scholarly journals Wide Acoustic Bandgap Solid Disk-Shaped Phononic Crystal Anchoring Boundaries for Enhancing Quality Factor in AlN-on-Si MEMS Resonators

Micromachines ◽  
2018 ◽  
Vol 9 (8) ◽  
pp. 413 ◽  
Author(s):  
Muhammad Siddiqi ◽  
Joshua Lee
Keyword(s):  
Quality Factor ◽  
Phononic Crystal ◽  
Center Frequency ◽  
Very High Frequency ◽  
Mems Resonators ◽  
Solid Disk ◽  
Cell Topology ◽  
Transmission Measurements ◽  
Quality Factor Q ◽  
Very High

This paper demonstrates the four fold enhancement in quality factor (Q) of a very high frequency (VHF) band piezoelectric Aluminum Nitride (AlN) on Silicon (Si) Lamb mode resonator by applying a unique wide acoustic bandgap (ABG) phononic crystal (PnC) at the anchoring boundaries of the resonator. The PnC unit cell topology, based on a solid disk, is characterized by a wide ABG of 120 MHz around a center frequency of 144.7 MHz from the experiments. The resulting wide ABG described in this work allows for greater enhancement in Q compared to previously reported PnC cell topologies characterized by narrower ABGs. The effect of geometrical variations to the proposed PnC cells on their corresponding ABGs are described through simulations and validated by transmission measurements of fabricated delay lines that incorporate these solid disk PnCs. Experiments demonstrate that widening the ABG associated with the PnC described herein provides for higher Q.

scholarly journals Measurement of Electrical Properties of Superconducting YBCO Thin Films in the VHF Range

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3360
Author(s):  
Yakir Dahan ◽  
Eldad Holdengreber ◽  
Elichai Glassner ◽  
Oz Sorkin ◽  
Shmuel E. Schacham ◽  
...  
Keyword(s):  
Thin Films ◽  
Theoretical Model ◽  
Quality Factor ◽  
High Frequency ◽  
Unit Length ◽  
Superconducting Thin Films ◽  
Electrical Parameters ◽  
Very High Frequency ◽  
Production Constraints ◽  
Very High

A new measurement technique of electrical parameters of superconducting thin films at the Very High Frequency (VHF) range is described, based on resonators with microstrip (MS) structures. The design of an optimal resonator was achieved, based on a thorough theoretical analysis, which is required for derivation of the exact configuration of the MS. A theoretical model is presented, from which an expression for the attenuation of a MS line can be derived. Accordingly, simulations were performed, and an optimal resonator for the VHF range was designed and implemented. Production constraints of YBa2Cu3O7 (YBCO) limited the diameter of the sapphire substrate to 3″. Therefore, a meander configuration was formed to fit the long λ/4 MS line on the wafer. By measuring the complex input reflection coefficients of a λ/4 resonator, we extracted the quality factor, which is mainly affected by the dielectric and conductor attenuations. The experimental results are well fitted by the theoretical model. The dielectric attenuation was calculated using the quasi-static analysis of the MS line. An identical copper resonator was produced and measured to compare the properties of the YBCO resonator in reference to the copper one. A quality factor of ~6·105 was calculated for the YBCO resonator, three orders of magnitude larger than that of the copper resonator. The attenuation per unit length of the YBCO layer was smaller by more than five orders of magnitude than that of the copper.

EFFECTS OF POROSITY ON SEISMIC ATTENUATION

1994 ◽  
Vol 02 (01) ◽  
pp. 53-69 ◽  
Author(s):  
YUE-FENG SUN ◽  
JOHN T. KUO ◽  
YU-CHIUNG TENG
Keyword(s):  
Quality Factor ◽  
Crack Density ◽  
Seismic Attenuation ◽  
Center Frequency ◽  
Fluid Content ◽  
Intrinsic Attenuation ◽  
Resolution Mapping ◽  
Waveform Change ◽  
Optimization Schemes ◽  
Quality Factor Q

Effects of porosity on the attenuation of wave propagation are studied. The effects of pore fluids and porous structures are significant on changing the shapes of propagating wavelets. The waveform change of a propagating wavelet is much more sensitive to porosity than intrinsic attenuation. The attenuation occurred in natural rocks may largely due to these porous effects in addition to the internal friction of the solid represented by the intrinsic quality factor Q. The waveform of a propagating wavelet is quantitatively associated with attenuation, porosity, and fluid content, and is characterized by three parameters: the porosity ϕ, the quality factor Q, and the center frequency f0. Estimations of attenuation, porosity, and fluid content can be made by optimal wavelet analysis. High-resolution mapping of subsurface structures can be achieved by solving the integral equation with the nonlinear optimization of the time-variant wavelets. The inversion and the optimization schemes have been applied to study the porous sea floor and the crustal axial magma chamber (AMC) on the East Pacific Rise. These results provide porosity, attenuation information, and the highly resolved wave events, for further evaluation of compressional and shear wave velocities and other physical properties such as crack density and aspect ratio.

scholarly journals Fully-Integrated Tunable Q-Enhanced Linear Low Noise Amplifier for Wireless Receivers

2020 ◽  
Vol 9 (3) ◽  
pp. 1762-1766
Keyword(s):  
Quality Factor ◽  
Tuning Range ◽  
Low Noise ◽  
Wireless Receivers ◽  
Center Frequency ◽  
Third Order ◽  
Fully Integrated ◽  
Noise Amplifier ◽  
Quality Factor Q ◽  
Peak Gain

