9.4 A 27µW 0.06mm2 background resonance frequency tuning circuit based on noise observation for a 1.71mW CT-ΔΣ MEMS gyroscope readout system with 0.9°/h bias instability

A digital mode-matching control system based on feedback calibration, where two pilot tones are applied to actuate the sense mode by the robust feedback controller, is presented for a MEMS gyroscope in this paper. A dual-mass decoupled MEMS gyroscope with the integrated electrostatic frequency tuning mechanisms, the quadrature correction electrode, and the feedback electrode is adopted to implement mode-matching control. Compared with the previous mode-matching method of forward excitation calibration, the proposed mode-matching scheme based on feedback calibration has better adaptability to the variation in the frequency of calibration pilot tones and the quality factor of the sense mode. The influences of calibration pilot tone frequency and the amplitude ratio on tuning performance are studied in theory and simulation. The simulation results demonstrate that the tuning error due to the amplitude asymmetry of the sense mode increases with a frequency split between pilot tones and the drive mode and is significantly reduced by the amplitude correction technology of pilot tones. In addition, the influence of key parameters on the stability of the mode-matching system is deduced by using the average analysis method. The MATLAB simulation of the mode-matching control system illustrates that simulation results have a good consistency with theoretical analysis, which verifies the effectiveness of the closed-loop mode-matching control system. The entire mode-matching control system based on a FPGA device is implemented combined with a closed-loop self-excitation drive, closed-loop force feedback control, and quadrature error correction control. Experimental results demonstrate that the mode-matching prototype has a bias instability of 0.63°/h and ARW of 0.0056°/h1/2. Compared with the mode-mismatched MEMS gyroscope, the performances of bias instability and ARW are improved by 3.81 times and 4.20 times, respectively.

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A Digital Calibration Technique of MEMS Gyroscope for Closed-Loop Mode-Matching Control

Micromachines ◽

10.3390/mi10080496 ◽

2019 ◽

Vol 10 (8) ◽

pp. 496

Author(s):

Cheng Li ◽

Bo Yang ◽

Xin Guo ◽

Lei Wu

Keyword(s):

Theoretical Analysis ◽

Real Time ◽

Closed Loop ◽

Mode Matching ◽

Loop Analysis ◽

Calibration Technique ◽

Mems Gyroscope ◽

Real Time Mode ◽

Digital Excitation ◽

Bias Instability

A digital excitation-calibration technique of dual-mass MEMS gyroscope for closed-loop mode-matching control is presented in this paper. The technique, which takes advantage of the symmetrical amplitude response of MEMS gyroscope, exploits a two-side excitation signal to actuate the sense mode to obtain the corresponding DC tuning voltage. The structural characteristics of dual-mass decoupled MEMS gyroscope and the tuning principle of excitation-calibration technique are introduced firstly. Then, the scheme of digital excitation-calibration system for the real-time mode-matching control is presented. Simultaneously, open-loop analysis and closed-loop analysis are deduced, respectively, to analyze the sources of tuning error and system stability. To verify the validity of the scheme and theoretical analysis, the system model was established by SIMULINK. The simulation results are proved to be consistent with the theoretical analysis, verifying the feasibility of the digital excitation-calibration technique. The control algorithms of the system were implemented with a FPGA device. Experimental results demonstrate that digital excitation-calibration technique can realize mode-matching within 1 s. The prototype with real-time mode-matching control has a bias instability of 0.813 ∘ /h and an ARW (Angular Random Walk) of 0.0117 ∘ / h . Compared to the mode-mismatching condition, the bias instability and ARW are improved by 3.25 and 4.49 times respectively.

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Resonance frequency tuning in vibration-based energy harvesting systems

10.23889/suthesis.51431 ◽

2018 ◽

Author(s):

Hadi Madinei

Keyword(s):

Energy Harvesting ◽

Resonance Frequency ◽

Frequency Tuning ◽

Harvesting Systems

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Optically Tunable Terahertz Metasurfaces Using Liquid Crystal Cells Coated with Photoalignment Layers

Crystals ◽

10.3390/cryst11091100 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1100

Author(s):

Yi-Hong Shih ◽

Xin-Yu Lin ◽

Harry Miyosi Silalahi ◽

Chia-Rong Lee ◽

Chia-Yi Huang

Keyword(s):

Liquid Crystal ◽

Resonance Frequency ◽

Pump Beam ◽

Frequency Tuning ◽

Ring Resonators ◽

Split Ring ◽

Split Ring Resonators ◽

Terahertz Region ◽

Crystal Cells ◽

Terahertz Filter

An optically tunable terahertz filter was fabricated using a metasurface-imbedded liquid crystal (LC) cell with photoalignment layers in this work. The LC director in the cell is aligned by a pump beam and makes angles θ of 0, 30, 60 and 90° with respect to the gaps of the split-ring resonators (SRRs) of the metasurface under various polarized directions of the pump beam. Experimental results display that the resonance frequency of the metasurface in the cell increases with an increase in θ, and the cell has a frequency tuning region of 15 GHz. Simulated results reveal that the increase in the resonance frequency arises from the birefringence of the LC, and the LC has a birefringence of 0.13 in the terahertz region. The resonance frequency of the metasurface is shifted using the pump beam, so the metasurface-imbedded LC cell with the photoalignment layers is an optically tunable terahertz filter. The optically tunable terahertz filter is promising for applications in terahertz telecommunication, biosensing and terahertz imaging.

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Measurement of resonance frequency by amplitude and phase methods using digital frequency scanning

Izmeritel`naya Tekhnika ◽

10.32446/0368-1025it.2021-6-51-58 ◽

2021 ◽

pp. 51-58

Author(s):

Valery Ya. Fateev

Keyword(s):

Resonance Frequency ◽

Noise Level ◽

Frequency Tuning ◽

Phase Method ◽

Random Errors ◽

Amplitude Noise ◽

Frequency Scanning ◽

Digital Frequency ◽

Systematic And Random Errors ◽

Analytical Expressions

A theoretical and experimental study of methods for measuring the resonance frequency from the amplitude-frequency and phase-frequency characteristics of the resonator (amplitude and phase methods, respectively) has been carried out. In this case, digital frequency scanning was used to determine the resonant frequency. On the basis of the theory of probabilities, analytical expressions are derived that describe the dependences of systematic and random errors on the position of the resonance frequency in the interval between the nearest discrete frequencies, as well as on the noise level. The reliability of the derived expressions was confirmed in the course of a virtual experiment with a computer model of the resonator. It is also shown that the errors of the amplitude and phase methods for the noise level, at which no more than two discrete frequencies are recorded, practically coincide. However, if more than two discrete frequencies are recorded, then the indicated errors differ significantly, which is demonstrated using the experimental graphs. In this case, the errors in measuring the resonance frequency by the phase method practically do not depend on the frequency tuning step with a decrease in this step and linearly depend on the phase noise level. When measuring the resonance frequency by the amplitude method, the errors decrease with decreasing frequency tuning step, and for this case, an empirical formula is proposed for the dependence of systematic and random errors on the frequency tuning step and the amplitude noise level. The research results can be used in the construction of digital resonance sensors.

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