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An optimized harmonic probe with tailored resonant mode for multifrequency atomic force microscopy
摘要： For simultaneously measuring specimen’s surface morphology and material properties, multifrequency atomic force microscopy is often employed. In this kind of atomic force microscopy, if the probe’s higher-order resonance frequencies match the integer multiples of its fundamental frequency, the probe’s responses at such harmonic frequencies will be enhanced. Meanwhile, an enlarged effective slope during vibration at the probe’s tip results in an improved probe sensitivity. Moreover, increasing the probe’s natural frequency leads to a fast scanning speed. In this study, we propose to design cantilever probes that satisfy the aforementioned requirements via a structural optimization technique. A cantilever probe is represented by a three-layer symmetrical geometric model, and its width profile is continuously varied through the optimization procedure. Thereafter, an optimized design of probe considering the fifth harmonic is prepared by focused ion beam milling. Both simulation and experiment results show that the prepared probe agrees well with design requirements.
关键词： resonant frequency,tapping-mode,structural optimization,modal assurance criterion,Multifrequency atomic force microscopy
更新于2025-09-23 15:22:29
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Characterization of the lossy dielectric materials using contour mapping
摘要： The imaginary part of the complex permittivity of a lossy dielectric material is large and couples with its real part. The resonant frequency of a cavity with the sample depends not only on the real part of the complex permittivity of the sample but also the imaginary part, resulting in serious ambiguity in determining the sample’s complex permittivity. This work proposes a contour mapping method to determine the complex permittivity. The full-wave simulation gives us the contours of the resonant frequency and the quality factor, which are functions of the relative dielectric constant and the loss tangent. By mapping the measured resonant frequency and the measured quality factor, one can uniquely determine the complex permittivity of the sample. Five liquids were examined, including three low-loss materials for benchmarking and two lossy materials. The measured complex permittivities of the three low-loss materials agree very well with the other methods. As for the lossy materials, the measured relative dielectric constant and the loss tangent of alcohol are 6.786 and 0.895, respectively. Besides, the measured dielectric constant of glycerin is 6.811, and its loss tangent is 0.562. The proposed contour mapping technique can be employed to measure the complex permittivity of liquids and solids from lossless to lossy materials.
关键词： lossy dielectric materials,resonant frequency,contour mapping,complex permittivity,quality factor
更新于2025-09-23 15:21:21
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Simulation and Measurement of Properties of Metallic Photonic Crystal Point-Defect-Cavities with a Centrally-Loaded Rod
摘要： Properties of a class of M-PhC (metallic-photonic-crystal) point-defect-cavities (PDCs) with a centrally-loaded rod are theoretically and experimentally investigated. After the computation of the resonant frequencies and Q-factors of the resonant modes, the PDCs are fabricated and experimentally measured to validate the simulation results.
关键词： resonant frequency,M-PhC,Q-value,bandgap,point-defect cavity
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Zhenjiang, China (2019.8.4-2019.8.8)] 2019 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Study on Anti-reflection Performance of Titanium Alloy Based on the Change of Repeat Times of Nanosecond Laser Processing
摘要： A new and accurate edge extension formula based on the Taguchi method is proposed to calculate the resonant frequency of electrically thin and thick rectangular patch antennas with an air gap (RPAAG) and rectangular patch antennas without an air gap. Based on 3205 antennas data random distribution in the electrical substrate thickness h/λd ranging from 0.001 to 0.2 and the dielectric constant ranging from 1.0 to 10.2, the edge extension formula is created with the Taguchi method. The resonant frequencies predicted using the proposed formula are in better agreement with simulated and measured results than those calculated with the existing formulas in other literatures, especially for electrically thick substrates. Furthermore, experimental results for the RPAAG are given, which shows that h/λd should be less than 0.13 in the design of a capacitively fed RPAAG.
关键词： Edge extension formula,resonant frequency,electrically thin and thick substrates,rectangular patch antenna with and without an air gap,Taguchi method
更新于2025-09-23 15:21:01
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The laser power effect on the performance of gas leak detector based on laser photo-acoustic spectroscopy
摘要： The use of a homemade gas leak detector based on laser photo-acoustic spectroscopy for fast and sensitive trace gas detection is reported. To obtain optimal acoustic resonator dimensions, resonant frequency variations in terms of resonator's length and radius were simulated, and then a gas leak detector based on photo-acoustic theory was designed and fabricated. The system limit of detection to trace NO2, SO2 and SF6 was 92, 270 and 8 ppb respectively. Therefore, this system can be used as a sensitive gas sensor for detecting partial leakage of some environmental and industrial pollutants. Variations of the resonant frequency versus various concentrations of NO2, SO2 and SF6 in the presence different buffer gases were studied, and results showed that the lighter buffer gas gives a higher resonance frequency. Also, variations of the photo-acoustic signal and SNR of these gas samples in terms of various CO2 laser power at the presence different buffer gases were investigated, and the saturation laser power for each experiment was obtained. Finally, it was shown that experimental results are in good agreement with photo-acoustic theory.
