Frequency reconfigurable Microstrip-Fed annular slot antenna

In this paper, a frequency reconfigurable annular slot antenna is presented. The tuning system, which consists of diode switch, is located in the microstrip feed. Different bias voltages are supplied over the diode switch to change the length of the feed and thus two different resonance modes are generated for the antenna. The frequency reconfigurable antenna and two reference antennas are fabricated and measured. Experimental results showed a frequency shift of 43 % from 1.63 GHz to 2.34 GHz. Only a small effect by the tuning system on the impedance bandwidth of the proposed antenna compared to the reference antennas is observed. According to the measurement, the proposed tuning method also enabled the antenna to radiate with an acceptable level of efficiency.