Analysis and design of wideband dielectric resonator antennas in frequency and time domains

Dielectric resonator antennas (DRAs) are a class of antennas that offer promising solutions to many advanced wireless communication systems due to their high radiation efficiency, compactness, light-weight and simple feed mechanisms. This thesis presents the design and characterization of novel yet simple configurations of DRAs for wideband and ultrawideband (UWB) applications. A multitude of DRAs made by stacking multiple dielectric segments are considered since they are simple to fabricate and offer wide impedance bandwidth. This thesis proposes a DRA with a full ground plane to achieve contiguous10-dB return-loss bandwidth of 115%, which fully encompasses the Federal Communications Commission (FCC) UWB band. This antenna is composed of two different dielectric segments and a full ground plane to produce realized mean gain of 4-5 dBi. Unlike printed planar UWB antennas with partial ground planes, the proposed DRA has a full ground plane to reduce unwanted radiation to the lower hemisphere. When used in UWB-IR system, the antenna has to receive or transmit pulsed signals. Therefore, investigating it only in the frequency domain is not enough to fully assess its performance; time-domain characterization of the antenna is essential to assess its pulse-preserving capabilities. Therefore, pulse-preserving capabilities and effective isotropically radiated power (EIRP) spectra of the tetrahedron DRA are rigorously investigated for several types of UWB input pulses. The correlations between the input pulses and the radiated pulses show that average correlation factors in elevation planes and azimuthal plane are 0.833 and 0.912, respectively. Nevertheless, EIRP spectrum calculations indicate that none of those pulses efficiently fill the FCC UWB mask when applied to this tetrahedron DRA. Hence, a third-order Rayleigh pulse is introduced and tuned in to efficiently make use of the allowed spectrum limits whilst radiating highly correlated pulses. It is worth noting that spectrum efficiency of the DRA improves from 40% to 52% as a result of the optimized input pulse. The thesis also presents the design, implementation and testing of low-profile multi-segment dielectric resonator antennas (MSDRAs) for wideband systems. The paramount contribution of this design is to reduce the height of MSDRA for high-data-rate wireless devices. Extensive exploitation of a multitude of different dielectric segments, with respect to effective permittivity and Q factor, has provided the physical insight of the MSDRA, and led to a compact antenna design with a wide impedance bandwidth. The bandwidth-to-volume ratio of MSDRA is increased up to 73% as compared to the state-of-the-art design of a tetrahedron DRA. The proposed design is tested with both a large ground plane (40×40mm2) and a small rectangular ground plane (6×20 mm2). The measured results of MSDRA with large ground plane show a 10-dB return-loss bandwidth of 83%from 4.5-10.5 GHz, and the MSDRA with the small rectangular ground planes how a a 10-dB return-loss bandwidth of 94% from 3.7-10.2 GHz. These antenna configurations are good candidates for both impulse radio and carrier-based UWB systems and they can be used in a myriad of portable wireless applications such as wireless USB and personal area networks.