Low Radar Cross Section Antenna Research Articles

A low radar cross section antenna array based on a liquid metal metasurface

AbstractA low RCS (radar cross section) slot array antenna based on a liquid metal metasurface is proposed. The metasurface consists of 6 × 6 nested ring‐shaped element. The inner ring with a checkerboard distribution can realise 180° ± 37° phase difference, which can effectively reduce the scattering performances for the slot array. The outer and inner ring together can excite more energy from the slot array, thus resulting in increased radiation gains. Therefore, by changing the layout of liquid metal on the metasurface, scattering and radiation enhancement modes can be switched. The measured results show that in the scattering mode, the RCS can be reduced from 8.1 to 17 GHz. While in the radiation enhancement mode, the proposed array with the metasurface can achieve a −10‐dB impedance bandwidth of 9.4–11.2 GHz (17.4%) with a maximum gain of 8.12 dBi. Compared with the slot array without the metasurface, the realised gain is enhanced by 1.2 dBi from 6.9 dBi. The measured results correspond well with the simulated ones.

A Low RCS Waveguide Slot Antenna array with Metamaterial Absorber

We propose a novel design to reduce the radar cross section (RCS) of ridged waveguide slot antenna array with metamaterial absorber (MMA). The MMA consists of metallic pattern and solid metal on sides of a dielectric slab, of which the absorbing characteristics and mechanism are analyzed. The PEC ground plane of a ridged waveguide slot antenna array is covered by MMA. Both the simulated and measured results show that compared with the waveguide slot antenna array with a PEC ground plane, the RCS of proposed antenna array are reduced dramatically without degradation of antenna performance. Combining with the bandpass frequency selective surfaces technology, the guideline illustrated by the proposed examples will serve as a good candidate for the future design of low RCS antenna.

A broadband AMC metasurface for radar cross section reduction and application in microstrip antenna

ABSTRACTA broadband checkerboard artificial magnetic conductor (AMC) metasurface with a 61% bandwidth is proposed. Two different AMC unit cells with 180° (±37°) effective reflection phase difference over a wide frequency range from 7.3–14 GHz are designed. A checkerboard metasurface is structured with two AMC unit cells and is applied in a microstip antenna for radar cross section (RCS) reduction. The simulated results show that the antenna can achieve more than 10 dB RCS reduction from 7.2–13.1 GHz. The maximum RCS reduction is 36 dB. Meanwhile, the radiation performance of the antenna has been well kept. Finally, the low RCS antenna is manufactured and measured. The measured results are in agreement with the simulations.

A monostatic RCS reduction study for an antenna in structural mode at X band

ABSTRACT In this paper, a radar cross-section (RCS) reduction of a microstrip antenna is investigated both experimentally and numerically. A traditional metal ground plane antenna and a bandstop frequency selective surface (FSS) filter are designed at 5.4 GHz. In order to reduce RCS and reflectivity of the reference antenna, the bandstop filter structure is set up instead of the full metal ground plane. The study observed a wide frequency range between 3 GHz and 14 GHz. The maximum RCS reductions between the reference antenna and the low RCS antenna in-band and out of band are obtained at 9.2 dBsm and 28 dBsm, respectively. The antennas are analysed under different θ – and φ – polarised incidence conditions. Low RCS antenna shows satisfactory results especially at X band in terms of reflectivity and RCS under these angular conditions.

Metasurface Radome to Achieve a Wideband High Gain, Low RCS, and Low SLL Antenna

A Phase- and amplitude-adjustable metasurface radome (PAMR) is proposed to achieve a wideband high gain and low radar cross-section (RCS) antenna with arbitrary sidelobe levels (AS-PGMA) at a 9.8 GHz operating frequency. The proposed PAMR is a special multilayer phase gradient metasurface lens whose amplitude distribution is modified based on the Dolph-Tschebyscheff technique. The AS-PGMA simulation results indicate that a high gain, low RCS, and low sidelobe level (SLL) antenna can be achieved over a broad impedance frequency bandwidth of 9.25–10.1 GHz with in-band average values of 17 dB, −7.5dBsm, −20 dB/−27 dB for gain, RCS, and E-/H-plane SLL, which are measured at 9.8 GHz as 17.4 dB, −9dBsm, and −23.02 dB/−27.91 dB, respectively. Additionally, a novel analytical method for calculating the RCS of the proposed PAMR and AS-PGMA is described and verified by measurement and simulation findings. Measurement results show that the E-/H-plane SLL of the AS-PGMA is improved by 12.2 dB/5.1 dB at the operating frequency, respectively, while its gain and RCS reduction are reduced by 1.6 and 2.1 dB, respectively. Moreover, RCS of the AS-PGMA is reduced over an ultrawide bandwidth of 1–20 GHz for orthogonal polarizations. The analysis, simulations, and measurements are all in good agreement.

