Matched Multiplier Circuit Phase Shift Reduction in MEMS Gyroscopes
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Solution Overview
Problem
MEMS gyroscopes face inaccuracies in measuring angular rate of rotation due to phase shifts introduced by multiplier circuitry, which causes unwanted quadrature components to drift into the in-phase signal, leading to distortion and offset drift in output.
Innovation Solution
A multiplier circuit configuration with forward and feedback multipliers matched to have nearly identical transfer functions, effectively canceling phase shifts, is implemented to reduce phase shift in the feedback path of the closed-loop system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiplier circuitry is used to demodulate and modulate electrical signals in MEMS gyroscope feedback path, then signal processing capability is improved, but phase shift is introduced causing quadrature component drift into in-phase component
Solution Approach 1:
The patent changes the parameters of the multiplier circuits by implementing precise matching between forward and feedback multipliers, adjusting their transfer functions to be nearly identical. This parameter matching approach minimizes differential phase shift while maintaining the signal processing capability provided by the multiplier circuitry.
Solution Approach 2:
The patent applies feedback by implementing a closed-loop system where the feedback multiplier processes the feedback signal in conjunction with the forward multiplier. The matched feedback path compensates for phase shifts introduced during demodulation, allowing the system to maintain measurement precision while utilizing multiplier circuitry for signal processing.
2Adaptability or versatility
If conventional multiplier circuitry is used in feedback path, then demodulation and modulation functions are achieved, but phase shift causes unwanted distortion and offset drift in output
Solution Approach 1:
The patent modifies the parameters of the multiplier circuits by precisely matching their transfer functions. The forward and feedback multipliers are designed with matched characteristics, which changes their phase response parameters to be nearly identical, thereby eliminating differential phase shift that would otherwise cause distortion and offset drift in the output signal.
Solution Approach 2:
The patent implements copying by creating a feedback multiplier that is a precise copy of the forward multiplier in terms of transfer function characteristics. This copying approach ensures that both multipliers introduce identical phase shifts, which cancel out in the feedback loop, maintaining output signal stability while achieving demodulation and modulation functions.
3Measurement precision
If phase shift cancellation is achieved through matched multipliers, then measurement accuracy is improved, but circuit complexity increases
Solution Approach 1:
The patent achieves phase shift cancellation by changing the parameters of the multiplier circuits through precise matching of their transfer functions. This approach improves measurement accuracy by minimizing differential phase shift while maintaining a relatively simple circuit configuration that can be implemented using standard analog circuit design techniques.
Data Source
AI summary
Apparatus and methods are provided for multiplier circuits having reduced phase shift. A multiplier circuit comprises an input node for an input signal and an output node for an output signal. A first multiplier is coupled to the input node and has a first multiplier output, wherein the first multiplier multiplies the input signal by a first signal to produce a second signal at the first multiplier output. A second multiplier is coupled to the output node and is matched to the first multiplier. The second multiplier multiplies the output signal by a third signal to produce a fourth signal at a second multiplier output. An amplifier is coupled to the first multiplier output and the second multiplier output and produces the output signal at an amplifier output coupled to the output node based upon the second signal and the fourth signal.