Bistatic Radar Cross Section Research Articles

The Second-Order Bistatic High-Frequency Radar Cross Section of Ocean Surface for an Antenna on a Floating Platform

. The 2nd-order bistatic high-frequency radar cross section of ocean surface is derived for the case of a fixed receiver and a floating transmitter. The 2nd-order radar cross section contains both the hydrodynamic contribution and the electromagnetic contribution. The 2nd-order hydrodynamic contribution is obtained based on the 1st-order bistatic model with antenna motion. The derivation of the 2nd-order electromagnetic contribution begins with a general expression for the bistatically received 2nd-order electric field for the case of a floating antenna. A new bistatic electromagnetic coupling coefficient, which, unlike some earlier versions, produces no nonphysical singularities in the radar cross section, is derived. The new bistatic radar cross section model is verified by comparing it with that of a monostatic swaying antenna case and that of the bistatic case without antenna motion. The effect of platform motion on simulated Doppler spectra is considered for a variety of sea states and operating frequencies. The motion-induced 2nd-order peaks appearing in the spectrum are seen to have significantly less energy than those in the 1st-order case.

A Wideband and Polarization-Independent Metasurface Based on Phase Optimization for Monostatic and Bistatic Radar Cross Section Reduction

A broadband and polarization-independent metasurface is analyzed and designed for both monostatic and bistatic radar cross section (RCS) reduction in this paper. Metasurfaces are composed of two types of electromagnetic band-gap (EBG) lattice, which is a subarray with “0” or “π” phase responses, arranged in periodic and aperiodic fashions. A new mechanism is proposed for manipulating electromagnetic (EM) scattering and realizing the best reduction of monostatic and bistatic RCS by redirecting EM energy to more directions through controlling the wavefront of EM wave reflected from the metasurface. Scattering characteristics of two kinds of metasurfaces, periodic arrangement and optimized phase layout, are studied in detail. Optimizing phase layout through particle swarm optimization (PSO) together with far field pattern prediction can produce a lot of scattering lobes, leading to a great reduction of bistatic RCS. For the designed metasurface based on optimal phase layout, a bandwidth of more than 80% is achieved at the normal incidence for the −9.5 dB RCS reduction for both monostatic and bistatic. Bistatic RCS reduction at frequency points with exactly 180° phase difference reaches 17.6 dB. Both TE and TM polarizations for oblique incidence are considered. The measured results are in good agreement with the corresponding simulations.

The Study of Full-Size Objects’ Bistatic Rader Cross Section Measurement Based on Photoelectric Conversion

In the past years, bistatic Radar Cross Section (RCS) characteristic has been caught increasing attention. The paper presents a bistatic RCS measurement system of full-size goals, which uses photoelectric conversion technology to solve the problem that excessive electrical signal attenuation exits because of the large distance between sending and receiving antenna. The paper analyzes the basic principle of photoelectric conversion and RCS measurement system, applies photoelectric conversion technology to RCS measurement system, and tests whether RCS measurement system works well while using photoelectric conversion technology. The test results show that the system can efficiently obtain the bistatic RCS characteristic of full-size targets.

Bistatic High Frequency Radar Ocean Surface Cross Section for an FMCW Source with an Antenna on a Floating Platform

The first- and second-order bistatic high frequency radar cross sections of the ocean surface with an antenna on a floating platform are derived for a frequency-modulated continuous wave (FMCW) source. Based on previous work, the derivation begins with the general bistatic electric field in the frequency domain for the case of a floating antenna. Demodulation and range transformation are used to obtain the range information, distinguishing the process from that used for a pulsed radar. After Fourier-transforming the autocorrelation and comparing the result with the radar range equation, the radar cross sections are derived. The new first- and second-order antenna-motion-incorporated bistatic radar cross section models for an FMCW source are simulated and compared with those for a pulsed source. Results show that, for the same radar operating parameters, the first-order radar cross section for the FMCW waveform is a little lower than that for a pulsed source. The second-order radar cross section for the FMCW waveform reduces to that for the pulsed waveform when the scattering patch limit approaches infinity. The effect of platform motion on the radar cross sections for an FMCW waveform is investigated for a variety of sea states and operating frequencies and, in general, is found to be similar to that for a pulsed waveform.