This paper presents the design of a fully-integrated tunable Q-enhanced LNA resonator filter designed to tune the circuit center frequency and quality factor Q. The proposed circuit achieves a 600 MHz 3dB bandwidth tunable center frequency at 2.4 GHz with a 5.5 dB Quality Factor Q tuning range. The proposed circuit utilize a distortion transistor compensator to improve linearity of the circuit. The results show an 18 dBc of third order intermodulation IM3 cancellation. The overall proposed circuit peak gain is 16.5 dB and the minimum NF is 0.94 dB at 2.4 GHz frequency with power consumption of 5.2 mA

scholarly journals Concentric Split Aluminum with Silicon-Aluminum Nitride Annular Rings Resonators

Micromachines ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 296 ◽  
Author(s):  
Muhammad Ammar Khan ◽  
Jing-Fu Bao ◽  
Fei-Hong Bao ◽  
Xin Zhou
Keyword(s):  
Finite Element ◽  
Quality Factor ◽  
Phononic Crystal ◽  
Perfect Match ◽  
Band Gaps ◽  
Element Analysis ◽  
Vibration Displacement ◽  
Filling Fraction ◽  
Finite Element Analysis Simulation ◽  
Quality Factor Q

This paper presents a novel approach of annular concentric split rings microelectromechanical resonators with tether configuration to reduce anchor loss and gives very high-quality factor (Q) 2.97 Million based on FEA (Finite Element Analysis) simulation. The operating frequencies of these resonators are 188.55 MHz to 188.62 MHz. When the proposed SR (square rectangle) hole shaped one dimensional phononic crystal (1D PnC), and two dimensional phononic crystal (2D PnC) structure consist of very wide and complete band gaps is applied to novel design rings MEMS resonators, the quality factor (Q) further improved to 19.7 Million and 1750 Million, respectively, by using the finite element method. It is also observed that band gaps become closer by reducing the value of filling fraction, and proposed SR PnC gives extensive peak attenuation. Moreover, harmonic response of ring resonator is verified by the perfect match layers (PML) technique surrounded by resonators with varying width 1.5λ, and 3λ effectively reduce the vibration displacement.

Charge Carrier Absorption in Doped Microcrystalline Silicon Films

1996 ◽  
Vol 452 ◽  
Author(s):  
M. Heintze ◽  
E. Lotter ◽  
C.-D. Abel ◽  
M. B. Schubert
Keyword(s):  
Chemical Vapor ◽  
Transport Parameters ◽  
Infrared Transmission ◽  
Microcrystalline Silicon ◽  
Very High Frequency ◽  
Silicon Thin Films ◽  
Carrier Absorption ◽  
Transmission Measurements ◽  
Very High ◽  
Infrared Data

AbstractThe infrared absorption in doped microcrystalline silicon thin films is analyzed by modelling the complex permittivity as the sum of the contributions resulting from interband transitions and from absorption by charge carriers. Their density and the drift mobility within grains is described by free carrier motion according to the Drude theory. However, for a good fit to experimental data a small trapping energy, reflecting the effect of grain boundaries, is included in the model. By comparing results obtained from the analysis of infrared data with conductivity and Hall measurements in films grown in a very high frequency (VHF) plasma and by hot-wire chemical vapor deposition (CVD), we show that infrared transmission measurements provide a simple access to transport parameters in these films.

NÉEL LINES STRUCTURES IN UNIAXIAL FERROMAGNETS WITH QUALITY FACTOR Q > 1

1988 ◽  
Vol 49 (C8) ◽  
pp. C8-1947-C8-1948
Author(s):  
J. Miltat ◽  
P. Trouilloud
Keyword(s):  
Quality Factor ◽  
Quality Factor Q

Experimental Investigation of very High Frequency Slot Antenna on M-60A-1 Tank

1977 ◽  
Author(s):  
D. V. Campbell ◽  
William Kennebeck ◽  
A. Zanella ◽  
Paul Sexton
Keyword(s):  
Experimental Investigation ◽  
High Frequency ◽  
Slot Antenna ◽  
Very High Frequency ◽  
Very High

Evaluation of the mechanical properties of Inconel 718 to SCM 440 dissimilar friction welding through real-time monitoring of the acoustic emission system

2021 ◽  
pp. 146442072199383
Author(s):  
Yu Sik Kong ◽  
Muralimohan Cheepu ◽  
Jin-Kyung Lee
Keyword(s):  
Acoustic Emission ◽  
Friction Welding ◽  
Inconel 718 ◽  
Low Voltage ◽  
Dissimilar Materials ◽  
Average Frequency ◽  
Very High Frequency ◽  
Cumulative Count ◽  
Emission System ◽  
Very High

Friction welding was chosen for its versatility in the joining of dissimilar materials with high quality. The aim of this study is to determine the optimal welding conditions for attaining quality joints by using online monitoring of acoustic emission system signals. During friction welding, the formation of cracks, defects, or any abnormalities in the joining process which have a detrimental effect on the joints quality was identified. The most widely used materials in the aerospace industry—Inconel 718 and molybdenum steel—were joined by friction welding. The precision of the joints, internal defects, and quality are major concerns for aerospace parts. The results of the present research determined the optimal welding conditions for high tensile strength by nondestructively inducing acoustic emission signals. During friction time and upset time periods, the typical waveforms and frequency spectrum of the acoustic emission signals were recorded, and their energy level, average frequency, cumulative count, and amplitude were analyzed. Both cumulative count and amplitude were found to be useful parameters for deriving the optimal welding conditions. In the initial stage of friction welding, a very high voltage of continuous form was generated with frequency characteristics of 0.44 MHz and 0.54 MHz. The signals generated during the upset stage had a low voltage, but a very high frequency of 1.56 MHz and 1.74 MHz with a burst-type signal. The amplitude of the signal generated for the optimally welded joints was about 100 dB at the friction time and about 45 dB at the upset time.

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