Dielectric Resonator Materials Research Articles

High-Qf value and temperature stable Zn2+-Mn4+ cooperated modified cordierite-based microwave and millimeter-wave dielectric ceramics

Cordierite-based dielectric ceramics with a lower dielectric constant would have significant application potential as dielectric resonator and filter materials for future ultra-low-latency 5G/6G millimeter-wave and terahertz communication. In this article, the phase structure, microstructure and microwave dielectric properties of Mg2Al4–2x(Mn0.5Zn0.5)2xSi5O18 (0 ≤ x ≤ 0.3) ceramics are studied by crystal structure refinement, scanning electron microscope (SEM), the theory of complex chemical bonds and infrared reflectance spectrum. Meanwhile, complex double-ions coordinated substitution and two-phase complex methods were used to improve its Q×f value and adjust its temperature coefficient. The Q×f values of Mg2Al4–2x(Mn0.5Zn0.5)2xSi5O18 single-phase ceramics are increased from 45,000 GHz@14.7 GHz (x = 0) to 150,500 GHz@14.5 GHz (x = 0.15) by replacing Al3+ with Zn2+-Mn4+. The positive frequency temperature coefficient additive TiO2 is used to prepare the temperature stable Mg2Al3.7(Mn0.5Zn0.5)0.3Si5O18-ywt%TiO2 composite ceramic. The composite ceramic of Mg2Al3.7(Mn0.5Zn0.5)0.3Si5O18-ywt%TiO2 (8.7 wt% ≤ y ≤ 10.6 wt%) presents the near-zero frequency temperature coefficient at 1225 °C sintering temperature: εr = 5.68, Q×f = 58,040 GHz, τf = −3.1 ppm/°C (y = 8.7 wt%) and εr = 5.82, Q×f = 47,020 GHz, τf = +2.4 ppm/°C (y = 10.6 wt%). These findings demonstrate promising application prospects for 5 G and future microwave and millimeter-wave wireless communication technologies.

CHARACTERIZATION OF (Mg0.5ZN0.5)TiO3 CERAMICS AS MATERIAL CANDIDATES FOR DIELECTRIC RESONATOR AT MICROWAVE FREQUENCY

MgTiO3 ceramic is one of the dielectric materials used as a signal generator (dielectric resonator) in microwave telecommunication devices. This research is intended to explore the possibility of a new composition of MgTiO3-based ceramic, i.e. (Mg0.5Zn0.5)TiO3 (abbreviated MZT05) as a dielectric resonator material. The aim was to characterize the resonant frequency of the ceramics on the microwaves (measured using spectrum analyzer), and the results were correlated to structure (X-Ray Diffraction, XRD), microstructure (Scanning Electron Microscope, SEM), and bulk density data (Archimedes method) of the ceramics. The work was begun by compacting the MZT05 crystalline powder in a cylindrical shape with a diameter of 5 mm using a uniaxial die press to produce tablets. The tablets were sintered at 1300 ºC with variations holding times of 6, 8, and 10 h to produce ceramics. The structural data revealed that the MgTiO3 phase was identified as the main ceramics, i.e. (96.32-98.70) %molar. The bulk density increased with increasing sinter holding time, from 2.75 g/cm3 (6 h), 2.84 g/cm3 (8 h) to 2.99 g/cm3 (10 h) due to the increase in grain size diameter from 919.75 nm (6 h), 1090.62 nm (8 h) to 1180.72 nm (10 h) accompanied by a decrease in the size of the pore diameter from 924.14 nm (6 h), 917.05 nm (8 h) to 800.22 nm (10 h). The ceramics produced resonant frequencies of 5.07–5.08 GHz, which implies that the ceramics are proven to be potential candidates for dielectric resonator materials at microwave frequencies, especially at 5.07-5.08 GHz. The varying sinter holding time seems not to influence the resonant frequency of the ceramics because the variation holding times produce similar resonant frequencies.

