Maximum Radar Cross Section Reduction Research Articles

Low RCS and High-Gain Patch Antenna Based on a Holographic Metasurface

In this letter, a low radar cross section (RCS) patch antenna based on a holographic metasurface (HM) is proposed. An HM is designed to form the proposed antenna. As a parasitic structure of the antenna, the proposed HM can effectively increase the antenna radiation aperture; thus, a relatively high gain is obtained. At the same time, the HM has the ability to transform a propagating wave into a surface wave. Therefore, the backscattering is greatly reduced, resulting in a low monostatic RCS. A high gain as much as 10 dBi and a wideband radar cross section reduction (RCSR) ranging from 5.5 to 21.5 GHz have been achieved. It is also worth pointing out that the maximum RCSR is 21.64 dB around 8 GHz for both x - and y -polarized incident waves. The proposed antenna has been fabricated and measured. Good agreements beween the simulated and measured results are observed.

Wideband radar cross section reduction of a microstrip antenna with square slots

AbstractThis paper proposes a new radar cross section (RCS) reduced microstrip antenna incorporating 475 square slots on the patch. The proposed antenna achieves wideband RCS reduction with radiation performance sustained. The modified and reference antenna are simulated and analyzed in radiating and scattering mode, respectively. Prototypes of two antennas are fabricated and measured. Compared with the reference antenna, the simulated result shows the modified antenna RCS reduced in the frequency range 1.1–2.6 GHz, which contains the in-band and out-of-band frequency band simultaneously. And the maximum RCS reduction is 7.6dB at the frequency of 1.19GHz. Besides, the modified antenna can achieve the antenna RCS reduction in the case of oblique incidence. The prototypes of two antennas are fabricated and measured, and the accuracy of the simulation is proved by the measured result. Due to its advantages of simplicity, wideband RCS reduced, broad-angle RCS reduced, the method in this paper is suitable for wideband antenna RCS reduction in space-limited environment.

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.

Wideband High-Gain Circularly-Polarized Low RCS Dipole Antenna With a Frequency Selective Surface

A low radar cross-section (RCS) wideband circularly-polarized (CP) dipole antenna using a frequency selective surface (FSS) is presented in this paper. A planar dipole antenna consists of a pair of slotted patches fabricated on top and bottom sides of the substrate is designed. The slotted patches are connected through a circular ring, which acts as a delay line to achieve circular polarization. In the proposed configuration, a band-stop FSS is employed for the antenna reflector, which improves the radiation performance and reduces the RCS of the dipole antenna. The impedance bandwidth (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ≤−10 dB) of the proposed antenna is 0.95 to 3.1 GHz and 3-dB axial ratio bandwidth (ARBW) is 1.9 to 2.35 GHz. The proposed antenna shows the maximum and average RCS reduction of 20 dB and 6.9 dB, respectively, in the frequency range of 3.7 to 18 GHz. The simulated and measured results show that the maximum gain of the antenna increases by 5.9 dB by using FSS.

Design, Characterization, and Optimization of a Multilayer U-type Hexaferrite-Based Broadband Microwave Absorber

Design and development of broadband thin multilayer microwave-absorbing materials (MAMs) are described in this paper. Design and analysis of single-, two-, three-, and four-layered MAM are covered in detail. CoCr-based U-type hexaferrite MAMs Ba4(Co1-3 x Cr x )2 Fe36O60 for various values of x ( x = 0.05, 0.1, 0.2, and 0.25) have been used as base materials. Thickness and material layers have been optimized using genetic algorithm (GA). Reflection loss ( RL ) of −50 dB has been obtained using single-layered MAM at 2.21 mm thickness with effective bandwidth of 1.5 GHz. RL value has been optimized in two-, three-, and four-layered MAM and RL of −80.94 dB has been obtained using four-layered MAM at 1.801 mm thickness with effective bandwidth of 3.948 GHz. MAMs have been applied on an artillery shell and using electromagnetic (EM) simulation software radar cross-section (RCS) reduction simulation has been carried out for single- and multilayered MAM. RCS reduction of 9.14 dB has been obtained using single-layered MAM and a reduction of 19.86 dB has been obtained for four-layered MAM at 10 GHz. RCS reduction simulations have been carried out in entire X band and a maximum RCS reduction of 29.76 dB has been obtained at 9.5 GHz at 0° aspect angle.

