Resonant Oscillation Demodulation Without Lock-In Amplifiers
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Solution Overview
Problem
Current demodulation techniques for oscillating elements, such as those used in atomic force microscopy, are complex, costly, and prone to noise, making them inefficient for determining the amplitude and phase of modulated oscillations.
Innovation Solution
A method involving exciting a vibrationally mounted bar-shaped oscillating element with a temporally varying excitation signal and using a sensor to detect the modulated oscillation, generating a comparison signal that is proportional to the amplitude or phase of the oscillation, allowing for demodulation without the need for expensive lock-in amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If lock-in amplifiers are used for demodulation, then measurement precision is improved, but device complexity increases and cost increases
Solution Approach 1:
The patent replaces the complex electronic lock-in amplifier system with a simplified computational demodulation approach. Instead of using hardware-based phase-sensitive detection, the invention uses software-based correlation methods where the sensor signal is multiplied by a reference signal and integrated over time. This substitution of mechanical/electronic complexity with computational simplicity resolves the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent creates a virtual model of the oscillation reference signal and uses it to demodulate the sensor signal through correlation. By copying the reference signal characteristics and using it for comparison, the system achieves lock-in amplifier precision without the associated hardware complexity and cost.
2Measurement precision
If lock-in amplifiers are used for demodulation, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent replaces expensive lock-in amplifier hardware with cost-effective computational methods implemented in software or simple digital circuits. The demodulation is achieved through digital signal processing techniques that require minimal hardware resources, thereby resolving the contradiction between measurement precision and manufacturing cost.
Solution Approach 2:
The patent uses inexpensive computational resources and simple digital circuits instead of expensive analog lock-in amplifier components. The approach treats complex signal processing as a disposable computational task rather than requiring permanent, expensive hardware infrastructure.
3Device complexity
If simple demodulation techniques are used, then device complexity is reduced, but measurement precision deteriorates due to noise sensitivity
Solution Approach 1:
The patent performs preliminary correlation between the sensor signal and reference signal before final measurement extraction. By pre-multiplying the signals and integrating over multiple oscillation cycles, the system prepares the data in advance to enhance signal-to-noise ratio, thereby achieving high precision without complex hardware.
Solution Approach 2:
The patent uses the known reference signal characteristics to guide the demodulation process. The correlation method provides inherent feedback where the reference signal continuously guides the extraction of amplitude and phase information, improving precision against noise while maintaining system simplicity.
4Device complexity
If simple demodulation techniques are used, then device complexity is reduced, but measurement precision deteriorates due to frequency component sensitivity
Solution Approach 1:
The patent performs preliminary integration over complete oscillation cycles before extracting the final measurement. This pre-integration step acts as a natural frequency filter that eliminates sensitivity to non-synchronous frequency components, achieving robust precision without complex frequency analysis hardware.
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 provides a simpler, cost-effective method for demodulating oscillations, enabling reliable measurement of amplitude and phase, applicable beyond atomic force microscopy for various applications.
Implementation Method 1
The deformation of the cantilever leads to a change in the electrical resistance of the piezoresistive sensors
Implementation Method 2
exciting a vibrationally mounted, at least sectionally bar-shaped oscillating element for oscillating in the range of a resonance frequency of the oscillating element
Data Source
AI summary
A method for demodulation including the following steps: exciting a vibrationally mounted, at least sectionally bar-shaped oscillating element for oscillating in the range of a resonance frequency of the oscillating element, wherein a temporally varying, in particular periodic, excitation signal is used for excitation, and wherein at least the temporal variation of the excitation signal is known or determined; detecting a modulated oscillation of the oscillating element by means of at least one sensor, wherein the sensor supplies a sensor measurement variable that varies versus time as a function of an amplitude and a phase of the modulated oscillation of the oscillating element. According to the present teaching, it is provided that the method includes the following step: generate a first comparison signal by amplitude modulating a known temporally varying, in particular periodic, demodulation signal by means of the temporally varying sensor measurement variable.