端馈阵列天线瞬变效应及其对角分辨性能的影响

本文证明,端馈阵列天线的瞬变效应将使雷达的角分辨性能降低,对于窄脉冲幅度敏感的雷达,这种影响尤为严重。     

导航雷达距离分辨力问题

本文分析了目标的随机相位、接收机频率响应及天线瞬变效应等因素对导航雷达距离分辨性能的影响,提出了比较符合实际的距离分辨力的定义和计算方法。     

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。     

双层宽波束天线设计

针对宽波束天线在车载雷达中的应用,突破角雷达方位面3 dB波束宽度的限制,实现微带阵列天线在水平面的宽波束覆盖,设计了一款1×10串馈微带双层结构天线。线阵单元采用道尔夫-切比雪夫（Dolf-Chebyshev）综合法电流分布来达到降低天线俯仰面副瓣的效果,在串馈阵列上方加载寄生贴片和介质基板拓展天线方位面的3 dB波束宽度。分析了双层天线展宽波束的原理,加工并实测了双层宽波束天线,其方位面的3 dB波束宽度为134.6°,增益达到10.6 dB,副瓣电平为-19.8 dB,可以满足车载角雷达天线需求。     

阵列雷达评论

一、引言在作战中部署大功率、高距离分辨力(2.5英尺)的COBRA DANE(“丹麦眼镜蛇”)大型雷达和两部全固态大功率的大型超高频PAVE PAWS雷达,研制即将生产的面对空导弹制导多功能PATRIOT(“爱国者”)雷达,研制并生产有限扫描精密进场雷达(AN/TPN-25和AN/GPN-22),在阵列雷达中结合进积化捷变,研制半球状的全向覆盖天线、     

二维天线的冲激响应

本文从夫累涅尔-基尔霍夫标量衍射场方程出发,导出了并馈和串馈矩形天线在口径分布可分离时的冲激响应,以及并馈和中心串馈圆形天线在口径分布圆对称时的冲激响应它们都可以用口径幅度分布表达出来。     

弧形杂乱回波现象的分析

本文阐明了弧形杂乱回波现象的两个起因:天线稳态旁瓣会在PPI上引起光点较大但角度范围较小的杂乱回波,而端馈天线在脉冲信号激励下的瞬变过程则会引起光点较小但角度范围较大的杂乱回波。     

X 波段宽带宽角扫描相控阵天线的设计

设计了一种X波段宽带宽角扫描相控阵雷达系统的小型阵列天线,该天线采用Vivaldi 天线做为阵列单元。在考虑阵列单元间的互耦效应下,仿真设计了9*9 小型阵列天线,使该阵列天线在相对带宽达40%下的有源驻波系数小于2,其有源单元方向图E面、H面的波瓣宽度分别达到120度、110度以上。对9*9天线阵的实物进行了加工与测试,测试结果说明了该阵列天线具有良好的宽带宽角扫描特性。因该天线结构简单,重量轻,在相控阵雷达天线中有很大的应用价值。     

极化阵列雷达单脉冲测角方法研究

极化阵列雷达兼具阵列雷达的优势和极化信息处理能力,是当前先进体制雷达研究的热点。研究了极化阵列雷达单脉冲测角的问题。在明确雷达采用的天线结构的基础上,建立了极化阵列雷达接收信号模型,提出了基于极化并联的单脉冲测角方法,分析了该方法测角性能,给出了测角性能与SNR及回波极化角的关系。通过仿真验证了方法的有效性,研究表明:极化阵列雷达单脉冲测角性能优于任意单(同)极化阵列雷达,且测角性能与回波极化状态无关。     

改进实孔径雷达角分辨力的广义逆滤波方法

本文寻求一种在扫描实孔径雷达中,利用方位信号处理获得优于天线波束宽度的角分辨力的途径。文中建立了扫描过程的数学模型,并提出了采用广义逆滤波处理实现波束“伪压缩”的方法,阐明了这种方法的物理本质,解决了这种方法最佳解的确定问题。文中用这种方法对雷达实测数据进行了处理,使雷达的角分辨力提高约4倍。     

Investigation of time-domain response of microstrip quasi-horn antennas for UWB applications

The time-domain response of a microstrip quasi-horn antenna was investigated to confirm its suitability for ultra-wideband (UWB) impulse applications. Results show that antenna performance is enhanced using 130 Omega, instead of the usual 377 Omega, for the antenna aperture. The antenna exhibits good impulse return losses of around 13 and 17 dB at the feed-point and aperture, respectively, and high signal fidelity in radiating and receiving UWB signals. Good impulse response with minimum waveform distortion and small reflection together with a planar structure make the microstrip quasi-horn antenna a very good candidate not only for UWB impulse applications but also for direct integration with UWB integrated-circuit transmitters and receivers     

天线尺寸对冲激信号SAR方位向积累的影响

该文分析了冲激信号/极窄脉冲SAR成像系统的天线在辐射与接收时存在的时-空耦合问题。结合冲激信号SAR成像方法反向投影法(BP),本文在时域上分析了天线尺寸对SAR方位向积累的影响,给出了方位向积累与天线尺寸的定量关系,最后给出了关于超宽带SAR天线设计及发射信号参数选择的有用的结论．     

口径天线在远场区的冲激响应的含义和适用范围——兼评“也谈口径天线辐射场的瞬态特性”

本文阐明了在使用口径天线在远场区的冲激响应的概念时,远场区是对激励天线的实际信号而言,并非对为求冲激响应而施加在天线上的δ函数而言;远场区的冲激响应在距离上的适用范围决定于激励信号的频率范围。     