Wideband radar cross-section reduction of a microstrip antenna using slots

AbstractIn this study, a new microstrip patch antenna with wideband radar cross-section (RCS) reduction is presented. The RCS of the proposed antenna was reduced by subtracting the current-direction slots of the patch, with the radiation performance sustained not only for the current-direction subtraction, but also for the no modification in the ground plane. Modified and reference antenna were fabricated and measured. The simulation and measurement results showed that the modified antenna reduced the in-band and out-band RCS simultaneously with no detriment to the radiation performance. In the frequency band from 3.9 to 8.1 GHz, the RCS of the modified antenna was reduced in the whole band compared with the RCS of the reference antenna. The maximum RCS reduction was 7 dB at a frequency of 6.7 GHz.

Effect of plasma volume on monostatic radar cross section control

ABSTRACTUnder atmospheric pressure, dielectric barrier discharge (DBD) with a plasma layer is utilized to produce large-volume plasma without a vessel. When a 16-kV bias at 1 kHz is applied to 85 copper strips, the DBD actuator generates plasma with the dimensions 170 × 170 × 1 mm. When the incident wave with an electric wave vector perpendicular to the strip array is illuminated, the monostatic radar cross section (RCS) is reduced by a maximum of 3.5 dB. The measured results are validated using full-wave simulation based on homogeneous plasma, with estimated plasma parameters. By changing the number of copper strips connected to the feed line, the relative volume of plasma can be changed. If the relative volume decreases by 20%, the maximum RCS reduction is reduced by nearly 20%. This demonstrates the possibility of using plasma to control monostatic RCS in a wide bandwidth.

Low Scattering Microstrip Antenna Array Using Coding Artificial Magnetic Conductor Ground

In this letter, a low scattering microstrip antenna array has been designed and fabricated using a coding artificial magnetic conductor (AMC) ground. Two different AMC unit cells are designed first, and then they are combined to replace the conventional metallic ground of an antenna array. It is found that the radar cross section (RCS) of the novel antenna array is reduced in a wideband from 6 to 13.4 GHz for the broadband diffusion property of an AMC ground. The maximum RCS reduction of 17 and 16.65 dB can be obtained at 10 GHz for both polarizations. Moreover, the antenna radiation properties are hardly influenced owing to the antenna array and an AMC ground work at different frequencies. The measured results are in good agreement with the simulations, verifying the validity of the proposed design method.

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.

Double‐layer miniaturised‐element metasurface for RCS reduction

A novel double-layer miniaturised-element metasurface is investigated to obtain the in-band and out-of-band radar cross-section reduction (RCSR) of a patch antenna. The modified traditional square-rings, with centre edges bent inward into hollow crosses and eight resistors welt on each side, are adopted to form the first-layer metasurface. It is for the out-of-band incident wave absorption. The second layer consists of four V-shaped polygonal metallic patches and four resistors. Each resistor connects two adjacent V-shaped patches together. The second layer is for in-band (2.76–2.86 GHz) RCSR of the antenna. Simulated and measured results showed that the RCSR of the new antenna with proposed metasurface has been dramatically accomplished from 2.0 to 15.5 GHz. It is worth mentioning that the obtained RCSR at 2.8 GHz is as much as 14.6 dB and the maximum RCSR at 10 GHz is 30.1 dB. The monostatic radar cross section (RCS) of the proposed antenna is significantly reduced over a wide angular domain at the same time. Since the metasurface has little effects on the radiation performance of the antenna, this method can be used to achieve antenna RCSR at broadband and over wide angular range.

A Wideband Absorber With a Multiresonant Gridded-Square FSS for Antenna RCS Reduction

This letter proposes a wideband absorber using a multiresonant gridded-square frequency-selected surface structure. Equivalent circuit models of parallel LC resonant circuits in series are given to clarify the multiresonant working principle. Using this method, a quad-resonant absorbing ground plane is designed. Surface current distributions are shown to explicate the multiresonant modes. By using the proposed absorbing ground, a wideband dipole's radar cross section (RCS) can be reduced effectively. Measured results show that 50% absorption bandwidth of the proposed absorbing ground plane is from 2 to 2.7 GHz, and maximum RCS reduction of the antenna with absorbing ground is 5 dB. The peak gain of the antenna still maintains above 6.8 dBi in the frequency range from 1.66 to 2.76 GHz. The proposed absorbing ground has advantages such as multiresonant mechanism, wideband absorbing bandwidth, and polarization independence. Thus, it can be used to reduce antenna's RCS with maintained radiation performance.

