Broadband Radar Cross Section Reduction Research Articles

Polarization Conversion Metamaterial Surface With Staggered-Arrangement Structure for Broadband Radar Cross Section Reduction

A polarization conversion metamaterial surface (PCMS) with low radar cross section (RCS) is presented in this letter. The PCMS is composed by a periodic array of lantern-shaped metal units. The optimized effective phase difference is about 40.6%, and the 10 dB RCS reduction bandwidth is from 11.0 to 17.0 GHz. To further broaden the operational bandwidth, a staggered-arrangement PCMS (SPCMS-2) is adopted. The overall phase difference is shifted to lower frequency, and a 10 dB RCS reduction bandwidth is obtained over a wide band from 9.0 to 16.0 GHz. To verify the correctness of these designs, both the PCMS and SPCMS-2 arrangements are fabricated and tested. The measured results are consistent with the simulation results very well.

Broadband radar cross section reduction by in-plane integration of scattering metasurfaces and magnetic absorbing materials

An in-plane hybrid design is proposed to achieve broadband radar cross section (RCS) reduction based on the integration of a diffusion scattering electromagnetic band-gap (EBG) metasurface and a magnetic absorbing material (MAM) at a thin thickness (d). A scattering field calculation formula is derived for the hybrid design, in which the MAM and EBG metasurface have complementary dominant working bands. Moreover, they are able to achieve strong RCS reduction in broad band by working together. As a result, the as-designed hybrid metasurface show in both simulation and experiment an unprecedented broadband RCS reduction of 6 dB in the frequency range of 5–34 GHz with d of only 2 mm. The design strategy proposed here provides a feasible and extendable approach to broaden the bandwidth of RCS reduction by multiple mechanisms and hybrid materials based on the concept of metasurface.

An efficient reflective polarization rotation meta surface for broadband RCS reduction

A compact and broadband reflective polarization rotation meta surface (PRMS) with high polarization conversion ratio (PCR) and radar cross section (RCS) reduction is proposed. A linearly polarized incident electromagnetic (EM) wave is reflected with 90° polarization rotation using the proposed PRMS. The reflective PRMS unit cell consists of complementary stacked quasi fractal patch along with logarithmic stepped patch. This reflective PRMS is printed on stacked FR4 substrates covered by FR4 superstrate and is backed by a ground plane. The patches are connected to the metallic ground using non symmetric metallic vias and the overall dimension of the unit cell in terms of its minimum operating wavelength is only 0.088λ0 × 0.088λ0 × 0.082λ0. A polarization bandwidth of 97.69% with a maximum PCR of 99% is achieved. Further, the proposed reflective PRMS is arranged periodically in a checkerboard surface to obtain a broadband RCS reduction of 10 dB in the required band. A prototype of the checkerboard surface is fabricated and tested for the validation of simulation results. A good pact is obtained between the simulation and experimental results.

Broadband RCS reduction in microstrip patch antenna using L-shape stepped polarization rotation reflective surface

A novel L-shape stepped polarization rotation reflective surface (PRRS) for achieving broadband radar cross section (RCS) reduction of a microstrip patch antenna is proposed. The proposed PRRS consists of two scaled pairs of L-shape stepped patches and is printed on FR4 substrate backed by a metallic ground plane. The arrangement of PRRS in four orthogonal directions around the microstrip patch antenna reduces RCS in a broad frequency range of 7.07 GHz-11.06 GHz. To understand the RCS reduction throughout the entire frequency band, angled slot is introduced in the microstrip patch antenna to provide frequency shift. The microstrip patch antenna with RCS reduction is fabricated and tested. The experimental results reveal that the proposed PRRS intensely reduces the microstrip patch antenna RCS by a maximum of 35 dB with improved radiation characteristics like gain, directivity and radiation efficiency.

Low radar cross section checkerboard metasurface with a transmission window

In this paper, we propose the design of a hybrid surface with a low radar cross section (RCS) at lower frequencies and a transmission window at higher frequencies. The hybrid surface comprises two parts: a frequency selective surface (FSS) on the bottom and a checkerboard metasurface on the top. The FSS exhibits low-stop and high-pass properties, which reflects waves at lower frequencies and allows transmission of waves at higher frequencies. The checkerboard metasurface, with a reflective substrate, can reduce RCS at lower frequencies by means of scattering cancellation. Due to the low-stop property of the FSS, the hybrid surface can achieve broadband RCS reduction at low frequencies since the FSS acts as the reflective substrate. Simultaneously, the transmission window at higher frequencies of the FSS can be kept. Simulation results show that the RCS can be reduced by more than 10 dB in 4.1–7.7 GHz and the insertion loss in the transmission window is lower than 1.0 dB in 11.3–13.3 GHz. A prototype was fabricated and measured. The experimental results agree well with the simulation results. This work provides an effective alternative to the design of functional devices such as stealthy radomes, etc.

