Square Microstrip Antenna Backed By Modified Ground Plane For Circularly Polarized Response

The circular polarized response in microstrip antenna is realized when two orthogonal modes placed nearby in their frequency, are present. This paper presents a details study to analyze the effects of slots in the ground plane and substrate layers, in realizing circular polarized response in multi-layer suspended configuration. The study is presented using FR4 and Arlong substrates. The slots in ground plane modifies the surface current lengths at patch fundamental orthogonal modes to yield optimum separation between them to realize CP response. The placement of thicker dielectric in suspended configuration further enhances the realized axial ratio bandwidth at the cost of marginal decrement in broadside antenna gain. The optimum response in terms of axial ratio bandwidth and gain is obtained using FR4 substrate in three layer suspended design employing thicker FR4 substrate in bottom layer. The realized circular polarized bandwidth here is more than 75 MHz (>7%) with broadside gain of nearly 5 dBi over the BW. The proposed simpler design can find usage in mobile communication systems which are operating in 1000 MHz frequency spectrum.