提高非相参雷达发射信号相干性的研究

接收相干算法为磁控管脉冲体制雷达实现动目标检测提供了依据。本文分析了几种相干接收处理算法,根据雷达系统结构和发射信号的特点,评述了各算法之间的适用性和优缺点,通过仿真分析研究各算法对MTI改善因子的限制。采用接收相干算法,可以实现准相参系统,其MTI性能不低于全相参雷达。     

一种收发分置雷达的幅相监测网络

介绍了一种收发分置雷达的幅相监测网络设计方法,分析了不同幅相监测方法的优缺点.结合收发分置雷达特点,提出了利用接收通道进行发射通道监测的方法.与传统方法相比,采用本方法减少了幅相监测网络设备量.对本方法进行了试验验证,结果表明,可有效的实现幅相监测和校正.     

一种超分辨OFDM雷达通信一体化设计方法

传统OFDM雷达通常不考虑传递通信信息,该文设计出一种新的基于OFDM的雷达发射方式以实现雷达和通信的一体化,并提出一种基于通信信息补偿的目标距离速度联合高分辨估计方法。所设计的雷达发射方式,采用脉冲发射,每个脉冲由多个OFDM符号构成,在脉冲内实现通信功能;在雷达相干处理时间内,对回波进行通信信息补偿和解相干处理后,采用子空间投影方法实现对目标距离和速度的联合超分辨估计。理论分析和仿真实验表明,所提方法能够在保证通信功能的条件下,可有效实现雷达目标距离和速度的联合超分辨估计。     

稀布阵综合脉冲孔径雷达系统标定与实测数据分析

稀布阵综合脉冲孔径雷达(SIAR)采用多路发射和多路接收天线系统,各个天线阵元不可避免地存在一定的幅相误差,需对系统进行标定。本文介绍了该雷达的一种标定方法,并通过实测数据验证了该方法的有效性。     

脉冲式磁控管雷达多普勒化的一种简单方法

1 引言 理想脉冲式多普勒雷达应用全相干发射和接收。在高功率多普勒雷达中,全相干发射和接收通常要在发射器中采用昂贵的调速管或TWT放大器。一忡较便宜的替代品是磁控管,但是磁控管存在着随机的起始相位,而且它的频率在发射脉冲信号间线性调频。为     

一种有效的MIMO雷达相干信源波达方向估计方法

提出了一种基于接收数据样本复用的MIMO雷达相干信源波达方向估计方法.算法利用MIMO雷达发射波形的分集以及MIMO雷达收、发阵列之间的对偶性,对MIMO雷达回波数据矩阵进行了样本复用以等效地增加样本数量,获得基于发射阵和基于接收阵的虚拟子阵接收信号.利用各个子阵之间的平移不变特性计算空间平滑之后的协方差矩阵,提高了相...     

微波稀布阵雷达发射阵列的幅相误差校正

建立了微波稀布阵综合脉冲孔径雷达发射阵列的幅相误差模型,研究了基于近场窄脉冲和基于远场直达波的2种幅相误差校正方法:前者通过近场天线接收不同频率窄脉冲并进行通道分离、频谱分析等处理后提取幅相误差;后者通过远场天线接收直达波并在去调频后再提取幅相误差。前者运算量较小适用于工程实现;而后者运算量较大,在接收站定位精度较高时这种方法可获得较高的估计精度。仿真结果表明2种方法均能较好地估计幅相误差。     

MIMO雷达理论和试验结果

摩尔定理的不断发展使得开发同时从多相位中心发射和接收多种编码波形并采用过去不可用的方法进行处理成为可能。来自这种MIMO雷达系统的可用于处理的信号表现为与发射和接收孔径相位中心卷积对应的空间样本。这种样本提供激励和测量由发射／接收传播路径、目标和伴随的散射和杂波组成的信道的能力。这些信号可以处理并组合形成自适应相干发射波束,或以单一次扫描高分辨率搜索扩展区域。接收数据的自适应组合提供对发射波形的自适应控制,空间扩展改善边跟踪边扫描的精度。本文介绍改进的监视雷达性能后面的理论,通过测量MIMO试验雷达进行说明。     

双基地MIMO雷达多目标定位及幅相误差估计

本文提出了一种存在幅相误差下的双基地MIMO雷达角度估计方法.利用三次迭代最小二乘算法估计存在幅相误差下的收、发阵列流形,根据信号子空间和噪声子空间的正交性,无需幅相误差的任何信息,采用MUSIC-like算法得到目标的DOD和DOA,且角度自动配对.针对MIMO雷达孔径扩展的特点,分别通过第一个发射阵元和第一个接收阵...     

