A Study on Multivariable Interactions Concerning Radar Cross Section Reduction through Geometric Attributes

This resolution 5 (25−1 factorial) study aimed to ascertain an understanding of the interactions between different geometries on the resulting Radar Cross Section (RCS) of a target. The results of the study are in line with the general understanding of the impact different geometries have on RCS but show that geometries can also influence the variance of measured RCS, and typical attributes that reduce RCS increase the variance of the measured RCS. Notably, an increased angle between the front face of a plate and the direction of the radar signal decreased RCS but increased the variance of the RCS measured.

Solution for polarimetric radar cross section measurement and calibration

The exact radar cross-section （RCS） measurement is difficult when the scattering of targets is low. Ful polarimetric cali-bration is one technique that offers the potential for improving the accuracy of RCS measurements. There are numerous polarimetric calibration algorithms. Some complex expressions in these algo-rithms cannot be easily used in an engineering practice. A radar polarimetric coefficients matrix （RPCM） with a simpler expression is presented for the monostatic radar polarization scattering matrix （PSM） measurement. Using a rhombic dihedral corner reflector and a metal ic sphere, the RPCM can be obtained by solving a set of equations, which can be used to find the true PSM for any target. An example for the PSM of a metal ic dish shows that the proposed method obviously improves the accuracy of cross-polarized RCS measurements.

Recognition of the major scattering sources on complex targets based on the high frequency radar cross section integrated calculation technique

Based on the high frequency （HF） integrated radar cross section （RCS） calculation approach, a technique of detecting major scattering source is developed by using an appropriate arithmetic for scattering distribution and scattering source detection. For the perfect adaptability to targets and the HF of the HF integrated RCS calculation platform, this technique is suitable to solve large complex targets and has lower requirement to the target modeling. A comparison with the result of 2-D radar imaging confirms the accuracy and reliability of this technique in recognition of the major scattering source on complex targets. This technique provides the foundation for rapid integrated evaluation of the scattering performance and 3-D scattering model reconstruction of large complex targets.

Radar Cross Section Prediction and Reduction for Naval Ships

Radar cross section（RCS） is the measurement of the reflective strength of a target.Reducing the RCS of a naval ship enables its late detection,which is useful for capitalizing on elements of surprise and initiative.Thus,the RCS of a naval ship has become a very important design factor for achieving surprise,initiative,and survivability.Consequently,accurate RCS determination and RCS reduction are of extreme importance for a naval ship.The purpose of this paper is to provide an understanding of the theoretical background and engineering approach to deal with RCS prediction and reduction for naval ships.The importance of RCS,radar fundamentals,RCS basics,RCS prediction methods,and RCS reduction methods for naval ships is also discussed.

Impact of emulsification of crude oil on normalized radar cross section

The emulsification of crude oil is caused by the oil flowing into the water,resulting in the increase of oil film tension,viscosity,water content,and volume,which brings great harm to the marine ecological environment and difficulties for the cleanup of marine emergency equipment.The realization observation of emulsification crude oil will increase the response speed of marine emergency response.Therefore,we set up crude oil emulsification samples to study the physical property in laboratory and conducted radar measurements at different incidence angles in outdoor.The radar is C band in resolution of 0.7 m by 0.7 m.A fully polarimetric scatterometer(HH,VV,and VH/HV)is mounted at 1.66 m(minimum altitude)height at an incidence angle between 35°and 60°.An asphalt content of less than 3%crude oil and the filtered seawater were used to the outdoor emulsification scattering experiment.The measurement results are as follows.The water content can be used to describe the process of emulsification and it is easy to measure.Wind speed,asphalt content,seawater temperature,and photo-oxidation affect the emulsifying process of crude oil,and affects the normalized radar cross section(NRCS)of oil film but wind is not the dominant factor.It is the first time to find that the emulsification of crude oil results in an increase of NRCS.

Ultra-wideband low radar cross-section metasurface and its application on waveguide slot antenna array

A novel approach devoted to achieving ultra-wideband radar cross section reduction（RCSR） of a waveguide slot antenna array（WGSAA） while maintaining its radiation performance is proposed. Three kinds of artificial magnetic conductors（AMCs） tiles consisting of three types of basic units resonant at different frequencies are designed and arranged in a novel quadruple-triangle-type configuration to create a composite planar metasurface. The proposed metasurface is characterized by low radar feature over an ultra-wideband based on the principle of phase cancellation. Both simulated and measured results demonstrate that after the composite metasurface is used to cover part of the antenna array, an ultrawideband RCSR involving in-band and out-of-band is achieved for co-and cross-polarized incident waves based on energy cancellation, while the radiation performance is well retained. The proposed method is simple, low-cost, and easy-tofabricate, providing a new method for ultra-wideband RCSR of an antenna array. Moreover, the method proposed in this paper can easily be applied to other antenna architectures.

