In-band Radar Cross Section Reduction Research Articles

An In-Band Low-Radar Cross Section Microstrip Patch Antenna Based on a Phase Control Metasurface

An in-band low radar cross section (RCS) microstrip patch antenna based on a phase control metasurface is proposed. As the size of the phase control metasurface changes, it will have different phase adjustments to the incident electromagnetic wave. Two kinds of phase control metasurfaces with a 90° reflection phase difference are arranged in a checkerboard configuration and loaded above a microstrip array antenna. The metal of the microstrip array antenna can fully reflect the electromagnetic wave, so the incident wave passes through the metasurface again and forms a reflected wave with a phase difference of 180° ± 37° when passing through the phase control metasurfaces of different sizes. Thus, the microstrip array antenna can achieve in-band RCS reduction. The metamaterial forms a transmission window in the microstrip patch array antenna band to maintain the radiation performance. Finally, a reasonable agreement is obtained between the measured and simulated results.

In-band dual-polarization RCS reduction of waveguide slot array antenna integrated with AMC and PEC chessboard structure

An in-band low radar cross section (RCS) waveguide slot array antenna (WSAA) is proposed by using a chessboard structure composed of artificial magnetic conductor (AMC) and perfect electric conductor (PEC), which serves as the antenna radiator. The method for RCS reduction is the reflection energy cancellation. Standing wave array is used to achieve higher energy efficiency and more compact antenna structure. Experimental results show that the in-band monostatic RCS is sufficiently reduced with the chessboard structure application for both co- and cross-polarized incident waves, where 10-dB RCS compression is realized among the frequency range of 9.7–9.91 GHz for co-polarization and 9.5–9.85 GHz for cross-polarization with maximum RCS reductions of −13.3 dB and −11.9 dB, respectively. Meanwhile, the designed WSAA maintains the high gain characteristics of the original WSAA. The paper provides a simple, practical and effective strategy for stable RCS compression in the operation band of waveguide antenna array, which has potential applications in stealth platforms.

In-Band Radar Cross Section Reduction and Enhancement of Gain for a Patch Antenna Array by Using a 1-D Periodic Metasurface Reflector

Abstract: Based on far-field cancellation, a low-profile metasurface (MS) for both x- and y-polarizations is created. This concept uses a 1-D MS instead of a typical MS with a low RCS that uses checkerboard architecture. The proposed MS can be integrated more freely in various applications because it does not require periodicity in two dimensions. A patch antenna array is proposed based on the proposed MS. Under normal incidence, full-wave calculations and measurements demonstrate that integrating the proposed MS reduces the scattering of the antenna array by more than 5 dB over the antenna working frequency band of 10.7 to 12 GHz (11.45 percent). Moreover, when the array radiates, parasitic radiation from the slots of the MS can be activated, increasing the array's boresight gain.

In-band Radar Cross Section reduction for electromagnetic window by simultaneously enhancing transmission and coding reflection

For electromagnetic windows (EWs), although the in-band transmission is satisfactory, reflection always exists at interfaces, which leads to considerable in-band RCS, especially for large-size EWs. The conventional manner of reducing the in-band RCS is focused on enhancing transmission, which is always limited by the unavoidable impedance mismatch at interfaces. To overcome this limit, in this paper, we propose to reduce the in-band RCS of EWs by simultaneously enhancing transmission and coding reflection using dimer metasurfaces. The dimer structure is composed of two unidentical meta-atoms patterned on the front and back surfaces of the EW, respectively, which can enhance the transmission in the band of interest. More importantly, when the dimer structure is flipped, the transmission is unaffected due to reciprocity, whereas the reflection will be different. Therefore, by coding the reflection phase, the in-band backward reflection can be further reduced due to scattering cancellation. Proof-of-principle prototypes were designed, fabricated and measured to verify this strategy. The experimental results are consistent with the simulation results, which proves the feasibility of this strategy. This work provides an alternative way of reducing the in-band RCS of EWs and may find practical applications in radomes, lenses and other areas.

