Design and implementation of dual-band circularly polarized antenna

Abstract

A dual band circularly polarized (CP) rectangular loop antenna is presented. The antenna comprises two rectangular loops with parasitic rectangular elements inside the driven elements. The bandwidth is enhanced by adding parasitic elements. Antenna structure is situated above a finite ground plane. Two parasitic rectangular loops are connected by a short dipole. To get circular polarization, one gap on the longer side of each rectangular loop is introduced symmetrically with respect to the center of the structure. Each driven loop is fed through short dipole connecting two parasitic rectangular loops. One more feeding is introduced for each driven loop through finite ground plane. Antenna resonance frequency is mainly depends on the circumference of the rectangular loop. The operating bandwidth and symmetry of the pattern is mainly depends on the aspect ratio of the rectangular loop. To get good axial ratio (AR) and return loss, the position of gap and the height of the rectangular loop from the ground plane are very important. The proposed loop antenna has a impedance bandwidth at the frequency of 1.575 GHz and 2.45 GHz are 296 MHz and 600 MHz respectively. Maximum gain of around 8.9 dBi and 7.86 dBi has been achieved at the frequency of 1.575 GHz and 2.45 GHz respectively. The acceptable axial ratio value has been achieved. The proposed antenna can be used for Global Positioning System (GPS) and ISM band applications.