Broadband RCS Reduction of Microstrip Antenna Using Coding Frequency Selective Surface

In this letter, an optimized coding frequency selective surface (FSS) is designed using a genetic algorithm to reduce the radar cross section (RCS) of a microstrip antenna in a wide frequency band. The RCS reduction is realized by replacing the antenna ground plane with a coding FSS. By doing so, the maximum and average RCS reduction of the proposed structure in the X-band becomes 24 and 11.9 dB, respectively. A prototype of the proposed antenna and reference antennas were fabricated and tested. The measurement results were compared with full-wave simulation ones to benchmark the performance of the proposed antenna. Experimental results show that the 10 dB RCS reduction is from 6.25 to 12 GHz (63%).

Gain enhancement and broadband RCS reduction of a circularly polarized aperture-coupled annular-slot antenna using metasurface

A circularly polarized microstrip slot antenna with low radar cross-section (RCS) and high gain was designed using a metasurface composed of a $$6 \times 6$$ array of corner-truncated square patches placed on top of the upper substrate. By optimizing the geometry of the metasurface patches and L-shaped feed of the proposed antenna, broadband RCS reduction and improved overall antenna performance were achieved. A prototype antenna was fabricated, and the results showed that the proposed antenna exhibited an impedance bandwidth of 29.08 % in the frequency band of 4.29–5.75 GHz. The designed antenna achieved good 3-dB axial ratio (AR) bandwidth of about 30.18 % with center frequency of 5.3 GHz, and gain in the broadside direction of 9.9 dBi. Using the designed metasurface, remarkable monostatic RCS reduction was obtained in the frequency range from 4 to 13 GHz.

Carbon fiber assisted glass fabric composite materials for broadband radar cross section reduction

Carbon fibers (CFs) have been widely used as absorbing materials for radar cross section (RCS) reduction. Here, an alternative approach for CFs is proposed to achieve the same goal and has been performed by the glass fabric composites loaded with a small number of CFs. The reduction mechanism of our proposal is phase cancellation instead of absorption. Two prototypes in chessboard and random patterns are analyzed numerically and measured experimentally. The short CF yarns are designed as the patterned configurations and embedded into the composite surface layers. It is demonstrated that the proposed composites allow for remarkable suppressing of the specular scattering over a broad frequency band. The designed RCS reduction level more than 10 dB covers the frequency range from 8.7 to 19.2 GHz, while the overall thickness is 2.7 mm. The proposed composites are of a simple configuration and robust for the defects. It is also believed that the study of this work can be easily extended to the curved surfaces.

Novel Design of Ultrabroadband Radar Cross Section Reduction Surfaces Using Artificial Magnetic Conductors

A novel technique for designing ultrabroadband radar cross section (RCS) reduction surfaces using artificial magnetic conductors (AMCs) is proposed in this paper. This technique overcomes the fundamental limitation of the conventional checkerboard design where the reflection phase difference of (180±37)° is required to achieve 10-dB RCS reduction. Initially, a planar surface for broadband RCS reduction is designed with two properly selected AMCs in a blended checkerboard architecture. A 10-dB RCS reduction is observed for more than 83% of the bandwidth (3.9–9.45 GHz) with this blended checkerboard design. After modifying the blended checkerboard design using the proposed novel technique, the 10-dB RCS reduction bandwidth increased to 91% fractional bandwidth (3.75–10 GHz) as the criteria of (180 ± 37)° reflection phase difference is no longer required. Measured data show an excellent agreement between the predicted, simulated, and measured data. Bistatic performance of the surface at various frequencies is also presented. Key steps for designing ultrabroadband RCS reduction checkerboard surface are summarized.

Broadband and wide-angle RCS reduction using a 2-bit coding ultrathin metasurface at terahertz frequencies.

A novel broadband and wide-angle 2-bit coding metasurface for radar cross section (RCS) reduction is proposed and characterized at terahertz (THz) frequencies. The ultrathin metasurface is composed of four digital elements based on a metallic double cross line structure. The reflection phase difference of neighboring elements is approximately 90° over a broadband THz frequency. The mechanism of RCS reduction is achieved by optimizing the coding element sequences, which redirects the electromagnetic energies to all directions in broad frequencies. An RCS reduction of less than −10 dB bandwidth from 0.7 THz to 1.3 THz is achieved in the experimental and numerical simulations. The simulation results also show that broadband RCS reduction can be achieved at an incident angle below 60° for TE and TM polarizations under flat and curve coding metasurfaces. These results open a new approach to flexibly control THz waves and may offer widespread applications for novel THz devices.

