柱面波激励的超宽带口径辐射特性的研究

如何高效而又较少畸变地将信号辐射出去是超宽带天线的设计关键，本文利用FDTD方法研究了柱面波激励不同形状、尺寸口径时口径的辐射特性，并用空时方向图表征口径在主辐射面的辐射波形与口径尺寸、形状以及激励脉冲的脉宽在自由空间展布的宽度之间的关系。通过与平面波正投射时口径的辐射特性进行比较，得出在上述两种激励脉冲激励口径的情况下不同形状和尺寸的口径的辐射特性的差异。     

毫米波空馈径向线缝隙阵列天线的优化设计北大核心CSCD

本文设计了一种毫米波空馈径向线缝隙阵列（RLSA）天线。首先采用空气波导取代介质波导以降低天线的馈电损耗，接着分析加载辐射缝隙对造成径向线波导的慢波传输效应，以及不同长度的缝隙对引起的不同辐射相位滞后，然后修正各辐射单元之间的径向距离，以使口径面上所有缝隙对单元能够等幅同相地辐射。这一修正避免了栅瓣的产生，在35GHz工作频率和直径为10个波长的圆口径上实现了53.3%的口径效率。之后，放松各单元等相位辐射的要求，进一步减小单元径向间距Sρ，优化口径效率。最终研制出左旋圆极化RLSA天线，峰值增益达到27.71dBic，口径效率为59.8%,3dB增益带宽为8.37%；实测增益为27.51dBic，轴比0.46dB。     

大型毫米波射电望远镜——主动表面反射器天线的分析

分析了不完善的分块式面板调整对大型毫米波望远镜的口径效率的影响。正在设计一种直径为50m、工作波长为1mm的且具有可控主面的设备。通过对该控制系统性能特性的仿真，生成了倾斜和柱塞形误差的一些标本，据此计算了天线的辐射方向图和口径效率。将这些结果与Ruze导出的天线公差理论的模型进行了比较，后者把口径效率与均方根相位误差联系起来。我们发现当采用口径rms相位误差而不是rms表面误差作参数时，Ruze公式具有不同的有效范围。当大型分块式天线中出现明显的倾斜误差时，口径的均方根相位误差趋于常数值，与口径照射和分块的形状无关。所得出的结论是天线均方根表面误差是一种口径效率指示器，比采用Ruze公式时的口径均方根相位误差要好一些。对大型分块式反射面天线，认为这个众所周知的表达式对大型分块式反射器天线性能限制较小。     

红外/射频共口径目标模拟器电场相位分析

为了在实验室内进行复合寻的制导系统的性能验证和评估,需要产生模拟射频/红外的复合信号,红外/射频共口径目标模拟器是产生该复合信号的一个关键部件.采用(MOM)和物理光学法(PO)相结合的方法具体分析了红外/射频共口径系统中辐射近场区和远场区电场强度相位分布情况,并对辐射近场区电场,强度相位进行了实际测试,两者取得了较好的吻合.在辐射近场区完成了通常情况下天线远场才能实现的目标模拟,大大缩短了测试距离.     

中波红外鱼眼镜头杂散辐射仿真分析

分析了中波红外镜头点源透过率与视场角之间的变化规律。在相同光学结构下,以相同的通光口径、焦距和光机结构,建立视场角20°、40°、60°、80°和110°的中波红外镜头杂散辐射模型,分析了模型的点源透过率曲线。随着视场角增大,红外镜头的点源透过率曲线趋于平缓,对视场外杂散辐射的抑制能力下降。降温能减少镜头自身的杂散辐射,在小视场角情况下可以改变点源透过率曲线的形状,但随着视场角增加,降温对点源透过率曲线的影响逐渐减小。视场角增大是影响红外镜头杂散辐射强度和分布的显著因素,降温对红外鱼眼镜头点源透过率曲线的影响不明显。     

口径辐射场的时域分析

鉴于瞬态民磁脉冲辐射研究的重要性，天线的时域辐射特性是当前备受关注的重要问题，然而口径辐射场的完整时域解尚未有报道。本文采用时域法利用场等效原理分析电磁脉冲辐射场，得到时域中口径辐射场的解析解，得出的公式对近场，远场都适用。     

