Radar Cross Section

In this paper, we propose a computer simulation model for the study of the large-scale effects on narrowband wireless transmission systems. The development of the path loss model is based on the ray tracing technique. This study concentrates on the first-order scattering effects, namely each multipath signal is a two-hop signal that involves a single scattering object. The first hop is directed toward the scatterer from the transmitter; and the second hop goes from the scatterer to the receiver. For each hop the signal is described using a tworay model accounting for wave propagation along the direct path and along the ground-reflected path. The simulation results are consistent with the empirical models that are derived from measurements, including the Hata model and the Lee model. More importantly, two key observations are made: First, the path loss is affected by the number of scattering objects, their radar cross sections, and the ground reflection. Second, coherent multipath signals can cause the path-loss exponent falling below 2, which corresponds to free-space propagation.

A uniform geometrical theory of diffraction solution is developed for the two-dimensional problem of high-frequency plane wave diffraction by a planar junction of two thin dielectric/ferrite half planes. Each material half plane in this two-part configuration is assumed to be electrically thin so that it can be replaced in the analysis by a generalized resistive boundary condition of 0(t), where t is the corresponding material slab thickness. The solution obtained is based on the Wiener-Hopf technique, and it is shown that the present boundary value problem can be completely solved by imposing a junction condition at the junction of the two dielectric half planes in addition to the boundary and radiation conditions as well as the usual edge condition. This junction condition can be obtained if the field near the junction is modeled by a quasi-static solution. The solution developed here can be further specialized to limiting cases for which either of the material half planes can become free space, perfectly conducting, or purely resistive, respectively. Several numerical examples are presented, and it is shown that the present solution reduces to known results and agrees very well with a moment method solution.

The avoidance of enemy's radar detection is very important issue in the modern electronic weapon system. Researchers have been studied to minimize reflected signals of radar. In this research, two types of radar absorbing structure (RAS), "C"-type shell and "U"-type shell, were fabricated using fiber-reinforced composite materials and their radar cross section (RCS) were evaluated. The absorption layer was composed of glass fiber reinforced epoxy and nano size carbon-black, and the reflection layer was fabricated with carbon fiber reinforced epoxy. During their manufacturing process, undesired thermal deformation (so called spring-back) was observed. In order to reduce spring-back, the bending angle of mold was controlled by a series of experiments. The spring-back of parts fabricated by using compensated mold was predicted by finite element analysis (ANSYS). The RCS of RAS shells were measured by compact range and predicted by physical optics method. The measured RCS data was well matched with the predicted data.

A new empirical model for the retrieval, at a field scale, of the bare soil moisture content and the surface roughness characteristics from radar measurements is proposed. The derivation of the algorithm is based on the results of three experimental radar campaigns conducted under natural conditions over agricultural areas. Radar data were acquired by means of several C-band space borne

The authors introduce maximum likelihood techniques for optimised discrimination between agricultural and wooded regions, based on a multitemporal sequencc of ERS images. The inherent resolution of the system is inadequate to make such a classification on an individual image. However, the different temporal change patterns of the two classes can be exploited. One approach uses joint annealed segmentation of the image sequence, providing optimised exploitation of the speckle model in determining the common set of region boundaries in the underlying radar cross-section. This is followed by maximum likelihood change detection using a normalised log temporal texture measure. This is shown to be superior to constructing the normalised log measure directly, including speckle fluctuations, followed by a single annealed segmentation process. Finally, it is demonstrated how simple filtering of this normalised log measure can provide reasonable classification with greatly reduced computation load. 0 IEE, 2001 /EE Proceedings online no. 20010114

The accurate analysis of scattering from objects with dimensions large compared to the wavelength using rigorous methods (finite element, FDTD, method of moments) with a personal computer is almost impractical. In asymptotic methods, physical optics (PO), geometrical theory of diffraction (GTD), the accurate modeling of the object's boundary is too cumbersome. The parabolic equation method gives accurate results in calculation of scattering from objects with dimensions ranging from one to tens of wavelengths. Solving parabolic equation with the marching method needs limited computer storage even for scattering calculations of large targets. In this paper, first the calculation procedure of radar cross section using parabolic equation in three dimension is studied and the necessary equations are derived. In order to show the validity of the parabolic equation, the RCS of a conducting sphere is calculated and the results are compared with analytic results. The airplane RCS has been computed by using a staircase model in the parabolic equation and the results are compared with physical optics results.

