A Printed Semi-Circular Disc UWB MIMO/Diversity Antenna with Cross Shape Slot Stub

The paper presents a combination of microstrip and CPW fed semicircular patch antennas for UWB polarization diversity applications. The overall size of the diversity antenna is 40 mm x 40 mm x 1.6 mm. Both the patches are placed in an orthogonal arrangement to provide polarization diversity and to improve the isolation. The measured impedance bandwidth is from 3.0 to 10.6 GHz for the CPW fed antenna while it is from 2.7 to 11.0 GHz for the microstrip fed antenna. An extra operating band is obtained at around 1.2 GHz (measured) due to the common ground plane. The measured isolation is between 20 and 25 dB over most of the band. A detail parametric study is done to analyze the effect of the different parameters on the return losses of both the ports and the isolation between them. The radiation patterns are measured and found to be omnidirectional in the H-plane and dumb-bell shape in the E-plane. The peak gain is between 3 and 5 dBi over most of the band while the radiation efficiency is more than 80 %. Diversity parameters such as envelope correlation coefficient and diversity gain are also calculated and found to be within acceptable limits. The antennas will be useful for diversity applications in the ultra wideband region and for GSM/GPS applications in the first operating band.