Frequency-Selective Rasorber Based on High-Q Minkowski Fractal-Shaped Resonator for Realizing a Low Radar Cross-Section Radiating System

In this article, a novel design of compact frequency-selective rasorber exhibiting absorption–transmission–absorption characteristics and having high passband selectivity has been proposed. A square-loop resonator with mounted lossy elements serves as the elemental broadband absorber from 4 to 12 GHz. The transmission frequency at 8.4 GHz is realized by printing a Minkowski fractal-shaped resonator with a high-Q factor on the resistive layer, which provides a transmission pole at the frequency corresponding to the passband of a double-cross-slot-shaped bandpass layer. The functioning of the proposed frequency-selective rasorbers (FSR) is explained by a corresponding equivalent circuit model. The proposed FSR exhibits higher selectivity at the passband, thus making it a suitable candidate for shielding the narrowband radiating system. Measurements performed on the fabricated prototype of a 17 × 17 unit cell array provides experimental validation. Further, a low radar cross-section antenna is realized by integrating a patch antenna with the proposed FSR, which achieves an average out-of-band monostatic radar cross-section (RCS) reduction of 11.92 and 5.04 dB in the lower (4–7.5 GHz) and upper (9.2–10.8 GHz) absorption bands, respectively, while maintaining the other antenna parameters. Furthermore, the bistatic total RCS reduction of 77% and 60% are achieved in the lower and upper frequency bands, respectively.

A broadband and low‐profile magnetoelectric dipole antenna with low radar cross section

AbstractIn this study, a novel broadband and low profile magnetoelectric dipole (MED) antenna with a low radar cross section (RCS) is proposed. The 10 dB RCS reduction is achieved by shifting the reflected energy to six directions, which is an efficient optimization method based on convolutional operations. Specifically, the polarization conversion metasurface (PCM) unit with high polarization conversion rate is constructed and employed in the MED antenna for RCS reduction. The proposed antenna is fabricated and measured. Measured results depict that the low RCS antenna offers good impedance matching in 12–15.6 GHz (relative bandwidth 26%). Compared with the reference antenna, the RCS of the proposed antenna is reduced by more than 10 dB from 9.9 to 16 GHz. It is proved that the proposed antenna has broadband and stable radiation performance and outstanding specular reflecting suppression capabilities.

Wideband Low RCS Antenna Based on Hybrid Absorptive-Diffusive Frequency Selective Reflector

A method for designing a wideband low radar cross section (RCS) antenna is proposed based on hybrid absorptive and diffusive frequency selective reflector (AD-FSR) in this paper. The low RCS antenna exhibits manifold frequency responses in three artificial bands, which are created by its different components. A simple U-slot patch antenna is borrowed, which is integrated with the diffusion metasurface, and placed under the absorptive sheet with about quarter wavelength. Then, the out-of-band incident wave is captured by the absorber in the lower frequency band, and diffused by the metasurface in the upper frequency band achieving the RCS reduction. The design strategies are explained and verified with the aid of the corresponding equivalent circuit model and current distributions. To illustrate the efficacy of the proposed approach, the low RCS antenna using the proposed hybrid AD-FSR structure is fabricated and tested, and the results demonstrate that the proposed structure is an attractive candidate for designing wideband low RCS antennas.

Composite polarization conversion metasurface and its application in integrated regulation radiation and scattering of antenna

The transmission polarization conversion metasurface has been widely concerned, because it has the advantage of being easy to be conformal with the antenna. Based on the reasonable arrangement of transmission polarization conversion units, various and complex electromagnetic functions can be realized. As the electromagnetic open window on the flight platform, the antenna is the bottleneck that restricts the decrease of radar cross section (RCS) of the whole flight platform. It is difficult to simultaneously realize the normal and efficient radiation of the antenna and the decrease of the RCS of the antenna. When the designed transmission metasurface is used in the antenna design, the radiation and scattering of the antenna can be regulated comprehensively. In this paper, a composite polarization conversion metasurface is proposed and verified. The unit cell of composite polarization conversion metasurface consists of two mirror symmetrical anisotropic metal patches in the upper layer, a dielectric layer and a polarization gate in the lower layer. When the polarization direction of the incident electromagnetic wave is perpendicular to the extension direction of the polarization gate and arrives at the composite polarization conversion surface, the conversion surface can realize the conversion from transmission linear polarization to right-hand circular polarization in a frequency range from 9.3 GHz to 10.9 GHz. When the polarization direction of the incident electromagnetic wave is parallel to the extension direction of the polarization gate, co-polarized total reflection can be realized. The chessboard arrangement metasurface is composed of composite polarization conversion unit and its mirror unit. A novel linearly polarized chessboard arrangement metasurface antenna is composed of the linearly polarized source microstrip antenna with a bandwidth of 9.4–10.7 GHz and the chessboard arrangement metasurface. By using the counter rotating cancellation characteristic of circular polarization, the chessboard arrangement metasurface antenna maintains linearly polarized radiation. Comparing with the source microstrip antenna, the linear polarization purity of chessboard arrangement metasurface antenna is improved from 9.5 GHz to 10.5 GHz. At the same time, the forward gain of the chessboard arrangement antenna increases and the radar cross section decreases. The maximum reduction is 39.2 dB. To further verify the practicability of the design and analysis, the chessboard arrangement metasurface antenna sample is fabricated and measured in microwave anechoic chamber with an Agilent 5230C network analyzer. The experimental results are in good agreement with the simulation results. This study has important reference value in the design of high gain, low RCS antenna and integrated regulation radiation and scattering of antenna.

