Waveguide higher mode pumping through a dielectric resonator

During the last time open dielectric resonators (DR) excited on whispering-gallery type waves due to their high Q-factor on the higher modes are used to investigate the dielectric properties of not only solid substances but also of liquids. For these purposes in the first experiments DR (which was used as measuring cell) being immersed directly in tested liquid. The investigated liquid influenced on external caustic of DR that led to frequency sift and changes of resonator Q factor. New achievement in creation of the dielectrometer measuring cells have appeared after the creation of the resonant structures in which certain geometrical parts of resonators are used. At first, such DR were created with metal mirrors. The subsequent researches [1] have shown that oscillations exist also without a mirror, which itself leads to condensate of a spectrum and reduction of the quality of resonator.

The electromagnetic characteristics of the shielded hemisphere dielectric resonator in 8-mm waveband were investigated experimentally. The utilization of a slotline for the excitation of whispering gallery modes in such resonator was suggested. It has been defined that the suggested excitation technique is efficient. It provides an opportunity to excite the high Q-factor higher order modes in shielded dielectric resonator without additional energy losses. It has been proved experimentally that the unloaded Q factor achieved in the resonator under investigation may exceed the threshold values, which are limited by the dissipative losses in the dielectric resonator material, due to the shift of the resonance field in the air gap between the metal and the dielectric resonator elements. It was demonstrated that the symmetry breakdown of the investigated resonator leads to a significant deterioration of its electromagnetic characteristics.

The paper presents a new dielectric resonator structure that allows to obtain a larger distance between the resonant frequency of TE011 mode and higher resonant modes: HE111, TM011 and EH111. Obtaining a sufficiently large frequency distance of the higher modes from the basic one allows realization of filters with much better spurious response. The proposed structure is based on a ring dielectric resonator in which the outer edge is flat and cone-shaped regions are cut symmetrically (from the top and bottom) to form the inner edge. To determine the resonant frequencies of the new structure the radial mode matching method has been applied. The proportions of the dimensions of the cut volume of the dielectric resonator were investigated in order to obtain the maximum frequency shift of higher resonant modes from the fundamental one (TE011). The obtained results show that it is possible to achieve a much wider spurious free frequency range than in the structures used so far.

In this article, a dielectric resonator (DR) excited wideband metasurface (MTS) antenna with differential feeding is proposed, which uses two modes of the MTS and the fundamental mode of the DR to achieve multimode operation and obtain wide bandwidth. Initially, based on the characteristic mode theory, relevant modes of the MTS are analyzed. Then, a DR operating at the fundamental mode ( ${\mathrm {TE}}_{\delta 11}^{\mathrm {x}}$ ) is introduced as the magnetic current source to feed the MTS, exciting the dominant mode and high order mode (HOM) of the MTS simultaneously. However, this HOM has a weak gain at the broadside direction and large side lobes. According to the superposition principle of radiation patterns, the maximum at the broadside generated by the DR is utilized to enhance the boresight gain of the HOM, thus transforming the top-weak radiation pattern of this HOM into a broadside one and improving the gain flatness. Additionally, the differential feeding technique is introduced to improve the asymmetry of radiation pattern. Furthermore, by analyzing the out-of-phase currents and the periodicity of the MTS patches, three measures —loading transverse open-ended slots, shortening periodicity and loading longitudinal slots— are introduced to reduce the high side lobe level of the HOM while preserving radiation patterns undistorted and improving the gain stability. As a result, this HOM and the dominant mode of the MTS are combined with the fundamental mode of the DR, achieving multimode operation. Finally, the proposed antenna was fabricated and measured. The measured results agree well with the simulated ones, indicating an impedance bandwidth of 51.4% (4.38-7.41 GHz), a 5–9 dBi in-band gain and a 15 dB front-to-back ratio (FBR) within the operating band.

This article investigates a dual band multiple input multiple output (MIMO) cylindrical dielectric resonator antenna (cDRA) for WLAN and WiMAX applications. It consists of two symmetrical orthogonally placed radiators. Each radiator is excited through a narrow rectangular aperture with the help of a microstrip line. For higher mode excitation, the proposed structure uses dual segment DRA which apparently looks like stacked geometry. The aperture fed dielectric resonator works as a feed for upper cDRA to generate higher order mode. The presented radiator covers the band between 3.3-3.8 GHz and 5-5.7 GHz. The measured isolation is better than 20 dB in the desired band. The average gain and radiation efficiency achieved for the proposed antenna is 6.0 dBi and 85%, respectively at the operating frequency band. In the proposed geometry, broadside radiation patterns are achieved by exciting HEM11δ and HEM12δ modes in a stacked geometry. Different MIMO performance parameters (ECC, DG, MEG, and CCL) are also estimated and analyzed. The prototype of proposed antenna is fabricated and tested. The measured outcomes are in good accord with the simulated one.