Fog is a significant factor affecting the Air Traffic Control (ATC). Significant limitations of the airport capacity are due to fog that causes the reduction of the visibility (Runway Visual Range, RVR). Today METAR (Meteorological Aviation Report

The feasibility of using GPS as a bistatic radar illuminator for the purposes of air target detection is examined. The power budget analysis is first performed assuming the use of a single satellite, but is followed by a discussion of the expected improvements when multiple satellites are employed. The analysis includes the effect of GPS signal strength dynamic range, also known as the 'near-far' problem. The difference between the radar cross-section (RCS) of a typical air target and groundbased clutter reflections is discussed, followed by an estimation of the effect of ground clutter on the operation of such a system.

Multiple-input-multiple-output (MIMO) radar makes use of orthogonal signals to obtain the phase delay for each transmitting/receiving antenna pair, and thus increasing the accuracy of direction estimation. The previously proposed MIMO radar assumes narrowband signals that guarantee the waveform orthogonality during the signals' transmission, propagation and reception. However, a narrowband system is unstable in target localisation because of the fluctuation of the target's radar cross section. An MIMO-OFDM radar is proposed for target localisation. It adopts the OFDM technique to simultaneously transmit and receive a set of multiple narrowband orthogonal signals at orthogonal frequencies. A practical model accommodating a physical target is presented to simulate the MIMO-OFDM radar. As an example, a composite target composed of five infinite dielectric cylinders is localised by a four-element uniform linear array. The performance of the MIMO-OFDM radar is investigated by examining the estimation error for different numbers of sub-bands, different signal-to-noise ratios and different target directions. It is demonstrated by simulation that the MIMO-OFDM radar gives more statistically stable estimation by spreading the signal power over a wider spectrum.

We describe a numerically efficient strategy for solving a linear system of equations arising in the Method of Moments for solving electromagnetic scattering problems. This novel approach, termed as the characteristic basis function method (CBFM), is based on utilizing characteristic basis functions (CBFs)-special functions defined on macro domains (blocks)-that include a relatively large number of conventional sub-domains discretized by using triangular or rectangular patches. Use of these basis functions leads to a significant reduction in the number of unknowns, and results in a substantial size reduction of the MoM matrix; this, in turn, enables us to handle the reduced matrix by using a direct solver, without the need to iterate. In addition, the paper shows that the CBFs can be generated by using a sparse representation of the impedance matrix-resulting in lower computational cost-and that, in contrast to the iterative techniques, multiple excitations can be handled with only a small overhead. Another important attribute of the CBFM is that it is readily parallelized. Numerical results that demonstrate the accuracy and time efficiency of the CBFM for several representative scattering problems are included in the paper.

Although it is a time-domain method, the finitedifference time-domain (FDTD) method has been used extensively for calculating frequency domain parameters such as specific absorption rate, radar cross-section, and S-parameters. When a broad frequency band is of interest, using a broad-band pulsed excitation can provide this frequency response with a single FDTD simulation. The frequency domain data can be calculated from the time domain data using either a discrete Fourier transform (DFT) or a fast Fourier transform (FFT). This letter examines both methods and analyzes why the DFT is generally more efficient and easier to use than the FFT for FDTD time-tofrequency domain conversions.

Trihedral corner reflectors are the preferred canonical target for SAR performance evaluation for many radar development programs. The conventional trihedrals have problems with substantially reduced Radar Cross Section (RCS) at low grazing angles, unless they are tilted forward, but in which case other problems arise. Consequently there is a need for better low grazing angle performance for trihedrals. This is facilitated by extending the bottom plate. A relevant analysis of RCS for an infinite ground plate is presented. Practical aspects are also discussed.