A coding metasurface antenna array with low radar cross section

An aperiodic metasurface antenna array with low radar cross section (RCS) is designed. The upper patches of the two antenna elements have the same shape and are placed at an orthogonal position, which can effectively reduce the workload of simulating the reflection characteristics of the patch. As antenna elements, they have identical operational band and polarization mode, and as metasurfaces, they can form an effective phase difference of 180° ± 37°. The RCS of the array is reduced mainly by phase cancellation under the <i>x</i> polarization and by absorption under the <i>y</i> polarization. According to the coding metamaterial theory, the two elements can be coded aperiodically by using the programming software. Regarding element A and element B as “0” and “1”, respectively, the coding matrix can be solved by a genetic algorithm. Element A and element B are arranged according to positions “0” and “1” to obtain a proposed array. The scattering field of proposed array is diffusive, and the peak RCS is effectively reduced. In order to highlight the characteristics of the proposed array, the chessboard-type array is designed for comparison. The simulation results show that the radiation performance of proposed array is good. Comparing with the metal board of the same size, the 6 dB reduction bandwidth of the monostatic RCS is 4.8－7.4 GHz (relative bandwidth is 42.6%) under the <i>x</i> polarization and 4.6－7.8 GHz (relative bandwidth is 51.6%) under the <i>y</i> polarization. Comparing with the chessboard type array, the scattering energy distribution of the designed antenna array is very uniform and the peak RCS in space reduces obviously. When a 4.8 GHz electromagnetic wave is incident with different incident angles and polarization modes, the scattering field is diffusive. Compared with other similar arrays, the proposed array has advantages of simple design process and even scattering field. The experimental results are in good agreement with the simulation results. This work makes full use of the scattering characteristics of the antenna element itself to solve the problem that the array antenna possesses both good radiation characteristics and low scattering characteristics at the same time, and improves the design process of the antenna patch. This design method has certain universality and reference significance for designing the low RCS antenna array.

Design and development of low radar cross section antenna using hybrid metamaterial absorber

AbstractAn efficient approach is presented in this article, to reduce radar cross section (RCS) of a microstrip patch antenna, without affecting other radiation characteristics by the application of a novel hybrid metamaterial (MM) structure. The microstrip antenna is designed to operate at 4.2 GHz. Three different configurations of MM structures (ie, CB_1, CB_2, and hybrid) with splitted square and ring shaped two nonidentical MM cells are designed and critically analyzed in the range of 2‐18 GHz. A hybrid MM configuration is chosen for the design and implementation of low RCS antenna due to its exceptional performance as compared to CB_1 and CB_2. The hybrid MM is organized in chessboard configuration, comprises of splitted square and ring shaped MM unit cell. The results show that proposed antenna gives substantially out of band RCS reduction from 6 to 18 GHz and the proposed antenna has a lower RCS than the reference antenna. Proposed antenna attains wideband bandwidth around 7.4 GHz (ranging 2.0‐4.4 GHz, 7.8‐9.1 GHz, and 14.3‐18 GHz). The maximum reduction of −30.1 dBsm at 16.4 GHz is achieved in the hybrid MM structure impinged microstrip patch antenna. Finally, the fabrication and performance evaluation of MM loaded antenna is carried out. Moreover, measured results of the fabricated samples are closely matched with simulated results, which prove the effectiveness of the adopted approach for practical applications.

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.

Development of a Low Radar Cross Section Antenna With Band-Notched Absorber

A low radar cross section (RCS) antenna designed with band-notched absorber is described. First, a dual-polarization absorber with relative bandwidth more than 80% is designed using loaded resistors. Pairs of circular slot resonators and metal strip array resonators are introduced in the absorber to realize a notch band with full reflectance in the vertical polarization, while a wide absorption band in the horizontal polarization is maintained. The proposed band-notched absorber is thus realized. Within the notch band, the absorber can be served as a metal ground for antenna; while a great RCS reduction is obtained out of the notch band and in the horizontal polarization band. Then, a dipole antenna rigorously designed is mounted above the band-notched absorber, whose operating frequency is exactly in accordance with that of the notch band. The proposed low RCS antenna is established based on assembling the dipole antenna and the band-notched absorber together. The measured results demonstrate that the proposed antenna has fairly good radiation patterns. Added to that, more than 10 dB RCS reduction in two polarizations is realized simultaneously compared with that one of a conventional dipole antenna.

