MULTI-BAND CYLINDRICAL DIELECTRIC RESONATOR ANTENNA USING PERMITTIVITY VARIATION IN AZIMUTH DIRECTION

A new excitation method using a solder-through probe is used to excite the cylindrical ring dielectric resonator antenna (DRA). The return loss, radiation pattern and antenna gain are studied experimentally. A simple formula for estimation of the TM/sub 01/spl delta// mode resonant frequency of the DRA is presented.

The eigenmode expansion method is used to evaluate the resonant frequency of a probe fed cylindrical dielectric resonator (DR) antenna, which radiates above an infinite conducting ground plane. A parallel grounded conducting plane is added above the DR, thus allowing the use of cylindrical harmonic field expansions in the regions between the two parallel ground planes. The eigenmode expansion coefficients are found by enforcing the boundary conditions at conducting surfaces and regional interfaces. Then, from the induced currents on the probe surface, the input impedance and the resonant frequency of the DR antenna are evaluated. The results are compared with those of a previous configuration which has no upper ground plane. It is found that the deviation of the calculated resonant frequency is less than 2% for epsilon εr>9.

A cylindrical dielectric resonator antenna with nested structure is designed. The antenna is nested by cylindrical dielectric resonators and ring dielectric resonators with different dielectric constants and fed by microstrip lines and cross slots. Simulation results show that when S11<-10dB, the antenna center frequency is about 25.56GHz, fractional bandwidth reaches 21.9% (23.75GHz-29.35GHz), gain reaches 6.43dBi, and circular polarization radiation exists in the passband. The bandwidth of the axial ratio less than 3dB is 7.57%(25.68GHz-27.71GHz).

Cylindrical and conical ultra-wideband (UWB) dielectric resonator antennas are presented in this paper. The first part of this work is a parametric study of cylindrical and conical dielectric resonator antennas for Ultra-Large Band applications ranging from 3.1GHz to 10.6GHz. The second part of the work consists of creating a reconfigurable rejection band inside this UWB in order to minimize interference between UWB system and some narrowband systems operating in this frequency range (3.1GHz to 10.6GHz), Such as WiMAX and WLAN. To obtain the rejection band, we etch a rectangular ring slot on the micro-strip-line-fed patch. The control of the band notch is made by displacing the cylindrical or the conical resonator. The results obtained showed that the band notch ranges from 3.2GHz to 4.7GHz for the cylindrical resonator and from 3.2GHz to 5.2GHz for the conical resonator. The proposed structures are simulated with the commercial electromagnetic simulation software “Ansoft HFSS.” The numerical results from different simulations are presented in terms of reflection coefficient and radiation pattern.

Dielectric resonators (DR) find application in the design of microwave antennas. The radiation patterns of DR antennas are related to their excited resonant model(s). Dielectric resonators of low dielectric constant are usually employed to give a reasonable impedance bandwidth. We demonstrate that the bandwidth of a center probe-fed cylindrical dielectric ring resonator antenna can be increased by stacking another DR of the same dimensions on the top of the fed DR. The return loss and the radiation patterns of the stacked DR antenna are computed using the finite difference time-domain (FD-TD) method. The numerical results so obtained are compared to experimental measurements. >

A low-profile cylindrical dielectric resonator antenna (CDRA) with enhanced impedance bandwidth is proposed via sharing a single triple-mode dielectric resonator. Initially, the resonant frequencies of TM 01δ and TM 02δ modes of a conventional CDRA are maintained far away from each other under central probe feed. Next, a circular disk with an annular ring is loaded around the conventional CDRA, aiming to excite an additional mode between these dual modes. The electric fields demonstrate that the previous TM 02δ mode is transformed into the TM 03δ mode for the modified CDRA, and an additional TM 02δ mode is successfully excited between the TM 01δ and TM 03δ modes. As a result, the resonant frequencies of these three radiative modes are reallocated in proximity to each other, thus achieving the desired bandwidth enhancement. In addition, considering the small input impedance of the CDRA, a microstrip feeding line is introduced underneath the central probe for good impedance matching. With these arrangements, the resultant antenna can generate an extended bandwidth under simultaneous radiation of TM 01δ , TM 02δ , and TM 03δ modes. Finally, the proposed CDRA is designed, fabricated, and measured to validate the predicted performance. The simulated and measured results show that the impedance bandwidth (|S 11 | < −10 dB of the antenna is dramatically extended from 8% to about 62% (2.83∼5.36 GHz), while keeping a stable conical radiation pattern. In particular, a low profile property of about 0.15 free space wavelength is achieved as well.

This paper presents a multiple input multiple output (MIMO) system for sub-6 GHz using a two-port cylindrical dielectric resonator (CDR). This band is ideal for 5G applications, providing a balanced combination of coverage and capacity, as well as offering high data rates and low latency. The proposed MIMO is excited by an aperture-coupled feed structure composed of driven elements consisting of an elliptical-shaped step impedance transform line to enhance CDR coupling. Aperture coupling is used to excite the HEM 11δ mode without the involvement of any hybrid mode. The purpose of the aperture coupling in the CDR antenna is to launch the HEM 11δ mode, which is a magnetic dipole that provides a stable radiation pattern in the 3.2–3.7 GHz band, allowing for efficient transmission and reception of the data. Symmetrically oriented CDR and the presence of orthogonal fields provide good isolation, which can be further improved by the insertion of an asymmetric cross slot. The designed CDR-based MIMO antenna achieves excellent isolation of over 20 dB and demonstrates improved envelope correlation coefficient (ECC) values, resulting from low field correlation, across the entire frequency band of operation. Almost all the major diversity analysis was carried out for the desired sub-6 GHz band while maintaining a relatively compact size. Based on the measured results, it is confirmed that the proposed CDR-based MIMO antenna is appropriate for sub-6 GHz applications.

