Radar Cross Section Reduction Of Antenna Research Articles

Reconfigurable polarization rotation surfaces applied to the wideband antenna radar cross section reduction

A reconfigurable polarization rotation surface (PRS) using chessboard-like geometry is introduced for the radar cross section (RCS) reduction of a Yagi-Uda antenna in this article. The reconfigurable PRS reflector can be switched between low-RCS PRS reflector and metal reflector. When the reconfigurable PRS reflector with ON-state diodes is used in the Yagi-Uda antenna, the antenna has a similar radiation characteristic compared with Yagi-Uda using metal reflector. The PRS reflector can be used to achieve a low-RCS characteristic reflector by chessboard configuration with OFF-state diodes. Finally, the status of RCS can be switched according to the working state of diodes. The results show that the radiation performance of the Yagi-Uda is preserved. The monostatic RCS of the Yagi-Uda using PRS reflector with OFF-state diodes can be reduced more than 25 dB.

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

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.

Wideband RCS reduction of patch antenna using PRRS

A polarisation rotation reflective surface (PRRS) is proposed to achieve radar cross-section (RCS) reduction of a patch antenna at a broadband. The PRRS consists of two pairs of L-shaped patches, which are printed on a substrate backed by a metallic ground. By arranging the PRRS around the patch antenna in four orthogonal directions, a wideband RCS reduction can be obtained in the frequency band of 10–18 GHz. The proposed low-RCS patch antenna is fabricated and measured in an anechoic chamber. The experimental results show that the designed PRRS makes the antenna RCS dramatically reduced. What is more, the introduction of PRRS has little influence on the antenna performance.

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.

Wideband RCS Reduction of Microstrip Array Antenna Based on Absorptive Frequency Selective Surface and Microstrip Resonators

An approach for wideband radar cross section (RCS) reduction of a microstrip array antenna is presented and discussed. The scheme is based on the microstrip resonators and absorptive frequency selective surface (AFSS) with a wideband absorptive property over the low band 1.9–7.5 GHz and a transmission characteristic at high frequency 11.05 GHz. The AFSS is designed to realize the out-of-band RCS reduction and preserve the radiation performance simultaneously, and it is placed above the antenna with the operating frequency of 11.05 GHz. Moreover, the microstrip resonators are loaded to obtain the in-band RCS reduction. As a result, a significant RCS reduction from 1.5 GHz to 13 GHz for both types of polarization has been accomplished. Compared with the reference antenna, the simulated results exhibit that the monostatic RCS of the proposed array antenna in x- and y-polarization can be reduced as much as 17.6 dB and 21.5 dB, respectively. And the measured results agree well with the simulated ones.

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.

Left-handed material superstrate applied to the RCS reduction of microstrip antenna

Left-handed material (LHM) is applied to reduce the radar cross section (RCS) of microstrip antenna when the incident wave is non-perpendicular to antenna. The LHM having the magnitude of its refractive index close to zero can be used to the total reflection phenomenon and focus the electromagnetic wave. Therefore, the method of RCS reduction with LHM superstrate is presented. Two kinds of the LHM structure are proposed and two application examples are present. The simulated and measured results show that 5–20 dB RCS reduction under the condition of oblique incidence is obtained when the LHM superstrate is used. The RCS reduction angle range can be changed by adjusting the size of the LHM superstrate.

