A new approach for the gain enhancement and wideband radar cross section (RCS) reduction of an antenna based on the chessboard polarization conversion metasurfaces (CPCMs) is proposed. Compared with the previous low-RCS antennas, high gain and wideband low RCS of a circularly polarized (CP) antenna are achieved simultaneously. The proposed CPCM is the chessboard configuration of the polarization conversion metasurfaces (PCMs), which is made up of adjoining two-layer substrates with three metallic patterns. Low RCS is realized by 180° (±30°) reflection phase variations between two neighboring PCMs. Gain enhancement is achieved by employing a Fabry-Perot cavity, which is constructed by the PCM and the ground of the antenna. The antenna with CPCM operating at the $X$ -band, excited by a sequentially rotated feeding network, is fabricated and measured. Simulated and measured results show that the left-hand CP gain of the antenna with CPCM is at least 3 dB higher than that of the reference antenna from 8.5 to 9.5 GHz and the monostatic RCS is effectively reduced from 6 to 14 GHz.

A Circularly Polarized High-Gain Antenna With Low RCS Over a Wideband Using Chessboard Polarization Conversion Metasurfaces

By loading the lumped resistances into the double octagonal rings metamaterials, a wideband, thin, and polarization-insensitive perfect absorber is investigated theoretically and experimentally. The perfect absorber is constructed of double octagonal rings loading the eight lumped resistances and the substrate with height of 3 mm. The effects of the double octagonal rings and eight lumped resistances are explored by absorption and the electric field distributions. The simulated results indicate that the structure obtains 9.25 GHz-wide absorption from 7.93 to 17.18 GHz with absorptivity larger than 90% at the incident angles from 0° to 20° and achieves above 12.2 GHz-wide absorption from 5.8 to 18 GHz with a full width at half maximum at wide incident angles from 0° to 70°. The fabricated metamaterial absorber device was measured and analyzed. A good agreement is observed between the simulation and the measurement.

Wideband, thin, and polarization-insensitive perfect absorber based the double octagonal rings metamaterials and lumped resistances

The simultaneous improvement in radiation and scattering performance of an antenna is normally considered as contradictory. In this paper, wideband gain enhancement and radar cross section (RCS) reduction of Fabry–Perot (FP) resonator antenna are both achieved by using chessboard arranged metamaterial superstrate (CAMS). The CAMS is formed by two kinds of frequency-selective surfaces. The upper surface of CAMS is designed to reduce RCS based on the phase cancellation principle, and the bottom surface is used to enhance antenna gain on the basis of FP resonator cavity theory. Both simulation and measured results indicate that compared with primary antenna, the gain of the proposed FP resonator antenna is enhanced by 4.9 dB at 10.8 GHz and the 3 dB gain bandwidth is from 9.4 to 11.1 GHz (16.58%). Meanwhile, the RCS of the proposed FP resonator antenna is reduced from 8 to 18 GHz, with peak reduction of 39.4 dB. The 10 dB RCS reduction is obtained almost from 9.6 to 16.9 GHz (55.09%) for arbitrary polarizations. Moreover, the in-band RCS is greatly reduced, owing to the combined effect of CAMS and FP resonator cavity.

Wideband Gain Enhancement and RCS Reduction of Fabry–Perot Resonator Antenna With Chessboard Arranged Metamaterial Superstrate

A methodology for designing a frequency selective reflector with two-sided absorption bands is proposed. This method is based on utilizing multimode resonators inside a 3-D unit cell to obtain an absorption-reflection-absorption response. Detailed analysis of this 3-D absorptive frequency selective reflector (AFSR) is provided with the aid of an equivalent circuit model to reveal the operating principle. To show the benefit of the new structure in antenna’s radar cross section reduction (RCSR), a dual-polarized 3-D-AFSR integrated with monopole and dipole antennas are simulated, fabricated, and then measured. Compared with their counterparts with normal ground plane, AFSR-backed antennas have shown a remarkable out-of-band RCSR. The −10 dB RCSR has fractional bandwidths of at least 64.7% and 41% with center frequencies of 3.4 and 8.3 GHz, respectively. The radiation characteristics of AFSR-backed antennas are nearly maintained. The realized gains are enhanced by 0.9 and 2.3 dB for monopole and dipole antennas mounted on a 3-D-AFSR, respectively.

3-D Absorptive Frequency Selective Reflector for Antenna Radar Cross Section Reduction

In this communication, a new frequency selective surface (FSS)-based isolation technique is proposed for multiple-input-multiple-output (MIMO) antennas. In the proposed method, a conventional ground plane of monopole-based MIMO antenna is replaced with FSS to improve the isolation between the antenna elements as well as to reduce MIMO antenna radar cross section (RCS). In this communication, two FSS designs have been presented, and they are named as FSS and M_FSS. M_FSS is a slightly modified version of FSS. With FSS, isolation enhancement and RCS reduction have been achieved by altering antenna characteristics. With M_FSS, the same can be achieved by preserving the antenna characteristics. The RCS reductions of 25 and 20 dBsm have been achieved by replacing the PEC ground plane with FSS and M_FSS, respectively. Also, by using the proposed FSS, a stable RCS reduction up to 60° for TE polarization and up to 45° for TM polarization has been achieved. The proposed MIMO antenna with FSS has been fabricated, and the simulation results are experimentally verified.

Isolation Enhancement and Radar Cross Section Reduction of MIMO Antenna With Frequency Selective Surface

A design approach aimed at reducing the radar cross section (RCS) of microstrip antenna in wide frequency band is proposed. First, two different artificial magnetic conductor (AMC) unit cells are designed to obtain 180 $^\circ $ ( $ \pm 30^\circ $ ) reflection phase difference over broadband frequency range. Then, chessboard configuration is structured with the two AMC unit cells and is applied to a microstrip antenna for RCS reduction. The simulated results indicate that the proposed antenna possesses remarkable RCS reduction from 8.0 GHz to 20.0 GHz for both polarizations, covering the working band of the original antenna. The maximum reduction is 31.9 dB. Moreover, the radiation performance of the antenna has been well kept. Measured results of the fabricated prototype are in good agreement with the simulations.

Wideband RCS Reduction of a Microstrip Antenna Using Artificial Magnetic Conductor Structures

A low radar cross section (RCS) metamaterial absorber (MMA) with an enhanced bandwidth is presented both numerically and experimentally. The MMA is realized by assembling three simple square loops in a three-layer structure according to the idea of separating electric and magnetic resonances. Difierent from one- layer MMA, the proposed MMA can efiectively couple with the electric and magnetic components of the incident wave in difierent positions for flxed frequency, while, for difierent frequencies, it can trap the input power into difierent dielectric layers and absorb it in the lossy substrate. Experimental results indicate that the MMA exhibits a bandwidth of absorbance above 90% which is 4.25 times as that of one-layer MMA, and 10dB RCS reduction is achieved over the range of 4.77{5.06GHz. Moreover, the cell dimensions and total thickness of the MMA are only 0:17‚ and 0:015‚, respectively. The low RCS properties of the MMA are insensitive to both polarization and incident angles.

Zidong Yuan

Papers

Wideband RCS Reduction of a Microstrip Antenna Using Artificial Magnetic Conductor Structures

Low RCS Metamaterial Absorber and Extending Bandwidth Based on Electromagnetic Resonances