Hollow Dielectric Resonator Research Articles

Dielectric resonator used as radome and antenna: A new concept for large frequency ratio shared aperture antenna design

AbstractThis paper presents a novel transmissive type L/Ku dual‐band dual‐polarization (DBDP) shared aperture antenna (SAA) with a large frequency ratio. The L‐band antenna employs a balanced‐fed hollow dielectric resonator antenna (DRA), which has broadband and low cross‐polarization; also, it can be used as a radome to protect the Ku‐band array. The Ku‐band uses a 4 × 4 dual‐polarized microstrip antenna array placed inside the hollow DRA and radiates through it. In order to verify the design, a prototype antenna was manufactured and measured. The measured result shows that the SAA covering the frequency bands of 0.95–1.42 GHz and 13.16–13.84 GHz with the reflection coefficient below −10 dB, the isolation between polarizations is better than 40 dB for L‐band and 25 dB for Ku‐band, the measured gain is 4.8 dBi for L‐band and 16.7 dBi for Ku‐band, and the cross‐polarization level for L‐ and Ku‐band is lower than −28 and −20 dB, respectively.

A differential‐fed dual‐polarized antenna with gain enhancement using hollow dielectric patch resonator

A differential-fed dual-polarized dielectric patch (DP) antenna with high gain, wide bandwidth, and high isolation is investigated in this article. Based on the analysis of the anisotropic property of the DP antenna, further exploration of gain enhancement is carried out. The introduction of the square air hole in the substrate to obtain a hollow DP resonator is a crucial technique. It not only increases the electromagnetic radiation from the sidewalls of the DP resonator to further improve the gain to 8.9 dBi, but also shifts the dominant TM101 mode upward to get close to the higher-order TM121 mode to achieve bandwidth expansion of 19.4%. By using the differential-fed scheme to excite the TM101 mode, TM121 mode and their degenerate modes, dual-polarization operation and high isolation level can be obtained simultaneously.

Low-Dispersion Leapfrog WCS-FDTD With Artificial Anisotropy Parameters and Simulation of Hollow Dielectric Resonator Antenna Array

An optimized three-dimensional one-step leapfrog finite-difference time-domain (FDTD) method has been investigated, which is with a weakly conditional stability (WCS) to reduce numerical dispersion further. By introducing the artificial anisotropy parameters in a cross-correspondence manner, the phase velocity error is effectively limited without additional computational time and memory cost. An auxiliary field variable is adopted to simplify the iterative formulae with few additional processes, and the same stability has been validated between methods of conventional leapfrog WCS-FDTD and ourselves. Moreover, much lower numerical dispersion is shown to withstand larger Courant-Friedrich-Levy number under the same error condition. To verify our method efficiently, a newly designed hollow dielectric resonator antenna (DRA), instead of a solid one, is conducted effective calculation. Furthermore, two forms of four-element arrays have been developed with the DRA element above, and a T-shaped power divider is designed as a fed network and subjected to calculations and experimental analyses. Reflection coefficients and radiation patterns are shown the effectiveness of both DRA and arrays. The most noteworthy aspect is that our low-dispersion WCS-FDTD scheme can be effectively simulated the hollow DRA and arrays, and with excellent performance in terms of memory occupation, calculation accuracy, and efficiency.

A Broadband Differential-Fed Dual-Polarized Hollow Cylindrical Dielectric Resonator Antenna for 5G Communications.

A broadband differential-fed dual-polarized hollow cylindrical dielectric resonator antenna (DRA) is proposed in this article. It makes use of the HEM111, HEM113, and HEM115 modes of the cylindrical hollow DRA. The proposed DRA is simply fed by two pairs of conducting strips and each pair of strips is provided with the out-of-phase signals. After introducing four disconnected air holes into the DRA, a broadband characteristic is achieved, with little effect on the antenna gain of its higher-order modes. To verify this idea, frosted K9-glass is applied to fabricate the hollow cylindrical DRA. The differential S-parameters, radiation patterns, and antenna gain of the DRA are studied. It is found that the proposed differential-fed dual-polarized DRA is able to provide a broad differential impedance bandwidth of ~68% and a high differential-port isolation better than ~46 dB. Moreover, symmetrical broadside radiation patterns are observed across the whole operating band. The proposed DRA covers the frequency bands including the 5G-n77 (3.4–4.2 GHz), 5G-n79 (4.4–5.0 GHz), WLAN-5.2 GHz (5.15–5.35 GHz), and WLAN-5.8 GHz (5.725–5.825 GHz), which can be used for 5G communications.

