RCS characterization of a finite ground plane with perforatedapertures: simulations and measurements

The monostatic radar cross section of a finite-size perfectly conducting flat plate with perforated apertures is investigated by simulations and measurements. The geometry of a finite ground plane with triangular apertures resembles airplane and automobile windows. The method of moments surface patch formulation is used to compute the radar cross section of a solid plate, a plate with two widely spaced apertures, and a plate with two closely spaced apertures. The characteristics of the triangular patch mesh can impact the accuracy of the computed results with this formulation. The paper presents a methodology to achieve high quality meshes to ensure that the time and convenience gained by developing the general method of moments code is not lost in mesh construction and convergence tests. The results obtained using the method of moments are compared with results obtained by measurements and physical optics. It is shown that the method of moments simulations and measurements are in good agreement. The key features of the influence of the aperture separation on the RCS patterns are discussed     

An investigation of bistatic calibration objects

Several popular metallic bistatic calibration objects are investigated, including a sphere, long and short cylinders, dihedral, trihedral, circular disk and wire mesh. Comparisons are made between the advantages and disadvantages of various objects for calibration. The analysis addresses sensitivity to object alignment error, availability of accurate radar cross section (RCS) calculations and bistatic RCS levels. Both theoretical concepts and practical considerations are discussed based on measurements accomplished at the European Microwave Signature Laboratory (EMSL) of the EC Joint Research Center (JRC) in Ispra, Italy. This facility has the capability to produce far-field fully polarimetric precision bistatic measurements in a 30 cm diameter quiet zone, suitable for comparing different calibration objects.     

RF Characteristics of thin dipoles

This paper considers the average bistatic scattering cross section of thin cylindrical dipoles as a function of frequency, bistatic angle, and transmitting and receiving polarization. The averaging is over all orientations of the dipole with all orientations equally likely. Section II is essentially tutorial, approaching the problem of scattering cross section from the equivalent circuit point of view. Using this approach, the maximum scattering cross sections of lossless dipoles in the Rayleigh region and at the first and second resonances are derived. Section III presents a novel method of predicting cross section at the first resonance with the effect of loss included. Numerous measurements indicate that this method is widely applicable. Section IV describes our microwave scattering range and the results of measurements made on dipoles resonant at X band. In Section V the averaging of cross sections is considered. The average bistatic cross sections for resonant half-wave and full-wave dipoles are plotted vs bistatic angle for various transmitting and receiving polarizations. These results, which are new, were obtained using a digital computer. The average cross section for short (Rayleigh region) dipoles is also obtained as a function of bistatic angle for various polarizations. Section VI is a summary of parameters of the West Ford dipoles.     

地面双基地雷达箔条干扰研究

在充分考虑双基地雷达工作特点的条件下，首先根据箔条干扰的性质，分析其雷达截面积，其次建立了双基地条件下箔条云团的雷达截面积模型，通过与现有理论的比较，证明了该模型的合理性。最后，建立了箔条云团干扰回波的模型。     

The physical optics radar cross section of an elliptic cone

The physical optics approximation is used to evaluate the backseattering radar cross section of a semi-infinite metallic elliptic cone. The resulting formula can be directly interpreted as a generalization Of the well-known formula for the baekscattering cross section of a circular cone. In addition the bistatic radar cross section of the elliptic cone is calculated.     

Some results in the bistatic radar cross section (RCS) of complexobjects

The author describes the history of the bistatic radar cross section (RCS) of complex objects. Beginning with the first (predominantly bistatic) radars before World War II, the discussion proceeds through the current experimental and analytical modeling methods. Finally, data are presented from experiments on cylinders and missiles     

变基线地空双基地雷达动态探测性能研究

给出了一种接收机置于隐身飞行平台的T/R-R地空双基地雷达,研究了这种变基线地空双基地雷达的动态探测性能,并与单基地雷达的探测性能进行了比较;通过仿真分析了目标的雷达截面（RCS）、收发天线功率增益等雷达系统参数的变化对地空双基地雷达探测性能的影响;通过对仿真结果的分析得出了一些有价值的结论,为双基地雷达的设计提供一定的理论基础。     

Calculation and analysis of electromagnetic scattering by helicopter rotating blades

This paper describes an application of physical optics and the method of equivalent currents to the calculation of radar cross section (RCS) of a helicopter rotor. The problem is treated using a quasi-stationary approach. The calculation can be parameterized as a function of the locations of the radar transmitter and receiver in relation to the rotor center. Therefore, this offers the possibility of monostatic and bistatic simulations in the far field and near field. Blade geometry is taken into account using a triangular meshing generated by the I-DEAS meshing software. Digital applications are presented and the effects on the RCS spectrum of incidence, frequency, blade number, and the near field are analyzed.     

Electromagnetic scattering from a chiral cylinder-general case

A generalized finite-difference (FD) scheme combined with the measured equation of invariance (MEI) is presented for the analysis of electromagnetic scattering from an inhomogeneous and lossy chiral cylinder with electrically large, arbitrarily shaped cross section. A new FD mesh in both chiral and achiral regions is formed, and the FD equations in a chiral medium are derived; then a large sparse matrix is formulated. The numerical results of bistatic scattering width (two-dimensional radar cross section) are given for the chiral cylinders of rectangular, elliptical, and complex cross section, respectively. Some results are compared with available data     

An alternative formulation for the fast multipole method

This paper describes an alternative formulation for the fast multipole method based on spherical waves decomposition. It is somewhat simpler to implement than the standard fast multipole method and also better suited at low frequencies. The new formulation is mainly based on a technique for the interpolation of the bistatic radar cross section derived from the Wacker's method for antenna measurements.     

