Design and testing of a compact circularly polarised microstrip antenna with fractal defected ground structure for L-band applications

A compact circularly polarised (CP) microstrip antenna for mobile satellite communication band of India (1.492-1.518 GHz) is presented. Two asymmetric length rectangular shape slots, perpendicular to each other are printed on the circular patch for realisation of CP radiation. To improve the performance parameters of patch antenna such as axial ratio (AR) bandwidth, return loss bandwidth, radiation efficiency and so on a new technique of combination of fractal theory and defected ground structure (DGS) is proposed for the first time in design of CP antennas. 44.74% size reduction in patch size, enhancements of 62.73% in AR bandwidth, 70.74% in return loss bandwidth and 4.03% in radiation efficiency is achieved as compared with conventional patch antenna, after incorporation of Koch curve fractal DGS in the ground plane. The performance of the developed antenna has been compared with other available L-band planar antennas in the literature, and it is found that the developed structure is better one in many aspects. Laboratory prototype of the antenna is fabricated and experimentally measured for cross verifying the simulated results.