Design of the Single-/Dual-Port Wideband Differential Dielectric Resonator Antenna Using Higher Order Mode

In this letter, a wideband differential hollow rectangular dielectric resonator antenna (DRA) designed using higher order mode is investigated. The fundamental TE111 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sup> and higher order TE113 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sup> modes of the rectangular DRA were employed for the design. To merge these two DRA modes together, the hollow DRA with its air region displaced from the center is employed. Both the single- and dual-port wideband differential DRAs are considered. For the dual-port version, a wide differential impedance bandwidth of ~46% was achieved. For the single-port version, a 180° hybrid coupler was designed to feed the differential DRA compactly. The measured result shows that its impedance bandwidth can be achieved as ~44%. In addition, the proposed differential DRA provides a stable broadside radiation pattern with lower cross-polarized field.

Cylindrical air spaced high gain dielectric resonator antenna for ultra-wideband applications

A new geometry of ultra-wideband (UWB) hollow dielectric resonator antenna (DRA) has been designed, simulated, and fabricated. The antenna consists of a rectangular dielectric resonator and excited by a transformer type microstrip feedline. A hollow cylindrical-shaped structure is extracted from a rectangular DR to improve the gain and impedance bandwidth of the antenna. The present work shows that the shifting within the UWB range along with the gain enhancement is observed by increased diameter of the hollow structure and the use of defective ground structure in the ground plane. The antenna provides four different radiating modes, namely TE11δ at 3.8 GHz, TE22δ at 6.4 GHz, TE 23 Z at 8.8 GHz, and TE33δ at 10 GHz that support to give widen impedance bandwidth. The simulated and measured results are in good agreement as an impedance bandwidth of 104.09% (3.28 to 10.4 GHz) and 103.86% along with a peak gain of 7.2 dB.

Active Integrated Dielectric Resonator Antenna-in-Package Design

This letter proposes a packaged active integrated dielectric resonator antenna-in-package (AIDRAiP), which consists of a hollow rectangular dielectric resonator antenna (RDRA), and internally packaged power amplifier and bandpass filter chips. First, a modified annular slot feeding structure is proposed to design an RDRA with a wide −10 dB bandwidth of 20.6%. Then, by integrating an amplifier and a filter chip into a hollow RDRA, a well-packaged AIDRAiP is developed with the circuits and antenna on the same side of a substrate. The size of the AIDRAiP is the same as that of the hollow RDRA. A −10 dB band of 2.38–2.52 GHz (determined by the bandpass filter) and a gain of about 15.0 dBi are achieved for the AIDRAiP prototype, with a reasonable agreement obtained between the measured and cosimulated results.

A Dielectric Resonator Antenna-in-Package Design and its Electromagnetic Interference Investigation on Amplifier

A highly shielded and easy-integration antenna-in-package (AiP) configuration based on the rectangular hollow dielectric resonator antenna (DRA) is presented. The surfaces of the hollow are made conductive to form a metal cavity, isolating the DRA from the RF circuits. Both passive and active antennas for 2.4-GHz WLAN applications are designed, measured, and compared. The two antennas are excited in the TE $^{x}_{\delta 11}$ mode and perform similarly. To know the effect of the perfect-electric-conductor (PEC) boundary, the DRA without any metal cavities is also studied for comparison. Two sets of experiments are designed to investigate the electromagnetic interference between the AiP and a low-noise amplifier (LNA) inside the hollow. The influences of the DRA on the packaged LNA are measured and analyzed for both the no-PEC-boundary and PEC-boundary cases. It is found that the output of the LNA will be significantly affected by the DRA input power when the latter is sufficiently high.

Dual-Fed Hollow Dielectric Antenna for Dual-Frequency Operation With Large Frequency Ratio

A new dual-fed dual-frequency antenna that integrates a microwave hollow dielectric resonator antenna (DRA) with a high-gain millimeter-wave dielectric Fabry–Perot resonator antenna (FPRA) is investigated. To obtain the dual-frequency operation, the dielectric and air regions of the hollow DRA are designed to satisfy the resonance condition of the FPRA. The DRA and FPRA are excited by a strip and a WR-34 waveguide, respectively. For demonstration, a prototype that covers both 2.4- and 24-GHz ISM bands was fabricated and tested. The S-parameters, radiation pattern, antenna gain, and antenna efficiency are studied, and reasonable agreement between the measured and simulated results is found.