Based on EuroNCAP regulations the number of autonomous emergency braking systems for pedestrians (AEB-P) will increase over the next years. According to accident research a considerable amount of severe pedestrian accidents happen at artificial lighting, twilight or total darkness conditions. Because radar sensors are very robust in these situations, they will play an important role for future AEB-P systems. To assess and evaluate systems a pedestrian dummy with reflection characteristics as close as possible to real humans is indispensable. As an extension to existing measurements in literature this paper addresses open issues like the influence of different positions of the limbs or different clothing for both relevant automotive frequency bands. Additionally suggestions and requirements for specification of pedestrian dummies based on results of RCS measurements of humans and first experimental developed dummies are given.

A low-cost ultrawideband (UWB), 1.926-4.069 GHz, phased array radar system is developed that requires only one exciter and digital receiver that is time-division-multiplexed (TDM) across 8 receive elements and 13 transmit elements, synthesizing a fully populated 2.24 m long (λ/2 element-toelement spacing) linear phased array. A 2.24 m linear phased array with a 3 GHz center frequency would require 44 antenna elements but this system requires only 21 elements and time to acquire bi-static pulses across a subset of element combinations. This radar system beamforms in the near field, where the target scene of interest is located 3-70 m down range. It utilizes digital beamforming, computed using the range migration synthetic aperture radar (SAR) algorithm. The phased array antenna is fed by transmit and receive fan-out switch matrices that are connected to a UWB LFM pulse compressed radar operating in stretch mode. The peak transmit power is 1 mW and the transmitted LFM pulses are long in time duration (2.5-10 ms), requiring the radar to transmit and receive simultaneously. It will be shown through simulation and measurement that the bi-static antenna pairs are nearly equivalent to 44 elements spaced λ/2 across a linear array. This result is due to the fact that the phase center position errors relative to a uniform λ/2 element spacing are negligible. This radar is capable of imaging free-space target scenes made up of objects as small as 15.24 cm tall rods and 3.2 cm tall metal nails at a 0.5 Hz rate. Applications for this radar system include short-range near-real-time imaging of unknown targets through a lossy dielectric slab and radar cross section (RCS) measurements.

... Cherniakov, M., Kubik, KKT and Nezlin, D. (2000) Radar sensors based on communication low earth orbiting satellites microwave emission. Proceedings IGARSS 2000, IEEE 2000 Int. ... The University of Queensland. Brisbane St Lucia, QLD 4072 +61 7 3365 1111. ...

Simulations of the radar cross section of a heatseeking air-to-air missile model were performed using the CADRCS software. In these simulations at a frequency of 10 GHz, the surface of the missile was considered to be a perfect conductor and to be coated with a radar absorbing material (RAM). The comparison of results from the simulations shows how different parts of the missile contribute to the radar cross section (RCS). Also, it is shown how the RCS of the missile is reduced with the use of RAM.

Physical optics (PO) and the method of equivalent currents (MEC) are used for the formulation and calculation of the backscatter cross section of both the triangular and square trihedral corner reflectors. Scattering from a trihedral corner reflector is dominated by single, double, and triple reflections by the interior walls. A physical optics integration is performed on the entire surface of each plate for the evaluation of the singly reflected fields. Doubly and triply reflected fields are evaluated by first using geometrical optics (oo) at initial reflections to calculate the incident plane wave on the plate where the last reflection occurs. Physical optics is then applied on the illuminated area of that plate. First-order diffractions, which are based on the fringe current expressions for the exterior edges of the trihedral, are also included in the analysis. Predictions compare very well with both experimental and FDTD data.