基于参数转移的岸-舰双基地波超视距雷达发射阵幅相扰动估计

 岸-舰双基地波超视距雷达采用岸基阵列发射不同载频的信号进行几乎全向辐射,舰载单根天线接收,接收端利用综合脉冲孔径技术得到等效发射方向图.本文结合该雷达系统特点,利用接收到的直达波信号,提出基于参数转移的幅相扰动估计方法.该方法引入新的未知量,通过参数转移,将由接收站方位误差引起的相位扰动估计误差转移到新的未知量中.论文详细推导了基于参数转移的发射阵幅相扰动估计模型以及幅相扰动估计的克拉-美罗界.计算机仿真表明了所提方法的有效性.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

培养细胞中病毒共感染的形态学依据

本文综合报道根据电镜下病毒的形态学和形态发生学的特征,从134份普通感冒和2份SARS患者鼻腔分泌物或咽拭子分离病毒阳性或可疑阳性的体外细胞培养物中发现有9份是两种病毒的共感染。它们是：腺病毒与副粘病毒共感染2份;疱疹病毒与副粘病毒共感染2份;鼻病毒与冠状病毒共感染1份;鼻病毒与正粘病毒共感染1份;鼻病毒与副粘病毒共感染1份以及冠状病毒与呼肠病毒共感染2份。十分罕见的是,在两份冠状病毒的感染细胞内分别观察到与鼻病毒和呼肠病毒的共感染,在感染细胞内和/或细胞外两种病毒的成熟病毒粒子均较多,而且在细胞浆内相互紧密接触。提出,在病毒共感染的培养细胞内,病毒在复制和组装的过程中各自病毒的基因和毒力是否会发生变异均值得病毒学工作者深入研究。     

可重构双频段低噪声放大器的设计和实现

A reconfigurable dual-band LNA is presented. The LNA employs switching capacitors and circuit in to realize the dual-band operation. These methodologies are used to design and implement a reconfigurable LNA for IMT-A and UWB application. The LNA is implemented using TSMC-0.13 μm CMOS technology. Measured performance shows an input matching of better than -13.5 dB, a voltage gain of 18-22.8 dB, with an NF of 4.3-4.7 dB in the band of 3.4-3.6 GHz, and an input matching of better than -9.7 dB, a voltage gain of 14.7-22.4 dB, and with an NF of 3.7-4.9 dB in the band of 4.2-4.8 GHz. According to the measure results, the proposed LNA achieves dual-band operation, and it proves the feasibility of the proposed topology.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Fabrication of blazed gratings used in ultraviolet region by holographic ion beam etching based on photoresist melting

A novel technology to manufacture holographic ion beam etched diffraction gratings based on surface therrnokinematics is presented. The surface roughness of photoresist gratings is solved by this technology. According to this technology, a holographic ion beam etched blazed grating of 1200 l/mm for use in the ultraviolet region is manufactured. The experimental results show that the grating has good surface quality, low stray light and high diffraction efficiency. In addition, the performance of thes gratings satisfies the operating requirements of ultraviolet spectrograph.     

A Frequency Selective Silicon Vibration Sensor with Direct Electrostatic Stiffness Modulation

In the field of industrial machinery an increasing demand for low cost vibration measurement equipment exists. The described frequency selective structures represent a low-cost alternative to the commonly used wide band accelerometers. To continuously cover a wide frequency range with a small number of resonators the sensor structures possess a resonance frequency tuning capability. Electrostatic forces applied to the seismic mass lead to a softening of the system and thus a lowering of the resonance frequency. Experimental results gained from fabricated test structures demonstrate the suitability of the tuning principle for wide range resonance tuning and the obtained linearity of the sensor behaviour. By grouping eight cells with stepped base frequencies and overlapping tuning ranges into an array one decade from 1 to 10 kHz is continuously covered with tuning voltages below 40 V.     

我国有线电视产业的SWOT分析

在国外,有线电视生来就是商业化的,可是,长期以来我国有线电视被当作是公益性的服务.尽管我国有线电视拥有丰富的用户资源、带宽资源、频道资源以及内容资源,可是却未能得到充分发挥.未能产业化运营是其低效益运作的根本原因.在新的时代,有线电视的巨大市场价值将被得到认识.但同时,我国有线电视产业也面临着严峻的挑战.     

P-μc-Si1-xGex:H thin film by VHF-PECVD

In this paper,a series of boron doped microcrystalline hydrogenated silicon-germanium(p-μc-Si1-xGex:H)was deposited by very high frequency plasma-enhanced chemical vapor deposition(VHF-PECVD)from SiH4 and GeF4 mixtures.The effect of GeF4concentration on films'composition.structure and electrical properties was studied.The resuIts show tllat with the increase of GeF4 concentration,the Ge fraction x increases.The dark conductivity and crystalline volume fraction increase first,and then decrease.When the GC is 4%,p-μc-Si1-xGex:H matefiai with high conductivity,low activation energy(σ=1.68 S/cm,Eg=0.047 eV),high crystalline volume fraction (60%)and with an average transmission coefficient over the long wave region reaching 0.9 at the thickness of 72 am was achieved.The experimental results were discussed in detail.     

Complete approach to automatic identification and subpixel center location for ellipse feature

To meet the need of automatic image features extraction with high precision in visual inspection, a complete approach to automatic identification and sub-pixel center location for similar-ellipse feature is proposed. In the method, the feature area is identified automatically based on the edge attribute, and the sub-pixel center location is accomplished with the leastsquare algorithm. It shows that the method is valid, practical, and has high precision by experiment. Meanwhile this method can meet the need of instrumentation of visual inspection because of easy realization and without man-machine interaction.