Electronically Switchable Circular Microstrip Antenna with Sector-slot for Multiple Frequency Operation

Design of an electronically switchable microstrip antenna for multiple frequency operation, suitable for GSM and DCS band, is proposed. The antenna is a circular patch with a sector-slot that is fed by electromagnetic coupling. The resonant frequency of this antenna can be varied electronically by shunting the slot at appropriate points using PIN diode. Under different switching conditions of the diode, the effective resonating length changes so that the antenna resonates at different frequencies with same polarisations. This antenna has the added advantage of size reduction of up to 46% at the lowest frequency compared to conventional circular patch without significant reduction in gain