Radar memancarkan gelombang elektromagnetik mendapatkan data-data yang berkaitan dengan pesawat
terbang yang meliputi jarak, ketinggian, arah dan kecepatan. Untuk identifikasi, radar dilengkapi dengan peralatan
interogator Identification Friend or Foe (IFF) sebagai bagian dari Secondary Surveillance Radar (SSR). Interogator
IFF mengirimkan sinyal pertanyaan kepada pesawat terbang yang ingin diidentifikasi. Pesawat terbang yang
dilengkapi dengan transponder (transmitter responder) akan menjawab sinyal pertanyaan tersebut secara otomatis
berupa kode identifikasi pesawat. Bila pesawat tidak dapat merespon pertanyaan yang diberikan, maka pesawat akan
diidentifikasikan sebagai penerbangan gelap (black flight). Proses identifikasi pada kasus penerbangan gelap dapat
dilakukan dengan menganalisa data Radar Cross Section (RCS) dan kecepatan dari pesawat terbang.
Seringkali data yang tertangkap di radar berupa RCS dan kecepatan pesawat dari sebuah pesawat terbang
tidak selalu sama. Agar proses identifikasi pesawat terbang di udara dapat dilakukan dengan cepat dan memiliki
tingkat keakuratan yang tinggi diperlukan sebuah sistem identifikasi pesawat terbang adaptif yang mampu
mengidentifikasi data yang berubah-ubah namun tetap stabil. Untuk tujuan tersebut, pada makalah ini akan
disampaikan aplikasi Jaringan Saraf Tiruan model Adaptive Resonance Theory 1 (JST-ART1) pada Sistem
Identifikasi Pesawat Terbang (SIPT-ART1) dengan memanfaatkan RCS dan kecepatan pesawat terbang sebagai
parameter identifikasi. Untuk meyakinkan akurasi hasil identifikasi kedua parameter, dilakukan fusi informasi untuk
menyatakan hasil identifikasi.

If several closely spaced targets fall within the same radar beam and between two adjacent matched filter samples in range, monopulse information from both of these samples can and should be used for estimation, both of angle and of range (i.e., estimation of the range to sub-bin accuracy). Similarly, if several closely spaced targets fall within the same radar beam and among three matched filter samples in range, monopulse information from all of these samples should be used for the estimation of the angles and ranges of these targets. Here, a model is established, and a maximum likelihood (ML) extractor is developed. The limits of the number of targets that can be estimated are given for both case A, where the targets are in a beam and in a range "slot" between the centers of two adjacent resolution cells (that is, from detections in two adjacent matched filter samples), and case B, where the targets are in two or more adjacent slots (among three or more adjacent samples). A minimum description length (MDL) criterion is used to detect the number of targets between the matched filter samples, and simulations support the theory.

1] The physical optics approximation is employed in the derivation of a closed form expression for the radar cross section (RCS) of a flat, perfectly conducting plate of various shapes, located over a dielectric, possibly lossy half-space. The half-space is assumed to lie in the far field region of the plate. The well-known "four-path model" is invoked in a firstorder approximation of the half-space contribution to the scattering mechanisms. Numerical results are compared to a reference, Moment Method solution, and the agreement is investigated, to assess the accuracy of the approximations used. The analytical expressions derived can facilitate very fast RCS calculations for realistic scatterers, such as ships in a sea environment, or aircraft flying low over the ground.

The purpose of this study was to begin development of an Inverse Synthetic Aperature Radar imaging capability for the AFIT anechoic chamber. This began with an evaluation of the capabilities and limitations of the existing radar system and the chamber itself for this application. Then, after deciding on the image processing approach, software had to be written to collect the data necessary for image processing. This constituted the majority of this study, and resulted in a versatile, user-friendly program that automates the process of collecting data for high-resolution radar images. The program checks that the data to be collected will lead to a valid radar cross-section (RCS) image, but will allow data collection for general radar images. Finally, the image processing software was begun. This made use of commercially available software packages called PC-MATLAB and PRO-MATLAB. Further work is needed on the image processing software to generate calibrated images, and to perform focusing.

1] Creeping waves play an important role in the analysis of electromagnetic scattering by large objects with curved boundaries. In this paper, an asymptotic model is presented for the back-scattered field on a dielectric-coated cylinder at aspect angles near broadside incidence, a region where the creeping wave has maximum intensity. The monostatic radar cross section is analytically derived from creeping wave poles and their residues, and is validated with data extracted from rigorous method of moments computation of the scattered field by utilizing a novel state space spectral estimation algorithm. Detailed computations reveal a stark contrast between dielectric-coated objects and uncoated metallic ones with regard to creeping wave propagation. Because of smaller curvatureinduced leakage and coherent interaction between incident wave and the dielectric coating, creeping waves, strongly attenuated by metallic objects, become quite pronounced for coated objects. As the frequency increases, the creeping waves are partially trapped inside the dielectric layer and the scattered field becomes quite small. Therefore, in contrast to leakage on a metallic cylinder, which displays smooth monotonic reduction in amplitude with increasing frequency, creeping waves on a coated cylinder exhibit a strong cutoff akin to a guided wave.