RECONFIGURABLE RADAR ABSORBING STRUCTURE APPLIED TO THE ANTENNA RADAR CROSS SECTION REDUCTION

An active reconfigurable radar absorbing structure (RAS) with the pin diode was proposed to reduce the radar cross section (RCS) of antenna. The operating states of the RAS reflector can be switched by using the pin diode. For ON-state and OFF-state diodes, the reflection coefficients of the RAS reflector were less than −25 dB and more than −0.8 dB around 8.3 GHz, respectively. The RAS reflector with ON-state diodes can be used as a dipole antenna reflector and has the same radiation performance as a dipole with a metal reflector, while the RAS reflector with OFF-state diodes can be used as a radar absorber for RCS reduction. Meanwhile, chessboard-like geometry RAS reflector was proposed to achieve wideband RCS reduction. The RCS reduction band covers the working band and is extended to 5-18 GHz. The results show that the reconfigurable RAS reflector can contribute to the antenna RCS reduction at working frequency without loss of radiation performance of dipole antenna. With the detection and stealth technology developing rapidly, radar cross section (RCS) reduction (1-4) has been a serious problem in military applications and has attracted significant attention recently. Since the scattering of the antennas has contributed a lot to the total RCS for low observable platforms, more and more attention has been paid to antenna scattering. Shaping, coating with radar absorbing materials (RAM) and using passive and active cancellation technology are basic methods in stealth technology (5-7). Furthermore, a number of new structures and materials are applied to the RCS reduction of antenna, such as artificial magnetic conductor (AMC), radar absorbing structure (RAS), frequency selective surface (FSS), etc. (8-11). However, these structures and materials cannot be used for stealth in the working band. When RAS is used, the gain of the antenna has a large degeneration (12), and the application of AMC will increase the profile of the antenna. All of them greatly deteriorate the stealth performance and application of radar system or other platform. In early years, antennas did not need to work in airborne or missile borne systems continuously. To realize the stealth of antenna, the radar was opened in close proximity to the target and shut down through the dangerous area. This method has the advantages of simple, feasible, and good stealth characteristic. In addition, the radiation performance of the antenna is preserved. However, this method can only reduce the antenna mode scattering, and the structural mode scattering still exists. Meanwhile, general metamaterials are completely passive structures, and the properties of these metamaterials cannot be changed. Therefore, in the complex electromagnetic environment, these metamaterials cannot be able to quickly adapt to the changes in the external electromagnetic environment and reduce its effect. In order to overcome these problems, reconfigurable RAS is put forward as a new concept. Reconfigurable technology has been successfully applied to antenna design. Early research focused on changing the current distribution by adjusting the radiator structure, which made the frequency, pattern, polarization or impedance of antenna changed. Currently, the reconfigurable metamaterial is

Single-layer wideband FSS for the RCS reduction of spiral antenna

A single-layer frequency selective surface (FSS) with wide stop band is proposed and applied in reducing the radar cross section (RCS) of the spiral antenna in this article. The element of the FSS consists of toothed spindle-shaped cross and rings. With the spindle-shaped cross and the toothed edges, the operating band of the FSS is enhanced and extended to the high frequency range. The metal rings are laid between the arms to decrease the coupling. The results show that the stop band of the FSS is 3.4–5.8 GHz under the condition of |S21| < −10 dB and the RCS of the spiral antenna is reduced in the band of 4–15 GHz while the radiation performances hold.

Low-RCS waveguide slot array antenna based on a metamaterial absorber

A method of reducing the in-band radar cross section (RCS) of waveguide slot array antenna by utilizing a metamaterial absorber (MA) is preflented. A novel ultra-thin (the thickness is only 0.01λ, λ is the wavelength corresponding to the MA resonant frequency) MA with high absorptivity and no surface lossy layer is designed; the absorber is composed of two metallic layers separated by a lossy dielectric spacer. The top layer consists of an etched oblique cross-gap patch set in a periodic pattern and the bottom one is a solid metal. Effective impedance of MMA will match the free space impedance by adjusting the dimensions of electric resonant component and magnetic resonant component in the unit cell, and so the reflection will be minimized. Meanwhile, the MMA can obtain a resonant loss to fulfill the high absorption. By finely adjusting the geometric parameters of the structure, we obtain the MA with absorption 99.9%, and its absorbing mechanism being interprefled by analyzing surface current, surface electric field, and volume power loss density distribution, respectively. The metallic area between slots in E plane direction of waveguide slot array antenna is covered by MA, and a distance between the radiating slot and the MA is suitably arranged. Antenna radiation performance is kept in good order because this arrangement does not destroy the amplitude distribution of antenna aperture, and the high absorptivity of MA that contributes the reduction of structure mode scattering. Simulation and experimental results demonstrate that the array antenna loaded with MA gets more than 6 dB RCS reduction both in the x-and y-polarized incident conditions; and the RCS of antenna has obviously a reduction from -25° to +25°, the most reduction value exceeds 10 dB in the boresight direction, while the reflectance, gain and beam width are guaranteed. This idea has an important significance and engineering application for the RCS reduction of array antenna.

