A new broadband circularly polarized dielectric resonator antenna

Open dielectric resonators (DRs) have been increasingly studied as antenna elements in recent years. They offer advantages such as small size, mechanical simplicity, no conduction loss, easy coupling to most transmission lines, ability to obtain different radiation characteristics using different modes of the DR, etc. Further, desired impedance bandwidth (in the range of about 1%-20%) can be obtained by the suitable choice of DR shape and permittivity. Of various possible shapes, a rectangular shaped DR antenna (DRA) provides advantages over other shapes, such as cylindrical and spherical. It is known that three TE/sub 111/ modes (TE/sub 111//sup x/,TE/sub 111//sup y/ and TE/sub 111//sup z/) of a rectangular shaped DRA radiate like x, y and z directed magnetic dipoles respectively. Given the advantages of DRAs, a circularly polarized (CP) element may provide useful benefits over other existing designs. In this paper, we report the development of a new rectangular CP DRA with a single slot or probe feed. The circular polarization is obtained by the excitation of two nearly degenerate orthogonal magnetic dipole modes. Measured results show that the antenna has a low axial ratio (AR) over a wide frequency band and has a wide beamwidth. The antenna element is easy to design and construct, and the dimensional tolerances are not stringent. The slot fed antenna is also compatible with MIC's and MMIC's and should be therefore useful in high frequency applications. Theoretical development, design and experimental results on DRAs of various permittivities (/spl epsiv//sub r/=10.8, 20 and 40) with both slot and probe feed are presented.