Broadband High-Gain Microstrip Array Antennas for WiMAX Base Station

Two novel array antennas (3 x 2 and 3 x 3) with broadband and high gain characteristics are proposed for the application of WiMAX base station. To maintain the same electric current intensity with identical phase for each array element, an asymmetrical feed-network which composed of microstrip T- junctions with 2: 1 power ratio, quarter-wavelength impedance transformers, and 180 degrees phase shifters are devised, which in turn exhibits a desirable gain of more than 17 dBi at boreside direction for the proposed array antennas. Furthermore, by embedding a U-slot into all array elements, enhanced operating bandwidth measured along 14-dB return loss can be achieved, so that the WiMAX band operating between 3.3 and 3.8 GHz can be covered.