Reflectarray antenna based on grounded loop-wire miniaturised-element frequency selective surfaces

摘要

A reflectarray antenna based on a metal-backed co-planar loop-wire Miniaturized Element Frequency Selective Surface (MEFSS) is presented in this paper. Since the unit cells are small compared to the wavelength, an equivalent lumped-element model can describe the spectral behaviour of the proposed MEFSS structure. It is shown that the proposed unit cell provides a wider and gentler phase variation as a function of the loop size compared to a metallic patch or loop element and that the phase response of the loop-wire element has very low sensitivity to the angle of incidence. In addition, the response of the unit cell, to a great extent, depends on the geometric and electrical parameters of the cells themselves with minimum dependency on the neighbouring elements and therefore the reflected signal phase can be controlled locally. Three samples of the proposed MEFSS structure, each giving different reflection phase values, are fabricated and measured to validate the circuit model and the design procedure. A prototype MEFSS-based reflectarray antenna at X-band is fabricated and measured. The prototype (260 mm ?? 260 mm and F/D = 1.02) shows a maximum gain of 26.3 dBi with a 1 dB-gain bandwidth of 17% and 3-dB beamwidth of 6?? in agreement with the design parameters.