To identify an object in the air, Radar will transmit Identification Friend, Foe, or Neutral (IFFN) signal. The detected object then will be manually matched to the flight data. If the air object detected by the Radar is unregistered then this object will be identified as a black flight. In order that this object identification process can be quickly and accurately done, an Identification Friend, Foe, or Neutral (IFFN) system based on Adaptive Resonance Theory 1 Neural Network (ART1-NN) and information fusion is proposed and designed. The system uses the air object Radar Cross Section (RCS) and velocity data as the identifier data. The ART1-NN matches the RCS and velocity data of the detected air object to the data it already learned. The final identification process is done by fusing the information resulted from the ART1-NN matching process by using voting and Boolean AND methods to obtain the identity of the observed air object. The IFFN system is hoped to be able to give a worth contribution in order to guard the Republic of Indonesia sovereignty in the sky

Untuk mengidentifikasi suatu obyek di udara, Radar akan memancarkan sinyal Identification Friend, Foe, or Neutral (IFFN). Obyek yang ditangkap Radar akan dicocokkan dengan data penerbangan yang ada secara manual. Bila obyek udara yang ditangkap oleh Radar tidak terdaftar maka obyek udara tersebut akan diidentifikasikan sebagai penerbangan gelap (black flight). Agar proses identifikasi obyek udara dapat dilaksanakan dengan cepat dan akurat, diajukan dan dirancang satu sistem Identification Friend, Foe, or Neutral (IFFN) berbasis Jaringan Syaraf Tiruan model Adaptive Resonance Theory 1 (JST-ART1) dan fusi informasi. Sistem menggunakan data Radar Cross Section (RCS) dan kecepatan obyek udara sebagai data pengidentifikasi. JST-ART1 bertugas mencocokkan data RCS dan kecepatan obyek udara yang dideteksi dengan data yang telah dipelajarinya. Proses identifikasi akhir dilakukan dengan memfusikan informasi hasil pencocokan JST-ART1 menggunakan metoda voting dan Boolean AND untuk memperoleh identitas obyek udara dalam pengamatan. Sistem IFFN ini diharapkan dapat memberikan satu kontribusi berharga dalam rangka menjaga kedaulatan Negara Kesatuan Republik Indonesia (NKRI) di udara

Inspired by recent advances in multiple-input multiple-output (MIMO) communications, this proposal introduces the statistical MIMO radar concept. To our knowledge, this is the first time that the statistical MIMO is being proposed for radar. The fundamental difference between statistical MIMO and other radar array systems is that the latter seek to maximize the coherent processing gain, while statistical MIMO radar capitalizes on the diversity of target scattering to improve radar performance. Coherent processing is made possible by highly correlated signals at the receiver array, whereas in statistical MIMO radar, the signals received by the array elements are uncorrelated. Radar targets generally consist of many small elemental scatterers that are fused by the radar waveform and the processing at the receiver, to result in echoes with fluctuating amplitude and phase. It is well known that in conventional radar, slow fluctuations of the target radar cross section (RCS) result in target fades that degrade radar performance. By spacing the antenna elements at the transmitter and at the receiver such that the target angular spread is manifested, the MIMO radar can exploit the spatial diversity of target scatterers opening the way to a variety of new techniques that can improve radar performance. In this paper, we focus on the application of the target spatial diversity to improve detection performance. The optimal detector in the Neyman-Pearson sense is developed and analyzed for the statistical MIMO radar. It is shown that the optimal detector consists of non-coherent processing of the receiver sensors' outputs and that for cases of practical interest, detection performance is superior to that obtained through coherent processing. An optimal detector invariant to the signal and noise levels is also developed and analyzed. In this case as well, statistical MIMO radar provides great improvements over other types of array radars. April 26, 2004 DRAFT SUBMITTED TO THE IEEE TRANSACTIONS ON SIGNAL PROCESSING 3 mechanical elements in the system and the ability to steer multiple beams at once are two examples of such advantages.

