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941.
This paper deals with direction of arrival (DOA) estimation and blind signal separation (BSS) based on independent component
analysis (ICA) with robust capabilities. An efficient demixing procedure of complex-valued ICA is presented here, which combines
the signal-subspace demixing procedure exploiting individual signal-subspace projection and Newton’s iteration algorithm based
on maximization of the approximate negentropy of non-Gaussian signal for array signal processing. It resolves the problems
of order ambiguity and identifiability of traditional ICA for time-domain BSS. The proposed method could be directly applied
to radar, sonar, radio surveillance, and communications systems for separating signals and estimating relative DOAs of signals.
Several computer simulation examples for perturbations to the array manifold, unknown noise environments, and Rayleigh fading
channel are provided to illustrate the effectiveness of the proposed method. 相似文献
942.
943.
Frank Amoroso William W. Jones 《International Journal of Satellite Communications and Networking》1991,9(2):99-110
A geometric propagation model is developed for simulating the reception of direct sequence pseudonoise (DSPN) satellite signals by a directional or omni antenna in the dense scatterer mobile environment. The model is first validated for narrowband signals by a direct comparison of both simulated cumulative signal strength statistics and simulated diffuse Doppler spectra with classical theory. The model is then used to predict fading statistics for DSPN signaling, either with omni or directional antennas. As expected, the mitigation of fading is closely related to the ratio of DSPN chip duration to delay spread of the scatterer medium for both the omni and directional antennas. 相似文献
944.
本文对短波测向天线场直击雷防护的几种方法进行分析,提出了一种使用提前放闪电避雷针进行天线场直击雷防护的简单实用方法。 相似文献
945.
A semiconductor laser diode stack is used for pumping and 8 semiconductor laser diode arrays of the stack are put on a sphere,and the output of every bar is specially off-axis compressed to realize high coupling efficiency.The output beam of this semiconductor laser diode stack is shaped by a hollow duct to the laser active medium.The efficiency of the hollow light pipe,which is used for semiconductor laser diode stack coupling,is analyzed by geometric optics and ray tracing.Geometric optics analysis diagnoses the reasons for coupling loss and guides the design of the structure.Ray tracing analyzes the relation between the structural parameters and the output characteristics of this pumping system,and guides parameter optimization.Simulation and analysis results show that putting the semiconductor laser diode arrays on a spherical surface can increase coupling efficiency, reduce the optimum duct length and improve the output energy field distribution. 相似文献
946.
M. Walther R. Rehm F. Fuchs J. Schmitz J. Fleißner W. Cabanski D. Eich M. Finck W. Rode J. Wendler R. Wollrab J. Ziegler 《Journal of Electronic Materials》2005,34(6):722-725
An infrared camera based on a 256×256 focal plane array (FPA) for the second atmospheric window (3–5 μm) has been realized
for the first time with InAs/GaSb short period superlattices (SLs). The SL detector structure with a broken gap type-II band
alignment was grown by molecular beam epitaxy on GaSb substrates. Effective bandgap and strain in the superlattice were adjusted
by varying the thickness of the InAs and GaSb layers and the controlled formation of InSb-like bonds at the interfaces. The
FPAs were processed in a full wafer process using optical lithography, chemical-assisted ion beam etching, and conventional
metallization technology. The FPAs were flip-chip bonded using indium solder bumps with a read-out integrated circuit and
mounted into an integrated detector cooler assembly. The FPAs with a cut-off wavelength of 5.4 μm exhibit quantum efficiencies
of 30% and detectivity values exceeding 1013 Jones at T=77 K. A noise equivalent temperature difference (NETD) of 11.1 mK was measured for an integration time of 5 ms
using f/2 optics. The NETD scales inversely proportional to the square root of the integration time between 5 ms and 1 ms,
revealing background limited performance. Excellent thermal images with low NETD values and a very good modulation transfer
function demonstrate the high potential of this material system for the fabrication of future thermal imaging systems. 相似文献
947.
In order to solve the problem that the high computational burden of the multiple signal classification algorithm of non-circular signal (NC-MUSIC) in direction-of-arrival (DOA) estimation,a novel computationally efficient DOA estimation algorithm based on subspace rotation technique was proposed.Firstly,the partitioning of noise subspace matrix and the subspace rotation technique (SRT) were used to construct a new reduced-dimension noise subspace.Then,the two-dimensional peak searching was converted to the one-dimensional peak searching on the basis of the separation of variables and the orthogonality between the new reduced-dimension noise subspace and the space spanned by the columns of the extended manifold matrix.The proposed algorithm can enhance the computational efficiency by means of the conversion of the two-dimensional peak searching into the one-dimensional peak searching and the removal of redundant computations.Theoretical analysis and simulation results show that the proposed algorithm can reduce the computational complexity to less than 5% as compared to NC-MUSIC algorithm on the premise of ensuring the accuracy of DOA estimation.Especially,the efficiency advantage of the proposed algorithm is more obvious in scenarios where the large numbers of sensors are required. 相似文献
948.
由于孔径效应和孔径渡越时间的限制,传统的相控阵雷达难以在大扫描角下实现大瞬时带宽,有机聚合物光波导延迟线可解决这一问题。先介绍了有机聚合物光波导延迟线的原理和优点,接着综述了三种延迟线:利用聚酰亚胺制成的4位有机聚合物光波导延迟线,多层结构的有机聚合物光波导延迟线,开关选择的超长有机聚合物光波导延迟线。 相似文献
949.
950.