In‐band dual‐polarization radar cross section reduction of patch array antenna using hybrid resistive metasurface

In this article, a hybrid resistive metasurface (RM) based on the different field distributions of radiation and scattering is designed and realized for dual-polarization radar cross section (RCS) reduction of patch array antenna without enlarging its original dimensions. The hybrid RM is composed of two RMs located on the same plane, which is both transmissive for electromagnetic waves from antenna below at resonant frequency of 12.3 GHz. The combination of the RMs and the metal ground of antenna form absorbers, which absorb in-band co-polarized (RM1) and cross-polarized (RM2), waves respectively. The hybrid RM is arranged by RM2 placed directly above the radiation patches while RM1 placed elsewhere. Therefore, the radiation performance of antenna is basically unaffected meanwhile realizing the in-band dual-polarization RCS reduction. Simulation results demonstrate that the hybrid RM exhibits RCS reduction of co-polarization and cross-polarization reaches 10.7 and 3.3 dB respectively by the window-like layout, and main lobe gain achieves to 18.0 dB, which is 2.2 dB lower than that of reference antenna. The experimental results are consistent with the simulation results in the main.

In-band RCS reduction antennas using an EBG surface

AbstractThe paper has proposed a multilayer, polarization rotation featured, low radar cross-section (RCS) antenna using electromagnetic band-gap (EBG)-based frequency selective surface (FSS) at 8.25 GHz. Cross-shaped EBG unit cells offer zero reflection phase and −25 dB reflection magnitude at 8.25 GHz. The FSS layer consists of eight cross-shaped EBG unit cells sandwiched between two substrates to offer high absorptivity at the desired band. The circular patch antenna resonating at 8.25 GHz is placed on the top substrate having a lower dielectric constant. Four circular-shaped patches are etched at the four corners of the top layer and are coupled with two feed lines which are aligned 90° to each other at the bottom layer and interconnected diagonally to achieve polarization rotation. The proposed antenna offers a gain of 6.72 dB and an in-band RCS of −21.4 dBsm. Incident energy is backscattered into eight directions separated by angle ϕ = 45°. The proposed antenna has the RCS reduction band of 7.7–9.4 GHz. It offers normalized polarization rotation ratio more than 0.8 within the −40° to 40° angular region at the frequency band 8–8.5 GHz. The measured result using the fabricated prototype agrees well with the simulated one.

Wideband, low radar cross section circularly polarized array antenna based on metasurface and sequential phase feed

A planar circularly polarized (CP) array antenna based on polarization conversion electromagnetic band-gap (PCEBG) and sequential phase (SP) feed network with wideband circular polarization and low radar cross section (RCS) is presented. The array is formed by 2 × 2 PCEBG elements. The CP performance is obtained due to the PCEBG, and the SP feed network contributes to the wide bandwidth and symmetric radiation pattern. The proposed array antenna, with an overall size of 64 mm × 64 mm × 2.008 mm (1.6 λ0 × 1.6 λ0 × 0.05 λ0 at 7.5 GHz) has been fabricated and measured. The measured results are as follows, an impedance bandwidth of 42.90% (6.61-10.22 GHz), a 3-dB axial ratio bandwidth (ARBW) of 28.3% (6.65-8.83 GHz) and a 3-dB gain bandwidth of 23.7% (6.7-8.5 GHz). The antenna exhibits left-hand CP(LHCP) characteristics with a peak broadside gain of 14.1 dB. The proposed antenna achieves an in-band and out-band RCS reduction more than 8 dB under normal incidence. The measured results are in agreement with the simulated results.

