频率选择表面机载雷达天线的研究

研究了降低机载雷达天线散射截面的频率选择表面(FSS)极化扭转板。根据Floquet定理利用模式电压概念建立矢量模式,对二维周期阵列的频率选择表面进行理论分析和计算。设计并加工了一种降低机载雷达天线散射载面的频率选择表面极化扭转板结构。计算和实验表明:频率选择表面的极化扭转板在雷达天线工作通带内保持与原极化扭转板的性能不变,而在工作通带外具有降低雷达散射载面的效果。降低雷达散射截面7～10dB。     

单根任意长度箔条双站散射截面积研究

计算单根任意长度箔条的双站散射截面积对于确定混装箔条弹散射截面积具有重要意义。通过建立单根任意长度箔条的散射模型,得出了表征箔条表面电流分布的积分方程;利用矩量法对方程进行求解,得出表面电流分布的数值解;在此基础上,利用电基本振子辐射场公式得到了单根任意长度箔条远区辐射电场表达式,最后利用散射截面积计算公式给出了单根箔条双站散射截面积的数值计算式,并对单根箔条的单双站散射截面进行了仿真分析。     

The Jet Fighter Radar Cross Section

Two jet fighter models, 1/8th of original size, have been measured in the "radar range" installed in the anechoic chamber of the Armament Technology and Procurement Group in Berne. The measurements have been made at a frequency of 40 GHz (5 GHz for full scale), with an accuracy of ± 2 dB and a dynamic range of 80 dB. The statistical distribution of the radar cross section has been calculated with the help of a computer, based on the measured data. The detection probability has been calculated with the help of a correlation procedure. This procedure allows explanation of the symmetry relation between the detection probability and the cumulative distribution of the radar cross section, and of a well-known characteristic of the median value of the radar cross section. A statistical model is proposed for the distribution of the radar cross section of jet fighters, consisting of the distribution of a spheroid in which each element itself exhibits a Rayleigh fluctuation. This model presents a certain number of interesting characteristics, and there is an acceptable degree of coincidence with the measured values.     

“飞鱼”一类导弹隐身突防性能的分析

 通过对“飞鱼”一类导弹的两种有代表性的突防方式的定量分析,得到对此类导弹提高隐身突防能力的三项措施:压低掠海飞行高度;超视距发射;减少正前方的雷达散射截面。     

飞行器翼身结合部的散射特性分析

飞行器翼身结合部构成的两面角反射器是一个很强的电磁散射源,但由于其一个表面弯曲,分析这种结构的散射十分困难。采用复射线展开法和几何绕射法分别处理镜面多次反射和边缘绕射,计算了这种复杂结构产生的电磁散射和雷达截面贡献,分析了翼身两面角和机身半径等几何参数对目标雷达截面的影响。结果表明是一种有效的雷达截面预估方法,通过结构几何参数的计算机优化,可以显著地减小翼身结合部的雷达截面贡献。     

二维机翼影区爬行波RCS的研究

分析了机翼前后缘处于影区时的散射机理,建立了机翼爬行波雷达散射截面（ＲＣＳ）的计算模型。该模型反映出外形参数对ＲＣＳ的影响,便于工程计算。针对典型试件进行了理论计算和一维成像实验,结果吻合良好     

飞艇吊舱隐身特性研究

吊舱的雷达散射特性决定了飞艇的隐身性能。为得到最优的设计方案,需要综合计算各种方案吊舱的雷达散射截面值。本文提出了采用多截面曲面对飞艇吊舱数字化建模的原理和通过形状因子描述吊舱脊线的方法,推导出利用物理光学法估算吊舱雷达散射截面的公式并总结了程序流程。通过典型吊舱分析了飞艇的隐身性能,结果表明：采用形状因子对吊舱的数字...     

Probability of Detecting Aircraft Targets

The statistics of aircraft radar cross section (RCS) are estimated by fitting members of the chi-square family of distributions to empirical distributions obtained from blocks of RCS data, each block of data corresponding to a particular aircraft azimuth aspect. The parameters of the fitted distributions vary with azimuth aspect angle, type of aircraft, and radar frequency. Detection probabilities based on the estimated statistics are calculated and compared with detection probabilities based on Rayleigh statistics. This comparison indicates that the average value of radar cross section has much more effect on probability of detection than the normalized variance of RCS, and in the usual situation tends to mask the effect of the normalized variance on probability of detection.     

格栅对进气道的气动性能和电磁散射特性的影响

给出了在进气道内加装格栅对进气道的气动性能和电磁散射特性的影响。结果表明,格栅明显地降低了S弯进气道出口二次旋流,且使原始单涡旋流消失,出口流场畸变度减小,进气道的雷达散射截面值显著降低,但同时也降低了进气道出口截面上的平均总压恢复系数。还给出了格栅几何尺寸的影响,及设计中如何选择格栅尺寸。     

Quantization and Saturation Noise Due to Analog-to-Digital Conversion of Radar Returns from Targets with Log-Normal Radar Cross-Section Distributions

An analysis of the saturation and quantization noise generated by analog-to-digital (A/D) conversion of radar returns from targets with log-normal radar cross sections is presented. The results of the analysis show that the high-cross-section tails of the log-normal distribution require higher saturation levels to be set in the A/D converter. The setting of the higher saturation level in the converter results in an increase in quantization noise. Thus the minimum achievable distortion in the output of the A/D converter signal is considerably higher than that for radar targets if their radar cross section had an exponential power distribution.     

