共查询到19条相似文献,搜索用时 140 毫秒
1.
The influence of a rigid spherical baffle on the response of a uniform circular microphone array (UCA) is analyzed and two eigen-beam beamforming arrays are designed in the eigen-beam subspaee derived from the soundfield decomposition. Expressions of white noise gain (WNG) and directivity index (DI) are derived for the designed arrays. Performance analyses are carried out for the designed arrays and compared between those of the delay-and-sum beamforming array using UCA with and without a rigid sphere. Computer simulations demonstrate that the designed arrays have frequency-independent directivity with the cost of reduced robustness at low frequency band. The delay-and-sum beamforming array has constant WNG at all frequencies, while its directivity of which is reduced at low frequency band. The rigid sphere can improve the robustness for all the arrays. 相似文献
2.
Analysis of crosstalk in HgCdTe p-on-n heterojunction photovoltaic infrared sensing arrays 总被引:1,自引:0,他引:1
C. A. Musca J. M. Dell L. Faraone J. Bajaj T. Pepper K. Spariosu J. Blackwell C. Bruce 《Journal of Electronic Materials》1999,28(6):617-623
In this paper, an experimental and theoretical study is carried out of crosstalk between nearest-neighbor devices within a
backside-illuminated linear HgCdTe photovoltaic infrared sensing array. The dominant form of crosstalk that occurs in high
performance photovoltaic arrays is associated with photogenerated minority carriers that diffuse laterally between adjacent
devices within the array. To measure crosstalk, a scanning laser microscope is used to obtain a spatial map of spot-scan photoresponse
at a temperature of 80K for individual p-on-n photovoltaic devices within the linear array. These experimental results are
compared to calculations performed on a commercial two-dimensional device simulation package. The crosstalk measurements and
calculations presented in this paper include results on mid-wavelength infrared planar device structures, as well as long-wavelength
infrared mesa-isolated devices, which give measured crosstalk values of 6.2 and 8.3%, respectively. The results indicate that
the device simulations are in good agreement with experimental results. Further simulations are carried out to determine the
sensitivity of crosstalk to various material and device parameters such as epitaxial layer thickness (7 to 25 μm), illumination
wavelength (1.047 to 11.0 μm), minority carrier diffusion length (8 to 90 μm), and diode pitch. It is found that the dominant
feature influencing the value of crosstalk is the distance between the region of photogeneration and the collecting p-n junction. 相似文献
3.
Self-mixing interference (SMI) technique can be used for measuring vibration, displacement, velocity and absolute distance. In this paper, a simple demodulation algorithm for fast measuring frequency and amplitude of a simple harmonic vibration target is proposed based on the basic theoretical model of self-mixing interference effects. The simulative results show that the error between the vibration parameters which are demodulated by this algorithm and initial settings merely results from the sample rate. Further, the experimental system of self-mixing vibration measurement is built. The experimental results have a good agreement with simulation analyses. The maximum error of frequency demodulation is less than 1 Hz in our experiment. 相似文献
4.
《液晶与显示》1994,(4)
The frequency shift in the-optieal-field-induced Freedericksz matisition in a nematic Iiquid crystal film is in-
vestigated theoretically and experirnentally. We obtain the temporal evolution of the frequency shift, and find
that the maximum frequency shift is proportional to the square of the light beam intensity. The experimental results are in agreement with the theoretical prediction. 相似文献
5.
A simple experiment for laser diffraction of capillary waves on liquid film surface (LFS) is realized. Steady and visible diffraction patterns are obtained. The dispersion relation of capillary waves on LFS is verified by laser diffraction. In particular, both the relation between the wave number and the film thickness at a fixed angular frequency and the relation between the angular frequency and the wave number at a fixed film thickness are investigated. The theoretical and experimental results are in good agreement. 相似文献
6.
