脉冲/连续高功率激光光斑分布阵列探测器

通过测量发射到远场的激光功率密度时空分布给出所需要的到靶总功率、光束质量、桶中功率、功率时间曲线等关键指标参数,是目前准确评价激光系统性能的重要技术手段。介绍了一种基于光电探测器阵列实现近红外脉冲激光功率密度时空分布的测量方法,可以实现900~1700 nm波长、动态范围大于2000倍的激光光斑参数测量。该阵列探测器具有测量面积大、单元一致性好、测量精度高等特点,并可同时实现脉冲和连续激光参数测试要求。给出了阵列探测器的总功率测量结果,测量值与激光器输出功率偏差在5%以内,且激光光斑分布测量结果准确可靠。该阵列探测器已在多套激光系统的参数测试中得到成功应用,可以作为响应波段内的脉冲/连续激光光斑参数测试一种有效技术方案。     

基于脉冲形成网络的超宽带脉冲产生与设计

分析了超宽带天线对冲击脉冲波形的要求.利用阶跃恢复二极管和微带传输线.通过延迟的方法设计并制作了超宽带双极脉冲发生器.根据超宽带脉冲发生器产生的脉冲参数,通过理论分析和时域有限差分法(FDTD)仿真,给出了一种微带脉冲形成网络的设计方法,并利用该方法成功地产生了纳秒级宽度的双极性超宽带窄脉冲信号.测量结果表明:经过脉冲形成网络产生的信号具有良好的波形,且拖尾振荡小,有利于提高天线的辐射效率.     

实时宽带示波器在快沿脉冲测量中的应用

脉冲信号的广泛应用使得对其测量准确度提出更高要求,而脉冲信号上升沿变窄的趋势则增加了测量难度。为了更精确地测量脉冲信号并保证测量结果准确可靠,分析了高性能实时宽带示波器在带宽、采样率、底噪、电缆去嵌和匹配校准快沿脉冲等方面的优点,讨论了其用于脉冲信号测量和校准所具有的无可比拟的精准性,说明了其作为脉冲信号测量和脉冲参数计量具有无可替代的作用。最后通过一个实例介绍了对10 ps以内快沿脉冲进行测量和校准的方法。     

一种波形可控的脉冲声源研制

脉冲回波方法是近年来较为常用的现场吸声测量技术,根据不同的测量原理,需要声源辐射特定的脉冲声信号。研究了一种可控脉冲声生成技术,介绍了声源设计方案以及脉冲声工作生成的主要原理。通过实验测量,该声源能够辐射需要的波形和不同长度的脉冲声信号,可用于时域现场吸声测量技术中。     

远场的薄色散介质对超短脉冲的影响

时空耦合效应导致超短脉冲在远场频谱分布的复杂性。这种复杂性使放置于远场的薄色散介质对光脉冲同时产生时间展宽和波前弯曲等变化。同时给出了解析结果和数值计算实例。     

焦点刀口法测量巨脉冲激光的光束发散角

本文介绍了焦点刀口法测量光束发散角的原理,并且实际测出了BBO晶体腔内倍频的灯泵Cr:LiSAF巨脉冲激光器的输出光束的远场发散角。     

光纤脉冲分析仪的设计

针对光纤色散特性会引起传输信号的畸变,限制通信容量,指出对光纤色散参数、光信号在长距离传输后脉冲展宽程度的准确测量,可以提供可靠的设计数据来源,在实际的工程应用中有着重要意义.根据对色散基本理论的讨论,分析光脉冲在光纤中传播的展宽现象.自行研制了一套用于多模光纤色散测量的脉冲展宽测试设备,已应用在教学实验和工程实践中.     

雷达全脉冲的数字分析方法研究

提出了一种雷达全脉冲分析算法——极值序列分析法。该算法能够分析雷达脉冲的载频、脉冲幅度、脉冲宽度、信噪比、脉冲到达时间、脉冲包络特征参数和脉内调制参数。该算法的特点是：参数测量精度高;识别信号类型准确率高;算法速度快和所需存储空间小。     

脉冲真空电弧离子能量的测量研究

离子能量是影响脉冲真空电弧离子镀镀膜质量的一个重要参数,因而测量真空电弧中离子的能量非常重要.本文介绍了一种测量脉冲真空电弧离子能量的装置-五栅网,分析了其测量离子能量的原理,并用它测量了脉冲真空电弧的离子能量.     

超短脉冲的测量

本文分析了利用强度自相关和干涉自相关信息获取超短光脉冲形状和啁啾特性的方法及其缺陷。提出了一种直接测量超短光脉冲幅度谱和相位谱的原理和测量装置，并对锁模脉冲进行了测量，然后由逆傅里叶变换即可得到脉冲时域特性（脉冲形状和宽度），且由相位可得超短脉冲的各阶啁啾系数。     

Optimization of photomixers and antennas for continuous-wave terahertz emission

We have studied terahertz emission from interdigitated finger photomixers coupled to planar antenna structures. Using both pulsed and continuous-wave excitation, polarization measurements reveal that the antenna design dominates the properties of the radiated output at frequencies below 0.6 THz, while the efficiency at higher frequencies is additionally dependent on the design of the photomixer fingers. We have produced terahertz maps of the device, characterizing the photomixer by measuring the generated power as a function of the excitation position. Together, these measurements have allowed us to understand better the distinct roles of the photomixer and antenna in emission at different frequencies and, hence, independently optimize these components.     