This paper demonstrates the role of Radar Cross Section (RCS) facilities, consisting of modelling and simulation (M&S), Hardware in the Loop-(HWIL) and field Test and Evaluation (T&E) environments, in a Radar and Electronic Warfare (EW) Defence Research and Evaluation capability. The link between the development and utilisation of radar and EW facilities and the scientific process is illustrated by examples.

All earth-orbiting spacecraft are susceptible to impacts by these particles, which can occur at extremely high speeds and can damage flight-and mission-critical systems. The traditional damage mitigating shield design for this threat consists of a ''bumper'' that is placed several cm away from the main ''inner wall'' of the spacecraft. Typical orbital debris risk analyses that include ballistic limit equations (BLEs) and curves (BLCs) assume that orbital debris particles are spherical in shape. However, spheres are not a common shape for orbital debris; rather, debris fragments might be better represented by other regular or irregular solids. This paper presents the results of a study comparing BLCs developed by NASA and the DoD for velocities up to 4 km/s considering spheres, cubes, and a ''flake'' shape that was proposed within NASA's Standard Breakup Model to represent orbital debris. It also compares performance of these shapes using hydrocodes at higher velocities (7-12 km/s), and generates a combined BLC for these shapes for the entire orbital debris velocity regime. In addition to shape, a multi-view method is used to examine the effects of a variety of cube and flake impact orientations on BLC, as well as a ''characteristic length'' parameter developed by NASA to compare the particle shapes on the basis of their radar cross section. The developed non-spherical BLCs are then evaluated for overall penetration risk considering the orbital debris environment. Their predictions of risk are compared to that predicted using sphere-based BLCs. This methodology is then extended to a single-wall shield design for velocities up to 15 km/sec, and the results of DoD predictions for a sphere and cube are compared with NASA predictions for a sphere having the same characteristic length. The results indicate that we may be over-predicting orbital debris risk for dual-wall shields by a factor of twodand for single walls by a factor of fourdby limiting our analyses to spheres instead of using more representative debris shapes, such as cubes and flakes, and its characteristic length as the primary particle parameter.

Fog is a significant factor affecting the Air Traffic Control (ATC). Significant limitations of the airport capacity are due to fog that causes the reduction of the visibility (Runway Visual Range, RVR). Today METAR (Meteorological Aviation Report) and forecasts TAF (Terminal Aerodrome Forecast) are only available to estimate the visibility variations, but not to estimate the RVR. Scope of this paper is to evaluate the performance of airport radar sensors to detect the fog. Received Power (dBm) Signal to Noise Ratio (dB) Attenuation No Attenuation dB W-band W-band

Signals from the Global Positioning System are constantly being scattered off the entire Earth's surface. These signals can be detected from airplanes, surface platforms and in Low Earth orbit and are known to contain information on the oceans. Recently, a new opportunity to study GPS reflections in space has been realized with the launch in October 2003 of the United Kingdom's Disaster Monitoring Constellation (UK-DMC) satellite. The UK-DMC carries a dedicated GPS reflections receiver and a custom designed downward facing antenna. Using this GPS experiment it is possible to process surface scattered signals and estimate the ocean wind and waves.

The paper describes a simple numerical FLAC model that was developed to simulate the dynamic response of two instrumented reduced-scale model reinforced soil walls constructed on a 1-g shaking table. The models were 1 m high by 1.4 m wide by 2.4 m long and were constructed with a uniform size sand backfill, a polymeric geogrid reinforcement material with appropriately scaled stiffness, and a structural full-height rigid panel facing. The wall toe was constructed to simulate a perfectly hinged toe (i.e. toe allowed to rotate only) in one model and an idealized sliding toe (i.e. toe allowed to rotate and slide horizontally) in the other. Physical and numerical models were subjected to the same stepped amplitude sinusoidal base acceleration record. The material properties of the component materials (e.g. backfill and reinforcement) were determined from independent laboratory testing (reinforcement) and by back-fitting results of a numerical FLAC model for direct shear box testing to the corresponding physical test results. A simple elastic-plastic model with Mohr-Coulomb failure criterion for the sand was judged to give satisfactory agreement with measured wall results. The numerical results are also compared to closed-form solutions for reinforcement loads. In most cases predicted and closed-form solutions fall within the accuracy of measured loads based on ± 1 standard deviation applied to physical measurements. The paper summarizes important lessons learned and implications to the seismic design and performance of geosynthetic reinforced soil walls.