WUCai-zhang MAOXiao-bo XUZhen-fang YE Hu-nian 《光电子快报》2007,3(4):289-293
A theoretical model is proposed in order to study the configuration resonance in s-SNOM. The electromagnetic coupling between the sample and the probe tip is described with the quasi-electrostatic field theory. This method permits us to analyze the configurational resonance evoked by the interaction between the probe tip and the sample in s-SNOM intuitively. The resonant conditions for a certain system are presented in an explicit form. On the condition of considering the actual size of the sample dipoles and the probe dipole, we discuss the possibility of realizing the configurational resonance for various material samples. The numerical results indicate that the polarizability of the dielectric probe tip is too small to arouse this resonance, whereas, with the surface plasmon resonance emerging on the metallic nanoparticles, the enhanced polarizability of the metallic probe tip ensures the requirements of fulfilling the resonance. 相似文献
7.
The single photonic quantum well (PQW) structures are successfully fabricated on p-type silicon wafer by electrochemical etching process, and are used for DNA detection firstly. The red shift of resonance peak is caused by the changing refractive index of PSi layer, which results from coupling of organic molecules into pores. When the porous silicon (PSi) based single PQW biosensors are immersed in complementary deoxyribonucleic acid (DNA) with different concentrations ranging from 0.625 μM to 10.000 μM, a good linear relationship is observed between the red shift of resonance peak and the complementary DNA concentration. Experimental results show that the detection sensitivity of PSi-based single PQW biosensors is 3.04 nm/μM with a detection limit of 32 nM for 16-base pair DNA oligonucleotides. 相似文献
8.
Correlation between dark current RTS noise and defects for AIGalnP multiple-quantum-well laser diode
The correlation model between dark current RTS noise and defects for A1GalnP multiple-quantum-well laser diode is derived. Experimental results show that dark current RTS noise caused carrier number fluctuations at the interface of the heterojunction in the active region. According to this correlation model, the defect types are determined, and the defects' energy levels are quantitatively determined. The comer frequency of RTS noise power spectral density is analyzed. The experimental results are in good agreement with the theoretical. This result provided an effective method for estimating the deep-level traps in the active region of A1GaInP multiple quantum well laser diode. 相似文献
9.
冯孔豫 《电子科学学刊(英文版)》1984,(3)
The ideal aperture current distribution of SAR antenna is discussed in theoretical sense.Onthe basis of the results derived by R.C.Heimiller and R.W.Bayma,the effects of current distributionwhich is out of phase on the synthetic array pattern and the Doppler-delay response are furtheranalysed and numerical results calculated for the case of quadratic and cubic phase distributions aregiven.These results show that such phase distributions will cause a drop in gain of the syntheticarray and in signal to ambiguity ratio of the Doppler-delay response.In consideration of these effects,the author proposes his additional remarks on the range of repetition frequency given by R.W.Bayma(1975). 相似文献
10.
This paper reports the experimental results of silica on a silicon ring resonator in a resonator micro optic gyroscope based on the frequency modulation spectroscopy technique by our research group. The ring resonator is composed of a 4 cm diameter silica waveguide. By testing at D1550 nm, the FSR, FWHM and the depth of resonance are 3122 MHz, 103.07 MHz and 0.8 respectively. By using a polarization controller, the resonance curve under the TM mode can be inhibited. The depth of resonance increased from 0.8 to 0.8913, namely the finesse increase from 30.33 to 33.05. In the experiments, there is an acoustic-optical frequency shifter(AOFS) in each light loop. We lock the lasing frequency at the resonance frequency of the silica waveguide ring resonator for the counterclockwise lightwave; the frequency difference between the driving frequencies of the two AOFS is equivalent to the Sagnac frequency difference caused by gyro rotation. Thus, the gyro output is observed. The slope of the linear fit is about 0.330 m V/(°/s) based on the 900 to 900 k Hz equivalent frequency and the gyro dynamic range is˙2.0 103rad/s. 相似文献
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12.
