Continuous-Time Sigma-Delta ADC With Half-Rate Chopping

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing continuous-time analogue/digital converters using sigma delta modulators are limited in converting high-frequency analogue signals due to high sampling frequencies, which also result in complex architectures and high-frequency noise issues, while discrete time converters face limitations in converting signals above certain frequencies and have complex architectures due to the use of multiple mixers.

Innovation Solution

A continuous-time analogue/digital converter with a sigma delta modulator incorporating a high-pass filtering mechanism where the chopping frequency is half the sampling frequency, eliminating the need for upstream signal processing and mixers, and utilizing resonators and variable-gain amplifiers to enhance filtering accuracy and bandwidth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a continuous-time sigma delta modulator uses a high sampling frequency to convert high-frequency analogue signals, then the conversion capability for high-frequency signals is improved, but the device complexity and noise issues increase

Engineering Contradiction:

Improveconversion capability for high-frequency signalsVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies chopping technique that inverts the conventional approach by modulating the signal at a lower frequency (chopping frequency) rather than sampling at the high signal frequency. The high-frequency input signal is converted to a lower frequency domain through chopping, allowing standard sigma-delta modulators to process high-frequency signals without requiring high sampling frequencies, thus reducing device complexity while maintaining high-frequency conversion capability

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the frequency parameter by introducing a chopping frequency that is distinct from and lower than the signal frequency. This parameter transformation allows the system to process high-frequency signals through low-frequency modulation, effectively decoupling the sampling frequency requirement from the input signal frequency, thereby reducing the complexity associated with high-frequency sampling

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

Engineering Contradiction:

Improveconversion capability for high-frequency signalsVSAvoidhigh-frequency noise

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The chopping technique inverts the noise generation mechanism by operating at a low chopping frequency rather than the high signal frequency. This generates low-frequency noise that can be more easily filtered and managed, while the high-frequency signal information is preserved through the modulation process, thus maintaining conversion capability while reducing high-frequency noise issues

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent converts the potential harm of frequency mismatch into a benefit by using the chopping frequency as a deliberate modulation mechanism. The low-frequency chopping generates noise at manageable frequencies that can be filtered out, while the modulation process itself preserves the high-frequency signal information, effectively converting what would be noise into a useful modulation carrier

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Adaptability or versatility

If a discrete-time converter uses multiple mixers to convert high-frequency signals, then the frequency conversion capability is improved, but the device complexity increases

Engineering Contradiction:

Improvefrequency conversion capabilityVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges the frequency conversion function and the modulation function into a single chopping-based modulation stage. Instead of using separate mixers for frequency conversion followed by a sigma-delta modulator, the chopping technique performs both functions simultaneously by modulating the high-frequency signal directly at a lower chopping frequency, thereby reducing device complexity while maintaining frequency conversion capability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The chopping mechanism serves multiple functions: it performs frequency conversion, modulation, and signal conditioning in a single stage. This multi-functional approach replaces the need for multiple specialized components (mixers, filters, modulators) required in discrete-time converters, achieving the same frequency conversion capability with reduced device complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9124293B2Continuous time analogue/digital converter

Publication Date: 2015.09.01 STMICROELECTRONICS FRANCE

AI summary

Continuous time analog/digital converter, comprising a sigma delta modulator (MSD1) configured to receive an analog input signal (x(t)) and comprising high-pass filtering means (MF) the chopping frequency of which is equal to half of the sampling frequency (Fs) of the quantization means (QTZ) of the modulator (MSD1).