The use of higher resonant modes, other than tradiationally used TE011 is discussed in connection with the so-called Courtney method of measuring the relative dielectric constant of dielectric resonators. An error analysis is developed, which takes into account also the presence of an airgap between the dielectric resonator and the two parallel metal plates.

Dielectric resonators @R) with whispering gallery modes (WGMs) are used at the wide range of frequencies (from microwave to optical). These modes are formed by the grazing traveling waves in quasioptical DR (D > lo&, where D is diameter of resonator) inside dielectric with small incidence angles, their reflection factor being close to 1. WGMs electromagnrtic fieldes are localized between the external and hner caustics. Near this region the electromagnetic fields are evanescent. Therefore these modes have a high value of Q-factor. Variouse advanteges of the DR with WGMs suggest their utilization in the microwave and millimeter wave devices such as the filters [l], power combiners [2], solid-state oscillators [3], sensors for study of various materials [4]. One of the most important limits of the DR using is the problem of their coupling with other elements and circuits because of the open nature of these resonators and parasitic wave radiation. The open nature of the DR with WGMs leads to the system sensitiveness to the external medium and elements. It can display in noncontrol modification frequency and Q-factor value of the WGMs and influence at other circuits. One of this problem solution is the shielding of the DR [5,6]. The problem of the open DR (ODR) compatitibility with other circuits may be solved by the design way in the case of the absorber screen using. Absorbing screen worsens of the shielded dielectric resonator (SDR) characteristics (size, mass, Q-factor value) in comparison with the ODR. The perspective of the SDR construction with the coaxial situated cylindrical DR and with reflective screen is represented in the famous theoretical papers [5,6]. The high Q-factor modes determined by the occurence of the localization of their fields in dielectric exist in this system. The investigations find the problem of the excitation of these modes in real condition, which are arised through the dense spectrum of the SDR modes and difficulty introduction of the couplers in the field of the WGM's. Besides it can note that the calculation of the characteristics of the own modes of the cylindrical resonators is possible by the approximation method. In this paper we investigate the problem of the excitation high Q-factor WGMs of the hemispherical SDR the field of which is localmting in the dielectric and compared characteristics of the WGMs SDR with characteristics of the WGMs hemispherical ODR. The excitation of the high Q-factor WGMs of SDR was investigating experimentally in resonator which is shown in Fig.1 (insect). Teflon dielectric hemiball 1 (E= 2.08, radius &= 39 mm) and metallic hemisphere 2 (radius R,= 42 mm) are situated on the local flat mirrors 3,4 with coupling slot with the external waveguide. In the experimental model of SDR there was a possibility to easy change the position of the radiation source and passive slot on the radial coordinate. In this case it's a possible the effective coupling of the radiation source with the resonator field, the first; the cleaning of the modes spectrum, the second; measurement of the radial field distribution, the third. The WGMs TM,,, (E,. f 0) or TEml(Er = 0) (n,m,l are field variations along the polar, azimuthal and radial coordinaters accordingly) are excited in the investigated resonator. The characteristics measurements of the lowest (l=I, m=1) WGMs are carried out by the sweep generator in the frequency range 27-37 GHz. The highest WGM's are suppresed by the methods which are described in papers [3,7]. The coupling values are installed on the frequency characteristic of the VSWR (voltage standing wave ratio) and are controlled by the smaller absorber body method. The values of the own Qfactor are determined by the full resistance method [8]. The fkquency dependences of the VSWR in the channel with the investigated resonators are obtained for the coupling slots with the different width by direct measurements. The dependence of the relative amplitude A /A, of resonance fiom the standardized radial coordinate of the passive slot center to the dielectric hemiball radius ro / Rd for the TM WGMs of the ODR (circuits) and SDR (points) is shown at Fig. 1. As can be seen the modes fields of these resonators are concentrated in dielectric between the caustics of WGMs of ODR. The frequency dependence of unloaded Q-factor Th4 WGMs of the ODR (circuits) and SDR (points) is shown at Fig. 2. The monotonous decreasing of Q-factor of the hemispherical ODR,when the frequency is decreased, is connected with the own radiative losses increasing. The Q-factor of the ODR WGMs at the high frequency

A new technique of implementing dual-bandpass filters built on rectangular dielectric resonators has been proposed. The possibility of simultaneous tuning of two passbands on one structure of coupled dielectric resonators using their intrinsic high-mode oscillations was investigated for the sake of reducing the size of design. The proposed analytical solution was compared with the results of simulation by the finite element method. Coupling coefficients of rectangular resonators were calculated and investigated by a numeric technique for the low dipole TE 01δ and high quadruple TE 02δ magnetic modes depending on the parameters of filter design. The proposed dual-bandpass filter built on dielectric resonators can be used in base stations and wireless access points of communication networks.

