Phase-Based Gyroscope AFE Circuit for Low Power High SNR

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Solution Overview

Problem

MEMS gyros face a trade-off between power consumption and performance due to limitations in analog front-end (AFE) noise, which restricts their dynamic range and signal-to-noise ratio.

Innovation Solution

The implementation of phase-based AFE circuitry and closed-loop operation in MEMS gyros, utilizing comparators to synchronize signal transitions with resonator motion and applying feedback to maintain constant phase, allowing for low power, low noise, and increased signal-to-noise ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional analog front-end circuitry with high-impedance feedback network is used, then gain and dynamic range are improved, but power consumption increases and thermal noise is generated

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces the traditional analog front-end circuitry with a phase-based digital signal processing approach. Instead of using analog amplifiers and feedback networks that consume power and generate thermal noise, the invention uses digital signal processing to detect phase shifts in the resonator signal. This substitution of analog mechanical/electrical systems with digital processing eliminates the trade-off between power consumption and signal-to-noise ratio, as digital circuits consume minimal power while providing high precision through phase measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If resistive feedback network is used, then circuit simplicity is improved, but thermal noise increases

Engineering Contradiction:

Improvecircuit simplicityVSAvoidthermal noise

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The patent eliminates resistive feedback networks entirely by replacing the analog measurement approach with digital phase detection. The system uses a digital signal processor to analyze the phase of the resonator signal directly, removing the need for physical resistors that generate thermal noise. This maintains circuit simplicity while eliminating the harmful thermal noise effect.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If switched-capacitor feedback network is used, then dynamic range is improved, but noise folding effects and power consumption increase

Engineering Contradiction:

Improvedynamic rangeVSAvoidnoise folding effects

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent replaces switched-capacitor feedback networks with digital signal processing techniques. The phase-based measurement system processes signals in the digital domain, eliminating the need for switched-capacitor circuits that cause noise folding effects. Digital processing maintains wide dynamic range capability while avoiding the harmful noise folding phenomenon inherent in switched-capacitor implementations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS10030976B2Phase-based measurement and control of a gyroscope

Publication Date: 2018.07.24 ROHM CO LTD

AI summary

A gyroscope includes a resonator, a transducer, and a comparator. The comparator is designed to receive an input signal from the transducer and compare the input signal with a reference signal to produce an output signal. Rising and falling edge transitions of the output signal are substantially synchronized with a motion of the resonator along a sense-axis of the transducer.