A Multilevel Fast High Frequency Scattering Method from Electrically Large Multi-layer Coated Scatterers

A planar low cost and thin metasurface is proposed to achieve ultra-wideband radar cross section (RCS) reduction with stable performance with respect to polarization and incident angles. This metasurface is composed of two different artificial magnetic conductor unit cells arranged in a chessboard like configuration. These unit cells have a Jerusalem cross pattern with different thicknesses, which results in wideband out-phase reflection and RCS reduction, consequently. The designed metasurface reduces RCS more than 10-dB from 13.6 GHz to 45.5 GHz (108% bandwidth) and more than 20-dB RCS from 15.2 GHz to 43.6 GHz (96.6%). Moreover, the 10-dB RCS reduction bandwidth is very stable (more than 107%) for both TE and TM polarizations. The good agreement between simulations and measurement results proves the design, properly. The ultra-wide bandwidth, low cost, low profile, and stable performance of this metasurface prove its high capability compared with the state-of-the-art references.

A novel hybrid reflection method is proposed to realize wideband gain enhancement and radar cross section (RCS) reduction properties for Fabry–Perot (FP) antennas. This method adopts two kinds of frequency-selective surface (FSS) units, which are etched on both sides of a single-layer substrate with chessboard arrangement to operate separately as a hybrid surface (HS) and a reflective surface (RS), to form a hybrid partially reflecting surface (HPRS). The two FSSs with different positive reflection phase gradient bands and reflection amplitudes collaborate to expand the 3 dB gain bandwidth and improve the gain enhancement on the RS. Meanwhile, the different compensation phases of the two FSSs can redirect reflected waves to reduce the RCS on the HS, and phase cancellation is applied between the retransmitted waves and reflected waves to further reduce the RCS. The simulated and measured results verify the correctness of the proposed method. The prototyped FP antenna has a measured 10 dB impedance bandwidth of 8.64–12.07 GHz (33.1%), a 3 dB gain bandwidth of 8.6–11.1 GHz (25.4%) with a peak gain of 17.08 dBi at 9.5 GHz, and an RCS reduction bandwidth of 8.6–14 GHz with a peak RCS reduction of 19.5 dB.

This 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.

In this paper, a hybrid mechanism metasurface (HMM) that incorporates absorption, polarization conversion and phase cancellation mechanisms is proposed for wideband and wide-angle radar cross section (RCS) reduction. The polarization conversion absorber (PCA) is proposed by embedding the lumped resistors into the polarization conversion structure, which integrates the absorption and polarization conversion mechanisms. Then, the phase cancellation mechanism is employed to redirect the scattering energy to the non-incident directions through the chessboard configuration, which exploits the opposite phase between the PCA and its mirror structure. Unlike previous HMMs that depended on nested or cascaded structures, the proposed strategy integrates the absorption and polarization conversion mechanisms in the same structure, and the two mechanisms are complementary to each other. Through the integration of multiple mechanisms, the HMM can achieve more than a 10 dB monostatic and bistatic RCS reduction in 8.7-32.5 GHz and 8.6-31.2 GHz, respectively. Furthermore, the specular and bistatic RCS reduction performances under oblique incident waves are also studied, and the stable scattering suppression performances are determined. The proposed hybrid mechanism strategy exhibits significant scattering suppression capability through the incorporation of multiple mechanisms, which have potential applications in the multifunctional metasurface.

In this paper, performance degradation of RFID system due to curving in tag antenna is investigated through radar cross section (RCS) analysis. While the limitation in the read range of passive RFID system is mainly dominated by the received RF power from reader on the tag side, RCS analysis of tag antenna provides a direct and effective way for the evaluation of overall system performance. For simplicity consideration without losing generality, a simple half-wavelength planar dipole at 900 MHz is used for RCS analysis under various curving conditions. Results show that the read range can be degraded significantly due to curving.

In this communication, a novel metasurface with multiple unit cells of different thicknesses based on optimized multielement phase cancellation (OMEPC) is proposed for extremely wideband, omnidirectional, and polarization-independent radar cross section (RCS) reduction under wide-angle oblique incidence. Omnidirectional characteristic refers to the capability of RCS reduction under all azimuth angles ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varphi ^{i}$ </tex-math></inline-formula> ) at certain elevation angles ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta ^{i}$ </tex-math></inline-formula> ). The equivalent circuit model of the square patch unit cell is analyzed under both normal and oblique incidences. Unit cells of multiple thicknesses are adopted to solve the in-phase reflection at certain frequencies. The scattered fields of the proposed multiple-element metasurface under different frequencies, polarizations, and incident angles are jointly optimized and simultaneously suppressed by OMEPC. When the range of incident angles is increased from 0° to 40°, the proposed multiple-element metasurface can achieve the 10 dB specular RCS reduction from 7.34 to 64.85 GHz with a ratio bandwidth of 8.84:1 for both TE and TM polarizations, and the 8 dB RCS reduction bandwidth is approximately 6.76–83.70 GHz. The measurement results are in agreement with the theoretical analysis and simulation results.

A full-wave analytical method using the addition theorems and Hertzian potential functions are used to compute the radar cross section of a sphere coated by several layers composed of common materials and metamaterials. The minimization and maximization of radar cross section of a perfectly electric conductor sphere with such coatings are realized in a frequency band-width and in a wide interval of angles. One of the novelities of this contribution is, taking into dispersion relations of physically realizable metamaterials. So that the optimization procedure for RCS reduction is applied due to the coefficients describing dispersion characteristics. The method of least square is used for the design of a class of radar absorbing materials. The minimization of the error functions are performed by the combination of genetic algorithm and conjugate gradient method. It is shown that the proposed method of computation of radar cross section and its extremization effectively leads to the design of dispersive and isotropic metamaterials for the realization of radar absorbing materials.

