This paper presents a new broad band circularly polarized slot antenna array based on substrate-integrated waveguide (SIW) and aperture feeding techniques. The antenna element's impedance and 3 dB axial-ratio (AR) bandwidths are from 8.8 to 10.4 GHz (16.67%) and 9.5–10.7 GHz (12%), respectively. Employing aperture-coupled feed and combining this method with sequentially rotated network, a 2 × 2 antenna array is achieved. Parametric optimization procedure is used to enhance the antenna specifications. In the presented scheme by reducing mutual coupling caused by the SIW technique and sequentially rotated feed network, all parameters of antenna are improved. Consequently a novel antenna array with impedance bandwidth of 2.8 GHz (8.7–11.5 GHz) and 3 dB AR bandwidth of 2.1 GHz (9–11.05 GHz) are obtained. The average gain of the proposed antenna is about 16.7 dBic. A new method is used to increase the gain of antenna array. The extracted result shows that side lob level, mutual coupling, impedance bandwidth, and performance of antenna simultaneously are controlled.
