Design of a wideband right-handed circularly polarized array of miniaturized mushroom-shaped antennas for direct broadcast satellite application

摘要

In this study, a wideband right-handed circularly polarized (RHCP) array of microstrip patch antennas, for direct broadcast satellite (DBS, 12.2-12.7 GHz) services have been presented. The single element of the array is a two-dimensional mushroom-shaped fractal antenna of resonating frequency 12.49 GHz and an impedance bandwidth of 1.12 GHz. The proposed single element is designed by etching a pair of Minkowski square boxes in one of the two opposite sides of a regular octagon. Furthermore, a thin slot of length equal to one side of the regular octagon is placed in-between the two Minkowski boxes, which results in the proposed mushroom-shaped radiating element. The proposed four-element linear array resonates at 12.47 GHz and gives an impedance bandwidth of 1.04 GHz. The feed network of the array is designed in such a manner to make the array structure very compact. The fabricated single element gives an RHCP gain of 5.25 dBic and its corresponding circular Polarization (CP) bandwidth of 200 MHz. The array gives an RHCP gain of 11.59 dBic and a CP bandwidth of 460 MHz. The measured CP bandwidth of the fabricated array prototype ensures 92% coverage of the entire DBS band with circularly polarized wave, and hence can be used for its related applications.