Authors: Prashant Garg
Source: FERMAT, Volume 37, Communication 4, Jan.-Feb., 2020
Abstract: In this presentation, various enhanced reflectarray (RA) antennas are analyzed, designed and fabricated. Initially, an enhanced RA built of elements with reduced reflection phase sensitivity is presented. The proposed unit element is composed of concentric, multiresonance circular-rings with variable sizes. By changing the outer and inner radius of the interior ring in the opposite directions, a reduction in the phase sensitivity to manufacturing inaccuracy is achieved without extra contribution to the 360° phase range and decreasing the losses in the unit element is achieved. In addition, the margin between normal and oblique incidence of phase response for angles up to 40°, is smaller than 10°, which results in a high-efficiency, wideband performance. Measurement results show a maximum gain of 26.4 dBi at 10 GHz, aperture efficiency of 44.27%, and 16.3% 1 dB gain bandwidth. In order to improve the bandwidth of antenna, the phase constant (ψ˳) value at the RA aperture is gradually tuned and optimized. The designed antenna with ψ˳ = -125° has a peak gain 26.6 dBi at 10.2 GHz, aperture efficiency of 44.56%, and the 1 dB gain bandwidth is about 23.3% (9.67-12 GHz). In comparison with the conventional antenna (ψ˳ = 0°), the 1dB gain bandwidth shows a 43% improvement without no additional cost. Finally, an RA antenna with a novel subwavelength frequency selective surface (FSS) is introduced as a ground plane. The triple-connected C-shaped resonator as FSS is used in each unit element instead of the ground plane, so that it is reflective in the frequency range of 9.42-12.55 GHz and is transparent outside the working frequency band of the antenna. The proposed FSS-backed RA has a peak gain of 26.26 dBi at 10 GHz with a 42.87% aperture efficiency and 15.4% 1 dB gain bandwidth. The gain of RA with the FSS ground plane is 0.3 dB lower than the RA with a solid-metal ground plane, while their 1 dB gain bandwidth is almost equal. Additionally, the radar cross section (RCS) and crosspolarization levels of the presented FSS-backed RA antenna are considerably improved compared to solid ground RA within the operational bandwidth.
Index Terms: Antenna, concentric rings, frequency selective surface, reflectarray, sub-wavelength, wideband
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Analysis of Reflectarrays with Design and Fabrication of Some Enhanced Prototypes