An Absorber-Integrated Taper Slot Antenna

The characteristic of quiet zone is essential for anechoic chambers that have been extensively used in the over-the-air tests. Multireflection in the anechoic chambers of the probe antennas could deteriorate the quiet zone and hence limit the capability of systems to detect small signals, throughput of multiple-input and multiple-output and radio frequency parameter measurement. In this paper, the authors developed an integrated approach of antenna-absorber codesign for a taper slot antenna (TSA) with low radar cross section (RCS). Low RCS antenna minimizes the reflection coefficient of the sampling antennas, the building block of anechoic chamber. This antenna is composed of an open-boundary TSA and shaped expanded polypropylene absorbers that surround the antenna. This new type of hybrid TSA is typically designed for anechoic chamber working from 0.6 to 6 GHz. The measured boresight reflectivity of the hybrid antenna has been achieved at least –27 dB from 0.6 to 6 GHz.

Design of shared aperture metamaterial and its applications for high gain and low radar cross section antenna

A shared aperture metamaterial (SA-MTM) with partially reflection and absorber characteristics is presented. The SA-MTM is composed of two metallic layers separated by a dielectric spacer; the top absorbing surface (AS) consists of oblique cross metallic pattern loaded with lumped resistances, and the bottom partially reflecting surface (PRS) consists of etched parallel slots in a metallic layer. An SA-MTM with partial reflection and absorption characteristics is fulfilled by making the absorbing surface and partially reflecting surface shared the same aperture in the vertical direction. The SA-MTM is applied to the waveguide slot antenna; the Fabry-Perot resonance cavity constructed by the PRS and the metallic ground layer of the waveguide slot antenna can achieve high gain, while the AS can obtain the low radar cross section (RCS) characteristic antenna by absorbing the incident wave. Simulation and experimental results demonstrate that the antenna with SA-MTM gain is enhanced above 3 dB in the operation frequency range, the backscattering RCS is obviously reduced in a frequency range of 2–9 GHz. This idea can help us design a high gain and low RCS antenna, which overcomes the conflict between scattering and radiation performance of antenna.

Low RCS Antenna Based on EBG Structure

In this paper, the application of stealth materials based on EBG structure in radar antenna system is studied. This materials is thinner and weaker, and can be well integrated with waveguide antenna. Radar cross section (RCS) is reduced effectively and stealth is realized.

APERTURE COUPLED MICROSTRIP ANTENNA WITH LOW RCS

Research of antenna Radar Cross Section (RCS) is very important for low observable platform. Aperture coupled microstrip antenna is fit for the low RCS antenna design because the feed network produce less effect on scattering of microstrip patch. A novel aperture coupled microstrip antenna is proposed, which utilizes the chip-resistor load, ground slot and miniaturization, to realize RCS reduction. Aperture coupled antenna with rectangular patch is chosen as the reference antenna. Two antennas are simulated and measured. The measured results show that the designed antenna realizes only 0.5 dB gain loss while RCS are reduced in almost all the frequency band.

Shipboard Low Observable Antenna Concepts

ABSTRACT Two new concepts for low radar cross section (RCS) shipboard‐mounted antenna systems are presented in this paper. The first concept for integration of low (RCS) antenna apertures into Low Observable (LO) ship super structures has been developed and evaluated in laboratory experiments. The concept consists of using conformal antenna apertures that have low monos‐tatic radar returns and placing them into a sloped deckhouse or mast structure. Critical to the concept is the ability to place multiple apertures close to one another in a small space. A Multiple Aperture Panel (MAP) concept containing antennas for Identification Friend or Foe (IFF), UHF Line of Sight, LAMPS data link, and Navigation Radar functions was developed. Detailed designs for the IFF and UHF antennas were completed and 1/2 scale versions of these antennas were built and tested. Measurements on the 1/2 scale antennas have demonstrated that the proposed antennas will perform well as transmitters/receivers and provide significantly reduced RCS. Conceptual designs and performance estimates for retrofit of the low RCS IFF antenna on a modern combatant and integration of the IFF antenna into a composite deckhouse structure have been completed. An alternate low RCS UHF antenna for the MAP concept, using a horizontally mounted annular slot aperture was designed, built and tested. The second low RCS antenna system concept is for a compact, self‐contained, low RCS antenna suite containing radar. GPS, IFF UHF communication, and UHF SATCOM antennas has been developed, built, and demonstrated in full scale tests.