CHARACTERIZATION OF (Mg0.6Zn0.4)TiO3 CERAMICS AS DIELECTRIC RESONATOR MATERIALS IN MICROWAVE FREQUENCIES

Ceramics based on magnesium titanate (MgTiO3) are dielectric materials that have the potential to be used in telecommunications systems at microwave frequencies, such as filters, antennas, and signal generators. This study aims to characterize the resonant frequency and output power of (Mg0.6Zn0.4)TiO3 ceramics (abbreviated MZT04) as a dielectric resonator (DR) material in a DRO circuit and relate it to the structure, microstructure, and bulk density data of the ceramics. The MZT04 ceramics were fabricated by compacting MZT04 powder at a pressure of 2.5 MPa using a cylindrical die press of 5 mm in diameter to become pellets with the same diameter. The pellets were sintered at 1300 ℃ by varying holding time for 6, 8, and 10 h to become ceramics. Data on the structure of the ceramics were obtained from the X-Ray Diffraction (XRD) pattern with Cu-Kα radiation which showed that the three ceramics contained MgTiO3 phase, each 87.02; 90.55; and 87.40 % molar, the rest % is MgO and TiO2 rutile phases. The increase in sinter holding time has increased the unit cell volume of the MgTiO3 phase from (307.94), (308.61), to (308.94) Å3; the size of the lattice parameters (a=b, c) also increased from (5.057, 13.903) Å, (5.058, 13.903) Å, to (5.061, 13.914) Å; like wise, the bulk density increased from 2.51, 2.82, and 3.04 g/cm3. As a DR material, the three ceramics exhibit a resonant frequency signal each at 5.20; 5.21; and 5.22 GHz with the output power of -19.70; -14.47; -15.70 dBm, and the FWHM of the signal is 59.3; 61.6; and 61.2 MHz. Therefore, MZT04 ceramics can be applied as the DR material in microwave frequencies, especially at ~5.20 GHz. The variations in sinter holding time is not significant effect on the position of the resonant frequency.

Advanced Modelling Techniques for Resonator Based Dielectric and Semiconductor Materials Characterization

This article reports recent developments in modelling based on Finite Difference Time Domain (FDTD) and Finite Element Method (FEM) for dielectric resonator material measurement setups. In contrast to the methods of the dielectric resonator design, where analytical expansion into Bessel functions is used to solve the Maxwell equations, here the analytical information is used only to ensure the fixed angular variation of the fields, while in the longitudinal and radial direction space discretization is applied, that reduced the problem to 2D. Moreover, when the discretization is performed in time domain, full-wave electromagnetic solvers can be directly coupled to semiconductor drift-diffusion solvers to better understand and predict the behavior of the resonator with semiconductor-based samples. Herein, FDTD and frequency domain FEM approaches are applied to the modelling of dielectric samples and validated against the measurements within the 0.3% margin dictated by the IEC norm. Then a coupled in-house developed multiphysics time-domain FEM solver is employed in order to take the local conductivity changes under electromagnetic illumination into account. New methodologies are thereby demonstrated that open the way to new applications of the dielectric resonator measurements.

Compact circularly polarized triband staired rectangular dielectric resonator antenna using single and dual sections WPD with phase shifter for navigation satellite applications

AbstractIn this paper, compact circularly polarized triband (L5‐, L1‐, and S‐bands) staired rectangular dielectric resonator antenna (RDRA) is designed, analyzed, fabricated, and tested for navigation satellite applications. For triband RDRA, circular polarization is generated in L5‐band (1.164‐1.188 GHz) and L1‐band (1.565‐1.585 GHz) using dual section Wilkinson power divider (WPD) with wideband 90° phase shifter. For S‐band (2.48‐2.5 GHz), circular polarization is obtained by single section WPD with wideband 90° phase shifter. Ground plane footprint area of triband staired RDRA is miniaturized to 0.16λ0 × 0.16λ0 (40 mm × 40 mm) at lowest resonance frequency f1 of 1.176 GHz using high dielectric constant (εr = 38.67) dielectric resonator material and high dielectric constant (εr = 10.2) dielectric substrate (Rogers RO3210). Broadside radiation patterns of triband RDRA are generated for L5‐, L1‐, and S‐bands using , , and modes, respectively. Simulated and measured return loss at port‐1 of RDRA for L5‐, L1‐bands and port‐2 of RDRA for S‐band are better than 10 dB. Simulated and measured isolation between port‐1 and port‐2 of triband RDRA are found to be better than 13 dB for all bands. Peak right hand circular polarization gain is in the range of 0.6 to 4.5 dB over all bands for simulated and measured values. Simulated axial ratio is found to be better than 3 dB of triband RDRA. While measured values it is in the range of 0.91 to 7.02 dB.

A Metallic WBAN Dielectric Resonator Antenna for ISM Band Applications

A compact cylindrical dielectric resonator antenna (CDRA) for Industrial, Scientific and Medical (ISM) applications is proposed in this article. The simple microstrip feeding system can be used to stimulate a certain CDRA. An implemented dielectric resonator delivers the functionalities for an efficient radiator with the feeding specifications. The permitted band can be accumulated by varying the design specifications. The standardized design comprises the resonator to attain frequency of 2.4 GHz. The ISM band is used in wireless body area networks (WBAN) technology for transmission of real time traffic such as video and information to monitor the health conditions. A U-shaped metal strip is located over the dielectric resonator material in order to miniaturize the size and enhance the resonator appearance. The consequences on antenna appearance for various radio wire specifications are explored. The intended model has competitive prices, lower volumes, and adequate containment. The evaluation of antenna illustrates the optimal bandwidth, coefficient of reflection (< -10 dB) as well as substantial gain across the specified bands. Coefficients of reflection, voltage standing wave ratio (VSWR) and radiation structure were discovered in each scenario. Architecture content and simulated results of Ansoft's HFSS are demonstrated. For ISM band implementations, the constructed antenna is sensible.

