Nested MEMS Resonator Feedback for Real-Time Frequency Drift Correction
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Solution Overview
Problem
Existing oscillators, particularly those using MEMS resonators, face challenges in maintaining frequency stability due to fabrication errors, external stresses, and temperature variations, which affect their precision and accuracy.
Innovation Solution
The implementation of a nested MEMS architecture with two MEMS resonators operating at different natural resonant frequencies, coupled with a correction circuit that includes frequency division, drive, sense, phase detection, and proportional integral derivative controller circuitry, allows for real-time detection and correction of frequency shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single MEMS resonator is used in the oscillator, then the device complexity is low, but the frequency stability and precision are insufficient due to fabrication errors and external stresses
Solution Approach 1:
The patent implements a nested MEMS architecture where a second MEMS resonator is integrated within the same package as the first MEMS resonator. The second resonator operates at a different frequency and serves as a reference to detect and correct frequency shifts in the first resonator, thereby improving frequency stability without requiring a completely separate correction system.
Solution Approach 2:
The patent employs a feedback mechanism where the output of the second MEMS resonator is used to generate a correction signal that compensates for frequency drift in the first resonator. This feedback loop continuously monitors and adjusts the frequency of the primary resonator, maintaining high precision despite environmental variations and fabrication tolerances.
2Measurement precision
If high performance specifications are required for timing oscillators (low jitter, high temperature stability), then the precision and accuracy improve, but the cost and size increase
Solution Approach 1:
By nesting the second MEMS resonator within the same package as the first resonator, the patent achieves high temperature stability and low jitter performance without proportionally increasing the overall device size. The shared package and integrated architecture allow high-performance specifications to be met while minimizing the volume increase.
3Volume of stationary object
If MEMS resonators are used in oscillators, then the size and cost are reduced compared to traditional oscillators, but frequency stability is compromised due to fabrication errors and external stresses
Solution Approach 1:
The patent uses the second MEMS resonator as a reference in a feedback loop to detect frequency shifts caused by fabrication errors and external stresses on the first resonator. The correction signal generated from this feedback compensates for these errors, maintaining frequency stability while preserving the compact size advantage of MEMS technology.
Solution Approach 2:
The patent exploits the different resonant frequencies of the two MEMS resonators to differentiate between the primary oscillation signal and the reference signal. By operating the second resonator at a different frequency, the system can selectively process and compare signals to generate accurate correction data without interference, thereby improving reliability while maintaining small form factor.
Data Source
AI summary
Systems and methods disclosed herein include a correction circuit. The correction circuit may include frequency division circuitry that is configured to receive and condition a reference signal. The correction circuit may include drive circuitry that is configured to receive the reference signal. The correction circuit may include a first resonator that is configured to receive the reference signal. The correction circuit may include sense circuitry that is configured to receive the reference signal from the first resonator. The correction circuit may include phase detector circuitry that is configured to generate at least one output signal based on receipt of a plurality of input signals from the drive circuitry and the sense circuitry. The correction circuit may include a proportional integral derivative controller that is configured to generate a temperature correction signal to correct frequency error in an oscillator based on receipt of the at least one output signal.