A novel circular shaped dual-band Dual-polarized Patch antenna and introducing a new approach for designing combined feed networks

In this paper, at first, a novel step by step method is introduced to design combined feed networks for dual-band dual-polarized patch (DDP) antennas; considered as a 4-port network, 4-port DDP antenna element having defined operation bands and defined input impedances is converted into a 2-port DDP antenna. In this method, excitation of unwanted modes is blocked, and impedance matching of the 2-port antenna in the operation bands is also obtained. The calculations are based on transmission line model. Moreover, a 4-port aperture coupled DDP antenna is presented here in a new form, circular form, for GSM (890-960 MHz) and DCS (1710-1880 MHz) bands. This antenna consists of two aperture-coupled patches: a circular ring patch for the GSM band and a notched circular patch for the DCS band; both are printed on the same layer. Finally, the introduced method is used for the presented 4-port DDP antenna, and a 2-port DDP antenna suitable for application in the GSM/DCS systems is obtained. Details of the design and the experimental results are presented.