한국형 발사체의 스킨 추적 성능 향상을 위한 RCS 분석

In this paper, we calculate monostatic RCS(Radar Cross Section) and bistatic RCS for improving the Performance of the skin tracking of KSLV-II and the results were compared. EM(Electromagnetic) simulator was used for numerical analysis. For the two paths(L, S), after the vehicle was launched, RCS was calculated for region from 280 to 400 seconds. In the case of using the bistatic radar system, when the vehicle was launched to the L path, tracking performance was better when we receive RCS in Jeju than in Goheung. When the vehicle was launched to the S path, tracking performance was better when we receive RCS in Goheung than in Jeju. In the case of using the monostatic radar system, when the vehicle was launched to the L path, tracking performance was better when we receive RCS in Goheung than in Jeju. When the vehicle was launched to the S path, tracking performance was better when we receive RCS in Jeju than in Goheung.

Aircraft classification based on radar cross section of long-range trajectories

The paper studies instantaneous Doppler signature extraction from within a very high frequency (VHF) band spectrogram presented by the authors in previous work. The context of the current method is long-range aircraft detection by VHF Doppler effect. The method proposed calculates bistatic radar (BR) cross-section (BRCS) profiles and the correlation between them for different types of aircraft. The analysis is based on data represented by automatic dependent surveillance-broadcast (ADS-B) trajectory collection and passive BR with TV station as an illuminator of opportunity. Throughout the analysis, ADS-B data on location of an aircraft were adjusted with the use of extracted Doppler shift information. Then, this ground truth information on location was used for proper evaluation of BRCS profiles and, finally, for validation of the extraction method. The method is able to classify common intercontinental aircraft by size class with 70% accuracy from a 100-km distance by using an illuminator of opportunity located 300 km away.

A novel combinatorial triangle‐type AMC structure for RCS reduction

ABSTRACTA novel combinatorial triangle‐type artificial magnetic conductor (AMC) structure for radar cross section (RCS) reduction is presented in this article. The AMC part in conventional chessboard configuration is replaced with four triangle‐type AMC parts, so that the power can be transferred into more directions leading to the peak scattered field reduction. A simplified model is constructed to analyze the behavior of the proposed structure. The simulated results show that the peak value is reduced by more than 5 dB compared with the conventional chessboard configuration and the bistatic RCS is below −10 dB in a wide angular range from theta = −25° to 25°. Moreover, measurement of the monostatic RCS for the proposed structure is also conducted. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2728–2732, 2015

Bistatic RCS of Spherical Chaff Clouds

Previous determinations of bistatic radar cross section (RCS) of dipole clouds assumed incoherent scattering which does not hold near the forward scatter direction. In order to obtain unified expressions that are valid for scattering in all directions, the average bistatic RCS of a spherical chaff cloud is derived as the sum of incoherent and coherent contributions. Simplified forms for these expressions are provided for five representative directions/polarizations. In the forward scatter direction, the coherent contribution is dominant, but in the angular region about that direction, the bistatic RCS pattern is beam-like and is dependent on both the coherent and incoherent contributions. An expression is provided for the width of this “beam.” The derived expressions are verified by statistical numerical RCS computations based on the method of moments. Since these numerical calculations include interparticle coupling, whereas the derived expressions assume that such coupling is not present, the numerical results also provide criteria for the interparticle distance that is required for this coupling to be ignored in bistatic RCS calculations. This distance is seen to depend on the direction of scatter.

Checkerboard EBG Surfaces for Wideband Radar Cross Section Reduction

Electromagnetic band-gap (EBG) structures have noteworthy electromagnetic characteristics that include their reflection phase variations with frequency. This paper applies this unique reflection phase property to alter the direction of the fields scattered by a radar target to reduce its radar cross section (RCS). This redirecting of the scattered fields occurs when a surface is covered with a checkerboard of alternating EBG structures, and results in a wider frequency band RCS reduction. RCS reduction compared to a PEC surface of 10 dB can be realized over 60% frequency bandwidth. Simulations of monostatic and bistatic RCSs of two dual EBG checkerboard surfaces, square and hexagonal, are compared with those of equal-sized PEC ground planes. The simulated monostatic RCS is also compared with measurements. Both TE <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</sup> and TM <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</sup> polarizations for oblique incidence are considered. Excellent agreement is obtained between simulated and measured patterns, for both the square and the hexagonal EBG checkerboard surfaces. An approximate analytical expression is provided as a guideline for a 10-dB RCS reduction of a dual EBG checkerboard surface compared to that of a PEC.