关键词： Photo-acoustic signal,CO2 laser power,gas leak detector,resonant frequency,Infrared spectroscopy
更新于2025-09-23 15:19:57
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Fast and accurate model for a coax-fed rectangular patch antenna with varying aspect ratio, feed location and substrate electrical parameters
摘要： An improved closed-form model based on cavity model and single resonant parallel R-L-C circuit analysis is proposed to predict the resonant frequency, quality factor, bandwidth, gain and input impedance of a coax-fed rectangular patch antenna as a function of aspect ratio, feed location and substrate electrical parameters. The computed values employing the present model are compared with our experimental results and experimental results available in open literature. We have also employed electromagnetic high-frequency structure simulator (HFSS) software to validate the model. The present model shows very close agreements with the experimental and simulation results compared to the other models. This model is very simple, fast and accurate. The present model can be directly applied to CAD program.
关键词： Improved closed-form model,microstrip antennas,gain,bandwidth,input impedance,resonant frequency,quality factors
更新于2025-09-19 17:15:36
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Split-ring resonator-based compact microstrip antenna
摘要： Compact microstrip antennas based on split-ring resonator (SRR) structure are proposed and fabricated in this paper. The resonant frequency of the antennas is discussed upon different geometric structures. The influencing mechanism of the antenna parameters on resonant frequency is analyzed. The analytical and experimental analyses are carried out and proved that the resonant frequency can be controlled from 13.5 GHz to 17.2 GHz by tuning some of the crucial parameters. A good agreement between the simulations and the measurement results suggests that the proposed antenna can be designed at different resonant frequencies while maintaining a small-size, low-profile structure and good performance.
关键词： Microstrip antenna,split-ring resonator,resonant frequency tunable.
更新于2025-09-19 17:15:36
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Interface Stress for Bidirectional Frequency Tuning of Prebuckled Vanadium Dioxide MEMS Resonators
摘要： Interface stress between structural materials and thin film coatings has a significant influence on the resonant frequency of microelectromechanical system (MEMS) resonators. In this work, the axial stress on different types of buckled bridge MEMS resonator structures is controlled through the solid-to-solid phase transition of a VO2 thin film coating. The devices have identical dimensions, but different buckling orientations and profiles due to the combined effect of overetching and residual thermal stress mismatch. Thermal actuation is used to tune the resonant frequency of the device, but the changes in frequency are found to be dependent on the type of buckling for the device. Thermal actuation is achieved by applying an electrical current to integrated heaters, or by uniform substrate heating. Bidirectional tunability is found when substrate heating is used, while Joule heating shows a monotonic change in frequency. This phenomenon can be attributed to the transition in boundary conditions, where the turning points are indicated by the prominent changes in buckling amplitude. In addition, devices with opposite buckling orientations exhibit different tuning behaviors which can be explained by different bending moments induced by beam stress interface modification.
关键词： MEMS resonators,interface stress,buckling,vanadium dioxide,resonant frequency tuning
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Experimental Study of the Resonant Frequency of an Optical Fiber Vector Sensor with Different Packages
摘要： The characteristic of resonant frequency of three different optical fiber vector sensors (OFVS) operating in water were studied. The effect of package types (spherical and cylindrical) and package masses are considered. The experimental results show that there are two resonant peaks in the OFVS, which were not reported in previous studies. A new model shall be proposed to characterize the performance of OFVS operating in some medium.
关键词： optical fiber vector sensors(OFVS),resonant frequency,package
更新于2025-09-16 10:30:52
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Microwave Method for Closure of Quasi-Spherical Resonator
摘要： Quasi-spherical microwave cavity resonators are widely used in primary thermometry. To realize high-accuracy microwave resonant frequency measurement, it is essential to close the two quasi-hemispheres correctly. We show how to do this using microwave resonance signals to monitor shape and sealing as torques to equatorial bolts are increased. The present resonator was closed with torques up to 105 cNm. The method should be useful to monitor the closing of other quasi-spherical cavities.
关键词： Quasi-spherical cavity,Resonant frequency,Thermometry,Microwave measurement,Thermodynamic temperature
更新于2025-09-10 09:29:36