Electrostatic Oscillator Characterization Without Frequency Sweeps
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Solution Overview
Problem
Current methods for determining the resonant frequency and quality factor of electrostatic actuation oscillators in MEMS/NEMS are either time-consuming or prone to measurement errors due to parasitic capacitance, limiting productivity and accuracy in characterizing multiple oscillators on a silicon plate.
Innovation Solution
A method involving a combined sinusoidal voltage and voltage pulse excitation, where the voltage pulse is shaped as a cardinal sine function, allows for rapid acquisition of response signals in the time domain and transformation into frequency domain to determine characteristic parameters without the need for multiple frequency sweeps or waiting for oscillator return to idle position, thereby minimizing measurement time and parasitic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency sweep method is used to measure resonant frequency and quality factor, then measurement accuracy is improved, but measurement time increases significantly
Solution Approach 1:
The patent applies periodic action by using a sinusoidal excitation voltage at a specific frequency F0 to periodically excite the oscillator, rather than performing a continuous frequency sweep. This periodic excitation allows the system to reach steady-state oscillations faster, eliminating the need to wait for the oscillator to return to idle position between measurements, thus reducing measurement time while maintaining accuracy through multiple successive measurements at the same frequency
Solution Approach 2:
The patent implements preliminary action by applying a voltage pulse before the sinusoidal excitation to rapidly bring the oscillator to its resonant frequency F0. This preliminary action eliminates the need for slow frequency sweeping and allows the measurement to start immediately at the resonant frequency, significantly reducing the time required to reach the measurement state
2Measurement precision
If multiple successive measurements are performed, then measurement accuracy is improved, but oscillator must return to idle position between measurements causing time loss
Solution Approach 1:
The patent applies continuity of useful action by maintaining the sinusoidal excitation voltage continuously across multiple successive measurements without requiring the oscillator to return to idle position between them. The excitation persists throughout the measurement sequence, allowing continuous data collection while the oscillator remains in steady-state resonance, thus eliminating waiting time while improving accuracy through multiple measurements
3Productivity
If broadband voltage pulse is used for excitation, then measurement speed is improved, but parasitic capacitance causes measurement errors
Solution Approach 1:
The patent applies local quality by using a bandpass filter with specific frequency selection characteristics to shape the voltage pulse spectrum. Instead of using a broadband pulse that excites all frequencies equally, the filter concentrates the excitation energy locally around the resonant frequency F0, reducing parasitic capacitance effects while maintaining measurement speed through targeted frequency excitation
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
This approach enables fast and reliable characterization of oscillators with improved accuracy and reduced measurement time, allowing for efficient determination of resonant frequency and quality factor, even in the presence of parasitic capacitance, thus enhancing productivity and sensor accuracy.
Implementation Method 1
The oscillator also includes actuation means configured to transform an excitation signal applied at an input of the oscillator into an electrostatic actuation force, also called an 'excitation force,' acting on the mobile component
Implementation Method 2
By sweeping a frequency range an amplitude spectral density of the oscillations is obtained, from which the resonant frequency can be determined. Indeed, the amplitude spectral density forms a resonance peak with a maximum amplitude attained at the resonant frequency
Implementation Method 3
The oscillator also includes detection means configured to deliver an output signal, also called a 'response signal,' which depends on the movements of the mobile component
Data Source
AI summary
A method for determining characteristic parameters of an electrostatic actuation oscillator, where the method includes generating a first excitation voltage defined as being the sum of a first sinusoidal voltage and a voltage pulse; applying the first excitation voltage at the input of the oscillator; acquiring in the time domain a first response voltage present at the output of the oscillator when the first excitation voltage is applied at the input of the oscillator; obtaining, by transformation in the frequency domain, a first amplitude spectral density of the first response voltage; determining the characteristic parameters of the oscillator from the first amplitude spectral density.