This paper explains the basic characteristics of dielectric resonator antennas (DRAs), with emphasis on the effect of the form factor on their resonance (operating) frequencies. It is followed by discussions on their recent developments in higher order mode, circularly polarized, dual function, and transparent designs over the last few years. The idea of using glass DRAs as decoration antennas is proposed and demonstrated for the first time.

This letter presents a new dual-band circularly polarized (CP) dielectric resonator antenna (DRA). The dual-band design utilizes the quasi- TE ₁₁₁ and -TE ₁₁₃ modes of the rectangular DRA, which is coupled by a simple underneath rectangular aperture. Two opposite corners of the DRA are removed at 45 ^° to obtain CP fields. A diagonal groove is introduced at the top face of the DRA to facilitate tuning of the DRA. A design guideline of the dual-band CP DRA is given. The reflection coefficient, radiation pattern, axial ratio, and antenna gain of the DRA are simulated and measured, with good agreement between them.

The wideband circularly polarized (CP) dielectric resonator antenna (DRA) is investigated with an underlaid quadrature coupler. The idea is used to realize a CP hollow rectangular DRA. Since the coupler is located beneath the DRA, it does not increase the footprint of the antenna, making the system very compact. The underlaid coupler is placed entirely inside the hollow region of the DRA and, thus, it can be designed easily as if there is no overlaid DRA. Two configurations are considered in this paper. In the first configuration, an external 50-Ω load is used for the matching port of the coupler. For the second one, a strip loaded by the DRA is used to provide a load and, thus, no lumped elements are required in this configuration. In this paper, a network model is also given to aid engineers in designing the proposed integrated DRA. The reflection coefficient, axial ratio, antenna gain, and radiation pattern for each configuration are studied. It was found that wide impedance and axial-ratio bandwidths can be obtained with the proposed CP DRAs. Measurements were carried out to verify the simulations, and reasonable agreement between them was obtained.

The transparent dielectric resonator antenna (DRA) for optical applications is proposed for the first time. For demonstration, a dual function transparent hemispherical DRA made of Borosilicate Crown glass (Pyrex) is investigated. The dual function DRA simultaneously works as an antenna and a focusing lens for an underlaid solar cell. The system is very compact because no extra footprint is needed for the solar cell. A conformal strip is used to excite the hemispherical DRA in its fundamental broadside TE₁₁₁ mode. Due to the focusing effect of the DRA, higher voltage and current outputs of the solar cell can be obtained. In this paper, the transparent rectangular DRA was also studied, and it was found that the rectangular DRA does not provide the focusing function. It was also found that the proposed transparent DRAs can provide a higher gain ( ~ 4 dBi) than for the state-of-the-art transparent microstrip antennas ( ~ -5 dBi to 0 dBi). The reflection coefficients, input impedances, antenna gains, and radiation patterns of the two transparent DRAs are studied, and reasonable agreement between the simulated and measured results was observed. The proposed configurations can potentially be used for applications that need a self-sustaining power.

The dual-function glass dielectric resonator antenna (DRA) that simultaneously serves as a light cover is investigated for the first time. This paper is the first part, which demonstrates the idea using omnidirectional hollow rectangular glass DRAs. Both linearly polarized (LP) and circularly polarized (CP) designs are given. The glass DRA can generate CP fields by adding metallic patches onto its side walls, with a 3-dB axial ratio bandwidth of ~ 7%. To obtain an entirely light-transmissible CP glass DRA, conducting indium tin oxide (ITO) patches are used in place of the metallic patches. For each of the LP and CP designs, powered light emitting diodes (LEDs) are placed inside the hollow region of the glass DRA to serve as the light source. It is shown that practically the lighting and antenna parts do not interfere with each other. The reflection coefficient, axial ratio (CP designs only), radiation patterns, and antenna gains of the proposed LP and CP antennas are studied, and good agreement between measured and simulated results is observed.

For the first time, the dielectric resonator antenna (DRA) is simultaneously used as a filtering device, named as the DRA filter (DRAF). The theory and design methodology of the DRAF are elucidated using the cylindrical DR. It was found that the operating frequency of the filter part can be made equal to, or different from, that of the antenna part. The return loss, input impedance, radiation patterns, and insertion loss of the DRAF are studied. To improve the insertion loss of the filter part, the DR is top-loaded by a metallic disk without significantly affecting the radiation efficiency of the antenna part. The disk, in addition, can be used to tune the frequency of the filter. It was found that the antenna and filter parts of the DRAF can be designed and tuned almost independently. A second-order DRAF is also designed in this paper. As the dual function DRAF is compact and cost effective, it should find applications in modern wireless communication systems.