MASH ADC Signal Transfer Equalization Without Separate Hardware

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Solution Overview

Problem

Multi-stage delta-sigma analog-to-digital converters (MASH ADCs) require separate and costly equalizers for signal transfer function (STF) correction, which is challenging, especially in high-speed applications where magnitude and phase responses are difficult to meet, and existing methods for quantization noise cancellation are not effective in achieving optimal SNR performance due to quantization noise leakage.

Innovation Solution

The method modifies the effective Signal Transfer Function (STF) of MASH ADCs by leveraging existing digital filtering hardware for quantization noise cancellation, incorporating calculations to account for equalization, thereby eliminating the need for additional equalization hardware and combining digital quantization noise cancellation and equalization in a single filter, using programmable filters to match analog and digital transfer functions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If separate equalizers are added for signal transfer function correction, then the STF equalization performance is improved, but the device complexity and cost increase

Engineering Contradiction:

ImproveSTF equalization performanceVSAvoidequalizer hardware complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the equalization function with the existing digital noise cancellation filter into a single integrated filter structure. The filter performs both STF correction and quantization noise cancellation simultaneously, eliminating the need for separate equalizer hardware while maintaining both functions' performance requirements

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The digital filter is designed to serve multiple purposes: it acts as both an equalizer for STF correction and a noise cancellation filter. This multi-functional approach allows one component to fulfill multiple roles that previously required separate dedicated hardware blocks

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If separate equalizers are added for signal transfer function correction, then the STF equalization performance is improved, but the manufacturing cost increases

Engineering Contradiction:

ImproveSTF equalization performanceVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

By merging the equalization functionality into the existing digital noise cancellation filter, the patent eliminates the need to manufacture and integrate separate equalizer hardware, thereby reducing manufacturing costs while maintaining STF correction capability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The multi-functional filter design reduces the total component count and simplifies the manufacturing process by requiring only one filter implementation instead of two separate hardware blocks, directly lowering production costs

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Device complexity

If existing digital filtering hardware is used for quantization noise cancellation without modification, then the device complexity is kept low, but the SNR performance deteriorates due to quantization noise leakage

Engineering Contradiction:

Improvefilter hardware complexityVSAvoidSNR performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent introduces programmable or adaptive coefficients in the digital filter that can be dynamically adjusted to optimize both noise cancellation and equalization performance. This dynamic capability allows the filter to adapt to different operating conditions and achieve optimal SNR performance without adding complex hardware

Inventive Principle:

Principle #15Dynamics

4Manufacturing precision

If separate equalizers are added for STF correction, then the magnitude and phase response accuracy is improved, but the device complexity and hardware requirements increase

Engineering Contradiction:

Improvemagnitude and phase response accuracyVSAvoidequalizer hardware requirements

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges magnitude correction and phase correction functions into the single digital filter structure, achieving precise control over both aspects of the frequency response without requiring separate equalizer hardware blocks for each function

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentEP3182598B1Signal transfer function equalization in multi-stage delta-sigma analog-to-digital converters

Publication Date: 2022.03.09 ANALOG DEVICES INC

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AI summary

Typically, complex systems require a separate and expensive equalizer at the output of an analog-to-digital converter (ADC). Rather than providing a separate equalizer, the effective Signal Transfer Function (STF) of a Multi-stAge noise SHaping (MASH) ADC can be modified by leveraging available digital filtering hardware necessary for quantization noise cancellation. The modification can involves adding calculations in the software previously provided for computing digital quantization noise cancellation filter coefficients, where the calculations are added to take into account equalization as well. As a result, the signal transfer function can be modified to meet ADC or system-level signal-chain specifications without additional equalization hardware. The method is especially attractive for high-speed applications where magnitude and phase responses are more challenging to meet.