Dielectric resonator antennas have been demonstrated to be an efficient radiator, especially with the possibility of fabricating it at low cost based on 3-D printing technologies. However, they have two main limitations which are: their relatively small gain (about 5dBi) and narrow bandwidth. To enhance the gain of DRA, higher-order mode excitation can be utilized; however, typically this has a limit of a few dB increments besides its negative effects on the bandwidth. This study employs a cavity-backed slot to provide an appropriate feeding method for a cylindrical dielectric resonator antenna (CDRA). This design effectively facilitates the excitation of higher-order modes, resulting in a significant gain of up to 15 dBi, which is essential for many wireless systems that are unable to support larger aperture sizes through the standard use of arrays. Additionally, two modes are excited to keep a relatively broadband of about 15 %. The proposed design consists of a cylindrical dielectric placed on top of a cavity-backed slot that is excited by a coaxial probe soldered to the top patch of the cavity. With this feeding, a good matching is achieved for different dielectric resonator heights, hence, the gain can be adjusted easily without the need of reoptimizing the antenna or the feed structures. The design process is explained in addition to performing a sensitivity analysis of fabrication tolerances which confirms that the 3-D printer provides enough accuracy with a negligible effect on the antenna’s performance. Then a prototype with a medium length is fabricated and measured to provide high realized gain and impedance bandwidth of 11 dBi and 14.5 %, respectively. The measured data demonstrate the good performance of the antenna with great matching compared to the simulated ones. Furthermore, the antenna presents a good performance in terms of sidelobes and polarization. This proposed design outperforms other DRA designs based on higher-order modes.

The results of a numerical study pertaining to the effect of an air gap on the input impedance and resonance frequency of a cylindrical dielectric resonator (CDR) antenna operating in the TM01 mode as a function of dielectric constant are presented. The CDR resides on a conducting ground plane and is excited by a coaxial probe through the bottom of the ground plane. Some of the numerical results are validated experimentally.

Dielectric resonators (DRs) are important elements of microwave integrated circuits, and are also used as millimeter wave DR antennas. Dielectric resonators are useful due to their small size, mechanical simplicity, relatively large bandwidth, simple coupling schemes to nearly all commonly used transmission lines, and their absence of conduction loss. When the DR is applied in a microwave circuit it is important to determine its resonant frequency, quality factor (Q-factor), and coupling factor. Cylindrical DRs may be analyzed by body of revolution methods, but there are few rigorous methods to study rectangular ones other that finite elements or finite difference techniques. We present a volumetric electric field integral equation formulation in conjunction with an entire domain Galerkin's method of moments solution to study the resonant frequencies and Q-factors of both cylindrical and rectangular DRs in general multilayered media. A three dimensional Fourier series basis function set is used, which contain as a subset the perfect magnetic conductor wall cavity modes.

A new omnidirectional circularly polarized (CP) cylindrical dielectric resonator (DR) antenna (DRA) is excited by four open-ended logarithmic spiral slots in the ground plane. Radiated E θ and E φ components are obtained from the TM 01δ mode of the DR and the slotted ground plane, respectively. Omnidirectional CP fields can be obtained when E θ and E φ are equal in magnitude but different in phase by 90°. This CP technique does not require any special shape or treatment of DR, greatly facilitating the design. To demonstrate the idea, a prototype using a glass DR was fabricated. It is a dual-function DRA that also serves as the cover of light sources. The prototype has a measured bandwidth of ~6.2%, covering the entire 2.4-GHz WLAN band.

A dielectric sample resonator design for enhanced sensitivity of EPR spectroscopy

A frequency-tunable broadband dielectric resonator antenna (DRA) with metasurface is proposed. The proposed antenna is comprised of a substrate with ground plane, a cylindrical dielectric resonator with two slots, a metasurface, a patch and a coaxial probe. The metasurface upon the substrate which consists of an array of "-" shaped units, the slots and the patch upon the cylindrical dielectric resonator (DR) have increased the working bandwidth of the antenna. The proposed DRA has realized the operating frequency band of 53.7% (3.5 GHz - 6.07 GHz). And according to the actual needs, the resonant frequency of the antenna can be adjusted by changing the length and height of the two slots. The tunable resonant frequency range is 4.7 GHz - 5.0 GHz. It has a good application in the communication systems which need more than one antenna.

Sequential rotation has the advantage of getting wider circular polarization (CP) bandwidth while each element is of CP design. The proposed structure consists of two cylindrical dielectric resonator (DR) antennas place on a cross-slot in the ground plane of a microstrip line. The measured return loss patterns are presented. For the proposed design, a large CP bandwidth, determined from the 3-dB axial ratio, as high as 5.15%, is obtained. Details of the proposed antenna designs are described, and experimental results of the CP performance are presented and discussed.

In this paper, a compact multi-band cylindrical dielectric resonator antenna (DRA) loaded with CSRR is presented. The DRA is composed of a semi-cylindrical dielectric resonator with metal ground sheet on the cut plane loaded with metamaterial structure. It is fed by aperture coupled microstrip line. The antenna size is about 50% decreased compared with the full cylindrical DRA. The SCRR is used to broaden bandwidth of the antenna. Simulation result shows that the antenna bandwidth can cover the 3G, 4G and WLAN usage. The antenna gain is above 5dB in its working band.