rate conversion capabilities, allowing for effective bandlimiting and resampling while decoupling the sample-rate clock from the conversion-rate clock, thereby reducing the impact of sampling jitter and enabling operation near the Nyquist limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional analog-to-digital converters process high-frequency signals near the Nyquist limit, then processing speed is improved, but sampling jitter causes significant degradation in conversion accuracy
Solution Approach 1:
The system divides the signal processing into multiple processing branches, each handling a specific frequency band with analog bandpass filters. This segmentation allows each branch to operate at optimized sampling rates while the overall system achieves high processing speed near the Nyquist limit without suffering from jitter-induced accuracy degradation in any single branch.
Solution Approach 2:
The invention changes the sampling rate parameter dynamically by decoupling the sample-rate clock from the conversion-rate clock. Sample-rate conversion is performed to transform signals sampled at one rate to another rate, allowing the system to process high-frequency signals at high speeds while maintaining conversion accuracy through appropriate rate transformation and filtering.
2Device complexity
If the sample-rate clock is coupled to the conversion-rate clock, then device complexity is reduced, but the converter cannot effectively mitigate low-frequency jitter and drift
Solution Approach 1:
The clocking system is segmented into separate sample-rate clock and conversion-rate clock domains. This segmentation allows independent optimization of each clock source, enabling effective mitigation of low-frequency jitter and drift in the conversion rate while maintaining simple overall architecture through modular clock management.
Solution Approach 2:
Sample-rate conversion acts as an intermediary mechanism between the sample-rate clock domain and the conversion-rate clock domain. This intermediary process allows the system to decouple the two clocks while maintaining proper signal transformation, enabling jitter mitigation without excessive device complexity.
3Measurement precision
If multiple processing branches with bandpass filters are implemented, then sampling jitter impact is reduced, but device complexity increases
Solution Approach 1:
The signal path is segmented into multiple processing branches with analog bandpass filters, where each branch processes a specific frequency band. This segmentation reduces the impact of sampling jitter on any single branch since each operates with relaxed timing requirements, while the combined output maintains high conversion accuracy. The modular branch structure manages device complexity through systematic design.
Solution Approach 2:
Each processing branch is optimized with local quality characteristics - analog bandpass filters tailored to specific frequency bands and sampling rates appropriate for each branch's signal content. This local optimization reduces jitter impact in each branch while the overall system achieves high precision through combination of all branches, managing complexity through specialized local design rather than uniform complex architecture.
Data Source
AI summary
Provided, among other things, is an apparatus that converts a signal from one sampling domain to another, and which includes: an input line for accepting an input signal and a processing branch. The processing branch includes a branch input coupled to the input line for inputting data samples that are discrete in time and in value, a quadrature downconverter, a first and second lowpass filter, a first and second polynomial interpolator, and a rotation matrix multiplier that provides a phase rotation. The processing branch generates data samples at a sampling interval that differs from the sampling interval associated with the signal provided to the branch input, e.g., with the difference in the sampling intervals depending on fluctuations in the output period of a local oscillator. Certain embodiments include multiple such processing branches, e.g., operating on different frequency bands of the input signal.