K.W. Leung

Designs of Single-, Dual-, Wide-Band Rectangular Dielectric Resonator Antennas

Designs of the single-, dual-, wide-band rectangular dielectric resonator antennas (DRAs) are discussed. Using new single-band formulas, the resonance frequency of the DRA can be determined easily from the given DRA dimensions and vice versa. Also, new formulas for designs of dual-mode rectangular DRAs are derived in this paper. From the derivation, the limit of the frequency ratio is also found and discussed. The formulas can be used to design a dualband DRA or a wideband DRA when the two resonance frequencies are close to each other. To validate our results, three single-, dual-, and wide-band rectangular DRAs were designed using the new formulas. In each case, the reflection coefficient, radiation pattern, and antenna gain were simulated and measured. Good agreement between the calculated, simulated, and measured results is obtained.

Bandwidth enhancement and frequency tuning of the dielectric resonator antenna using a parasitic slot in the ground plane

The slot-fed hemispherical dielectric resonator antenna (DRA) with a parasitic rectangular slot in the ground plane is studied in this paper. It is found that the length and position of the parasitic slot can be used to widen the DRA bandwidth or to tune the DRA frequency. The exact DRA Greens function is used in the formulation, and the unknown slot currents are solved using the method of moments. Measurements were carried out to verify the calculations, and good agreement between theory and experiment is obtained.

Rectangular waveguide excitation of dielectric resonator antenna

In this communication, the waveguide-fed dielectric resonator antenna (DRA) is proposed and investigated. The waveguide is terminated by a baffle ground plane in which a coupling slot is cut, and the DRA resides above the coupling slot. To enhance the coupling, a second DR is placed on the other side of the slot inside the waveguide. The measured return loss, radiation patterns, and antenna gain of this novel configuration are discussed in this paper.

Bandwidth and gain enhancement of a dielectric resonator antenna with the use of a stacking element

The stacked structure of an aperture-coupled cylindrical dielectric resonator (DR) antenna is studied experimentally. The effects of the offset and the air gap between the driven and parasitic DR elements are investigated. It is found that the bandwidth of the stacked structure can increase from the single-element value of 9% to 37%. The voltage standing-wave ratio, the radiation patterns, and the antenna gain are also reported.

A small dielectric resonator antenna

By covering a cylindrical dielectric resonator antenna with a metallic cap, the resonant frequency of the antenna can be reduced by 30.6%. The result finds applications in designing small antennas for wireless communication systems.

The Compact Circularly-Polarized Hollow Rectangular Dielectric Resonator Antenna With an Underlaid Quadrature Coupler

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.

Compact Differential Rectangular Dielectric Resonator Antenna

In this letter, a compact differential hollow dielectric resonator antenna (DRA) is investigated. The hollow DRA is fed by two identical conducting strips connected to the outputs of an underlaid 180° hybrid coupler (rat-race). With this compact configuration, loss of the feed network can be minimized and, thus, the differential gain can be made about the same as for the single-ended case. By using the differential feed, the DRA can be integrated with differential integrated circuits directly. Also, its cross-polarized fields are generally weaker than those of the single-ended version. The reflection coefficient, radiation pattern, and antenna gain of the proposed differential DRA are simulated, and the result agrees reasonably with our measurement.

Theory and experiment of the hemispherical cavity-backed slot antenna

The hemispherical cavity-backed slot antenna is studied theoretically and experimentally. The exact magnetic field Greens function of the cavity is derived rigorously and expressed in a form convenient for numerical computation. The moment method is used to find the equivalent magnetic current in the slot and, hence, the input impedance of the antenna configuration. The effects of the cavity size, of the slot length, and of the slot offset on the input impedance are studied and very good agreement between theory and experiment is obtained. The variation of the magnetic current around the slot and cavity resonances are discussed. Comparisons between the rigorous solution and the single-mode theory are given and the limitation of the single-mode theory is discussed.

A circularly polarized dielectric resonator antenna excited by an asymmetrical U-slot with a backing cavity

A cavity-backed circularly polarized dielectric resonator antenna (DRA) excited by an asymmetrical U-slot is investigated theoretically and experimentally. The finite-difference time-domain method using nonuniform orthogonal grids is employed to study the new configuration, with the excitation modeled by an independent resistive voltage source. The return loss, input impedance, axial ratio, and radiation pattern of the antenna are studied. Reasonable agreement between theory and experiment is obtained.

Frequency-tunable designs of the linearly and circularly polarized dielectric resonator antennas using a parasitic slot

A method for tuning the operation frequency of a dielectric resonator antenna (DRA) in the design stage is proposed. The method employs a parasitic annular slot, which can be applied to both the linearly-polarized (LP) and circularly-polarized (CP) DRAs. To demonstrate the former, an annular-slot-excited hemispherical DRA is used. By changing the radius of the parasitic slot, the operating frequency of the antenna can be adjusted while maintaining good impedance match and stable radiation patterns. For the CP case, a CP DRA excited by a shorted annular slot is used for the demonstration of this idea. It is found that good impedance matches and axial ratios can be obtained across the tunable frequency range. The radiation patterns are, again, stable across the frequency range. The problems are formulated using the Greens function approach, with the unknown slot currents solved using the method of moments. Measurements were carried out to verify the theory, and reasonable agreement between them is obtained.