该文针对非理想条件下换能器阵列指向性设计问题,建立了理论计算模型,并对呈正态分布和泊松分布的阵元振速及相位对换能器阵列三维指向性的影响规律进行了研究,通过仿真分析发现:非理想条件下换能器阵元性能的不一致性对阵列指向性的影响主要体现在指向性角和指向性三维对称分布两个方面,频率越低,影响越大;不同分布规律的阵元振速及相位对换能器阵列指向性的影响有差异,即其离散度越大影响越显著。该文提出的这种非理想条件下换能器阵列指向性的评估与分析方法可应用于指导换能器阵列指向性设计及大批量生产时换能器阵列指向性参数控制中,兼具理论指导意义与实际工程应用价值。 相似文献
13.
根据理论分析的结果,设计了中心频率为35 GHz的微带方形缝隙直线天线阵列与圆环天线阵列。通过计算机仿真技术(Computer Simulation Technology,CST)微波工作室仿真可知,直线阵列的方向性系数达到17.32 dBi,当电压驻波比(Voltage Standing Wave Ratio,VSWR)小于2时带宽为4.371 GHz;圆环阵列的方向性达到10.1 dBi,带宽为5.07 GHz(VSWR<2)。因此其符合相控阵雷达的要求。 相似文献
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15.
Cherrette A.R. Acosta R.J. Lam P.T. Lee S.-W. 《Antennas and Propagation, IEEE Transactions on》1989,37(8):966-978
Various aspects of reflector surface distortion compensation are explored by first assuming the reflector distortion is given and then designing the compensating feed array. The sensitivity of boresight directivity to changing surface distortion parameters for fixed feed-array geometries is examined. It is found that feed array compensation is feasible only for distortions with low spatial frequency content, such as those distortions induced by thermal and gravitational effects. The optimum directivity methods for determining element excitation is found to yield slightly better values of directivity than those for the conjugate field matching (CMF) technique. However, the CFM technique has, in general, much lower sidelobe levels and lends itself to simple realization in hardware. In view of these results, distortion compensation using an array feed is concluded to be a reasonable approach to improving antenna performance for large, space-based reflector antennas that are not easily accessible for tuning and have time-dependent surface distortions 相似文献
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17.
通过对微型声频定向换能器阵列的指向性参量研究,设计并制造了基于微机电系统(MEMS)的锆钛酸铅(PZT)薄膜换能器阵列,为声频定向扬声器的发声部件微型化提供了一种可行的实现方法.从理论上分析了阵元半径、阵元个数和阵元中心间距等结构参数对指向性的影响,确定各阵元正方形排列可获得预期的圆柱形声音传播空间,阵元数量越多,声波指向性越强,并指出当阵元间距约为波长的1/2时,旁瓣抑制效果量明显.最后对微型MEMS换能器阵列实物做指向性测试,实验结果与理论分析结果基本一致. 相似文献
18.
The influence of a rigid spherical baffle on the response of a uniform circular microphone array (UCA) is analyzed and two eigen-beam beamforming arrays are designed in the eigen-beam subspace derived from the soundfield decomposition. Expressions of white noise gain (WNG) and directivity index (DI) are derived for the designed arrays. Performance analyses are carried out for the designed arrays and compared between those of the delay-and-sum beamforming array using UCA with and without a rigid sphere. Computer simulations demonstrate that the designed arrays have frequency-independent directivity with the cost of reduced robustness at low frequency band. The delay-and-sum beamforming array has constant WNG at all frequencies, while its directivity of which is reduced at low frequency band. The rigid sphere can improve the robustness for all the arrays. 相似文献
19.
The purpose of this study is to obtain the optimum design of a three-row Yagi array antenna under constraints on bandwidth, directivity, or the length of the array. It is shown that the array configuration is determined if any two of these contraints are specified. It is also shown that a properly designed coupled Yagi array can be operated at certain frequency band with higher directivity and wider frequency bandwidth than those of a single-row Yagi array. 相似文献