Dualfunction Dielectric Resonator as Antenna and Phase-Delay-Line Load : Designs of Compact Circularly Polarized/Differential Antennas

Dualfunction cylindrical dielectric resonator (DR) used as the load of a broadband phase delay line (PDL) and as a DR antenna (DRA) is presented for the first time. In the broadband PDL design, the cylindrical DR is used as the load to improve impedance match and phase shift. At the same time, the delay line is used to feed the same DR for the antenna part. By designing 90° and 180° PDLs, circularly polarized (CP) and differential DRAs can be obtained, respectively. As compared with those using a hybrid coupler, the new CP and differential DRAs can be made much more compact. Also, the external 50 Ω load required by the hybrid coupler can now be avoided. For demonstration, two CP and differential cylindrical DRAs for 2.4 GHz WLAN applications are designed, fabricated, and tested. Good agreement between the measured and simulated results is observed. The CP design has an overlapping axial ratio and impedance passband of 24.2%. For the differential design, a broadside radiation mode with very low cross-polarization level is obtained.