RCS Reduction of a Patch Array Antenna Based on Microstrip Resonators

Microstrip resonators are used for reducing the in-band monostatic radar cross section (RCS) of a patch array antenna. The reference patch array antenna works at 4.5 GHz, and the proposed antenna with microstrip resonators is designed at the same frequency. The resonant frequency of the microstrip resonators is also 4.5 GHz so that it can cover the operating band of the patch array antenna. Compared to the reference antenna, which does not have the microstrip resonators, the simulation results demonstrate that the monostatic RCS of the proposed array antenna can be reduced at least 10 dB for both phi- and theta-polarized incident waves while preserving the desired radiation characteristics. Measurements on realized prototypes show good agreement with the simulations and prove the reliability and superior performance of the proposed approach.

Complex Spiral Antenna with Low Radar Cross Section Level

An ultra-wideband (UWB) circularly polarized complex spiral antenna with low radar cross section (RCS) is proposed in this paper. By replacing the metal reflect board of the antenna with a novel UWB frequency selective surface (FSS), the RCS of the spiral antenna is significantly reduced in a wide frequency range, while the radiation performances of the spiral antenna are maintained. The proposed antenna operates over the frequency band between 2GHz to 6.5GHz under the condition of axial ratio&lt;3dB and |S11| &lt; - 10dB. Simulation and measurement results demonstrate the validation of broadband spiral antenna RCS reduction by using the novel UWB FSS.

RCS REDUCTION OF QUASI-YAGI ANTENNA

A novel Quasi-Yagi antenna with low radar cross section (RCS) is proposed in this paper. By using arrow-shaped Koch dipoles as the driver and director and cutting the ground of the antenna, the RCS can be reduced in the operating band of 5 GHz-8 GHz when the incident wave is perpendicular to the antenna plane. Wideband radar absorbing material (WRAM) with frequency selective surface (FSS) is devised to replace the metallic reflect plate of the antenna to reduce the RCS in the maximum radiation direction. The average RCS reduction of the antenna in the frequency band of 3 GHz-12 GHz is 8.0 dB. The simulated and measured results show that there is a considerable RCS reduction of the Quasi-Yagi antenna with WRAM, and the radiation performance is preserved at the same time.

A NOVEL DUAL-BAND METAMATERIAL ABSORBER AND ITS APPLICATION FOR MICROSTRIP ANTENNA

In this letter, a novel dual-band metamaterial absorber is presented and analyzed. The absorber is composed of four patches on the top of a thin grounded dielectric substrate which can absorb incident wave at two difierent frequency bands efiectively. Then the absorber is loaded on the dual-band microstrip antenna, whose working frequency bands are overlapped with that of the absorber, to reduce the in-band RCS (Radar Cross Section) of antenna. The prototype is simulated, manufactured and measured. Simulated results show that the absorption of the absorber is as high as 98.6% at 4.29GHz and 99.8% at 6.49GHz. As to the dual-band antenna loaded with the proposed absorber, its radiation performance is unchanged while the RCS has declined by 8.59dB at 4.29GHz and 9.9dB at 6.49GHz respectively. There is a good agreement between simulated and measured results, which verifles that this absorber can be used for in-band RCS reduction of dual-band antenna so as to improve its in-band stealth performance.

RCS Reduction of Waveguide Slot Antenna With Metamaterial Absorber

This communication investigates the application of metamaterial absorber (MA) to waveguide slot antenna to reduce its radar cross section (RCS). A novel ultra-thin MA is presented, and its absorbing characteristics and mechanism are analyzed. The PEC ground plane of waveguide slot antenna is covered by this MA. As compared with the slot antenna with a PEC ground plane, the simulation and experiment results demonstrate that the monostatic and bistatic RCS of waveguide slot antenna are reduced significantly, and the performance of antenna is preserved simultaneously.