A Low Cost, Low in-Band RCS Microstrip Phased-Array Antenna With Integrated 2-bit Phase Shifter

In this article, we present a low-cost microstrip phased-array antenna, which is composed of electronically reconfigurable elements. The p-i-n diodes' integrated elements have various functions, such as tunable polarization characteristics and adjustable radiation phases. The high sidelobe level (SLL) due to the 2-bit phase shifter can be reduced by a randomly rotated (RR) array element. It is shown that the array can realize electronic beam-steering capabilities and keep -10 to -14 dB sidelobes without tapering. To verify the above theory, an eight-element linear array prototype working at 3 GHz was designed, fabricated, and tested. Numerical simulations and experimental results show that, by controlling the “ON” and “OFF” states of p-i-n diodes, the radiation beam can be controlled to steer in a circular polarization (CP) mode, wherein the scanning angle is up to ±45°. Furthermore, the principle of suppressing the vector scattering field by the opposite phasing cancellation method can achieve in-band radar cross section (RCS) reduction. Simulation results show that approximately 15 dB in-band RCS reduction can be realized for both bistatic and monostatic RCS reduction with an 8×8 array.

In-Band RCS Reduction and Isolation Enhancement of a 24 GHz Radar Antenna Using Metamaterial Absorber for Sensing and Automotive Radar Applications

A triple-band low radar cross-section (RCS) high isolation antenna is proposed for 24 GHz ISM band sensing and automotive radar applications. The proposed design consists of 2 x 2 patch array that acts as transmit and receive antennas. Low RCS and high isolation are achieved at 24 GHz by designing a metamaterial absorber (MA), which consists of a square ring with a resistor connected in its diagonal arm for the absorption of electromagnetic waves. The proposed MA shows near unity normalized impedance at 24.1 GHz with 90% absorptivity bandwidth of 1 GHz. An array of MA is placed in between and around the transmit/receive antennas to suppress surface current and reduce in-band RCS of the radar sensor. The −10 dB impedance bandwidths of the triple-band sensor antenna are 20.8 to 21.24 GHz, 23.94 to 24.55 GHz, and 27.18 to 27.5 GHz. The proposed sensor antenna achieves isolation of 34 dB between the transmit and receive ports, and peak RCS reduction of 11 dB, as compared to the reference antenna. The half-power beamwidth of the proposed sensor antenna is 38° for E-plane and 52° for H-plane at 24 GHz.

A High-Performance Rectenna for Wireless Power Transfer in CubeSats

This letter presents a high-efficiency circular-polarized (CP) rectenna at 5.8 GHz within wide input power range featuring low profile and radar cross section (RCS) reduction. Originating from the connection to a branch-line coupler, two identical subrectifiers in parallel combination are capable of extending the input power range and enabling the stability of dc output. The contribution of this combination in the performance of rectenna is experimentally demonstrated and a solution to RCS reduction by means of defected ground structure and complementary split-ring resonators is devised. The measured results show that the rectenna achieves a conversion efficiency of more than $60\%$ within the input power range from 2.2 to 17.6 dBm, and an in-band RCS reduction of 5.1 dB, verifying the applicability of wireless power transfer for CubeSats.

A Low-RCS, High-GBP Fabry–Perot Antenna With Embedded Chessboard Polarization Conversion Metasurface

A Fabry-Perot (FP) antenna with high gain-bandwidth product (GBP) and wideband radar cross section (RCS) reduction is proposed using an embedded chessboard polarization conversion metasurface (CPCM). A polarization conversion metasurface (PCM) unit and its mirror unit are etched on both sides of a dielectric substrate with chessboard arrangement to form a CPCM. The in-band and out-of-band low-RCS features of the FP antenna are realized by destructive interference, and the high GBP is attributed to the FP resonant cavity. Moreover, an additional small CPCM designed for another PCM unit is embedded into the original CPCM to construct an embedded CPCM, which helps to improve in-band RCS reduction and has a positive effect on gain enhancement and 10-dB impedance bandwidth. The measured results show that the FP antenna with embedded CPCM has a 10-dB return-loss bandwidth of 8.48-12.21 GHz (36.1%), a GBP of 1338, a 3-dB gain bandwidth of 8.9-11.5 GHz (25.5%) and a maximum realized gain of 17.2 dBi. Meanwhile, the measured RCS reduction band covers 8-26 GHz (105.9%) with a peak RCS reduction of 21.2 dB at 9.4 GHz.