A CIRCULARLY-POLARIZED METASURFACED DIPOLE ANTENNA WITH WIDE AXIAL-RATIO BEAMWIDTH AND RCS REDUCTION FUNCTIONS

A new circularly-polarized metasurfaced dipole antenna (MSDA) with wide axial-ratio (AR) beamwidth and radar cross section (RCS) reduction properties is proposed and studied in this paper. This antenna is a quite simple half-wavelength linear dipole right above a metasurface which consists of 9 double-head arrow-shaped unit cells arranged in a 3×3 layout. By cautiously choosing the geometrical parameters of the metasurface and tuning the distance between the dipole and the metasurface, the whole structure turns out to be a circularly-polarized antenna with RCS reduction feature. Simulation results show that the MSDA in circular polarization achieves an operating bandwidth of 410MHz and a wide AR beamwidth of 123◦ and 90◦ in φ = 0◦ and φ = 90◦ planes respectively, together with a maximum RCS reduction of 10.4 dB in the whole operating band.

Investigation and performance evaluation of carbon black- and carbon fibers-based wideband dielectric absorbers for X-band stealth applications

This paper presents the design, preparation, and electromagnetic testing of wideband dielectric absorbers based on carbon fibers and carbon black powders for stealth applications. The specially prepared absorbers are characterized using the partially filled waveguide technique for the complex permittivity, and the return loss of the sample is measured using the free-space system in the X-band frequency region. A maximum return loss of 29 dB i.e. absorption of 99% at 10.3 GHz is achieved with minimum 97% absorption throughout the X-band frequency region. The fabricated absorber having density of 0.28 gm/cc and thickness of 2 mm makes it a potential candidate for stealth applications especially for the defense targets. A multilevel fast multipole method-based electromagnetic simulation is carried out on the artillery shell model, and on the leading edge model of the aircraft using the measured electromagnetic properties of designed absorber for the radar cross-section (RCS) reduction. The maximum RCS reduction of 27 and 20 dB has been observed for the artillery shell model, and for the leading edge of stealthy aircraft model, respectively, as compared to that of the PEC structure at 10.3 GHz frequency.

FDTD simulations on radar cross sections of metal cone and plasma covered metal cone

Electromagnetic wave interaction with a plasma covered metal surface has been studied using the Radar Cross Section (RCS) changes of a 10 cm diameter and 30 cm height metal cone with and without plasma coverage. A Finite-Difference-Time-Difference (FDTD) method was use to calculate the case of a cone with and without a covering of a 1 cm thick sheet plasma for both S Band (2,3, and 4 GHz) and X Band (8, 10, and 12 GHz) frequencies. The characteristic plasma frequency ωpe was set at 10 GHz, and electron-neutral collision frequency νen chosen to be 20 GHz. The results indicate that the metal cone has very small RCS at head-on direction, and a large RCS looking from the back end. A Plasma covered metal cone was shown to achieve head-on direction monostatic RCS changes between −0.47 and −7.2 dBm2 from 2 to 4 GHz, and −11 to −3.2 dBm2 RCS changes from 8 to 12 GHz, but at the back end the RCS increases between 2.2 and 2.6 dBm2 from 2 to 4 GHz, and varies between −0.9 and 0 dBm2 from 8 to 12 GHz. In the two frequency bands investigated, maximum RCS reduction of −15 dBm2 occurs at 8 GHz at the same direction as the incident electromagnetic wave polarization. Plasma stealth offers advantages like frequency tunability, but the challenge is establishing an adaptive feedback mechanism that can main a constant plasma density and thus a constant RCS by adjusting the power supplied to plasma generator while monitoring the changes in air speed, altitude, and humidity.

Design of fractal patch antenna for size and radar cross-section reduction

This research study presents a novel design of star-shaped fractal patch antenna for miniaturisation and backscattering radar cross-section (RCS) reduction. The proposed fractal antenna gives 50% size reduction compared with a conventional circular microstrip patch (CCMP) antenna. The antenna is studied experimentally for return loss behaviour using vector network analyser R&amp;S ZVA40. It can be useful for wireless application in 0.85-4 GHz frequency band. Further, the study focuses on backscattering RCS (both monostatic and bistatic) reduction by the proposed antenna compared with the CCMP antenna. It is found that increase in number of fractal iterations included in the conventional patch to design fractal antenna geometry reduces backscattering RCS at multiband compared to the conventional patch antenna. This reduction in backscattering RCS by the antenna is observed at multiband. The antenna can be tuned for low backscattering by variation in the substrate dielectric constant and thickness and the superstrate dielectric constant and thickness. For maximum RCS reduction by the antenna, optimisation of substrate thickness becomes necessary. The study also deals with effect of frequency and aspect angle variation on backscattering RCS reduction.