Band Radar Cross Section Reduction Research Articles

Theoretic Study of Antenna Scattering Problems Based on Characteristic Modes and its Applications in Reducing Antenna Scattering

A new antenna scattering theory based on characteristic modes (AST-CMs) is proposed to analyze the antenna scattering mechanism and guide the design of antenna scattering reduction in this article. A specific set of modal electric fields, which of an antenna loaded with a short circuit, is used to express the structure mode and antenna mode scattering fields of the antenna with arbitrary loads. The contribution of each characteristic mode to the structure mode and antenna mode scattering fields can be clearly analyzed, which efficiently guides the antenna scattering reduction under the incident plane waves with arbitrary propagation direction and polarization. A typical microstrip antenna is given as an example to validate the proposed AST-CM. The radar cross section (RCS) of the microstrip antenna calculated by AST-CM agrees well with the result simulated by commercial simulation software Altair FEKO. Moreover, the design procedure based on AST-CM is used to guide the in- band RCS reduction of the microstrip antenna under both <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${x}$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${y}$ </tex-math></inline-formula> -polarized normally incident plane waves. Compared with the reference antenna, the proposed antenna achieves a notable RCS reduction in its operation band with the radiation performance well preserved. The proposed low-RCS antenna is fabricated and measured, and the experimental results are in good agreement with the numerical simulated results.

A metasurface design method for dual wide band radar cross section reduction

Metasurface has attracted much attentions due to its ability of flexible manipulation of electromagnetic wave. However, the metasurface is limited to the single operating band and poor design generality when it is used for radar cross section (RCS) reduction. In this paper, a stacked metasurface design method has been developed to flexibly achieve dual wide band RCS reduction. Two subarrays with polarization conversion characteristic are firstly designed to operate in two wide bands, respectively. Then a low-pass frequency selective surface (FSS) is developed and sandwiched between two metasurface subarrays to achieve a subarray with the dual-band polarization conversion performance. With the arrangement of the dual-band subarray into a 2×2 array in a rotation way according to the polarization cancellation, the resultant metasurface structure has two −10 dB RCS reduction bands covering 6.6-12.7 GHz and 27.8-38.1 GHz. The designed prototype is fabricated and measured. The simulation and measurement results are given to demonstrate the good dual-band RCS reduction performance.

Low cost, simple and broad band radar cross section reduction by modulated and holography metasurfaces

In this paper, the design and fabrication of modulated metasurfaces is proposed to achieve a wideband monostatic radar cross section (RCS) reduction. This structure is composed of holography and modulated surface tiles arranged in checkerboard configurations where the holography surface converts the incoming wave into the surface waves and the modulated surface redirects it into the other directions rather than the normal one. This surface reduces the RCS more than 10 dB from 11.57–26.1 GHz (77%) for normal incidence. Using only one low cost commercially available FR-4 substrate layer in this surface facilitates its applications rather than the state-of-the-art RCS reduction references.

Design of a wideband polarisation conversion metasurface and its application for RCS reduction and gain enhancement of a circularly polarised antenna

An improved loading method of checkerboard-based linear polarisation conversion metasurface (PCM) is proposed for gain enhancement and wideband radar cross-section (RCS) reduction of the circularly polarised patch antenna (CPA). The proposed metasurface consists of a checkerboard arrangement of PCM and its mirror unit cells, and an improved loading method is used to rearrange the PCM unit cells around the radiating patch. The PCM unit cell is composed of a metallic pattern on the top and bottom surface covered with metal. A wideband RCS reduction is realised by achieving 180° cross-polarisation reflection phase difference between the two neighbouring PCM unit cells and gain enhancement is achieved by the coherent superposition of energy in the far-field between the radiating patch and PCM cells. Simulated and measured results depict that the operating bandwidth of CPA and the proposed antenna is 12.6-13.76 GHz. The peak gain of the proposed antenna is 3.5 dB higher than the CPA and 3-dB axial ratio bandwidth of the designed antenna is 200 MHz. The proposed antenna achieves significant RCS reduction in the frequency range of 9.6-22.6 GHz with maximum in-band RCS reduction of 21 dB and maximum out of band RCS reduction of 34 dB.