大口径空间滤波调制红外光谱仪定标方法

红外辐射特性是对弱小目标进行探测与识别的重要依据,进行过辐射定标的大口径观测设备适用于弱小目标红外辐射特性的获取。大口径空间滤波调制红外光谱仪就是用于观测弱小目标的设备之一。文中讨论了一种适合应用于大口径空间滤波调制红外光谱测量系统的辐射定标方法,该方法由腔黑体加平行光管这种组合提供红外全谱段的标准辐射,计算了待定标光谱仪测量系统口面处各通道的辐射照度,用于红外短中长波的标校。用最小二乘法拟合得到光谱仪响应DN 值与辐射照度之间的定标曲线,并给出了实际定标结果。最后分析了辐射定标不确定度的来源及合成结果,合成定标不确定度在10%之内,满足大口径空间滤波调制红外光谱仪的定标需求。     

九米卫星通信天线辐射特性分析

本文介绍了在考虑馈源辐射场球面相位误差基础上，运用口径场积分和几何绕射理论（ＧＴＤ）相结合分析天线辐射特性的一种方法，并对口径场进行了优化设计，给出了分析和测试结果。该分析可方法可应用于 其它轴对称双反射面天线。     

口径天线在任意口径分布时的冲激响应

本文从夫累涅尔-基尔霍夫标量衍射场方程出发,证明了任意形状的并馈口径天线在任意口径幅度分布时的冲激响应和端馈矩形口径天线在任意口径幅度分布时的冲激响应都可以用口径幅度分布表达出来;而矩形口径天线在口径分布可分离时的冲激响应和圆形口径天线在口径分布圆对称时的冲激响应则为上述一般情况的特例。     

任意曲线形状介质栅漏波天线辐射特性的改进微扰法分析

本文是对作者前一工作(1990)的补充和发展,文中用改进的微扰法分析了任意曲线形状介质栅漏波天线的辐射特性。所得数据和用场匹配方法得到的精确值进行了比较。结果表明,本文方法在保持相同精度的情况下,极大地简化了求解过程;并据此系统地研究了周期槽形状对介质栅漏波天线辐射特性的影响。文中给出的曲线可供设计介质栅天线时参考。     

FDTD方法用于TEM喇叭天线传输效应的计算

如何高效而又有较少拖尾的将信号辐射出去是超宽带天线的设计关键，本文利用FDTD方法研究了TEM喇叭，得出喇叭的形状和激励脉冲的脉宽对TEM喇叭的传输波形的影响。     

Waveform optimisation of UWB radio systems over range of directions

The waveform of the source pulse applied at the input of an UWB antenna can be optimised to obtain maximum peak radiated field in one direction. Presented is a systematic technique that helps the UWB system designer to achieve the best peak radiated field in a range of directions. Since the transfer functions of all known printed UWB antennas are direction dependent, application of such a technique is crucial in the system design when an UWB system is required to radiate close to the peak over a range of directions.     

Photoconductive impulse generation and radiation

The generation of extremely narrow, high peak power pulses using an optically activated impulse generator is described. Radiative measurements at 1 Hz PRF have been conducted at pulse bias levels up to 15 kV, using an optical pulse from a Nd:YAG laser to trigger the device. The measured pulse from a wideband antenna has a pulsewidth of 1.5 ns with a risetime of 900 ps. The frequency spectrum of this radiated waveform ranged from 50 MHz to 1 GHz     

脉冲激励的长方形发射天线的分析与波形优化

在脉冲激励天线中，脉冲波形对于辐射功率有着重要的影响。对长方形行波天线的激励电流脉冲波形与其辐射功率的关系进行了分析。提出了激励电流的优化问题，使得天线在给定方向上的辐射能量最大化。并且给出了优化问题的解法和几种参数下的优化波形。通过具体的数值计算，与其他参考文献中使用的波形相比，优化波形在主辐射方向上可以辐射出更大的能量。     

Improvement of prompt response from impulse radiating antennas by aperture trimming