Bistatic scatter from rain

An experimental investigation of bistatic scatter from rain was conducted using a 143 km scatter path at frequencies of 4.5 and 7.7 GHz. The ratio of transmitted to received power (transmission loss) was measured for scattering angles ranging from6degto130deg. Simultaneous weather radar observations were made at a frequency of 1.3 GHz. Transmission loss estimates for the bistatic scatter path were computed using the weather radar data, the bistatic radar equation, and a model for the scattering cross section per unit volume of rain based upon Rayleigh scattering by an ensemble of water spheres. The measured and estimated transmission loss values were compared to test the use of the scattering model for the estimation of interference. The averaged ratio of measured-to-calculated transmission loss for the 4.5 GHz data is 1.2pm 0.4dB. The averaged ratio for the 7.7 GHz data is -1.6pm 0.5dB. Both these values are within the combined calibration uncertainties of each measurement system. The results show that the use of the simplified Rayleigh scattering cross section model for an ensemble of water spheres adequately describes bistatic scatter for a wide range of scattering angles and frequencies below 7.7 GHz for the hydrometeor types (rain, snow, and mixed rain and snow) encountered in New England.     

用MEI—FD方法分析Chiral媒质的电磁散射问题

本文应用不变性测试分程和有限差分方法分析Ｃｈｉｒａｌ媒质的电磁散射问题。应用该方法时，要在所讨论的区域内建立起一组有关电场和磁场的耦合差分方程，并且要在截断边界上应用不变性测试方程建立起有关边界点系数的方程。文中给出了一些非均匀、有耗且具有电大尺寸任意横截面Ｃｈｉｒａｌ柱的雷达散射截面的数值结果     

TNR型调频广播外辐射源雷达探测实验

针对信号带宽时变、目标RCS闪烁造成单调频广播外辐射源雷达探测性能下降的问题,研究了一种TNR型外辐射源雷达的试验方案,并开展了外场试验验证。首先,阐述了TNR型外辐射源雷达的定位原理。然后,基于外辐射源雷达探测原理和广播信号的特性,提出了TNR调频广播外辐射源雷达探测系统中多个辐射源的筛选原则。最后,构建试验系统并给出探测试验结果。结果表明,TNR型系统方案可以大幅度提高调频广播外辐射源雷达的发现概率和定位精度等性能。     

Laboratory measurements of the 36 GHz backscattering cross sectionfrom water waves

The backscattering cross section per unit area σ₀ of a roughened water surface at 36 GHz is needed in the development of new remote sensing instrumentation that will operate at this frequency. One instrument, the multimode airborne radar altimeter (MARA), will illuminate the surface at incidence angles ranging from nadir to 12° off-nadir. Laboratory tests were performed at the Wallops Wind-Wave Tank Facility to determine the variability of σ₀ at these angles and as a function of windspeed. The measurement procedures used in a 6-in.-diam aluminum sphere as the calibration source. The results are compared with earlier measurements at this frequency. Little variability with windspeed was found in the cross-section values for 12° off-nadir, while the cross section decreased with windspeed at nadir. The nadir cross section exceeded the off-nadir result by about 7 dB at a windspeed of 10 m/s (at a 10-m effective height above sea level)     

双基地前向基射系统雷达截面（RCS）的研究

研究了双基地前向散射系统中雷达截面RCS的有关特点和计算方法。给出了如何使用RCS来提高系统进行多目标跟踪和探测时的性能的方法。     

A technique for the rapid measurement of bistatic radar cross sections

Numerous techniques for measuring monostatic (backscatter) radar cross sections (RCS) are well known, but bistatic RCS measurements are inherently more difficult. In this paper we describe a bistatic RCS measurement technique which circumvents the major obstacles. It uses a variation of the CW "null-balance" approach resulting in rapid measurement times. A network analyzer and process computer were incorporated into an existing image ground plane system to improve the bistatic capability and add flexibility. Several objects were measured and compared with their known bistatic RCS to demonstrate the validity and utility of the technique.     

Polarimetric bistatic-measurement facility for point anddistributed targets

A fully polarimetric bistatic-radar facility has been constructed at the University of Michigan, to serve as a research tool for improved understanding of the nature of bistatic scattering for point and distributed targets. The facility is capable of operation at 10, 35, and 94 GHz, but only the 10-GHz system is described in the presentation. To meet both the size and design constraints both a horn antenna operating in the far-field, and a parabolic-dish antenna operating in a near-field focused mode, are utilized. A newly developed bistatic-calibration technique, using a flat metal plate, is used to calibrate the facility. Validation results, using a hemisphere over a conducting metal plate, show that the facility is capable of characterizing the radar cross section of a point target to within ±1 dB in magnitude and ±5° in polarization phase difference over a wide range of bistatic angles. Sample data for a point target and a distributed target are presented     

一体化双站散射图形算法

研究了图形算法计算双站RCS的方法，并将RCS分析与目标外形设计相结合，提出了一种一体化方法，将图形算法集成到CAD造型软件中，能够在目标外形设汁阶段随时分析其双站散射特性。计算实例说明．这种方法不但能够满足计算精度要求，而且可以简化RCS的前处理工作，提高目标设计的总体效率。     

A note on the scattering from a slightly rough surface

A Fourier transform approach is used to derive the bistatic radar scattering cross section of a slightly rough perfectly conducting infinite surface. A perturbation expansion is used to apply the boundary conditions, and the scattered fields are asympotically evaluated by means of the method of stationary phase. The resultant expression for the radar cross sectionsigma^{0}is shown to agree with that obtained using the method as outlined by Rice.