Design and fabrication of a dual-polarized, dual-band reflectarray using optimal phase distribution

Two main factors limiting the reflectarray bandwidth are different phase slopes versus the frequency at every point on the aperture and the phase limitation of comprising elements at different frequencies. Considering these two factors, a novel design method is proposed to implement a dual-band, dual-polarized reflectarray antenna in X and Ku bands. An optimization algorithm is adopted to find the optimum phase for each unit cell on the reflectarray aperture. The best geometrical parameters of the phasing elements are suggested based on the phase variation of the element versus frequency and the element position with respect to the antenna feed. Many different classes of phasing elements with identical base structures are investigated to provide a lookup table for the optimization algorithm. The optimum phases are obtained so that two collimated beams are realized within the frequencies of 10.95 GHz to 11.7 GHz and 14 GHz to 14.5 GHz with vertical and horizontal polarizations, respectively. From the experimental results, the peak directivity of 27.1 dBi and 30.6 dBi, aperture efficiency of 42% and 67%, and cross-polarization level of less than –15 dB and –20 dB were obtained in the lower and upper bands, respectively.