A Reflectarray based on Minkowski Ring Elements Backed by Frequency Selective Surface

In this paper, a novel subwavelength and FSS-backed reflectarray element is proposed. The element is composed of a Minkowski ring and a square ring. Due to its self-similar structure and unlimited space filling property, fractal element can achieve smaller element spacing and better phase performance. With the proposed reflectarray element, the element spacing is reduced to 0.38 lambda(0). The traditional metal ground plane is replaced by a frequency selective surface (FSS) that reflects the electromagnetic waves in the working frequency band and provides favorable conditions for smoother and linear reflection phase curve. A prototype with an aperture size of 220 mmx 220 mm is designed, fabricated and measured. The simulated results show that the antenna gain is 18.5 dBi at 5.8 GHz and a 15.7% 1-dB gain bandwidth is realized. Meanwhile, the simulated cross polarization and sidelobe level are -28.8 dB and -13.9 dB, respectively.