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

For the first time, a pattern-diversity cylindrical dielectric resonator (DR) antenna (DRA) is designed using the fundamental HEM11δand TM01δmodes 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 HEM11δmode is weakest but that of the TM01δmode is strongest. Therefore, increasing the dielectric constant around the central DR region can lower the resonant frequency of the TM01δmode with no virtual effects on the HEM11δmode. Using this approach, the frequencies of the HEM11δand TM01δmodes 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 HEM11δand TM01δmodes 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.