A new thin planar wideband radar cross section (RCS) surface is designed and fabricated by using two different artificial magnetic conductor (AMC) unit cells. These AMC unit cells are designed by both substrate height and relative permittivity variations to achieve an ultra wide bandwidth performance. Three layer low cost FR-4 substrates are used to simply implement these unit cells. The proposed structure reduces the RCS more than 10 dB from 13.1 GHz to 44.5 GHz (109% bandwidth), more than 20 dB from 16.43 GHz to 42.31 GHz (88.3%), and more than 30 dB from 24.7 GHz to 40.9 GHz (49.4%). Moreover, this surface has more than 103% RCS reduction bandwidth for TE polarized and more than 93% for TM polarized ones up to 50° oblique incident waves. The good agreement between the simulation and measurement results also prove the idea. In addition to using a low cost substrate, the proposed surface has a significant widest RCS reduction bandwidth compared with the state of the art references in the normal and oblique incident angles at both TE and TM polarizations.

This paper presents the design of single layer metasurface for wideband radar cross section (RCS) reduction. The phase distribution across the proposed metasurface aperture is implemented using cubic phase profile. The proposed cubic phased metasurface has a sub-wavelength periodicity. In addition, the unit cell was designed according the Pancharatnam–Berry (PB) phase theory to make the proposed metasurface insensitive to the polarization of the incoming EMwave which is very important for radar stealth application. When illuminated by far-field EM-plane wave, the proposed metasurface can significantly reduce the RCS by more than 10 dB from 10 GHz to 26 GHz. The proposed cubic phased metasurface severely diffuse the backscattered energy in numerous angles in front of the metasurface. The fractional RCS reduction bandwidth (FBW) of the cubic metasurface is 88.8%, which is much wider than the FBW of metasurfaces in the literature. The proposed cubic metasurface is under fabrication and the RCS measurements are on-going.

A Fabry-Pérot (FP) antenna with wideband dual-polarization and radar cross section- (RCS-) reconfigurability adopting water-based frequency selective surface (FSS) is presented. The feed antenna is designed to switch between horizontal polarization (HP) and vertical polarization (VP) by controlling the on/off states of two PIN diodes. By optimizing the height of the FP resonant cavity, the proposed FP antenna achieves wideband and high-gain properties. In addition, the incident wave can be absorbed when the polymethyl methacrylate (PMMA) container is filled with water, which reduces the monostatic RCS. This design can be selected to be in stealth mode or radiation mode by injecting water into or extracting water from the water container. The measured results indicate that in stealth mode, the 10-dB RCS reduction band is from 4.5 GHz to 6.4 GHz, and the peak RCS reduction is 31.5 dB at 5.2 GHz. In the radiation mode, the realized gains of the FP antenna in both HP and VP at 5.2 GHz reach 16.6 dBi. Simulated and measured results verify the realizability and operational concept of the designed FP antenna.

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 wideband radar cross section (RCS) that covering X and Ku band is achieved by using artificial magnetic conductor (AMC) structures. Dual-band Jerusalem crosses and wide-band square patches are selected to produce reflection phase values with a difference about 180° (±30°) over a broad frequency range. The calculated results indicate that a 10dB RCS reduction from 7.4 GHz to 17.0 GHz (78.7% relative bandwidth) for the both polarization is obtained, with a maximum reduction of 40.3 dB at 11.6GHz. A prototype has been fabricated and measured, and the measured results are in good agreement with the corresponding simulations.

Metasurface has attracted much attentions due to its ability of flexible manipulation of electromagnetic wave. However, the metasurface is limited to the single operating band and poor design generality when it is used for radar cross section (RCS) reduction. In this paper, a stacked metasurface design method has been developed to flexibly achieve dual wide band RCS reduction. Two subarrays with polarization conversion characteristic are firstly designed to operate in two wide bands, respectively. Then a low-pass frequency selective surface (FSS) is developed and sandwiched between two metasurface subarrays to achieve a subarray with the dual-band polarization conversion performance. With the arrangement of the dual-band subarray into a 2×2 array in a rotation way according to the polarization cancellation, the resultant metasurface structure has two −10 dB RCS reduction bands covering 6.6-12.7 GHz and 27.8-38.1 GHz. The designed prototype is fabricated and measured. The simulation and measurement results are given to demonstrate the good dual-band RCS reduction performance.

In this letter, a metasurface (MS) antenna array, which can realize both radiation and scattering performance at the same time, is proposed and simulated. Firstly, Jerusalem cross structure is chosen as the MS unit. And four kinds of unit cells of different sizes are constructed in chessboard configuration to achieve wide band radar cross section (RCS) reduction. Then, each MS unit cell is added with feeding structure while its internal properties of MS are sustained well. Simulated results indicate that this work provides a novel method to obtain excellent radiation and scattering characteristics simultaneously.

A composite artificial magnetic conductor (AMC) surface is presented for wide band radar cross section (RCS) reduction. The composite surface consists of two kinds of AMC cells with different resonance frequencies. The phase difference between them can be tuned to be within a range close to ±π over a wide bandwidth. Therefore, the reflections from these two different AMC cells cancel each other. The basic principle was discussed and a sample was measured. The results show that a nearly 10 dB RCS reduction was achieved with a 32% bandwidth. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:712–715, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25835