Single-feed dual-frequency rectangular microstrip antenna with a π-shaped slot

A novel slotted rectangular microstrip antenna for dual-frequency operation is proposed. The microstrip antenna is fed by a single probe feed and has a π-shaped slot embedded close to the patch´s radiating edge. The two operating frequencies have the same polarisation planes and similar broadside radiation characteristics. By varying the lengths and the spacing of the two alms of the π-shaped slot, the proposed antenna can have a tunable frequency ratio ranging from about 1.12 to 1.64. Simple semi-empirical formulas of the two operating frequencies have also been obtained. Details of the antenna design and experimental results are presented and discussed