A three-dimensional (3-D)-printed wideband multi-ring dielectric resonator antenna (DRA) is investigated for the first time. It consists of four concentric dielectric rings with decreasing effective dielectric constants in the radial direction. To facilitate the 3-D-printed design, a basic unit cubic cell that can be easily adjusted to provide different effective dielectric constants is used. An axial coaxial probe is used to excite the DRA in three transverse magnetic (TM) modes (TM01δ, TM02δ, and TM03δ), which are merged to provide a wide impedance bandwidth. For demonstration, a prototype operating in C -band is designed and fabricated using a 3-D printer. Its reflection coefficient, radiation pattern, antenna gain, and antenna efficiency are measured, and reasonable agreement between the measured and simulated results is observed. The prototype has a wide measured 10-dB impedance bandwidth of 60.2% (4.3–8.0 GHz) with a low profile of 0.18 λ 0, where λ 0 is the wavelength in air at the center frequency (6.15 GHz). The prototype has an average measured antenna efficiency of 89%, with the peak efficiency given by 95%.

3-D-Printed Wideband Multi-Ring Dielectric Resonator Antenna

A dielectric resonator antenna (DRA) with ${{{\varepsilon }}_{\text{r}}} = 35.9$ and excited by a printed microstrip line is considered. Such an element achieves 4% matching bandwidth with unidirectional radiation patterns. However, when a rectangular slot is fabricated on the ground plane under the DRA, a 60% bandwidth is achieved with bidirectional radiation patterns. The mutual coupling between two elements is found to be of low level for the entire bandwidth. To improve the front-to-back ratio of the antenna, a reflector made of conducting strips parallel to the antenna polarization is placed behind the slot window. Linear (H- and E-planes) and planar arrays are fabricated and tested achieving good agreement between simulated and measured results providing high confidence on the simulation.

Wideband DRA Array Placed on Array of Slot Windows

This paper presents a novel compact Koch snowflake fractal ring based Dielectric Resonator Antenna (DRA) for ultra wideband application. Firstly, Koch snowflake fractal geometry is implemented on the conventional Cylindrical Dielectric Resonator Antenna (CDRA). Further, the performance of the DRA is enhanced by fractal ring created on the snowflake geometry. With the application of the fractal and the fractal ring geometry, the Q-factor of DRA is reduced, thus the bandwidth of DRA is increased. The proposed antenna offers a wide impedance bandwidth of 90% ranging from 4.7 GHz–12.4 GHz. The effect of the fractal geometry enhances the gain of DRA. The proposed antenna achieves radiation efficiency more than 78%, throughout the bandwidth. Interestingly, the proposed configuration reduces the DRA volume by 76.63% with reduced volume of 7.91 cm3. The experimental verification of the proposed structure shows good agreement between simulated and measured results.

https://www.jpier.org/pierc/pierc67/08.16062007.pdf

A Novel Compact Fractal Ring Based Cylindrical Dielectric Resonator Antenna for Ultra Wideband Application

A wideband cylindrical dielectric resonator antenna (CDRA)-loaded with an annular column, namely the LCDRA, is proposed and analyzed. The antenna comprises two components—an inner cylindrical dielectric and a loaded concentric column dielectric. The proposed antenna is centrally fed by a coaxial probe, and has a low profile of $0.175\;{\lambda _0}$ ( ${\lambda _0}$ is the wavelength of the center frequency). Four conical radiation pattern modes ( ${\text{TM}_{01\delta }},{\text{TM}_{02\delta }},{\text{TM}_{03\delta }},\;\text{and}\;{\text{TM}_{04\delta }}$ modes) are excited and merged, providing an impedance bandwidth of 56% (3.14–5.56 GHz). A prototype of the proposed antenna is built and tested. Good agreement between the simulated and measured results, including the reflection coefficient and radiation patterns, is achieved.

Annular Column Loaded Cylindrical Dielectric Resonator Antenna for Wideband Conical Radiation

This paper postulates a novel omnidirectional low-profile ultra-wideband (UWB) antenna, which is structured by discrete embedded dielectric resonator antenna with features of both low-profile dielectric resonator (DR) and thin planar monopole antenna, where the laminated equilateral triangular DR and the rectangular metal patch monopole are stacked up. This new design can lower the profile of the antenna. Furthermore, the symmetric DR and the monopole structure are able to make the surface currents in some operating modes opposite in phase, together with the characteristics of the coplanar waveguide (CPW) feed structure and the DR, the cross-polarization is reduced effectively. The mode analysis has been done to show how the antenna achieves the UWB. The CPW which can integrate with integrated circuits easily is used to provide the excitation source. The antenna provides consistent omnidirectivity, consistent gain, low cross-polarization, and high-radiation efficiency within the entire operation band. A prototype (dimensions are 17.6 mm $\times33.6$ mm and 1.524 mm thickness) is fabricated and measured. The measurements are well correlated with the simulations.

/pdf/equilateral-triangular-dielectric-resonator-and-metal-patch-2t4b0b4bey.pdf

Equilateral Triangular Dielectric Resonator and Metal Patch Hybrid Antenna for UWB Application

Stacked conical ring dielectric resonator antennas (DRA) excited by an axi-symmetric coaxial monopole are investigated numerically and experimentally for improved bandwidth. The bandwidth improvement is due to an extra resonance which occurs near the frequency where the monopole height is about a full wavelength. We consider two cases of the hybrid antenna: one case in which the tips of both cones face up and a second case in which the top cone is inverted to form a “sand-glass” shaped DRA. Measured data were obtained to validate the results of simulations. The proposed hybrid antennas can easily offer a fractional impedance bandwidth up to 138% along with monopole type radiation pattern. The antennas have a relatively low peak gain around the extra resonance.

F. Ustuner

Papers

Stacked Conical Ring Dielectric Resonator Antenna Excited by a Monopole for Improved Ultrawide Bandwidth