Design of ultra-thin broadband metamaterial absorber and its application for RCS reduction of circular polarization tilted beam antenna

In order to reduce the radar cross section (RCS) of antenna, a wideband-enhanced ultra-thin metamaterial absorber is designed by reducing the distance between the two absorption peaks due to the double resonances. The absorber is composed of two metallic layers separated by a lossy dielectric spacer. The top layer consists of a single-square loop with four splits on the four sides and a square metal patch in the center and the bottom one is of a solid metal. A dipole resonance and an LC resonance are caused by the structure of the metamaterial absorber. By fine adjusting geometry parameters of the structure, we can obtain a polarization-insensitive and wide-incident-angle ultra-thin absorber whose absorption values are 91.6% and 96.5%. On condition that thickness is less than 0.01λ the absorber has a full-width at half-maximum of 8.2%. The absorber is applied to the circularly polarized tilted beam antenna for reducing RCS. Simulated and experimented results show that the RCS reduction of antenna is above 3 dB within the operation band from 5.5 GHz to 6.5 GHz, the gain is not changed and the bandwidth is increased due to the improvement of axial ratio. At the resonance, the most reduction values exceed 8 dBsm and 11 dBsm while the absorber has a good characteristic of RCS reduction at the boresight direction from -36° to +36°.

APPLICATION OF BIONICS IN FREQUENCY SELECTIVE SURFACE DESIGN AND ANTENNA RADAR CROSS SECTION REDUCTION

Bionics principle is applied to frequency selective surface (FSS) design in this paper. To authenticate the method, a novel bionic and miniaturized FSS is proposed by use of a model of alternate phyllotaxis. The simulated and measured results show that the proposed FSS has a much smaller size and maintains other FSS- related performances. To study the applications of the novel bionic FSS in practice, it is used for the ground plane of an antenna array to reduce the antenna radar cross section (RCS). Compared to a reference antenna, the antenna with bionic FSS has lower RCS and favorable radiation performance. Hence, applying bionics principle to FSS design and antenna RCS reduction is proved feasible, which will serve as a good candidate for the future design of FSS and antennas with or without a requirement of RCS control.

RCS Reduction of Patch Array Antenna by Electromagnetic Band-Gap Structure

In this letter, electromagnetic band-gap (EBG) structure is used to reduce the radar cross section (RCS) of the patch array antenna. The proposition of this method is based on the high impedance characteristic of the mushroom-like EBG structure. The basic patch array antenna is designed with a central frequency of 5.0 GHz while replacing the substrate of the array with the mushroom-like EBG structure. The frequency band in which RCS of the patch array antenna reduced significantly can be adjusted by parameters of the EBG. The backward RCS of the patch array antenna with EBG can be reduced as much as 10 dB compared to that of the conventional array antenna, and the degradation of the antenna performance is not significant.

RCS Reduction of Array Antennas with Radar Absorbing Structures

This paper introduces a radar absorbing structures (RAS) applied to reduce the in-band radar cross section (RCS) of the array antennas. The structure of the RAS is based on square patch structure loaded with lumped resistances. An array with four patch elements was designed and built, and the RAS was located between two adjacent patch elements. The simulated and measured results show that the radiation performance of the array antenna is preserved when RAS is used. At operating frequency, the RCS of array antenna with RAS is obviously reduced compared with that of the original array.

Differential Evolution Algorithm and Method of Moments for the Design of Low-RCS Antenna

This letter introduces a novel technique for low radar cross section (RCS) antenna designs. The differential evolution algorithm (DEA) and the method of moments (MoM) are combined to achieve the RCS reduction and satisfied radiation performance. The antenna geometric parameters are extracted to be optimized by DEA, and a fitness function is evaluated by MoM to represent the performance of each candidate design. The optimization example of the slot patch antenna is presented as a test of the proposed DEA/MoM algorithm. By optimizing the slot location, the given slot antenna realizes the RCS reduction in the broad frequency range of 2-12 GHz at different incident angles, which demonstrates the feasibility of applying the proposed method to antenna RCS reduction.