Multifunctional Scattering Antenna Array Design for Orbital Angular Momentum Vortex Wave and RCS Reduction

In this paper, a multifunctional scattering antenna array has been proposed to generate orbital angular momentum (OAM) vortex scattering wave and meanwhile reduce antenna radar cross section (RCS). Theoretical analysis for integration of the RCS reduction and the OAM wave is given, and a circular antenna array composed of a dual polarized microstrip antenna and a tunable connection line network is designed. By adjusting the ON/OFF state of the PIN diodes embedded in the connection line network, the OAM scattering waves with the modes of $l=1$ and $l=2$ are independently generated, and accordingly in-band RCS reduction of a circular patch antenna with an increase of the antenna gain over 2 dB is achieved. A multifunctional prototype antenna array is fabricated and measured. Simulated and measured results demonstrate -10dB RCS reduction and the OAM scattering waves with the tunable modes in the frequency band of 9.37~9.8 GHz.

Characteristic mode-based compact circularly polarized metasurface antenna for in-band RCS reduction

AbstractThis paper presents a novel design of a low profile circularly polarized (CP) metasurface (MTS) antenna with in-band radar cross-section (RCS) reduction property. The MTS is loaded as a superstrate on slot antenna and it can be viewed as a polarization-dependent MTS (PDMTS). The rectangular patch-based PDMTS is analyzed using characteristic mode analysis to find two orthogonal degenerate modes, which produces CP waves. Linearly polarized slot antenna is used to excite the PDMTS. The performance of PDMTS loaded slot antenna is analyzed numerically using full-wave analysis method. The PDMTS CP antenna is fabricated and its performance is tested experimentally. The proposed antenna has a compact structure and it has an overall size of $0.52{\lambda _0}\times 0.52{\lambda _0} \times 0.078{\lambda _0}$ (where ${\lambda _0}$ is the free space wavelength). The measured results show that the PDMTS antenna achieves $-10\,{\rm dB}$ impedance bandwidth of 29.41$\%$, 3-dB axial ratio bandwidth of 9.05$\%$, broadside gain of 6.34 dB, and monostatic RCS reduction of $-30.2\,{\rm dBsm}$ at the resonant frequency of 5.86 GHz. The simulated results are in well agreement with the measured results and it is well suited for C-band Radar and Satellite communication.

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.

A novel reconfigurable FSS applied to the antenna radar cross section reduction

Active reconfigurable FSS using pin diode for the antenna radar cross section (RCS) reduction is proposed. The reconfigurable FSS reflector is presented in this article. The proposed reconfigurable FSS reflector is able to be switched between band-stop FSS with OFF-state diodes and band-pass FSS with ON-state diodes around 3.8 GHz. The using of band-stop FSS reflector corresponds to the out-band RCS reduction during radar operating, and the using of band-pass FSS reflector corresponds to the in-band RCS reduction during radar nonoperating. Therefore, the state of the antenna scattering can be switched according to the working state of radar. The results show that the reconfigurable FSS reflector can contribute to the switchable RCS reduction between in band and out band of the antenna. The radiation performance of the antenna is preserved when the diodes are ON state. The monostatic RCS of the antenna with FSS reflector with ON-state diodes can be reduced more than 25 dB at operating band, and the out-band RCS reduction can be achieved with ON-state diodes.

Analysis and design of an ultra-thin metamaterial absorber and its application for in-band RCS reduction of antenna

ABSTRACTThis paper presents the analysis and design of an ultra-thin metamaterial absorber (MA) for the in-band Radar Cross Section (RCS) reduction of a patch antenna. The proposed MA consists of a periodic array of double square loop structures printed on an FR4 substrate with a thickness of 0.022 λo. A detailed theoretical analysis of the MA unit cell is conducted to investigate the absorbing characteristics of the MA. The simulated and measured results show that MA significantly reduces the RCS of the proposed antenna within its impedance bandwidth and a maximum RCS reduction of 15 dB is achieved at 6.75 GHz. The impedance bandwidth of the proposed antenna is 6.6–7 GHz, which is also improved by the loading of the MA. The results also show that after loading the MA on the patch antenna, the RCS of the proposed antenna is significantly reduced and there is no degradation observed in its radiation properties.

