室温光荧光谱分析中的几个典型问题

根据光荧光谱的测试原理,针对具体的化合物半导体材料的层次结构,归纳、总结出两个实用的分析模型:光荧光谱的厚度干涉模型和透明衬底发光模型。应用厚度干涉模型,对GaN外延材料、带DBR结构的MQW材料的光荧光谱曲线进行了分析,并解释了AlGaInP LED结构PL扫描图的强度分布。应用透明衬底发光模型,分析并解释了InGaAs材料的发光强度图案。实验结果表明,这两个分析模型能很好地解释薄膜外延层的PL光谱曲线,能够分析光荧光谱的曲线形状和强度分布与材料结构及表面状态的关系,对判断材料品质有较大帮助,具有一定的实用价值。     

高机动雷达机电主控箱电磁兼容研究

结合科研实践,介绍了高机动雷达机电系统电磁干扰的主要特征和危害,以及通过对机电主控箱进行电磁屏蔽的改善设计,从而保证机电系统各项测试指标满足电磁兼容性的要求,达到消除外部电磁干扰对机电系统可靠性的影响。文中提出了解决电磁兼容问题应该以预防为主的观点,同时提出了电磁兼容性是一项系统工程,应在装备研制、生产、使用和维护的各阶段都要予以充分的重视。     

Micro Fabry Perot light modulator for flat panel display

A new type of Fabry Perot light modulator for displays based on micro-electro-mechanical system technology is proposed. Multiple beam interference theory is used to design the modulator and analyze its characteristics. If Fabry Perot cavity length is one-quarter of the incident wavelength, the transmitted light is blocked by the modulator, and the modulator, which is illuminated from its backside, appears black. If the Fabry Perot cavity length is 0 or one-half of the incident wavelength, light may transmit the Fabry Perot modulator from its backside, and the modulator appears bright. Hence, the modulator may be used for flat panel displays. In this paper one Fabry Perot light modulator based on surface microma-chining technology is introduced. The designed modulator has a contrast ratio of 150 and can theoretically be driven by a voltage of 2.4 V.     

Nonequilibrium Operation of Arsenic Diffused Long-Wavelength Infrared HgCdTe Photodiodes

We demonstrated a device with a unique planar architecture using a novel approach for obtaining low arsenic doping concentrations in long-wavelength (LW) HgCdTe on CdZnTe substrates. HgCdTe materials were grown by molecular beam epitaxy (MBE). We fabricated a p-on-n structure that we term P ⁺/π/N ⁺ where the symbol “π” is to indicate a drastically reduced extrinsic p-type carrier concentration (on the order of mid 10¹⁵ cm⁻³); P ⁺ and N ⁺ denote a higher doping density, as well as a higher energy gap, than the photosensitive base π-region. Fabricated devices indicated that Auger suppression is seen in the P ⁺/π/N ⁺ architecture at temperatures above 130 K and we obtained a saturation current on the order of 3 mA on 250-μm-diameter devices at 300 K with Auger suppression. Data shows that about a 50% reduction in dark current is achieved at 300 K due to Auger suppression. The onset of Auger suppression voltage is 450 mV at 300 K and 100 mV at 130 K. Results indicate that a reduction of the series resistance could reduce this further. A principal challenge was to obtain low p-type doping levels in the π-region. This issue was overcome using a novel deep diffusion process, thereby demonstrating successfully low-doped p-type HgCdTe in MBE-grown material. Near-classical spectral responses were obtained at 250 K and at 100 K with cut-off wavelengths of 7.4 μm and 10.4 μm, respectively. At 100 K, the measured non-antireflection-coated quantum efficiency was 0.57 at 0.1 V under backside illumination. Received November 7, 2007; accepted March 19, 2008     

Modeling of LWIR HgCdTe Auger-Suppressed Infrared Photodiodes under Nonequilibrium Operation

The general approach and effects of nonequilibrium operation of Auger-suppressed HgCdTe infrared photodiodes are well understood. However, the complex relationships of carrier generation and dependencies on nonuniform carrier profiles in the device prevent the development of simplistic analytical device models with acceptable accuracy. In this work, finite element methods are used to obtain self-consistent steady-state solutions of Poisson’s equation and the carrier continuity equations. Experimental current–voltage characteristics between 120 K and 300 K of HgCdTe Auger-suppressed photodiodes with cutoff wavelength of λ _c = 10 μm at 120 K are fitted using our numerical model. Based on this fitting, we study the lifetime in the absorber region, extract the current mechanisms limiting the dark current in these photodiodes, and discuss design and fabrication considerations in order to optimize future HgCdTe Auger-suppressed photodiodes.     

机动式指挥系统无线设备间谐波干扰量分析

机动式指挥系统电磁兼容设计中,谐波干扰是最为严重且较难抑制的一个问题。本文首先探讨了无线设备间耦合干扰现象,建立了设备间耦合干扰的分析模型,并采用矩量法结合微波网络的方法求出模型中重要参数天线间耦合度,然后采用标准测试的方法求得设备间谐波干扰量。经过仿真数据与实测数据的对比,证实该方法理论正确,计算精度较高,对机动式指挥系统电磁兼容设计有较强的指导意义。     

汽车电磁兼容标准与测试

主要介绍了汽车电磁兼容的定义、汽车电磁兼容标准化组织、欧洲汽车EMC指令和法规,并从发射和抗扰度两个方面,分别对整车和零部件的测试标准和测试方法作了介绍。     

话务承载能力评估比较算法应用与拓展

在相关文献对蜂窝无线网络话务承载能力比较评估算法,以及基于测量统计的小区区权重向量算法、统计时分话务峰值算法等无线网络频率分配优化算法研究的基础上,对应不同干扰矩阵优化算法方案,给出了计算无线网络话务承载能力增益中测量统计干扰概率总量的具体算法过程。同时,为了对蜂窝无线网络的实时性能进行更有效、更准确的监测,作为算法理论的提升,对蜂窝无线网络话务承载能力比较评估算法进行了连续性拓展。     

基于FRESH算法的宽带干扰抑制技术

基于周期维纳滤波理论的LCL-FRESH(Linear-Conjugate-Linear-FREquency-SHift)滤波器,利用了信号在频域的谱相关性,分离时域交叠信号,可有效地抑制直接序列扩频系统当中的宽带干扰。该滤波算法的效果不会随干扰增强而下降,同时还能利用干扰的谱相关性进一步提高滤波的性能。此外,仿真结果也进一步表明,在干扰与信号有载波偏移的情况下滤波性能更好。     

QPSK非平衡性调制技术

正交相移键控(QPSK)调制技术已经在工程中得到了广泛应用,然而随着电子对抗技术的发展,QPSK的非平衡调制技术水平也得到了相应的提高,以专门针对通信或定位中的QPSK调制进行干扰.介绍一种实用的QPSK非平衡性调制技术及其系统构成,并对单片DDS调制芯片进行分析,对系统配置及软件开发的主要步骤分别说明.采用该技术可以有效解决干扰信号形成,并且与计算机接口兼容性好,可靠性高,具有较强的工程实用性.