FGTO — A fine structured GTO-thyristor with improved switching characteristics

Contents A fine structured GTO thyristor, abbreviated FGTO, has been developed to improve the switching characteristics. The new device has a cathode finger width of only 20 m and can be turned off without a negative gate bias at an anode current level of more than 200 A/cm². The turn-off time can be shortened down tot _off 500 ns by increasing the negative gate current. A snubber circuit is not necessary to turn off the FGTO's. The maximum rate of rise of anode voltage du/dl reaches more than 10 kV/s. Analytical models are developed to describe the turn-off transients of the FGTO's. Good agreement between the theoretical and experimental results could be achieved.

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FGTO — Ein feinstrukturierter GTO-Thyristor mit verbessertem Schaltverhalten

Übersicht Zur Verbesserung des Schaltverhaltens ist ein feinstrukturierter GTO-Thyristor, abgekürzt FGTO, entwickelt worden. Dieses neue Bauelement hat eine Kathoden-streifenbreite von nur 20 m und kann ohne negative Gatevorspannung bei einer Anodenstromdichte von mehr als 200 A/cm² abgeschaltet werden. Die Abschaltzeit läßt sich durch Erhöhung des negativen Gatestroms bis zut _off 500 ns verkürzen. Beim Abschalten von FGTOs ist keine RC-Beschaltung erforderlich. Der maximale du/dl-Wert erreicht mehr als 10 kV/s. Zur Beschreibung des Abschalt-verhaltens von FGTOs werden analytische Modelle entwickelt, die eine gute Übereinstimmung mit den Meßergebnissen liefern.

     

分布式冷热电联产技术在新建三级医院中的应用

医院是重要的公共服务性场所,也是能源消耗的大户。有关资料表明,医院建筑能耗是一般建筑的1.6-2.2倍,其中电力消耗占了各项能源消耗总量中相当大的比例。作为上海郊区新建的三级医院,我院在设计之初就确定建设分布式冷热电联产系统,自2012年12月投入使用以来,此系统在降低能耗上优势明显,但也发现仍存在可以不断改进的地方。现就我院分布式冷热电联产技术的应用现状,就其概念、原理、特点、存在问题和解决措施作一介绍。     

Off-Grid DOA Estimation Via Real-Valued Sparse Bayesian Method in Compressed Sensing

A novel real-valued sparse Bayesian method for the off-grid direction-of-arrival (DOA) estimation is proposed in compressed sensing (CS). The off-grid model is reformulated by the second-order Taylor expansion to reduce modeling error caused by mismatch. To apply the Bayesian perspective in CS conveniently, complex data are addressed to yield a real-valued problem by utilizing a unitary transformation. By assuming that sources among snapshots are independent and share the same sparse prior, joint sparsity is exploited for DOA estimation. Specifically, a full posterior density function can be provided in the Bayesian framework. The convergence rate and convergence stability of the proposed method can be guaranteed in the iterative procedure. Simulation results show superior performance of the proposed method as compared with existing methods.     

Adaptive subspace detection of extended target in white Gaussian noise using sinc basis

For the high resolution radar (HRR), the problem of detecting the extended target is considered in this paper. Based on a single observation, a new two-step detection based on sparse representation (TSDSR) method is proposed to detect the extended target in the presence of Gaussian noise with unknown covariance. In the new method, the Sinc dictionary is introduced to sparsely represent the high resolution range profile (HRRP). Meanwhile, adaptive subspace pursuit (ASP) is presented to recover the HRRP embedded in the Gaussian noise and estimate the noise covariance matrix. Based on the Sinc dictionary and the estimated noise covariance matrix, one step subspace detector (OSSD) for the first-order Gaussian (FOG) model without secondary data is adopted to realise the extended target detection. Finally, the proposed TSDSR method is applied to raw HRR data. Experimental results demonstrate that HRRPs of different targets can be sparsely represented very well with the Sinc dictionary. Moreover, the new method can estimate the noise power with tiny errors and have a good detection performance.     

海洋雨团的全极化SAR回波信号仿真研究

在海洋的合成孔径雷达图像中,降雨（雨团）通常能引起依赖于雷达频率和极化的形状不规则的亮暗斑状图案,影响着合成孔径雷达图像的正确解译。基于C.Melsheimer的双极化仿真方法,首次对海洋雨团C、X波段全极化合成孔径雷达归一化雷达后向散射截面积进行仿真。仿真结果补充了双极化仿真的不足,更加全面地揭示了海洋雨团合成孔径雷达回波在不同波段不同极化下的特点,有助于合成孔径雷达图像的正确解译和降雨定量化研究。     

基于Metasys系统车间空调机组自动化

为了实现我厂空调系统节能降耗、方便管理、达到工艺要求、提高经济效益等目标,我们选用Johnson Controls(美国江森自控)之Metasys系统对厂区车间的空调进行自控设计。     

基于PTS方法降低OFDM系统的峰均功率比

OFDM最主要缺点之一就是时域的大峰均功率比。为了降低大峰均比,PTS是最常用的方法之一,但传统的PTS方法是对频域数据进行IFFT运算后选择最优传输序列,一般需要多个IFFT,OFDM系统复杂度高。为了解决多IFFT这一问题,本文提出了一种新方法,即在频域里判决最优序列,而大大减少IFFT块的数目。     

太阳能半导体空调制冷装置模块化实验研究

建立了以水为热交换媒介的太阳能热电模块制冷实验系统.系统配置了双位能量存储装置,用以储存昼夜温差能和太阳光电转换电能,以备无日照或日照不足时系统能够连续工作.热电制冷装置模块化,用以适应制冷功率变化较大的空间制冷,并在制冷启动与温度维持不同阶段实现较大功率的切入或撤出.制冷模块以半导体热电元件为核心,冷热端均以导热性能良好的紫铜作为热交换材料,以热容量较大的水作为冷却液和散热循环液.热交换装置采取集合散热冷却分流的集散一体化热交换系统.对制冷模块制冷性能进行了实验分析,并对制冷效果进行了模拟实验,实验结果基本达到了设计的预期.     

利用时间门测量信号频谱

本文通过对超外差式频谱分析仪时间门功能的介绍,介绍了如何使用频谱分析仪对时域不连续信号的频谱进行准确测量,并且结合实际例子,给出了测量过程。     

高机动目标对雷达检测的影响分析

针对无人飞机、导弹、卫星等高速目标机动飞行的特点,分析了目标飞行过程中相对雷达径向速度、径向加速度以及加加速度随时间的变换关系,并利用高次幂相位回波信号建立了信号模型,研究了高次相位对常规方法进行目标检测的影响,获得了最佳积累脉冲数与信噪比、加加速度的关系;最后,提出一种利用短时分数阶傅里叶变换(STFRFT)对三次相位信号进行分析和参数估计的方法,仿真表明该算法处理性能高于傅里叶变换,可为实际雷达检测高机动目标提供理论参考。