Heterogeneous-frequency-dual-pulse Chain and WeakFBGs Array for Quasi-distributed Acoustic Sensingwith Improved Response Bandwidth

2021 ◽  
Author(s):  
guanhua Liang ◽  
Panpan Niu ◽  
Junfeng Jiang ◽  
Wang Shuang ◽  
Yixuan Wang ◽  
...  
Keyword(s):  
Response Bandwidth

Integrated Rib Waveguide-Photodetector Using Si/Si1−xGex Multiple Quantum Wells for Long Wavelenghts

1991 ◽  
Vol 220 ◽  
Author(s):  
V. P. Kesan ◽  
P. G. May ◽  
G. V. Treyz ◽  
E. Bassous ◽  
S. S. Iyer ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Internal Quantum Efficiency ◽  
Optical Quality ◽  
Silicon Substrates ◽  
Multiple Quantum ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Long Wavelength ◽  
Response Bandwidth ◽  
Soi Substrates

ABSTRACTWe have investigated the structural, electrical, and optical quality of epitaxial Si and Si1−xGex films grown by MBE on SIMOX (Separation by IMplanted OXygen) silicon substrates. Epitaxial films grown on these SOI substrates have been characterized using planar and cross-sectional TEM, high resolution X-ray diffraction, SIMS, and Seeco chemical etching to delineate defects. We have fabricated Si/SiGe P-i-N photodetectors integrated with Si waveguides on SOI for long wavelength applications. Low reverse leakage current densities were seen in these device structures. The photodetector exhibited an internal quantum efficiency of 50% at 1.1 μm with a frequency response bandwidth of 2 GHz.

Frequency Response Bandwidth Calibration of High Speed Photodetector Using Frequency-Stabilized Laser by Optical Heterodyne Technique

2014 ◽  
Vol 644-650 ◽  
pp. 1031-1034
Author(s):  
Nan Xu ◽  
Jian Wei Li ◽  
Jian Li ◽  
Zhi Xin Zhang
Keyword(s):  
Frequency Response ◽  
High Speed ◽  
Beat Frequency ◽  
Tunable Laser ◽  
Laser Source ◽  
Response Measurement ◽  
System A ◽  
Response Bandwidth ◽  
Heterodyne Technique ◽  
Frequency Stabilized Laser

In this paper, frequency-stabilized laser technology is introduced into photodetector frequency response measurement system. A 1531nm frequency-stabilized laser fulfilled by acetylene saturated absorption is employed to produce coherent light with a tunable laser source, gaining stable beat frequency light that reaches as high as several hundred ghz, fulfilling measurement of 40ghz high-speed photodetector frequency response bandwidth, and lowering impacts caused by instability of light frequency. In addition, measurement uncertainty analysis is conducted, which is better than 7 %(k=2).

scholarly journals All-in-One High-Power-Density Vibrational Energy Harvester with Impact-Induced Frequency Broadening Mechanisms

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1083
Author(s):  
Yongqi Cao ◽  
Weihe Shen ◽  
Fangzhi Li ◽  
Huan Qi ◽  
Jiaxiang Wang ◽  
...  
Keyword(s):  
Power Generation ◽  
Cantilever Beam ◽  
External Load ◽  
Peak Power ◽  
Vibrational Energy ◽  
Nonlinear Frequency ◽  
Electromagnetic Power ◽  
Response Bandwidth ◽  
And Performance ◽  
High Output Voltage

This paper proposes an electrostatic-piezoelectric-electromagnetic hybrid vibrational power generator with different frequency broadening schemes. Both the nonlinear frequency broadening mechanisms and the synergized effect of the electrostatic-piezoelectric-electromagnetic hybrid structures are investigated. The structure and performance of the composite generator are optimized to improve the response bandwidth and performance. We propose that the electrostatic power generation module and the electromagnetic power generation module be introduced into the cantilever beam to make the multifunctional cantilever beam, realizing small integrated output loss, high output voltage, and high current characteristics. When the external load of the electrostatic power generation module is 10 kΩ, its peak power can reach 3.6 mW; when the external load of the piezoelectric power generation module is 2 kΩ, its peak power is 2.2 mW; and when the external load of the electromagnetic power generation module is 170 Ω, its peak power is 0.735 mW. This means that under the same space utilization, the performance is improved by 90%. Moreover, an energy management circuit (ECM) at the rear end of the device is added, through the energy conditioning circuit, the device can directly export a 3.3 V DC voltage to supply power to most of the sensing equipment. In this paper, the hybrid generator’s structure and performance are optimized, and the response bandwidth and performance are improved. In general, the primary advantages of the device in this paper are its larger bandwidth and enhanced performance.

scholarly journals Response Analysis of Asymmetric Monostable Harvesters Driven by Color Noise and Band-Limited Noise

2021 ◽  
Vol 11 (19) ◽  
pp. 9227
Author(s):  
Shuangyan Liu ◽  
Wei Wang
Keyword(s):  
Output Power ◽  
Harmonic Excitation ◽  
Center Frequency ◽  
Response Analysis ◽  
Color Noise ◽  
Energy Harvesters ◽  
Output Performance ◽  
Response Bandwidth ◽  
Band Limited ◽  
The Moment

In this paper, we investigate the response of asymmetric potential monostable energy harvesters (MEHs) excited by color noise and band-limited noise. The motivation for this study is that environmental vibrations always have the characteristic of randomness, and it is difficult to modulate a perfectly symmetric MEH. For the excitation of exponentially correlated color noise, the moment differential equation was applied to evaluate the output performance of the asymmetric potential MEHs. Numerical and theoretical analyses were carried out to investigate the influence of noise intensity and internal system parameters on the output power of the system. Our results demonstrate that the output performance of the asymmetric MEH decreases with the increase in the correlation time, which determines the character of the color noise. On the contrary, the increase in the asymmetric degree enhances the output power of the asymmetric MEH subjected to color noise. For the band-limited noise excitation, numerical simulation is undertaken to consider the response of the asymmetric MEHs, and outcomes indicate that the frequency bandwidth and center frequency have a significant influence on the output performance. Regarding the asymmetric potential, its appearance leads the MEHs to generate higher output power at lower frequencies and this phenomenon is more obvious with the increase in the degree of asymmetry. Finally, we observed that the characteristics of the response bandwidth of asymmetric MEHs subjected to band-limited noise excitation are similar to the response under harmonic excitation.