How far can a radar system detect an object depends the radar cross section (RCS) of the target. Corner reflectors are the major scattering centers in the radar signatures of vehicles. The monostatic return from such structures can be reduced by ensuring that surfaces never meet at right angles and by application of radar absorbing materials (RAM). This paper deals

A practical technique is proposed for calibrating singleantenna polarimetric radar systems using a metal sphere plus any second target with a strong cross-polarized radar cross section. This technique assumes perfect isolation between antenna ports. It is shown that all magnitudes and phases (relative to one of the like-polarized linear polarization configurations) of the radar transfer function can be calibrated without knowledge of the scattering matrix of the second target. Comparison of the values measured (using this calibration technique) for a tilted cylinder at X-hand with theoretical values shows agreement within +0.3 dB in magnitude and +5" in phase. The radar overall cross-polarization isolation was 25 dB. The technique is particularly useful for calibrating a radar under field cohditions, because it does not require the careful alignment of calibration targets.

Through-lossy-slab radar imaging will be shown at stand-off ranges using a low-power, ultrawideband (UWB), frequency modulated continuous wave (FMCW) radar system. FMCW is desirable for through-slab applications because of the signal gain resulting from pulse compression of long transmit pulses (1.926-4.069 GHz chirp in 10 ms). The difficulty in utilizing FMCW radar for this application is that the air-slab boundary dominates the scattered return from the target scene and limits the upper bound of the receiver dynamic range, reducing sensitivity for targets behind the slab. A method of range-gating out the air-slab boundary by significant band-limiting of the IF stages facilitates imaging of low radar cross section (RCS) targets behind the slab. This sensor is combined with a 1D linear rail and utilized as a rail synthetic aperture radar (SAR) imaging system. A 2D model of a slab and cylinder shows that image blurring due to the slab is negligible when the SAR is located at a stand-off range of 6 m or greater, and thus, the two-way attenuation due to wave propagation through the slab is the greatest challenge at stand-off ranges when the air-slab boundary is range-gated out of the scattered return. Measurements agree with the model, and also show that this radar is capable of imaging target scenes of cylinders and rods 15.24 cm in height and 0.95 cm in diameter behind a 10 cm thick lossy dielectric slab. Further, this system is capable of imaging free-space target scenes with transmit power as low as 5 pW, providing capability for RCS measurement.

This research study presents a novel design of star-shaped fractal patch antenna for miniaturisation and backscattering radar cross-section (RCS) reduction. The proposed fractal antenna gives 50% size reduction compared with a conventional circular microstrip patch (CCMP) antenna. The antenna is studied experimentally for return loss behaviour using vector network analyser R&S ZVA40. It can be useful for wireless application in 0.85-4 GHz frequency band. Further, the study focuses on backscattering RCS (both monostatic and bistatic) reduction by the proposed antenna compared with the CCMP antenna. It is found that increase in number of fractal iterations included in the conventional patch to design fractal antenna geometry reduces backscattering RCS at multiband compared to the conventional patch antenna. This reduction in backscattering RCS by the antenna is observed at multiband. The antenna can be tuned for low backscattering by variation in the substrate dielectric constant and thickness and the superstrate dielectric constant and thickness. For maximum RCS reduction by the antenna, optimisation of substrate thickness becomes necessary. The study also deals with effect of frequency and aspect angle variation on backscattering RCS reduction.

This paper discusses alternative models for the determination of the interior irradiation contribution to the radar cross section (RCS) of open-ended cavities. Typical applications of practical interest include radiation field prediction of openended waveguides and signature prediction of jet engine air intakes and exhaust outlets. It is shown and explained why the classic perfectly conducting (PEC) ground plane (GP) model sometimes predicts measured cavity RCS very poorly. Examples where PEC GP model predictions are 5 dB or more off are provided. Verifications that the used PEC GP model is correctly implemented are provided. A physical optics based modification of the classic PEC GP model is provided and explained. A novel model where the cavity aperture forms an opening in an infinite radar absorbing (IBC) screen is proposed verified and validated. The IBC model resembles the common experimental set-up, and poses an efficient novel halfspace type replacement model approximating a full space setting. The modified PEC GP model or the IBC model can be used interchangeably for cavities with electrically large apertures.