Balanced inversion of simulated bistatic radar cross-section data for remote sensing of snow-covered sea ice

The reconstruction of the dielectric profile of snow-covered sea ice from simulated bistatic radar cross-section data is investigated. To this end, a cost function representing the discrepancy between the true radar cross-section data and the calculated radar cross-section data due to a predicted dielectric profile is formed. This cost function is iteratively minimized using the differential evolution algorithm so as to reconstruct the unknown dielectric profile. Herein, four different formulations for this cost function are considered. These formulations are distinguished by their utilized weighting factors for each data point within the bistatic radar cross-section data set. Although these cost functions use the same simulated bistatic normalized radar cross-section data set, it will be shown that the reconstruction accuracy achievable from each of them will be different. Finally, an appropriate weighting scheme for bistatic data sets, which emphasizes the scattering data points collected at the vicinity of the specular angle, is presented. It will be shown that the use of this weighting scheme results in enhanced reconstruction accuracy as compared to the other formulations. It is speculated that the proposed weighting scheme balances the individual data points more properly, thus, resulting in enhanced accuracy.

Analysis of absorption characteristics of stacked patch arrays on moderately lossy dielectric layers

It is demonstrated that a square patch array on a moderately lossy dielectric can be transformed into a near-perfect absorber by the addition of a metallic square loop layer between the patch array and the metal back. In this configuration, the condition of perfect absorption can be easily obtained by modifying loop dimensions. The absorption properties of this configuration are analyzed theoretically using an equivalent circuit model and full-wave electromagnetic simulations. Experimental investigations included a bistatic radar cross-section measurement, which ensured that there are no scattered fields in other directions. An array structure built on a commercially available FR4 substrate with copper metallization is used to experimentally validate these results.

Relativistic FDTD Analysis of Far-Field Scattering of a High-Speed Moving Object

Far-field scatterings of uniformly moving conducting and dielectric objects are analyzed in this letter. Using the Lorentz transformation, the scattering problem of a high-speed moving object in the laboratory frame, which is stationary with respect to the free space, is transformed to that of a motionless object in the rest frame that moves with the moving object. Then the near-zone scattered fields are solved by the Finite Difference Time Domain (FDTD) algorithm. Applying near-to-far field transformation, far-zone scattered fields are acquired in the rest frame. Subsequently, the scattered fields are transformed back to the laboratory frame. Our approach is validated against previously published results for the case of a uniformly moving two-dimensional object. Numerical examples show that the effects of the motion on the bistatic radar cross sections (RCS) and Doppler are non-negligible for high-speed objects.

Radar cross section reduction of microstrip antenna based on wide-band metamaterial absorber

We design a wide-band metamaterial absorber (WBMA) with stable polarization and wide incident angle by loading a lumped resistance. The full-width at half-maximum of the absorber is 98%, the bandwidth of absorbing rate of more than 90% reaches 10.42 GHz, and the peak absorbing rate is 99.9% in the normal wave incidence. Loading the WBMA around the microstrip antenna by sharing the same substrate and ground plane, we fabricate the WBMA antenna, whose radar cross section (RCS) sharply decreases in the wide frequency range. Simulation and experimental results show that the antenna's radiation pattern is almost unchanged: just only the former gain improves 0.53 dB after loading the WBMA. Under different polarized waves, the antenna's monostatic RCS reduction is more than 3 dB within the working frequency band and beyond the working frequency band (6.95-17.91 GHz), the maximum value is 21.2 dB. The bistatic RCS decreases significantly from -48° to 48° at the middle working frequency (8 GHz), which well achieves the antenna stealth at the wide-band frequency and wide angle.

