时域天线阵列半功率波束宽度计算

对于冲击雷达系统中的时域天线阵列,提出点源近似模型,用来计算时域超宽带天线阵列辐射瞬态电磁脉冲的场方向图以及辐射波束的半功率波束宽度。采用点源近似模型计算的半功率波束宽度和CST仿真结果一致,并和实验测试结果吻合得很好。实验表明,阵列辐射瞬态电磁脉冲具有波束聚焦特性,点源近似模型可以作为一种简便的方法,对时域天线阵列的参数进行分析。     

瞬态电磁脉冲能量传输特性的物理实质

根据矢量位方程,在均匀电流模型下,分别给出了圆形和方形单元天线轴线上电磁场分量的时域表达式以及能量密度的解析计算公式;用等腰梯形电脉冲给天线馈电,采用数值计算的方法分别绘出了圆形和方形天线轴线能量密度随距离的衰减曲线,瞬态电磁脉冲能量传输呈现三段式传输规律和慢衰减特性;通过对能量密度解析计算公式物理意义的讨论,给出了瞬态电磁脉冲慢衰减传输特性的物理实质解释;采用亚纳秒电子源给抛物面天线馈电,对抛物面天线轴线辐射电磁脉冲波形及能量作实验测试,实验测试结果与数值计算结果相符合。     

瞬态阵列电磁脉冲同相合成特性研究

根据电磁理论和光栅方程给出线源天线能量辐射的解析公式,得到波的矢量积分的最大值与阵元数目的平方成正比。并在不同实验条件下测试天线阵列在轴向的电场强度和能量密度,在实验误差范围内可以得出,电场强度与天线单元数成正比,能量密度与天线单元数的平方成正比。这说明瞬态阵列电磁脉冲可以很好的实现同相合成。     

三点源诱骗抗反辐射导弹合成场计算与仿真

为了解决反辐射导弹在三点源诱骗及多点源诱骗情况下被动雷达导引头处合成场的计算,分析了多点源诱骗系统抗反辐射导弹的条件,对三点源诱骗抗反辐射导弹合成场强和相位进行了推导计算,最后采用Matlab对导弹实时飞行过程中导引头处的合成场的幅度和相位进行了仿真分析,仿真结果验证了模型的有效性。     

太赫兹光导天线阵列功率空间合成规律研究

采用天线瞬态辐射理论和数值仿真方法,分别研究了阵元个数、阵元间距、激励延迟等物理参量对光导天线阵列功率空间合成效率的影响。通过深入分析和对比文献报道的实验数据,发现在不考虑非线性饱和效应和电磁屏蔽的条件下,对于轴向排列的偶极子光导阵列,导致功率合成效率不高的重要原因主要源自:偶极子的方向性辐射、电磁能量空间耗散和非同步光激励。     

瞬态阵列电磁脉冲同相合成特性研究

根据电磁理论和光栅方程给出线源天线轴线能量的解析公式,得到波的矢量积分的最大值与阵元数目的平方成正比.并在不同实验条件下测试天线阵列在轴线方向的电场强度和能量密度,在实验误差范围内可以得出:电场强度与天线单元数成正比,能量密度与天线单元数的平方成正比.这说明瞬态阵列电磁脉冲可以很好地实现同相合成.     

碳纳米管阵列辐射的实验研究

为了对碳纳米管阵列的辐射特性进行实验研究,通过采用在微带天线上加载碳纳米管阵列的方法对碳纳米管阵列进行馈电,并比较了两种微带天线加载碳纳米管阵列辐射方向图的变化,结果发现加载前后天线的S11以及辐射方向图均有明显变化,说明碳纳米管阵列能够显著改变天线的辐射特性,与理论预测相符。最后针对实验现象做了一些定性的解释。     

双指数源激励下垂直电偶极子产生的极低频近场

针对雷电过程在地面产生的近区极低频电磁脉冲,推导出了双指数模型激励下垂直电偶极子产生的极低频电磁场的瞬态近似表达式.该方案基于Sommerfeld积分在准静态近似下求解,从频域出发,利用单位脉冲响应的近似结果与双指数模型激励源卷积计算的方法,通过傅里叶逆变换,得到了双指数源激励下的瞬态解析表达式,其可用于模拟雷电信号产...     

稀疏阵列相干信号功率合成栅基仿真技术

稀疏阵列相干信号功率合成栅基仿真技术包括阵列功率合成数学建模、栅格尺度原则选定及计算机仿真实验设计实现等。文中从多点源稀疏阵列交汇区域相干信号的功率合成原理出发,建立其数学模型,设计了栅基实验流程,并对实验中重要参数栅格尺度的选定原则进行了推算分析,为利用计算机无失真地复现多点源功率合成能量分布规律打下了理论基础。     

激波辐射对红外成像探测影响的抑制方法研究

带有红外成像系统的大气层内高速飞行器的头罩窗口外激波的热辐射将降低系统的探测性能。采用单线组模型描述激波的辐射特性。由于激波辐射相对成像系统是近场辐射,建立相应的模型,计算了激波辐射在探测器阵列上产生的光子辐射照度,还计算了激波对目标辐射的吸收特性。得到了如下的计算结果:激波辐射在探测器阵列上产生的背景辐射可以近似为均匀的背景辐射;激波对目标辐射的吸收可以忽略;激波辐射具有强烈的光谱选择性。根据激波的这些辐射性质,在成像系统中通过分别选用不同的带通滤光片,不改变成像系统工作波段的波长宽度,而仅改变其位置,可以减小激波辐射对目标探测的影响,提高探测的信噪比。     

A transient array to increase the peak power delivered to a localized region in space .I. Theory and modeling

It is shown that an array of pulsed antennas (a transient array) can be used for providing a high concentration of electromagnetic energy into small regions. By controlling the timing of the pulses radiated from the individual elements, selected regions of space will see a coherent superposition of the radiated pulses forming "hot spots." The formation of "hot spots" is demonstrated by theoretical analysis. Using a highly damped sinusoid for the radiated pulse and dipole antenna elements, a contour plot of the peak electric field is determined for a linear array of six equally spaced sources. The impact of pulse-timing errors and the factors determining the size of the hot spot are also considered.     