A miniaturized rectangular resonator made of a novel anisotropic artificial dielectric material is investigated which has advantages of small size and big separation of the higher-modes. To obtain a property of anisotropic permittivity, artificial dielectric material is fabricated by lamination of rectangular metal strips etched on a printed circuit board. Artificial dielectric rectangular resonators are designed to excite TE 10δ mode selectively, aligning the rectangular metal patterns along the direction of the mode electric field line. The resonant frequencies and coupling coefficient of artificial dielectric rectangular resonators encapsulated in a metal waveguide are analyzed theoretically, and compared with the experimental result. As a microwave application, a high selectivity TE 10δ mode bandpass filter (BPF) using two artificial dielectric rectangular resonators is demonstrated. A two-stage BPF with the center frequency of 1.718 GHz, bandwidth of 78 MHz, and insertion loss of 1.3 dB is successfully realized in a rectangular waveguide.

A new and physically realizable feed employing a dielectric resonator (DR) has been conceived and demonstrated for ${\rm HEM}_{12\delta}$ mode in a cylindrical dielectric resonator antenna (CDRA). This indeed enables in realizing an improved version of dual-band dual-mode dielectric resonator antenna (DRA) with attractive broadside radiation along with wide bandwidth characteristics. It comprises of a two-element stacked geometry, where the lower element is excited by an aperture and the upper element is excited by the lower DR. The upper element is responsible for generating the higher mode $({\rm HEM}_{12\delta})$ , whereas the lower mode $({\rm HEM}_{11\delta})$ resonates in the entire composite mass. The conjecture has been verified with an S/C-band design using simulated and measured results indicating three different variants. The most improved geometry comprising of a “cone on top of a cylinder” promises 6.5 and 10.3 dBi gains in the lower and upper operating bands with, respectively, 8.3% and 13% matching bandwidth. This newly addressed technique can be of potential use for newer innovations in DRA feed and design.

ABSTRACTA hybrid dielectric resonator antenna (DRA) array is proposed for the wideband millimeter-wave communication. The radiator is composed with a pair of stacked dielectric resonators (DRs), which are H-shaped and Hexagon-shaped DRs, respectively. The dual-slots on the substrate integrated waveguide (SIW) cavity are utilized for higher mode generation in the DRA element. The antenna bandwidth is improved by the stacked DRs and dual-slot feeding. The structural characteristics and key parameters of feeding slots are discussed in detail. The DRA array fed with parallel power distribution feeding network is fabricated and measured to verify the reliability of the simulations, and the simulations and measurements have reasonable consistency. The impedance bandwidth is from 23.55 GHz to 27.28 GHz (14.7%), and the measured gain ranges from 13.1 dBi to 15.7 dBi. The radiation patterns are stable in the operation band. The proposed DRA array has a promising application prospect for 5 G communication system.

This communication deals with a novel concept of a liquid dielectric resonator antenna (DRA) which demonstrates omni-directional to bi-directional and uni-directional radiation patterns. The antenna design comprises of two peripheral Liquid ring dielectric resonators (DR) with changing heights of liquid dielectric filling, placed on both sides of an omnidirectional ring DRA. The antenna structure is positioned on a dielectric substrate. The liquid DRs with varying liquid heights become instrumental in reconfiguring omnidirectional $\mathrm{TE}_{01\delta}$ to bi-directional as well as uni-directional radiation patterns with frequency re-configurability in the higher mode. It provides bi-directional and uni-directional patterns along with frequency reconfigurability in the frequency band of 2.25-2.80 GHz and 3.62-4.32 GHz with higher gain.

A new design mechanism has been explored to realise a single higher mode driven wideband dielectric resonator antenna (DRA). It targets an aperture coupled cylindrical DRA to operate in HEM 11Δ mode, which indeed is a first-order repetitive form of HEM 11δ mode. Innovative engineering has been realised on the DRA body as a mode-filtering technique to maintain the modal purity and hence, the radiation uniformity. A C-band prototype has been experimentally verified indicating as much as 24% impedance bandwidth with 8.5 dBi maximum gain. This design appears commercially viable and superior to the earlier, higher mode based developments, especially in terms of gain, but without involving any additional cost, weight, or design complexity.

An analytical method is presented for calculating the resonant frequency and the Q-factor of shielded dielectric disk resonators excited in whispering-gallery modes. The method is based on a single-mode representation of electromagnetic fields in partial regions of the resonator. For high order modes with high degree of energy concentration in the dielectric this method gives a good agreement with experimental results obtained for different sapphire disks at both room temperature and cryogenic temperatures.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In this paper, a novel dielectric-resonator (DR) structure, called a modified ring resonator, has been proposed. In a microwave integrated-circuit configuration, the ring DR shape is modified in such a way that, for the TE/sub 01/spl delta// mode, the nearest hybrid (or TM/sub 01/spl delta//) modes are pushed farther to provide a higher mode separation simultaneous to no deterioration of the Q factor in the mode of interest. Further, the tunability studies reveal that degradation of mode separation in the proposed configuration is much lower than the conventional ring resonator for the tuning range studied here. The configuration also offers versatility in choosing the substrate thickness, which otherwise is limited in a ring resonator.