Characteristics of dielectric ring resonator antenna with an air gap

The characteristics of centre probe-fed cylindrical dielectric ring resonator antennas with an air gap are studied both theoretically and experimentally. The return loss of the TM_01δ mode is evaluated by using the finite-difference time-domain (FDTD) method and the result agrees well with the measured data. It is demonstrated that the impedance bandwidth can be improved by adjusting the air-gap spacing