Analytical Estimation of Radar Cross Section of Infinitely Long Conducting Cylinder Coated with Metamaterial

Aerospace structures can be approximately modeled as a combination of canonical structures such as cylinder,cone and ellipsoid.Thus the RCS estimation of such canonical structures is of prime interest.Furthermore metamaterials possess peculiar electromagnetic properties which can be useful in modifying the RCS of structures.This paper is aimed at calculating the RCS of an infinitely long PEC circular cylinder coated with one or two layers of metamaterial.The incident and scattered fields of coated cylinder are expressed in terms of series summation of Bessel and Hankel functions.The unknown coefficients of summation are obtained by applying appropriate boundary conditions.The computations are carried out for both principal polarizations.The computed results are validated against the numerical-based method of moments.Further,the variation of RCS of the metamaterial coated PEC cylinder with material parameters,frequency,aspect angle and polarization is analyzed.

Radar Cross Section Calculation for Wing-Body Blended Targets

A new method of calculating the radai cross section (RCS) for wing-body blended targets is presented and verified. The method utilizes a computer program for modeling targets' geometry in terms of small pieces. The calculation is based on physical optics approximation. Examples are given to show the validity of the method.

Radar Cross Section Analysis Using Physical Optics and Its Applications to Marine Targets

Radar Cross Section (RCS) is one of the most considerable parameters for ship stealth design. As modern ships are larger than their predecessors, RCS must be managed at each design stage for its reduction. For predicting RCS of ship, Radar Cross Section Analysis Program (RACSAN) based on Kirchhoff approximation in high frequency range has been developed. This program can present RCS including multi-bounce effect in exterior and interior structure by combination of geometric optics (GO) and physical optics (PO) methods, coating effect by using Fresnel reflection coefficient, and response time pattern for detected target. In this paper, RCS calculations of ship model with above effects are simulated by using this developed program and RCS results are discussed.

MONOSTATIC RADAR CROSS SECTION FOR REFLECTOR ANTENNAS

The calculation formulas of monostatic radar cross-section (RCS) of arbitrary re-flectors with arbitrarily polarized plane-wave incidence are derived, where the spicular field isobtained by geometrical optics (GO) and the edge-diffracted field is calculated by the method ofequivalent currents (MEC). Some typical calculated results are given by means of RCS spatialgraphs. For both horizontal and vertical polarizations, the theoretical results obtained in thispaper agree very well with the experimental results as well as the results from uniform theory ofdiffraction.

Radar cross section of arbitrary polished spheres at terahertz frequencies

We develop an efficient method for polished metallic sphere’s scattering prediction in terahertz band when its frequency dispersion property is considered. By deducing scattering solution of the lossy metallic sphere, the radar cross section(RCS)of different metallic spheres is given at terahertz frequencies. The investigation of the RCS of polished metallic spheres shows the normalized RCS is always same to the metals’ normal incidence reflectivity when the sphere becomes electrically large. The metals which have high reflectivity(such as Al, Cu, Ag and Au) show that the corresponding RCS of the spheres is almost πa2 in terahertz band. The sphere’s RCS of the transition metal such as Fe begins to decrease obviously since the far infrared.

CONTOUR DESIGN AND PRACTICE FOR A LOW RADAR CROSS SECTION VEHICLE

On the basis of the canard configuration a contour stealth design including chiefly the wing, the fuselage and their connection type is projected. The prime project of a blended wing body vehicle with canard is provided and through the change of the fuselage head form and the different fin disposals, the radar cross section (RCS) is optimized. The average value of RCS and the value of RCS in the ± 45 ° front sector for different designs are illustrated. The model measurement proves that the project having a sharp head fuselage and 30 ° angle double fin has the minimum value of RCS. The wind tunnel test to the model with RCS optimized proved that the vehicle project has excellent aerodynamic characteristics such as high lift curve slope, up to 26° stalling angle, high lift / drag ratio equal to 8, and also has low RCS value in the front sector and in the lateral sector.

Solving multi-object radar cross section based on wide-angle parabolic equation method

Based on a Pade approximation, a wide-angle parabolic equation method is introduced for computing the multiobject radar cross section （RCS） for the first time. The method is a paraxial version of the scalar wave equation, which solves the field by marching them along the paraxial direction. Numerical results show that a single wide-angle parabofic equation run can compute multi-object RCS efficiently for angles up to 45 ° . The method provides anew and efficient numerical method for computation electromagnetics.

Efficient Calculation of the Radar Cross Section at the Interior Resonance by the Inverse Power Method

It is well known that the incorrect results will be given using either the electric or magnetic field integral equation to calculate the radar cross section (RCS) of a closed body at the interior resonance. In this paper, an effective iterative technique is used to correct the calculated surface current density from the electric field integral equation. The radar cross section is computed for an infinite conducting circular cylinder at the interior resonance, and the obtained results are in good agreement with the analytical results. The backscattering cross section of an infinite triangular cylinder in the vicinity of a resonant frequency is also calculated. It is shown that the presence method is efficient and accurate.