The Influence of Plasma Induced by &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$\alpha $ &lt;/tex-math&gt;&lt;/inline-formula&gt;-Particles on the Radar Echoes

At the different radioactivity, temperature, pressure, heights, and incident angles, the influences of the electromagnetic wave propagating in the α-decay radionuclide layer (RNL) coated on a perfect electric conductor system were simulated by the finite-difference time-domain method. The maximum electron density ionized by 5.45-MeV α-particles is ~1.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> per cubic centimeter when the radioactivity is 10 Ci/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The decrease of the reflectivity at altitude is much better than at ground and the decreasing amplitudes could reach 1-20 dB in the frequency range from 300 MHz to 40 GHz at an altitude of 10000 m. In addition, the same RNL would significantly reduce the back scattering bistatic radar cross section (RCS) of the platform. The decrease of RCS along the direction of the originally strongest reflection wave is nearly 25.5 dB when the incident angle is 60°.

Measurement and evaluation of radar cross section for furniture in an indoor propagation channel

Abstract. This paper has attempted to evaluate the radar cross section (RCS) of two furniture items in an indoor environment in a frequency range of 3–7 GHz of the ultra-wideband (UWB) range. The RCS evaluation is achieved through an extended version of the radar equation that incorporates the channel transfer function of scattering. The time-gating method was applied to remove the multipath effect, a phenomenon which typically occurs in the indoor environment. Two double-ridged waveguide horn antennas for both vertical and horizontal polarizations were used to obtain the transfer function of scattering of the furniture prior to analysis in order to derive their bistatic RCS. The RCS results validate the applicability of the proposed extended radar equation to the indoor propagation prediction.

Calculation of electromagnetic waves scattering by non-homogeneous surface impedance using moment method

In this paper, using the method of moments to calculate the current density and mono-static and bi-static radar cross section of an unlimited strip by a non-homogeneous impedance. Here, incident wave is a plane wave. To authenticate the method, using the iterative method to solve the integral equations is engaged. Simulation results show that the surface with non-homogeneous impedance has reduced or increase in potential for bi- and mono-static radar cross section in certain azimuth.

A Retrodirective Antenna Array With Polarization Rotation Property

A planar passive retrodirective antenna (RDA) array with polarization rotation property is proposed in this paper using the substrate integrated waveguide (SIW) technology, which can be used in monostatic radar applications. The proposed RDA array adopts planar bandwidth-enhanced SIW cavity-backed wide slot antennas as the radiation elements. The polarization rotation property can be achieved by using radiation elements in two different configurations. A W-band prototype RDA array with 16 radiation elements is designed and fabricated using the single-layer printed circuit board (PCB) process at 79 GHz for automotive short-range radar applications. The measurement setup for monostatic and bistatic radar cross section (RCS) responses as well as the calibration process are presented. The retrodirective property and the polarization rotation property are realized by the proposed RDA array. The simulated and measured results of monostatic and bistatic RCS responses are in good agreement, which can cover an incident angle of ±17 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> from bore-sight with its normalized monostatic RCS response dropped by about 3 dB.

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.

Electromagnetic TE scattering by a conducting cylinder coated with an inhomogeneous dielectric/magnetic material

The problem of electromagnetic TE scattering by an infinitely long conducting cylinder coated with an inhomogeneous dielectric/magnetic material is analyzed. A volume-surface integral equation (VSIE) approach is utilized to model the problem. By imposing the boundary conditions on the conducting surface, a surface magnetic field integral equation (MFIE) is developed. Inside the volume of the coating region, volume MFIEs are applied. The resultant integral equations are solved using the moment method. Numerical results for the bistatic radar cross section for different structures are presented. The results are validated using the exact series solution for a conducting circular cylinder coated with multilayers of homogeneous materials. Two types of coating materials are studied: the conventional or double positive (DPS) materials and the double negative (DNG) materials.

Series expansion feasibility of singular integral in method of moments

When calculating electromagnetic scattering using method of moments (MoM), integral of the singular term has a significant influence on the results. This paper transforms the singular surface integral to the contour integral. The integrand is expanded to Taylor series and the integral results in a closed form. The cut-off error is analyzed to show that the series converges fast and only about 2 terms can agree well with the accurate result. The comparison of the perfect electric conductive (PEC) sphere's bi-static radar cross section (RCS) using MoM and the accurate method validates the feasibility in manipulating the singularity. The error due to the facet size and the cut-off terms of the series are analyzed in examples.