High-Gain Fabry-Perot Antennas With Wideband Low Monostatic RCS Using Phase Gradient Metasurface

The design of two high-gain Fabry–Perot antennas with wideband low monostatic radar cross section (RCS) is presented in this paper. First, a phase gradient metasurface (PGM) without lossy layer is used to realize in-band RCS reduction and high aperture efficiency, simultaneously. The simulated results show that its peak gain is 19.2 dBi, and a high aperture efficiency of 58.6% is achieved. By utilizing the PGM structure, the monostatic RCS is reduced from 7 to 11 GHz, and the in-band co-polarization RCS is reduced by 13.1 dB. After that, a PGM with metamaterial absorber is designed to broaden the bandwidth of RCS reduction. A prototype antenna is fabricated and measured. The peak gain of 17.9 dBi is obtained, and the monostatic RCS is reduced in a wider frequency band of 7–15 GHz.

RCS reduction and gain enhancement based on holographic metasurface and PRS

In this study, a high directivity slot-coupled patch antenna with low radar cross section (RCS) property using holographic metasurface (HM) and partially reflecting surface (PRS) is proposed. HM and PRS are printed on the two sides of a substrate, which is placed above the antenna. When an incident wave is illuminated on the HM, transmission wave is transferred into a surface wave, hence the low backscattering coefficient out-of-band and gain-enhancement are obtained. With the help of PRS and the metal plate, a Fabry-Perot resonator cavity is shaped. Not only in-band RCS reduction (RCSR), but also the high directivity of the antenna is obtained. Furthermore, simulated and measured results show remarkable RCSR are obtained ranging from 9 to 22 GHz, the maximum RCSR is 26.7 dB at 17.6 GHz, and the directivity of HM-PRS antenna is improved with the gain enhancement is 4.1 dB.

A Broadband Artificial Magnetic Conductor Reflecting Screen and Application in Microstrip Antenna for Radar Cross-Section Reduction

A miniaturized artificial magnetic conductor (AMC) reflecting screen with broad bandwidth (12.1-20.5 GHz, 51.5%) and polarization independence is proposed, which is arranged in a chessboard-like screen by combining two different square AMC unit cells to obtain a wide effective reflection phase difference of 180° ± 30°. It is applied in a microstrip antenna for radar cross-section (RCS) reduction based on the principle of destructive interference. The simulated results indicated that the in-band RCS reduction is achieved from 13.4-20.5 GHz (47.7%), corresponding to the range of effective phase difference. Besides, the out-of-band RCS reduction is also realized in this letter. The domain of -10 dB RCS reduction is widened to 13.4-26.9 GHz (67.0%) because of the cancellation between approximately perfect electric conductors and AMC. Moreover, the radiation performance of the composite antenna is kept well. Finally, the proposed low-RCS microstrip antenna is manufactured and measured. The measured results coincide well with the simulated counterpart.

In-Band Radar Cross Section Reduction of Slot Array Antenna

A slot array antenna is proposed for both in-band and out-of-band radar cross section (RCS) reduction. The presented slot array antenna is covered by the superstrate consisting of a polarization rotation reflective surface (PRRS). Four different configurations of the PRRS supersrtate are proposed and their effects on radiation and scattering performances of the slot array antenna have been investigated. By optimizing the arrangement of the unit cells of the PRRS, a good RCS reduction in an ultra-wide frequency band from 7 to 40 GHz is achieved. Besides, the in-band RCS of the proposed antenna is reduced by 12.4 dB compared with that of the reference antenna. Moreover, the 10 dB impedance bandwidth of the proposed antenna is enhanced from 3.5% to 14.2% and the gain remains nearly the same. Good agreement between the simulations and experiments is obtained.