HIGH-SPEED RESPONSE OF GaAs/AlGaAs MULTIPLE QUANTUM WELL (MQW) ASYMMETRIC FABRY PEROT (ASFP) REFLECTION MODULATOR

1993 ◽  
Vol 07 (08) ◽  
pp. 533-541
Author(s):  
M. NAWAZ ◽  
B. T. OLSEN ◽  
K. McILVANEY
Keyword(s):  
Quantum Well ◽  
High Speed ◽  
Multiple Quantum Well ◽  
Contrast Ratio ◽  
Multiple Quantum ◽  
Driving Voltage ◽  
Operating Wavelength ◽  
Response Bandwidth ◽  
Fabry Perot ◽  
Speed Response

The results of the high-speed response of GaAs/AlGaAs multiple quantum well (MQW) based asymmetric Fabry Perot (ASFP) reflection modulator are presented. The measured 3 dB electrical frequency response bandwidth of the modulator was 600 MHz. The contrast ratio of the modulator was 8.9 dB for a driving voltage of 13 V, at an operating wavelength of 862 nm.

scholarly journals Soft, tough, and fast polyacrylate dielectric elastomer for non-magnetic motor

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Li-Juan Yin ◽  
Yu Zhao ◽  
Jing Zhu ◽  
Minhao Yang ◽  
Huichan Zhao ◽  
...  
Keyword(s):  
High Performance ◽  
Crosslinking Agent ◽  
High Energy ◽  
Dielectric Elastomer ◽  
High Energy Density ◽  
Dielectric Elastomers ◽  
Dielectric Elastomer Actuators ◽  
Response Bandwidth ◽  
Electrically Actuated ◽  
Soft Actuators

AbstractDielectric elastomer actuators (DEAs) with large electrically-actuated strain can build light-weight and flexible non-magnetic motors. However, dielectric elastomers commonly used in the field of soft actuation suffer from high stiffness, low strength, and high driving field, severely limiting the DEA’s actuating performance. Here we design a new polyacrylate dielectric elastomer with optimized crosslinking network by rationally employing the difunctional macromolecular crosslinking agent. The proposed elastomer simultaneously possesses desirable modulus (~0.073 MPa), high toughness (elongation ~2400%), low mechanical loss (tan δm = 0.21@1 Hz, 20 °C), and satisfactory dielectric properties ($${\varepsilon }_{{{{{{\rm{r}}}}}}}$$ ε r  = 5.75, tan δe = 0.0019 @1 kHz), and accordingly, large actuation strain (118% @ 70 MV m−1), high energy density (0.24 MJ m−3 @ 70 MV m−1), and rapid response (bandwidth above 100 Hz). Compared with VHBTM 4910, the non-magnetic motor made of our elastomer presents 15 times higher rotation speed. These findings offer a strategy to fabricate high-performance dielectric elastomers for soft actuators.

Footprints of inhibition in the response of cortical delay-tuned neurons of bats

2014 ◽  
Vol 111 (8) ◽  
pp. 1703-1716 ◽  
Author(s):  
Julio C. Hechavarría ◽  
Manfred Kössl
Keyword(s):  
Aminobutyric Acid ◽  
Response Suppression ◽  
Fruit Bats ◽  
Strong Response ◽  
Inhibitory Processes ◽  
Response Bandwidth ◽  
Cortical Responses ◽  
Latency Shift ◽  
Delay Tuning

Responses of echo-delay-tuned neurons that encode target distance were investigated in the dorsal auditory cortex of anesthetized short-tailed fruit bats ( Carollia perspicillata). This species echolocates using short downward frequency-modulated (FM) biosonar signals. In response to FM sweeps of increasing level, 60 out of 131 studied neurons (47%) displayed a “paradoxical latency shift,” i.e., longer response latency to loud sounds and shorter latency to faint sounds. In addition, a disproportionately large number of neurons (80%) displayed nonmonotonic responses, i.e., weaker responses to loud sounds and stronger responses to faint sounds. We speculate that the observed paradoxical latency shift and nonmonotonic responses are extracellular footprints of inhibitory processes evoked by loud sounds and that they could represent a specialization for the processing of the emitted loud biosonar pulse. Supporting this idea is the fact that all studied neurons displayed strong response suppression when an artificial loud pulse and a faint echo were presented together at a nonoptimal delay. In 24 neurons, iontophoresis of bicuculline (an antagonist of A-type γ-aminobutyric acid receptors) did not remove inhibitory footprints but did increase the overall spike output, and in some cases it also modified the response bandwidth and shifted the neuron's “best delay.” We suggest that inhibition could play a dual role in shaping delay tuning in different auditory stations. Below the cortex it participates in delay-tuning implementation and leaves a footprint that is measurable in cortical responses, while in the cortex it provides a substrate for an in situ control of neuronal selectivity.

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