A Low-Profile Cylindrical Dielectric Resonator Antenna with Bandwidth-Enhancement under Triple-Mode Resonance

A low-profile cylindrical dielectric resonator antenna (CDRA) with enhanced impedance bandwidth is proposed via sharing a single triple-mode dielectric resonator. Initially, the resonant frequencies of TM01δ and TM02δ modes of a conventional CDRA are maintained far away from each other under central probe feed. Next, a circular disk with an annular ring is loaded around the conventional CDRA, aiming to excite an additional mode between these dual modes. The electric fields demonstrate that the previous TM02δ mode is transformed into the TM03δ mode for the modified CDRA, and an additional TM02δ mode is successfully excited between the TM01δ and TM03δ modes. As a result, the resonant frequencies of these three radiative modes are reallocated in proximity to each other, thus achieving the desired bandwidth enhancement. In addition, considering the small input impedance of the CDRA, a microstrip feeding line is introduced underneath the central probe for good impedance matching. With these arrangements, the resultant antenna can generate an extended bandwidth under simultaneous radiation of TM01δ, TM02δ, and TM03δ modes. Finally, the proposed CDRA is designed, fabricated, and measured to validate the predicted performance. The simulated and measured results show that the impedance bandwidth (|S11| < −10 dB of the antenna is dramatically extended from 8% to about 62% (2.83∼5.36 GHz), while keeping a stable conical radiation pattern. In particular, a low profile property of about 0.15 free space wavelength is achieved as well.