High Gain of Directional Ultra-Wideband Array Antenna Using Flat Reflector Structure for Microwave Imaging

UWB array antenna with high gain is proposed. The 4 × 1 array antenna consists of four identical copper circular patches are appropriately connected using quarter-wavelength transformer transmission line. The array elements and its feed network are properly optimized to have a high gain performance over wide range bandwidth frequencies. New additional flat reflector with distance of 20 mm enhances the proposed antenna gain. UWB antenna performance with reflector is better than UWB antenna without reflector structure. Antenna with reflector recorded wider operated bandwidth; 1.9GHz-10.6GHz with higher gain ranged from 3.5dB until 14.2dB compared with without reflector antenna operated from 2.2GHz to 10.6GHz with lower gain ranges of 1.9dB to 9.8dB. The reflector structure enhanced the antenna gain by 50% where the average gain throughout operated frequency for antenna with reflector and antenna without reflector is 10.2dB and 6.8dB respectively. Dimensions of 80 mm × 45 mm is considered as small UWB array antenna. The high gain and wide operator bandwidth of proposed antenna finds it very suitable to be integrated in human brain microwave imaging system due to ability of the wide signal with high energy penetrating human head structure.