Antenna patterns of nonsinusoidal waves with the time variation ofa Gaussian pulse

The development of antenna theory for nonsinusoidal electromagnetic waves has been based on the idealized rectangular pulse. In practice, an antenna that is designed to operate in the mode of an electric hertzian dipole would radiate a pulse that best approximates a Gaussian one when the driving current consists of a linear transient. The principle of radiation of nonsinusoidal electromagnetic waves with the time variation of Gaussian pulses is discussed. The properties of the Gaussian pulse are presented, i.e., the autocorrelation function, energy spectral density, and spectrum. Antenna patterns, such as peak-amplitude pattern, peak-power pattern, energy pattern, and slope pattern are derived for a Gaussian pulse received (or radiated) by a linear array antenna. Computer plots of the derived antenna patterns are presented that show a considerable improvement in the angular resolution capability over that of the antenna patterns that have been derived for a rectangular pulse     

线元天线阵列超短电脉冲传输特性实验研究

用脉冲电源产生亚纳秒高斯电脉冲给线元天线馈电,测试线元天线轴线能量的传输特性;实验结果表明:在相同轴线距离处,线元阵列天线轴线能量与单元天线轴线能量之比正比于天线阵列阵元数的平方;阵列天线轴线能量具有慢衰减传输特性;对线元阵列天线不同行、列作适当馈电延迟,可以实现辐射电磁波束的空间扫描.所有实验结果在误差范围内与理论计算结果符合.     

表面波放电狭缝天线辐射电磁场的三维数值分析

针对平板型表面波放电等离子体源,建立了表面波放电狭缝天线辐射电磁波模型,对狭缝天线辐射电磁场分布进行了三维数值计算,并与表面波电磁场进行对比分析,讨论了平板型表面波放电机理。结果表明:整个狭缝天线阵激发的电磁场是每个狭缝天线激发电磁场的线性叠加;狭缝天线阵直接激发的电磁场强度在临近波导壁面处很大,并且随着空间距离的增大迅速衰减;狭缝天线阵直接激发和表面波的电场均远大于各自的磁场,分析电、磁场对带电粒子的力作用时可以忽略磁场力的作用;表面波电磁场远大于狭缝天线阵直接辐射的电磁场,强电磁场范围也远大于狭缝天线阵直接激发的强电磁场范围,等离子体有增强电磁场强度、扩大强电磁场范围的作用。     

Excitation of a V-antenna by a pulse electromagnetic field

In order to measure short electromagnetic field pulses in EMC problems, transducers in the form of strip line segments are used. Such transducers reproduce undistorted pulses within the time interval equal to a double run of the signal along the line. However, the strip line has a low sensitivity. The V-antenna seems to be reasonable for recording weak signals, since it is more sensitive when compared to a strip antenna. The equations of V-antenna excitation by a pulse electromagnetic field are derived from Maxwell's equations considered in a space-time domain. The role of the magnetic field of the wave as a source of excitation has been clarified. The transient response of a V-antenna is calculated as a function of the material of a dielectric interlayer between the electrodes, the antenna opening angle and the electromagnetic wave incidence angle. Based on a nonsymmetric version of the V-antenna, transducers were fabricated and experimentally investigated. The results of calculations and measurements are in good agreement with each other. It is shown that one can obtain a transient response of an approximate step shape by adding signals from two oppositely directed antennas. The antenna proposed allows nanosecond low-amplitude electromagnetic pulses to be detected     

线元天线阵列波束扫描研究

由电磁场理论给出了平面线元天线阵列辐射的瞬态电磁脉冲沿径向坡印亭矢量时间积分的解析解及数值解结果,并利用物理光学理论对所得结果作了对比分析,得到结论:(1)线元天线阵列辐射问题可以简洁地由光栅方程求解;(2)被约束波束的坡印亭矢量时间积分的最大值与阵元数目的平方成正比;(3)保持同一列辐射器元馈电同步,而沿行方向依次作适当馈电时间延迟,可有效将波束控制在预期的很小角域内;(4)保持扫描的半角宽度,线元天线阵列有确定的波束扫描角范围。     

平面阵列天线轴线能量的慢衰减特性

根据电磁理论,给出了平面阵列天线在皮秒高斯脉冲激励条件下,轴线能量传播特性的解析计算公式和数值模拟结果。用实验直接验证了瞬态电磁波的慢衰减特性。在实验误差范围内,理论计算与实验结果符合较好。对布阵方式的初步实验表明,适当的稀疏布阵可提高传输效率。     

Free-space power combining and beam steering of ultra-widebandradiation using an array of laser-triggered antennas

A mode-locked laser is used to synchronize jitter-free ultrawideband (UWB) pulse generation at an array of UWB antenna elements. The jitter-free pulses radiated by each element add together in free space to produce a radiated field pattern that is steerable via optical true-time-delay techniques. The results from a three element array experiment are presented and used to develop a model for an N-element phased array. A transmission-line model is presented for a single array element, which includes the functions of energy storage, as well as UWB pulse generation and radiation