基于ARM的机载火控雷达元器件自动化检测技术研究

为解决传统技术针对机载火控雷达元器件检测吞吐率低的问题,设计基于ARM的机载火控雷达元器件自动化检测技术。确定机载火控雷达元器件自动化检测特征,基于ARM响应曲线拟合机载火控雷达元器件检测数据,表达其自动化检测特征属性值,以此实现机载火控雷达元器件自动化检测。设计实例分析,结果表明,设计检测技术检测吞吐率均在3reqs/s以上,对比传统手段具有明显的优势,能够解决传统检测技术检测吞吐率低的问题。     

MANET接入技术研究

以移动AdHoc网络(MobileAdHocNetworks)的接入技术为研究对象,介绍了该网络的特点及其采用的各种接入技术,并以双忙音多址(DBTMA)和RTS/CTS两种接入技术为例,比较了它们对网络性能的影响,最后是对MANET接入技术的总结。     

An Algorithm to Detect the Presence of 3D Target Motion from ISAR Data

We present an algorithm to detect the presence of 3D target motion from ISAR data. Based on the 3D point scatterer model, we first examine the effect of 3D motion on ISAR imaging. It is shown that existing motion compensation algorithms cannot properly focus targets exhibiting 3D motion during the imaging interval. An algorithm is then derived to blindly detect the degree of 3D target motion from raw radar data. It is based on measuring the linearity of phases between two or more point scatterers on the target. The phase estimation is implemented using the adaptive joint time-frequency technique. Examples are provided to demonstrate the effectiveness of the 3D motion detection algorithm with both simulation and real ISAR data. The detection results are corroborated with the truth motion data from on-board motion sensors and correlated with the resulting ISAR images.     

Far-infrared detector based on HgTe/HgCdTe superlattices

HgTe/Hg_0.05Cd_0.95Te superlattices (SLs) were grown on (112)B oriented Cd_0.96Zn_0.04 Te substrates using molecular beam epitaxy (MBE). The SLs, consisting of 100 periods of 80-Å-thick HgTe wells alternating with 77-Å-thick Hg_0.05Cd_0.95Te barriers, were designed to operate as detectors in the far-infrared (FIR) region. Infrared absorption spectroscopy, high-resolution transmission electron microscopy (TEM), Hall effect measurements, and x-ray diffraction were used to characterize the superlattice layers. A series of annealing experiments were initiated to quantify the temperature-dependent interdiffusion of the HgTe wells and Hg_0.05Cd_0.95Te barriers and consequently their degradation, which shifts the absorption edges of the SLs to higher energies, since a high-temperature ex situ anneal is normally required in order to produce the p-type material required for a photovoltaic detector. Results from infrared absorption spectroscopy, TEM, and Hall effect measurements for the annealed samples are presented. A FIR SLs single-element photoconductive (PC) device was designed and fabricated. Both material characterization and device testing have established the applicability of the HgTe/Hg_0.05Cd_0.95Te SLs for the FIR region.     

Efficient silicon light-emitting diode with temperature-stable spectral characteristics

The influence of temperature on the parameters of the band-to-band emission spectrum of a light-emitting diode based on single-crystal silicon was investigated; the unprecedentedly high stability against variations in temperature was observed for both the electroluminescence intensity at the peak of the spectral distribution (I _EL ^m ) and the wavelength corresponding to this peak (λ_m). The internal quantum efficiency of the light-emitting diode at room temperature is estimated as no lower than 0.1%. The value of I _EL ^m varies by no more than ～10% as the temperature is varied from 120 to 300 K. The value of λ_m remains virtually constant in the temperature range of 200–300 K. The unprecedentedly high stability of λ_m is related to interference effects in the oxide film through which the radiation of the light-emitting exits. It is shown that one of the important factors that govern the temperature stability of I _EL ^m is a decrease in the lifetime of the minority charge carriers with decreasing temperature.     

An efficient algorithm for electromagnetic scattering from rough surfaces using a single integral equation and multilevel sparse-matrix canonical-grid method

An efficient algorithm for wave scattering from two-dimensional lossy rough surfaces is proposed. It entails the use of a single magnetic field integral equation (SMFIE) in conjunction with a multilevel sparse-matrix canonical-grid (MSMCG) method. The Rao-Wilton-Glisson (RWG) triangular discretization is adopted to better model the rough surface than the pulse basis functions used in the well-established SMCG method. Using the SMFIE formulation, only one unknown per interior edge of the triangular mesh approximating the rough surface is required, and the iterative solution to the moment equation converges more rapidly than that of the conventional coupled equations for dielectric rough surfaces. The MSMCG method extends the applicability of the SMCG method to rougher surfaces. Parallel implementation of the proposed method enables us to model dielectric surfaces up to a few thousand square wavelengths. Simulation results are presented as bistatic scattering coefficients for Gaussian randomly rough surfaces.     

Orthogonal space-time block codes: maximum likelihood detection for unknown channels and unstructured interferences

Space-time coding (STC) schemes for communication systems employing multiple transmit and receive antennas have been attracting increased attention. The so-called orthogonal space-time block codes (OSTBCs) have been of particular interest due to their good performance and low decoding complexity. In this paper, we take a systematic maximum-likelihood (ML) approach to the decoding of OSTBC for unknown propagation channels and unknown noise and interference conditions. We derive a low-complexity ML decoding algorithm based on cyclic minimization and assisted by a minimum amount of training data. Furthermore, we discuss the design of optimal training sequences and optimal information transfer to an outer decoder. Numerical examples demonstrate the performance of our algorithm.     

A single-V/sub t/ low-leakage gated-ground cache for deep submicron

In this paper, we propose a novel integrated circuit and architectural level technique to reduce leakage power consumption in high-performance cache memories using single V/sub t/ (transistor threshold voltage) process. We utilize the concept of gated-ground (nMOS transistor inserted between ground line and SRAM cell) to achieve a reduction in leakage energy without significantly affecting performance. Experimental results on gated-ground caches show that data is retained (DRG-Cache) even if the memory is put in the standby mode of operation. Data is restored when the gated-ground transistor is turned on. Turning off the gated-ground transistor in turn gives a large reduction in leakage power. This technique requires no extra circuitry; the row decoder itself can be used to control the gated-ground transistor. The technique is applicable to data and instruction caches as well as different levels of cache hierarchy, such as the L1, L2, or L3 caches. We fabricated a test chip in TSMC 0.25-/spl mu/m technology to show the data retention capability and the cell stability of the DRG-Cache. Our simulation results on 100-nm and 70-nm processes (Berkeley Predictive Technology Model) show 16.5% and 27% reduction in consumed energy in L1 cache and 50% and 47% reduction in L2 cache, respectively, with less than 5% impact on execution time and within 4% increase in area overhead.     

基于汉语分词的信息抽取技术

随着信息时代的到来，如何将大量无序的信息及时准确地提取、整理、组织成便于查询检索的形式，巳成为研究开发的焦点。尤其是随着互联网技术的高速发展，为用户提供了更加丰富的信息。将基于汉语自动分词的综合信息抽取技术应用于信息检索，具有实际应用意义和价值。