Dual-band and dual-mode annular ring microstrip patch antenna with slots for GSM-1800 and GPS operations

In this study, a novel, dual-band and dual-mode annular ring microstrip patch antenna with 6 equal rectangular slots in ground plane is designed, fabricated and analyzed. Angle between two consecutive slots is 60 degrees. The antenna can be used simultaneously for GSM-1800 (1.710-1.880 GHz) and L2 frequency band GPS (1.215-1.240 GHz) operations, and functions in TM21 ve TM11 modes for the mentioned operations, respectively. Measured -10 dB return loss fractional bandwidths are 33.510% (1.540-2.160 GHz) and 15.130% (1.100-1.280 GHz) for GSM-1800 and GPS frequency bands, respectively. While the antenna has a conical radiation pattern for GSM-1800 operation, it has a unidirectional radiation pattern for GPS operation. Measured maximum gain for the operation frequency of 1.227 GHz is 7.410 dBi and this parameter is 5.600 dBi for the operation frequency of 1.800 GHz. The antenna is circularly polarized for GPS operation and its 3 dB axial ratio fractional bandwidth is 4.59% (1.192-1.248 GHz). Measurements are in good agreement with simulations.