Calibrated 90° All-Pass Phase Shifter for Low-Power MEMS Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing phase-shifter circuits for achieving a ninety-degree phase shift in MEMS gyroscopes require significant circuit resources and energy consumption, making them unsuitable for portable applications where area occupation and energy efficiency are concerns.
Innovation Solution
A phase-shifter circuit comprising a continuous-time all-pass filter stage, a comparator stage, and a calibration stage, which uses a calibration signal to adjust the RC time constant and maintain a ninety-degree phase shift across varying input frequencies without a phase-locked loop, reducing energy consumption and area occupation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phase-locked loop and switched-capacitor filtering stages are used to achieve a ninety-degree phase shift, then the phase shift precision is improved, but the energy consumption and area occupation increase significantly
Solution Approach 1:
The patent extracts and removes the phase-locked loop from the circuit architecture, retaining only the essential switched-capacitor filtering stages. This extraction eliminates the high energy consumption associated with PLL operation while preserving the core phase-shifting functionality through simplified filtering stages that consume significantly less power.
Solution Approach 2:
The patent employs a simplified switched-capacitor filter design that uses lower-cost, lower-power components compared to the full PLL architecture. The design accepts that the filter parameters may drift over time or with temperature, but uses periodic calibration to maintain accuracy, effectively using simpler, cheaper components that are recalibrated rather than maintained at constant high precision.
2Measurement precision
If a phase-locked loop and switched-capacitor filtering stages are used to achieve a ninety-degree phase shift, then the phase shift precision is improved, but the area occupation increases significantly
Solution Approach 1:
The patent extracts and removes the phase-locked loop from the circuit architecture, retaining only the essential switched-capacitor filtering stages. This extraction eliminates the large area occupation associated with PLL circuits while preserving the core phase-shifting functionality through simplified filtering stages that occupy significantly less silicon real estate.
Solution Approach 2:
The patent uses a simplified switched-capacitor filter topology that replicates the essential phase-shifting function without the complexity of a full PLL. The filter stages are designed to be area-efficient while maintaining the necessary phase shift characteristics, effectively creating a simplified copy of the full PLL functionality that achieves the same goal with much reduced area.
3Adaptability or versatility
If the input frequency varies due to environmental conditions or manufacturing process, then the adaptability of the system is improved, but maintaining a precise ninety-degree phase shift becomes more difficult
Solution Approach 1:
The patent implements dynamic calibration of the switched-capacitor filter parameters based on the actual input frequency. The calibration stage continuously or periodically adjusts the filter coefficients to match the current operating frequency, allowing the system to adapt to frequency variations caused by environmental conditions or manufacturing tolerances while maintaining precise ninety-degree phase shift accuracy.
Solution Approach 2:
The patent incorporates a calibration stage that uses feedback from the actual operating conditions (input frequency, temperature, etc.) to adjust the filter parameters. This feedback mechanism ensures that the phase shift remains precisely at ninety degrees despite variations in environmental conditions or manufacturing process, by continuously compensating for parameter drift.
Data Source
AI summary
A phase shifter, which carries out a ninety-degree phase shift of a sinusoidal input signal having an input frequency, at the same input frequency, envisages: a continuous-time all-pass filter stage, which receives the sinusoidal input signal and generates an output signal phase-shifted by 90° at a phase-shift frequency that is a function of a RC time constant of the all-pass filter stage; and a calibration stage, which is coupled to the all-pass filter stage and generates a calibration signal for the all-pass filter stage, such that the phase-shift frequency is equal to the input frequency of the sinusoidal input signal, irrespective of variations of the value of the input frequency and/or of the RC time constant with respect to a nominal value.