Tall microstrip transmission lines for dielectric resonator antenna applications

Dielectric resonator antennas (DRAs) excited by tall microstrip transmission lines (TMLs) are investigated. Two different TML–DRA structures are proposed and the impact of TML parameters on the antenna performance is studied when low-loss and lossy substrates are used. To validate the effectiveness of this approach, a set of prototype antennas was fabricated, measured and compared with simulation results. A good agreement is obtained. It is found that by adjusting TML parameters, excellent impedance matching and coupling to low-permittivity DRAs are achieved even on high-permittivity substrates. The impedance bandwidth of a single-mode simple-shape rectangular DRA with ɛrd = 9 can be as high as 25%. The radiation efficiency of the antenna on extremely lossy substrates is significantly improved and based on the measured results over 80% efficiency with a gain ranging from 4.2 to 5.5 dBi along the impedance bandwidth can be expected. Since TML is a low-loss transmission line, the DRA is a low-loss radiator and low-permittivity DRAs can be well matched by TML, the TML–DRA forms an excellent wideband antenna system with high radiation efficiency.