Broadband RCS reduction using a novel double layer chessboard AMC surface

A novel broadband chessboard surfaces with double layer structure to reduce the radar cross-section (RCS) of an object is presented. By combining two artificial magnetic conductor (AMC) cells and a novel structure, 73% frequency bandwidth of −10 dB RCS reduction compared with a metallic plate has been obtained. In order to increase the bandwidth in chessboard structures, boards with high thickness are required, cheaper boards’ thickness are limited. An RO4003 board on an air substrate has been used. This technique, in addition to accommodating the designer with a new parameter, decreases the costs and increases the bandwidth greatly and also simulation results and measurements are in good correspondence.

Broadband Low-RCS Metasurface and Its Application on Antenna

This paper presents a metasurface (MS) with broadband low radar cross section (RCS) and investigates its application on antenna. The MS is composed of polarization-dependent artificial magnetic conductors (PDAMCs) for backscattering cancellation. By orthogonally arranging the PDAMCs in a fencelike configuration, the scattering beam is deviated from specular direction, so that the MS achieves RCS reduction over a broad frequency band. As a potential application, the MS is employed to simultaneously promote the radiating and scattering performances of a slot antenna. Full wave simulations and measurements confirm that the novel antenna achieves broadband RCS reduction and significant gain enhancement compared with a reference antenna with metallic ground.

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.

Broadband RCS reduction and gain enhancement microstrip antenna using shared aperture artificial composite material based on quasi‐fractal tree

A shared aperture artificial composite material (SA-ACM) with broadband absorption and partial reflection feature is proposed. The SA-ACM is composed of artificial composite material absorber (ACMA) and partial reflection surface (PRS), where the ACMA and PRS share the same aperture in the vertical dimensionality. The ACMA consists of quasi-three-dimensional fractal tree loaded with lumped resistances and metallic pattern on the bottom side of a dielectric slab, and the PRS consists of etched parallel slots in a metallic plane. The SA-ACM as the role of superstrate is applied to the mircrostrip antenna. The Fabry–Perot resonator cavity constructed by the PRS and the metallic ground of the mircrostrip antenna can achieve high gain, while the ACMA can obtain the low radar cross section (RCS) characteristic by absorbing the incident wave. Simulation and experiment results demonstrate that the gain of the antenna with SA-ACM is enhanced over 3 dB in the operation frequency band, and the backscattering RCS is obviously reduced by 10 dB in a wide frequency range.

Design of high-gain broadband low-RCS waveguide slot antenna

A novel design for high gain and low radar cross section (RCS) waveguide slot antenna is proposed. Low RCS screen composed of orthogonal array of complementary split ring resonator etched square patch artificial magnetic conductor (CSRR-AMC) is exploited on the antenna for radiation improvement and broadband RCS reduction. Measured results demonstrate that the operating bandwidth is increased by 100 MHz and the gain is enhanced by 3.2 dB with the proposed structure. Meanwhile, 10 dB RCS reduction is achieved over the range of 5.52–6.63 GHz, implying 20% relative bandwidth.

Broadband Radar Cross-Section Reduction Using AMC Technology

This paper presents the design, fabrication, and characterization of a planar broadband chessboard structure to reduce the radar cross-section (RCS) of an object. The chessboard -like configuration is formed by combining two artificial magnetic conductor (AMC) cells. The bandwidth limitations intrinsic to AMC structures are overcome in this work by properly selecting the phase slope versus frequency of both AMC structures. A 180 ° phase difference has been obtained over more than 40% frequency bandwidth with a RCS reduction larger than 10 dB. The influence of the incidence angle in the working bandwidth has been performed. A good agreement between simulations and measurements is achieved.

Broadband RCS reduction and high gain waveguide slot antenna with orthogonal array of polarisation‐dependent AMC

A novel design for broadband radar cross-section (RCS) reduction and a high gain waveguide slot antenna is proposed. The orthogonal array of a polarisation-dependent artificial magnetic conductor (AMC) is exploited and contributes to the scattering and radiation improvement. The measured results demonstrate that, compared with the conventional antenna with a metallic plate, the novel antenna achieves a 20% relative bandwidth of 10 dB RCS reduction and 3.2 dB gain enhancement.