Dual Band RCS Reduction Using Modulated Grooves in A Conducting Plane

An electromagnetic boundary-value problem of modulated grooves in a conducting plane is rigorously solved based on the Fourier transform, eigenfunction expansion, and mode matching method. Radar cross section (RCS) of the modulated grooves is represented in a series form and calculated while varying depth, width, and period of the grooves to investigate scattering characteristics of dual band RCS reduction.

Ultra wide band radar cross section reduction using multilayer artificial magnetic conductor metasurface

A new thin planar wideband radar cross section (RCS) surface is designed and fabricated by using two different artificial magnetic conductor (AMC) unit cells. These AMC unit cells are designed by both substrate height and relative permittivity variations to achieve an ultra wide bandwidth performance. Three layer low cost FR-4 substrates are used to simply implement these unit cells. The proposed structure reduces the RCS more than 10 dB from 13.1 GHz to 44.5 GHz (109% bandwidth), more than 20 dB from 16.43 GHz to 42.31 GHz (88.3%), and more than 30 dB from 24.7 GHz to 40.9 GHz (49.4%). Moreover, this surface has more than 103% RCS reduction bandwidth for TE polarized and more than 93% for TM polarized ones up to 50° oblique incident waves. The good agreement between the simulation and measurement results also prove the idea. In addition to using a low cost substrate, the proposed surface has a significant widest RCS reduction bandwidth compared with the state of the art references in the normal and oblique incident angles at both TE and TM polarizations.

Wide band radar cross section reduction by thin AMC structure

A new thin and wideband RCS reduction metasurface is designed and fabricated by using two different AMC unit cell tiles arranged in chessboard like configuration. One of these tiles is formed by saltire arrow unit cells, whereas the other one is formed by Jerusalem unit cells which are designed to achieve out phase difference at broad frequency range. This metasurface reduces the RCS more than 10-dB from 15.75 GHz to 41.3 GHz (90% bandwidth). The designed metasurface works properly at both TE and TM propagation modes, also. Moreover, it has stable 10-dB RCS reduction bandwidth for TM propagation mode up to 50° oblique incident angle and 30° for TE ones. These good specifications prove the designed metasurface capability compared with the state of the art references.

Ultra Wide Band Radar Cross Section Reduction of a Perfectly Electric Conductor Sphere by the Application of Multilayer Metamaterial Coatings

A full-wave analytical method using the addition theorems and Hertzian potential functions are used to compute the radar cross section of a sphere coated by several layers composed of common materials and metamaterials. The minimization and maximization of radar cross section of a perfectly electric conductor sphere with such coatings are realized in a frequency band-width and in a wide interval of angles. One of the novelities of this contribution is, taking into dispersion relations of physically realizable metamaterials. So that the optimization procedure for RCS reduction is applied due to the coefficients describing dispersion characteristics. The method of least square is used for the design of a class of radar absorbing materials. The minimization of the error functions are performed by the combination of genetic algorithm and conjugate gradient method. It is shown that the proposed method of computation of radar cross section and its extremization effectively leads to the design of dispersive and isotropic metamaterials for the realization of radar absorbing materials.

Ultra-Broad Band Radar Cross Section Reduction of Waveguide Slot Antenna with Metamaterials

To reduce the radar cross section of the wave- guide slot antenna, a three-layer metamaterial is presented based on orthogonal double split-ring resonators. The absorption characteristics of three-layer metamaterial are demonstrated by simulation. Moreover, the metamaterials have been loaded on common waveguide slot antenna according to the surface current distribution. The ultra- broad band radar cross section reduction of the antenna with metamaterials had been theoretically and experimen- tally investigated by radiating and scattering perfor- mances. Experimental and simulated results showed that the proposed antenna with metamaterials performed broadband radar cross section reduction from 3.9 GHz to 18 GHz and the gain had been improved due to the cou- pling effect between slot and the period metamaterials structure. The maximal radar cross section reduction of the novel antenna achieved 17.81 dB at 8.68 GHz for x-polar- ized incidence and 21.79 dB at 6.25 GHz for y-polarized waves.

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.