A Helix Excited Circularly Polarized Hollow Cylindrical Dielectric Resonator Antenna

In this letter, we use a helix to excite two orthogonal HE11δ modes in phase quadrature in a hollow cylindrical dielectric resonator antenna to generate circular polarization. As compared to our previous work, it is shown that replacing the cylindrical dielectric resonator antenna with a hollow cylindrical-shaped one leads to a significant enhancement in the 3-dB axial-ratio bandwidth. A design guideline is provided, and three design cases are presented. A prototype for one of the designs is fabricated and measured. Measured and simulated data are presented and discussed. It is shown that the 3-dB axial-ratio bandwidth increases as the wall thickness of the hollow cylindrical dielectric resonator decreases. Furthermore, a reduction in the wall thickness requires a longer helix exciter for similar performance .

Theory and Experiment of the Hollow Rectangular Dielectric Resonator Antenna

For the first time, the dielectric waveguide model (DWM) is used to calculate the resonance frequency of the hollow rectangular dielectric resonator antenna (DRA). In the analysis, the transverse transmission line technique is used along with the effective dielectric constant method to obtain characteristic equations of the hollow DRA. Good agreement between the calculation, measurement, and HFSS simulation is observed. The theory was used to facilitate the design of a strip-fed circularly polarized (CP) hollow DRA. It provides a wide 3-dB axial-ratio bandwidth of 12.4%, which is ~ 3 times of that of the solid CP DRA.

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.

Discovery of Bragg confined hybrid modes with high Q factor in a hollow dielectric resonator

The authors report on observation of Bragg confined mode in a hollow cylindrical dielectric cavity. A resonance was observed at 13.4GHz with an unloaded Q factor of order 2×105, which is more than a factor of 6 above the dielectric loss limit. Previously, such modes have only been realized from pure transverse electric modes with no azimuthal variations and only the Eϕ component. From rigorous numeric simulations, it is shown that the mode is a hybrid mode with nonzero azimuthal variations and with dominant Er and Eϕ electric field components and Hz magnetic field component.

Novel Application of the Hollow Dielectric Resonator Antenna as a Packaging Cover

The dual functions of the rectangular hollow dielectric resonator antenna (DRA) as an antenna and a packaging cover are investigated. The design methodology is discussed, and the return loss, impedance, and radiation patterns for the fundamental mode are presented at 2.4 GHz, a popular frequency band for the WLAN and wireless communications. A low-noise amplifier is integrated successfully into the embedded cavity to form an active DRA, and the amplified radiation patterns are analyzed. The proposed DRA provides a possible solution to the size minimization of transceivers.

Microwave spectroscopy of novel superconductors

A hollow dielectric resonator technique has been developed for accurate measurements of the complex microwave surface impedance of novel superconductors from 2 to 20 GHz down to 100 mK. Illustrative measurements of the antiferromagnetic ordering and spin-dynamics of Gd ions in GdBa 2Cu 3O 7 and of microwave penetration and losses in MgB 2 wires and high quality single crystals of Sr 2RuO 4 are presented. Measurements on Sr 2RuO 4 imply an unchanged electron relaxation time τ on entering the superconducting state, a power law temperature dependence of the normal state fraction implying nodes in the superconducting order parameter, and residual low temperature losses on increasing frequency.

The Low Temperature Microwave Properties of GdBa2Cu3O7−δ and Sr2RuO4

Measurements of the microwave surface resistance Rs and reactance Xs of GdBa2Cu3O7−δ and Sr2RuO4 single crystals are reported in the temperature range 0.4 to 25 K at frequencies from 10 to 20 GHz, using a hollow dielectric resonator technique. The GdBa2Cu3O7−δ measurements are interpreted in terms of antiferromagnetic alignment of the Gd spins, resulting in a Neel transition at 2.25 K, with a strongly temperature spin relaxation time both above and below the transition. Above Tc = 1.45 K, the normal state surface impedance of the suspected p-wave superconductor Sr2RuO4 agrees rather well with that expected from dc measurements; however, below Tc, we observe an unusual increase in the surface reactance, which we attribute to a long electron relaxation time. Using a two-fluid model, we obtain a normal fluid component that decreases almost linearly with temperature and extrapolates to a finite low-temperature value.

Natural oscillations of shielded multilayer spherical dielectric resonators

Characteristic equations and analytic expressions for the Q-factors are derived for a three-layer spherical dielectric resonator in a metal shield. The effect of dielectric coatings on the Q-factors of dielectric resonators is examined. The effect of a metal shield on thinning of the spectrum of a hollow spherical dielectric resonator is investigated.

Coupling losses in laser resonators containing a hollow rectangular dielectric waveguide

This paper discusses the losses in coupling radiation from the guide into free space and back into the guide for a hollow rectangular dielectric waveguide laser resonator with external spherical mirrors. Computations of the coupling loss for the EH11 lowest-order mode of a square guide, as a function of mirror curvature and position, are presented in the limit of large mirror aperture. It is shown that some mirror positions and radii provide low coupling losses.