Design of a frequency selective surface‐backed microstrip reflectarray antenna using Minkowski ring elements

Abstract

A novel frequency selective surface (FSS)-backed subwavelength reflectarray element is proposed in this article. The element consists of an inner square ring and an outer Minkowski ring. The proposed fractal element could achieve smaller interelement spacing and better reflection phase performance due to its space-filling property and self-similar geometry. An 11 × 11-element reflectarray with reduced element spacing of 0.38 λ 0 ( λ 0 -the free space wavelength at 5.8 GHz) is designed. A FSS is used to replace the perfect electric conductor (PEC) ground. In the working frequency, the electromagnetic waves are reflected and result in a smoother and more linear reflection phase curve. Moreover, the radar cross section (RCS) of the reflectarray antenna is also reduced by using the FSS ground. A prototype antenna is then fabricated and measured. The measured results show that the antenna has a peak gain of 18.6 dBi, and an aperture efficiency of about 31.9%. A measured 1-dB gain bandwidth of 14.3% is obtained. Meanwhile, the measured cross-polarization and side-lobe levels are −20 dB and −13 dB, respectively. The simulated results demonstrate that the monostatic RCS can be significantly reduced with a fractional bandwidth of 32.76% and 44.83% for the lower and upper bands with reduced levels of 5 dB, respectively.