Scaled radar cross section measurement method for lossy targets via dynamically matching reflection coefficients in THz band

In the terahertz band,the dispersive characteristic of dielectric material is one of the major problems in the scaled radar cross section(RCS)measurement,which is inconsistent with the electrodynamics similitude deducted according to the Maxwell’s equations.Based on the high-frequency estimation method of physical optics(PO),a scaled RCS measurement method for lossy objects is proposed through dynamically matching the reflection coefficients according to the distribution of the object facets.Simulations of the model of SLICY are conducted,and the inversed RCS of the lossy prototype is obtained using the proposed method.Comparing the inversed RCS with the calculated results,the validity of the proposed method is demonstrated.The proposed method provides an effective solution to the scaled RCS measurement for lossy objects in the THz band.

Wideband radar cross section reduction based on absorptive coding metasurface with compound stealth mechanism

A scheme of combing wave absorption and phase cancellation mechanisms for widening radar cross section(RCS)reduction band is proposed.An absorptive coding metasurface implementing this scheme is derived from traditional circuit analog absorber(CAA)composed of resistive ring elements which characterize dual resonances behavior.It is constructed by replacing some of the CAA elements by another kind of resistive ring elements which is singly resonant in between the original two resonant bands and has reflection phase opposite to that of the original elements at resonance.Hence the developed metasurface achieves an improved low-RCS band over which the lower and higher sub-bands are mainly contributed by wave absorption mainly while the middle sub-band is formed by joint effect of wave absorption and antiphase cancellation mechanisms.The polarization-independent wideband RCS reduction property of the metasurface is validated by full-wave simulation results of a preliminary and an advanced design examples which employ the same element configuration but different element layout schemes as partitioned distribution and random coding.The advanced design also exhibits broadband bistatic low-RCS property and keeps a stable specular RCS reduction performance with regard to incident elevation angle up to 35◦.The advanced design is fabricated and the experimental results of the sample agrees qualitatively well with their simulated counterparts.The measured figure of merit(i.e.,low-RCS bandwidth ratio versus electrical thickness)of the sample is 40.572,which is superior to or comparable with those for most of other existing metasurface with compound RCS reduction mechanism.The proposed compound metasurface technique also features simple structure,light weight,low cost and easy fabrication compared with other techniques.This makes it promising in applications such as radar stealth and electromagnetic compatibility.

Wideband radar cross-section reduction using plasma-based checkerboard metasurface

For stealth technology,in order to overcome the limitations of thin-layer plasma for electromagnetic waves attenuation and further broaden the radar cross-section(RCS)reduction(RCSR)band of the metasurface,the plasma-based checkerboard metasurface composed of plasma and checkerboard metasurface is investigated to achieve better RCSR.We designed a checkerboard metasurface which can achieve abnormal reflection to reduce RCS and whose-10d B RCSR bandwidth is from 8.1 to 14.5 GHz,the RCSR principle of it lies in the backscattering cancellation,which depends on the phase difference of artificial magnetic conductor(AMC)units.The designed plasma-based checkerboard metasurface is a thin composite structure,including a checkerboard metasurface,a plasma layer,and an air gap which is between them.Full wave simulations confirm that the plasma-based checkerboard metasurface’s–10 dB RCS reduction bandwidth and RCS reduction amplitude,are both increased under different polarized waves compared with the only single plasma or the only metasurface.We also introduced the reason and mechanism of the interaction between plasma and the checkerboard metasurface to improve the RCSR effect in detail.As plasma-based checkerboard metasurface does not need the plasma to be too thick for plasma stealth,its application in practical scenarios is easier to implement.

Influence of plasma induced by radionuclide layer on the radar cross section of spherical objects

The influence of theα-decay radionuclide layer(the energy ofα-particles are 5.45 Me V)on the radar cross section(RCS)of sphere objects was calculated under different radioactivities,frequencies,and sphere radii.When the sphere radius is smaller than 50 cm,the tendency of the electron densities of the plasma slab is to ascend first and then descend,and the typical maximum electron densities with a radioactivity of 10 Ci/cm2raises from 7.02×1010to 1.76×1011when the sphere radii increases from 10 to 300 cm.The average data of a normalized RCS of a sphere with radius of 12.5 cm,which is coated with a radionuclide layer with different radioactivities are-0.35,-0.50,-0.79 and-1.13 d B when the radioactivity is 1,2,5 and 10 Ci/cm2,respectively.

Radar Cross-section Imaging of a Rotating Object with a Multi-frequency Holography

A new method called multi-frequency holography (MFH) for two-dimensional radar cross-section imaging of rotating objects is introduced, in which a constant coherent reference signal from transmitted signal is added into received signal over certain frequency-width. With the MFH only the intensity of received composite signals needs to be measured. Both imaging situations of far field and near field are considered in details. Special restrictions about the MFH are also discussed and simulated by numerical computation. Examples of numerical simulation show that the method is effective, applicable and perspective.