雷达散射截面面积对发现概率的影响

在深入分析了影响飞机生存力的几种因素的基础上,通过理论推导,建立了雷达输入端信噪比与发现概率及雷达散射截面面积与信噪比之间的关系,计算了雷达散射截面面积对发现概率影响.并在Matlab的环境下进行了数学仿真,仿真结果表明:当信噪比落在区间[5.6,12.5]内,发现概率随着信噪比的降低而陡降.在没有完全掌握敌方预警雷达参数的情况下,通过假设定量的给出调整雷达散射截面面积的最佳范围.     

Impact of target RCS fluctuations on radar measurement accuracy

The impact of target radar cross section (RCS) fluctuations on the thermal noise limited accuracy of radar measurements of range, range rate, and angle is evaluated for Swerling fluctuation models. The impact is expressed as a modification of the large-signal approximation to the standard deviation σ of measurement error     

军用飞机雷达吸波结构复合材料研究进展

对军用飞机雷达吸波结构复合材料研究所涉及的技术问题和难点进行论述，对其结构组成和国外应用研究情况进行介绍。     

Bistatic Radar Cross Sections of Horizontally Oriented Chaff

Bistatic radar cross sections are determined for scattering from a cloud of randomly positioned resonant dipoles (chaff). Dipoles are assumed to be horizontally oriented with axes randomly oriented in the horizontal plane. The cloud is arbitrarily located relative to an illuminating source having an arbitrary (elliptical) polarization. Cloud cross section is found for an arbitrarily located receiver that views the cloud with an antenna of arbitrary polarization. Cross section applicable to the receiver's orthogonal polarization is also found.     

Calculation of probability of detection for log-normal targetfluctuations

An accurate, simple, and reliable method for the computation of the probability of detection for a target whose radar cross section is constant within a scan but fluctuates log-normally scan-to-scan is presented     

Millimeter Radar Instrumentation

Millimeter wavelength radars are used to study plasma effects associated with ionized flow fields of projectiles launched at hypersonic speeds into a free-flight ballistic range. Two CW Doppler radars, at frequencies of 35 and 70 Gc/s, measure the nose-on backscattering radar cross sections during flight. The design and performance of the two radars are described in detail. A signal simulator provides absolute calibration. The purpose is to measure changes that occur in the radar cross sections of hypersonic projectiles caused by highly ionized flow fields. Under certain conditions the nose-on backscattering radar cross section of a blunt-nosed metal projectile decreases drastically when a thin, shock-produced layer of ionized gas covers the projectile. A theoretical analysis of this effect is given. Comparisons between theoretical predictions and experimental data show good correlation.     

隐身飞机在大仰角时的生存力评估

介绍了生存力基本概念;给出了飞机发现概率的计算;在缺少某些雷达参数时,所提出的发现概率计算方法仍然适用。讨论了几种减缩RCS的实际可行的方法,并就隐身设计给出了指导性的意见。     

基于鸟类目标散射特性分析的雷达探鸟实验

 鸟类目标散射特性研究是雷达探鸟系统探测性能分析的理论基础。基于此,首先进行了鸟类目标散射特性分析,采用实验数据构造的理论统计模型,估计出单只鸟和鸟群的雷达散射截面（RCS）量级范围。然后,详细介绍了雷达探鸟实验系统的系统结构、探测性能和飞鸟目标识别算法。最后,基于外场实验获取的雷达探鸟图像序列提取出飞鸟目标轨迹与相关信息,验证了雷达探鸟的可行性,并通过对不同实验结果的分析提出了抑制虚警和漏警的算法改进方向。     

Dynamic imaging and RCS measurements of aircraft

Results on radar cross section (RCS) measurements and inverse synthetic aperture radar images of a Mooney 231 aircraft using a ground-to-air measurement system (GTAMS) and a KC-135 airplane using an airborne radar are presented. The Mooney 231 flew in a controlled path in both clockwise and counterclockwise orbits, and successively with the gear down, flaps in the take-off position and with the speed brakes up. The data indicates that RCS pattern measurements from both ground-based and airborne radar of flying aircraft are useful and that the inverse synthetic aperture radar (ISAR) images obtained are valuable for signature diagnostics     

On the Statistical Representation of Targets for Detection Studies

Statistical distribution functions were determined ined for the radar cross section for flying aircraft. Most distributions could be adequately represented by one or another member of the family of chi-square functions. The degree of freedom parameter varied widely.