Pattern measurements of reflector antennas in the compact range andvalidation with computer code simulation

The measurements were performed at the University's compact range facility. They demonstrated: (1) the excellent dynamic range that can be achieved with antenna pattern measurements in a compact range facility; and (2) the excellent validation achieved for the calculated patterns of two 8-ft diameter reflector antennas. The compact range has a rolled edge modification to its reflector and uses a pulsed radar system to eliminate the clutter interference such that a dynamic range of more than 80 dB can be obtained. The measured far field patterns of two 8-ft reflector antennas, a prime focus fed antenna and a Cassegrain antenna, at 11 GHz were compared with those calculated by Ohio State University's Reflector Antenna Code. The computer code simulation's approach is also briefly described     

Finite-volume time-domain analysis of a cavity-backed Archimedean spiral antenna

This paper presents a comprehensive analysis of a broadband (2-18 GHz) cavity-backed Archimedean spiral antenna. The simulation of the device is performed using the finite-volume time-domain method. The high geometrical flexibility of this method permits a detailed modeling of the antenna including the thin substrate, the feeding balun, and the cavity loaded with a honeycomb absorber. The simulated far-field radiation patterns and the return loss are compared to measurements, showing an excellent agreement over the whole frequency band. The radiation mechanism of the spiral is visualized by observing the current distribution on the spiral arms for both pulsed and harmonic excitation modes.     

Measurement of electromagnetic fields near a monopole antennaexcited by a pulse

To observe transient radiation fields, a technique for reconstructing electromagnetic (EM) waveforms using the complex antenna factor (CAF) have been developed. However, the CAF is originally defined assuming plane wave incidence, while the waveforms are measured in a vicinity of the radiating source. In order to examine the reconstruction technique using the CAF in the near-field measurements, the EM fields radiated from a monopole antenna excited by pulsed input voltage was reconstructed and compared with calculated results. For the geometry of the experiment, the waveforms of the reconstructed and calculated EM fields have shown good agreement. Therefore, the reconstruction technique using the CAF can be used for similar dimensions or at a greater distance when sufficient sensitivity is provided     

Phase Equalization Problems in a Phased-Array Transmitter

Current RADAR systems employing programmed multiple antenna feeds to orient the antenna beam electronically require large numbers of parallel channels operating simultaneously with nearly identical phase-delay characteristics. These channels include active devices such as microwave amplifiers for which phase-delay, as well as gain and power output, must be identical to accomplish high pointing accuracy and maximum power addition. When the system is required to operate over a wide frequency band, all channels must track in phase. This paper describes problems encountered in the development of a prototype transmitter requiring multiple channel phase-delay equality. A new medium power pulsed TWT is described and measurements of its electrical length are discussed. Computer programming which reduced the vast amount of phase information derived from this development is described.     

冲激脉冲探地雷达天线的实验研究

本文提出了背载式脉冲天线的设计方案,并以此制作了扇形臂和矩形臂天线。利用实地探测数据,将上述新方案与无反射式连续电阻加载正交偶极天线和双菱形天线进行比较,从而肯定了背载式设计方案的优越性。     

天线副瓣对机载脉冲多普勒雷达地杂波影响的分析

用计算机仿真和实验测试数据分析了天线副瓣对机载脉冲多普勒雷达地杂波的影响。分析结果表明天线远区副瓣对雷达地杂波的影响较大 ,因此在雷达系统设计中要设法减小天线远区副瓣     

Short-pulse characteristics of the conical spiral antenna

The short-pulse charactersitics of the conical spiral antenna are examined in detail. The antenna is anlyzed using a time-domain integral equation. Various peculiarities associated with the numerical solution procedure are discussed, including the effects of a highQ, low-frequency resonance and impedance loading of the antenna. Special attention is directed to the radiated-pulse properties of the antenna for different types of time-varying excitation. Also presented is a quantitative assessment of the antenna's fidelity under pulsed conditions and an approach for obtaining the desired radiated-pulse shape by tailoring the time variation of the applied antenna voltage.     

Antenna Effects in Depolarization Measurements

The depolarization of electromagnetic energy scattered from natural terrain has been of interest to experimenters and theoreticians for many years. However, the reported measurements have not agreed with theoreticaly predicted results. Boresight axial ratio has commonly been used as a figure of merit to describe the polarization isolation properties of the measurement system antennas. Since depolarization measurements from terrain involve extended targets which fill the full antenna beam, boresight axial ratio is often an inadequate measure of antenna polarization purity. This paper describes antenna isolation characteristics which impact the quality of the depolarized measurements. Representative calculations demonstrate the effects of nonideal antenna systems on the observed measurements. A criterion for antenna specification is given which will provide high-quality cross-polarized measurements.