UWB Microstrip Patch Antenna with Flower shaped patch and Cavity Structure

Ultra-Wideband antennas ranging from 3.1 to 10.6 Ghz, have gained increasing attention mainly because of the high data transmission rates, well beyond those possible with currently available technologies such as 802.11a, b, g, Wi-Max, etc. A UWB antenna with dual polarization is designed and simulated using ANSYS HFSS simulation software and its performance was analyzed. The proposed structure of the antenna is designed with a hexagon shape and a flower shaped patch and their results are compared to know the best among the two shapes. It is found that Flower shaped patch structure gives better results and the structure consists of a flower shaped patch with two ports and four capacitively coupled feeds. The four feeds are formed from two shapes : Trapezoidal shape and Triangular shape which forms a vertical patch and a horizontal patch respectively. The feeds excite a square radiating patch as they are placed at the center of the antenna structure. The feeds are connected to the microstrip lines, which are printed on the dielectric substrate (FR4), via holes. Two tapered baluns are used for getting differential feeds and for exciting the entire antenna structure to improve the gain and also to achieve high isolation between the two ports. Port 1 provides Horizontal Polarization and Port 2 provides Vertical Polarization. The return loss measured for the dual polarized antenna with the hexagon shape is -10.7dB, the measured VSWR is 1.8 and the measured antenna gain value is 0.784dB. The return loss measured for the dual polarized antenna with the Flower shaped patch is -20.04dB, the measured VSWR is 1.2 and the measured antenna gain value is 1.8485dB. A Cavity structure is then introduced into the flower shaped patch design for the sake of improvement in gain of the proposed design and the results are analyzed. It is found that gain of 2.1989dB is got from the cavity structure. The main characteristic of UWB Antennas is its ability to provide Polarization Diversity, which enhances the channel capacity significally. This make them more attractive than the usual antennas with linear polarization.