Reflector impulse radiating antennas (IRA) traditionally have been constructed by terminating a self-reciprocal, transverse electromagnetic (TEM) transmission-line feed structure into a paraboloidal reflector. The section of the paraboloid used is usually circular in cross-section, with the outer boundary coinciding with the circle of symmetry of the TEM feed. The reflector converts the spherical TEM mode on the feed line into an approximate plane wave in the near field by geometric optics. The prompt radiated electric field in the direction of focus is given in the physical optics approximation in terms of the integral of the electric field of the TEM mode over the aperture plane inside the reflector boundary. Balanced feed structures have TEM modes that provide both positive and negative contributions to this integral in the aperture plane. Determination of the contour where the principal component of the electric field in the TEM mode is zero identifies portions of the aperture that contribute destructively to the integral. These portions are removed, thereby increasing the prompt radiated field without altering the feed structure or the applied voltage waveform. Furthermore, decreasing the size of the TEM feed relative to the aperture size, followed by appropriate aperture trimming, allows an even greater increase in radiated field. Results are presented that predict an increase in prompt radiated fields for all electrode configurations. Improvements are largest for electrode angles that are large (with respect to the vertical). The trends predicted by the numerical results are verified by an experiment conducted on a time-domain antenna range.     

定向辐射式核电磁脉冲场模拟器的研制

针对大型受试设备核电磁脉冲抗扰度试验评估要求，研制了基于Marx发生器脉冲源和横电磁波（Transverse Electro Magnetic，TEM）喇叭天线的可移动、极化方向可调的定向辐射式核电磁脉冲模拟器.实验分析了不同极化方向和终端负载对脉冲波形的影响，确定了定向辐射式核电磁脉冲模拟器的均匀区域.结果表明:辐射电磁脉冲场可用区域为近场区域，随着与口径面距离的增大，峰值场强近似按1/d2衰减，脉冲宽度显著减小；与传输式模拟器相比，辐射式核电磁脉冲模拟器具有更大的均匀区域，更适合大型设备电磁脉冲抗扰度试验.     

Impulse-radiating antenna with an offset geometry

An offset impulse-radiating antenna (IRA) is numerically analyzed and compared with a typical centered IRA. In the typical centered IRA, the transverse electromagnetic (TEM) feed arms block the aperture because they are located at the center of the aperture. This blockage causes multiple reflections inside the antenna and, thus, ripples in the tail of the radiated waveform. In the offset IRA, the TEM feed arms are removed from the aperture, lowering the tail ripples caused by multiple reflections between the TEM feed arms and the reflector. The boresight gains and the impulse amplitudes are seen to be essentially the same for both IRAs. The monostatic radar cross section of the offset IRA is significantly lower than that of the centered IRA for the plane wave incident from the boresight direction because the wave incident to the offset IRA is diverted toward the focal point of the reflector, which is away from the boresight direction. The offset IRA has a shadow behind the reflector. This feature can be useful in bistatic radar applications because the antennas can be placed in the shadows of each other.     

Copolar and cross-polar radiation of Vivaldi antenna on dielectricsubstrate

The copolar and cross-polar radiation patterns of the Vivaldi antenna on a dielectric substrate are calculated and validated by measurements. The method involves a two-step procedure. The electric field distribution across the antenna slot aperture is calculated first. The radiated fields are then calculated, using Green's functions. The continuous exponential tapered shape is approximated by annular linearly tapered sections. The conical transmission-line theory and a variational method yield the electric field in each section. The radiation calculation is based on closed-form expressions for the dyadic Green's function of an elementary electric field source in a conducting half sheet. Both copolar and cross-polar radiation patterns of the Vivaldi antenna are calculated by integrating the Green's functions weighted by the electric field distribution over the antenna aperture. The effect of lateral truncation is taken into account by defining weighting patterns. The method is validated by original measurements and limitations of the model are discussed. Antenna directivity and sensitivity are calculated     

超宽带TEM喇叭天线阻抗加载的时域分析

基于时域有限差分法中的阶梯近似方法,分析了超宽带TEM喇叭天线辐射场的时域波形.为了改善宽带TEM喇叭天线拖尾效应,文中利用集总元件的时域有限差分法,详细分析了不同阻抗加载条件下TEM喇叭天线辐射场的时域波形.计算机模拟结果表明,加载吸收电阻可以有效地解决TEM喇叭天线由于低频反射引起的拖尾振荡,改善辐射电场的波形特性.