Pattern-Diversity Cylindrical Dielectric Resonator Antenna Using Fundamental Modes of Different Mode Families

Abstract

For the first time, a pattern-diversity cylindrical dielectric resonator (DR) antenna (DRA) is designed using the fundamental HEM $_{11\delta }$ and TM $_{01\delta }$ modes of the HEM and TM mode families, respectively. It makes use of the fact that at the center of the DR, the $E$ -field of the HEM $_{11\delta }$ mode is weakest but that of the TM $_{01\delta }$ mode is strongest. Therefore, increasing the dielectric constant around the central DR region can lower the resonant frequency of the TM $_{01\delta }$ mode with no virtual effects on the HEM $_{11\delta }$ mode. Using this approach, the frequencies of the HEM $_{\mathrm {11\delta }}$ and TM $_{01\delta }$ modes can be made equal to obtain a pattern-diversity antenna. A cylindrical DRA centrally loaded by a dielectric with a higher dielectric constant is used to realize this idea. Its HEM $_{11\delta }$ and TM $_{01\delta }$ modes are excited by a rectangular cross slot and an axial coaxial probe, respectively. To demonstrate the idea, a two-port diversity antenna fabricated with two different transparent materials was designed for 2.4 GHz WLAN applications. It is found that the two ports of the pattern-diversity DRA have a measured overlapping impedance bandwidth of 23.4%, with an envelope correlation coefficient of lower than 0.007 and a mean-effective-gain ratio lower than 0.1 dB.