MEMS Resonator Frequency Matching via Noise Cross-Correlation
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Solution Overview
Problem
Microelectromechanical systems (MEMS) devices with multiple resonators often have resonance frequencies that deviate due to manufacturing imperfections, leading to mismatched frequencies during operation, which affects signal amplitude and signal-to-noise ratio.
Innovation Solution
A method and apparatus that use a noise signal to determine the resonance frequency of each resonator by cross-correlating the output signal with the noise signal, allowing for iterative adjustment to match the frequencies of multiple resonators during normal operation, without interrupting the input signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resonators are manufactured with standard processes, then manufacturing cost and ease of manufacture are improved, but resonance frequency matching between resonators deteriorates
Solution Approach 1:
The patent applies preliminary action by measuring the resonance frequencies of resonators during the manufacturing process and calculating compensation values before the resonators are fully assembled. This allows frequency matching to be prepared in advance, so that when resonators are combined in the final device, their frequencies are already matched or can be quickly adjusted using the pre-calibrated piezoelectric actuators.
Solution Approach 2:
The patent employs parameter changes by using piezoelectric actuators to dynamically adjust the physical dimensions of resonator components, which changes their resonance frequencies. The system measures the actual resonance frequency and applies voltage to the piezoelectric actuators to shift the frequency to the target value, thereby achieving frequency matching without requiring precise manufacturing tolerances.
2Reliability
If resonator frequencies are adjusted to match, then signal amplitude and signal-to-noise ratio are improved, but device complexity increases
Solution Approach 1:
The patent implements self-service through an automated feedback control system that automatically measures the resonance frequency of each resonator, calculates the required adjustment, and applies the appropriate voltage to piezoelectric actuators to match the frequency. This self-adjusting mechanism eliminates the need for manual tuning and reduces overall system complexity despite the addition of control circuitry.
Solution Approach 2:
The system uses feedback by continuously monitoring the resonance frequency of resonators and comparing it to the target frequency. Based on the frequency deviation detected, the control system adjusts the voltage applied to piezoelectric actuators to bring the resonator frequency back into alignment, creating a closed-loop control system that maintains frequency matching.
3Adaptability or versatility
If frequency matching is performed during operation, then adaptability to environmental changes is improved, but measurement precision requirements increase
Solution Approach 1:
The patent applies continuity of useful action by performing frequency measurements and adjustments during the normal operational periods of the device rather than requiring separate calibration phases. The system can continuously or periodically monitor resonance frequencies and make adjustments as needed, ensuring that the resonators remain frequency-matched despite environmental variations throughout the device's operational lifetime.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables continuous matching of resonance frequencies, improving signal amplitude and signal-to-noise ratio by allowing for real-time adjustment of resonators, even in the presence of environmental changes like temperature and humidity.
Implementation Method 1
The magnitude of the output signal is greatest when the frequency of the input signal matches the so-called 'resonance frequency' of the resonator
Implementation Method 2
cross-correlating the noise signal with a signal representing or derived from an output signal of the first mechanical resonator
Data Source
AI summary
Systems and techniques are described for matching the resonance frequencies of multiple resonators. In some embodiments, a resonator generates an output signal reflecting the resonator's response to an input drive signal and an input noise signal. The output signal is then compared to the noise signal to derive a signal representative of the resonance frequency of the resonator. Comparing that signal to the output signal of a second resonator gives an indication of whether there is a difference between the resonance frequencies of the two resonators. If there is, one or both of the resonators may be adjusted. In this manner, the resonance frequencies of resonators may be matched during normal operation of the resonators.