Aperture coupled patch antenna sub-arrays for wireless communications applications

Small planar antenna arrays incorporating printed microstrip patch elements are found attractive for newly emerging wireless communications applications including wireless local area network (WLAN), last mile connection and automatic road pricing systems. In order to increase the operational bandwidth of the microstrip patch antenna, different bandwidth enhancement techniques can be applied. A convenient solution is offered by an aperture coupled microstrip patch antenna where the patch substrate layer can be modified without affecting the feed layer. Two configurations of an aperture coupled microstrip patch are considered for bandwidth enhancement. The first configuration uses a thick substrate for the patch layer and a standard thin substrate for the feed network. The other uses a thin substrate in conjunction with a foam insert for the patch layer and a standard substrate for the feed layer. The two antenna configurations are used to build two X-band linearly polarised 4/spl times/4 element sub-arrays with a corporate feeding network. The design aims at approximately 10% operational bandwidth at a centre frequency of 10 GHz. The paper discusses advantages and disadvantages of the two antenna configurations in terms of their return loss, radiation pattern and manufacturing cost.