This paper presents a comparative study of target localization techniques for multiple-input multiple-output (MIMO) radar systems with widely spread elements with either non-coherent or coherent processing. The performance of localization techniques utilizing both processing techniques is evaluated based on a closed-form solution developed for the best linear unbiased estimator (BLUE). This estimator provides insight into the relation between the radar locations, target location, and localization accuracy through the use of the geometric dilution of precision (GDOP) metrics. The best achievable accuracy for the coherent case is obtained and a comparative study to the non-coherent case is provided. MIMO radar systems with coherent processing are shown to benefit from a coherency gain, compared with the case of non-coherent processing. This gain is proportional to the ratio of the signal carrier frequency to the effective bandwidth (typically of the order of hundreds). The footprint of multiple sensors provides a MIMO gain for both processing techniques. This MIMO gain is proportional to the product of the number of transmitting and receiving sensors. Further analysis of the later gain is made possible by the use of the GDOP contour maps that offer a clear understanding of the achievable accuracy at various target locations.

The objective of this study was to illustrate how different methods of obtaining the Radar Cross Section (RCS) of an object may produce different results. RCS diagrams of a metallic airplane model (length, 0.64 m) were obtained in an anechoic chamber, with a Lab-Volt RCS system, and simulated with a simulation software. The measurements and simulations were carried out at the radar frequency of 9.4 GHz. The resulting RCS diagrams show that although there was a good correspondence between the main features in the RCS diagrams, some differences can still be observed, highlighting the need for different techniques to fully represent the RCS of an object.

This paper presents a new and original approach for computing the high-frequency radar cross section (RCS) of complex radar targets in real time with a 3-D graphics workstation. The aircraft is modeled with I-DEAS solid modeling software using a parametric surface approach. High-frequency RCS is obtained through physical optics (PO), method of equivalent currents (MEC), physical theory of diffraction (PTD), and impedance boundary condition (IBC). This method is based on a new and original implementation of high-frequency techniques which we have called graphical electromagnetic computing (GRECO). A graphical processing approach of an image of the target at the workstation screen is used to identifi the surfaces of the target visible from the radar viewpoint and obtain the unit normal at each point. High-frequency approximations to RCS prediction are then easily computed from the knowledge of the unit normal at the illuminated surfaces of the target. The image of the target at the workstation screen (to be processed by GRECO) can be potentially obtained in real time from the I-DEAS geometric model using the 3-D graphics hardware accelerator of the workstation. Therefore, CPU time for RCS prediction is spent only on the electromagnetic part of the computation, while the more time-consuming geometric model manipulations are left to the graphics hardware. This hybrid graphic-electromagnetic computing (GRECO) results in realtime RCS prediction for complex radar targets.

We present a novel high-order method of moments (MoM) with interpolatory vector functions, on quadrilateral patches. The main advantage of this method is that the Hdiv conforming property is enforced, and at the same time it can be interpreted as a point-based scheme. We apply this method to field integral equations (FIEs) to solve time-harmonic electromagnetic scattering problems. Our approach is applied to the first and second Nédélec families of Hdiv conforming elements. It consists in a specific choice of the degrees of freedom (DOF), made in order to allow a fast integral evaluation. In this paper we describe these two sets of DOF and their corresponding quadrature rules. Sample numerical results on FIE confirm the good properties of our schemes: faster convergence rate and cheap matrix calculation. We also present observations on the choice of the discretization method, depending on the FIE selected.

MHz and its performance evaluation using simulated Radar Cross Section (RCS) are presented. The RCS variations of the tag antenna are evaluated over azimuth and elevation angular ranges for three cases of load: short, matched load and open. The tag exhibits appreciably good differential RCS between its switching states over wide azimuth angular ranges and over the entire elevation angular ranges. The measured read range variations over the azimuth and elevation angular ranges are also presented to validate the simulated results.