Miniaturization of UWB Antennas and its Influence on Antenna-Transceiver Performance in Impulse-UWB Communication

In this paper, a co-design methodology and the effect of antenna miniaturization in an impulse UWB system/transceiver is presented. Modified small-size printed tapered monopole antennas (PTMA) are designed in different scaling sizes. In order to evaluate the performance and functionality of these antennas, the effect of each antenna is studied in a given impulse UWB system. The UWB system includes an impulse UWB transmitter and two kinds of UWB receivers are considered, one based on correlation detection and one on energy detection schemes. A tunable low-power Impulse UWB transmitter is designed and the benefit of co-designing it with the PTMA antenna is investigated for the 3.1–10.6 GHz band. A comparison is given between a 50 $\Omega $ design and a co-designed version. Our antenna/transceiver co-design methodology shows improvement in both transmitter efficiency and whole system performance. The simulation results show that the PTMA antenna and its miniaturized geometries are suitable for UWB applications.     

Ultra-wideband impulse scattering measurements

A recently upgraded laboratory is described for measurement of ultra-wideband (1-20 GHz) impulse scattering responses from scale model radar targets. A linear systems model is introduced, leading to new measurement concepts and signal processing algorithms for estimating the target's scattering response to a user-defined impulse waveform. The experimental and processing procedures serve to eliminate clutter and antenna coupling, while compensating for antenna characteristics in the system. Experimental validations are examined and planned enhancements are discussed     

Transients in a resistively loaded linear antenna compared with those in a conical antenna and a TEM horn

The receiving and transmitting transient responses of the resistively loaded linear antenna, the TEM horn, and the conical antenna are investigated theoretically and experimentally using the fast Fourier transform (FFT) technique. The receiving transient response of the resistively loaded linear antenna indicates that the shape of a 70-ps impulse is well preserved.     

一种新型探地天线的优化设计

设计了一种新型超宽带平面天线.用FDTD研究了近地面天线的模拟计算问题,给出了天线的近场辐射性能.通过与平面蝶形偶极天线对比,结果表明该天线具有波形保真度好,对称的辐射方向图及后向辐射小等特点,进一步通过加载集中电阻优化设计,改善了天线的驻波特性.此天线不仅适用于探地雷达,还可以广泛地用于宽带通信和冲激雷达等系统.     

Improved feeding structures to enhance the performance of the reflector impulse radiating antenna (IRA)

This paper considers the improvement of the feeding structure of the reflector impulse radiating antenna (IRA). Full-wave analysis and measured results of the orthogonal cross-coplanar plate reflector IRA shows that the aperture fields are not uniform. The arm angle is varied as an optimization factor and it is shown that the arm angle of 70/spl deg/ has the maximum radiation efficiency. The termination load and the arm tapering effects are studied using simulation and measurement results. Furthermore, the effect of radius of circle of symmetry is studied and it is shown that a greater circle provides higher gain. A combination of transverse electromagnetic (TEM) horn antenna and the conical coplanar TEM transmission line is investigated to avoid tiny structure at the focal point and make the connection between the coaxial cable and the feeding arms more convenient. It is shown that a small triangle does not degrade the antenna performance but helps to excite the antenna by a coaxial cable. Finally a combination of the Vivaldi antenna and the coplanar transmission line is introduced to improve the antenna performance. The simulation results for the new antenna show that the antenna efficiency is improved to 45% at the frequency band between 2 GHz to 6 GHz in comparison to the 20.9% for the traditional design and 29.7% for the tapered design. The calculated far-field results of all these antennas are used to radiate a 0.5 ns impulse. The radiated impulse from the Vivaldi fed reflector IRA is 3.55, 2.41, and 2.12 dB higher than the same radiated impulses from the reflector IRA fed by a 45/spl deg/ traditional feeding arms, 70/spl deg/ traditional feeding arms, and 70/spl deg/ tapered feeding arms, respectively.     

Closed-Form Expressions of the Axial Step and Impulse Responses of a Parabolic Reflector Antenna

Electromagnetic pulses radiated by parabolic antennas and similar structures are needed in many applications like air and ground penetrating radar or high power microwaves (HPM) weapons. In this paper, an approach based on Skulkin and Turchin's work and on physical optics approximation in the time domain is developed to determine the radiated fields. Closed-form time-domain expressions of the electromagnetic step and impulse responses, along the axis of a classical parabolic reflector antenna, are derived. A closed-form expression of the impulse response duration is also given. The obtained E-field and H-field formula are valid along the axis, both near and far from the reflector. Using these closed-form expressions, the radiated fields are computed by means of a convolution product of the primary source excitation and the impulse response. Numerical results have been obtained in the case of a causal sine and a generalized Gaussian impulse excitations to illustrate some specific transients effects which occur with such an antenna     

Impulse response modeling of indoor radio propagation channels

If indoor radio propagation channels are modeled as linear filters, they can be characterized by reporting the parameters of their equivalent impulse response functions. The measurement and modeling of estimates for such functions in two different office buildings are reported. The resulting data base consists of 12000 impulse response estimates of the channel that were obtained by inverse Fourier transforming of the channel's transfer functions. It is shown that the number of multipath components in each impulse response estimate is a normally-distributed random variable with a mean value that increases with increasing antenna separations; a modified Poisson distribution shows a good fit to the arrival time of the multipath components; amplitudes are lognormally distributed over both local and global areas, with a log-mean value that decreases almost linearly with increasing excess delay; for small displacements of the receiving antenna, the amplitude of the multipath components are correlated; the amplitudes of adjacent multipath components of the same impulse response function show negligible correlations; and the RMS delay spread over large areas is normally distributed with mean values that increase with increasing antenna separation