Theoretical and Experimental Investigations on Rectangular Dielectric Resonator Antenna Array for Radar and Satellite Application

ABSTRACTIn this article, the theoretical, simulation, and experimental study of high gain dual segment 4-element linear broadside rectangular dielectric resonator antenna array shaping the -field components with copper sheet on one side, has been carried out. Copper strip connected to microstripline is introduced to excite the proposed dielectric resonator antenna array to achieve the coupling for dielectric resonator material with lower dielectric constant (≤10). Proposed antenna array with copper strip excitation has been successfully fabricated and tested. The voltage standing wave ratio, gain, and radiation characteristics of the proposed array have been explored using Ansoft HFSS 15.0 simulation software. Antenna array is also investigated using the finite-difference time-domain numerical technique. Good agreement between the simulated, calculated, and measured results is obtained. High gain and appreciable bandwidth together with low cross polarization is always defiance for researchers. The gain of the proposed array has been raised by a factor of 6.05, compared with the gain of a single dielectric resonator antenna. The proposed antenna provides a high gain of 10.50 dBi with a medium bandwidth of 512 MHz (3.44–3.95 GHz) and low cross-polarization, which is definitely better than previous reported literatures. The proposed structure is a good substitute to patch antennas in array applications as it offers high gain, medium bandwidth, and nice impedance matching. However, one disadvantage compared to microstrip arrays is the added fabrication complexity involved in having to place and bond the individual elements. In the future, for mass production applications, this process could be automated using robotic pick-and-place machines.

Implementation of higher order forced oscillations mode in shielded dielectric resonators by using slotline

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.

Design and analysis of stepped impedance transformer from air filled waveguide to dielectric filled waveguide for high power microwave window applications

This paper describes a design to achieve good microwave power transmission from an air filled rectangular waveguide to a narrow dielectric filled waveguide using a stepped impedance transformer. A novel material Ba(Zn1/3Ta2/3)O3 (BZT) having high dielectric constant and low dielectric loss has been proposed as a microwave window. The advantages of using such dielectric resonator materials for these applications is that they make the size reduction of such microwave components possible without unleashing microwave dissipation. A high density (more than 97%) and good microwave dielectric properties are obtained for BZT samples through the solid state reaction method. The obtained dielectric parameters are used to calculate the dimensions of the narrow dielectric window section in waveguide geometry and the resulting dielectric window structure is simulated using the IMST Empire simulator. The maximum power transmission is obtained by the simulated structure with a dielectric filled waveguide window of thickness 7.4 mm at 3.7 GHz with bandwidth of 780 MHz, which corresponds to an insertion loss (S21) magnitude of 0.008 dB, and the return loss (S11) obtained at the same frequency is −43 dB. The microwave dielectric properties of the material used as well as the simulated results for the BZT based window are studied and compared with those of a conventional window.

Synthesis and Characterization of Ceramic Dielectric Resonator Materials for Microwave Communication Technology

The Ceramic Technology has witnessed an exponential growth in last decade making available a number of newer materials with improved characteristics for several state of art engineering applications. Recently technological advancements and availability of suitable Ceramic Dielectric Resonators that function as the important circuit elements, the microwave communication technology has undergone a complete overhaul. The present work attempts to investigate these materials with special emphasis to Di-barium Nonatitanate (Ba2Ti9O20) that has low loss; quality factor Q>10,000, temperature stable high relative permittivity (∼39) and a very small change in resonant frequency as a function of temperature (∼4ppm/K). The fabrication of very dense bodies of Ba2Ti9O20 ceramic with phase purity is of great practical importance. The realization of monophasic Ba2Ti9O20 had, however, been a challenge. The synthesis of phase pure (Ba 1-x Cax)2Ti9O20 materials with improved characteristics using narrow particle size distribution among the nano-crystallites with higher surface area and better sinterability, obtained through internal combustion based Precursor Method has been reported in this paper. The results of characterization and evaluation have been discussed in terms of the physico-chemical aspects.

Coupling coefficient of a composite dielectric resonator with rectangular waveguide

Dependence of coupling coefficient between split dielectric resonator and rectangular waveguide on composed dielectric resonator and waveguide geometrical sizes and material permittivity was established. The coupling coefficient was estimated in terms of S parameter approximation calculated by finite element method. Improvement of dielectric resonator coupling with rectangular waveguide more than by 100% is proposed. Such effect was achieved by insertion of dielectric discontinuity perpendicular to DR’s electrical field. It results in increasing of attenuation in band-stop filters and decreasing of insertion loss in band-pass filters

Structural and optical properties of [formula omitted] thin films deposited by pulsed laser deposition

Ba(Zn 1/3Ta 2/3)O 3, (BZT), is a high-k and low loss dielectric resonator material which finds applications in the area of microwave communication and related areas. While there are reports on its bulk properties, there is hardly any report on its thin films. We report here preparation of thin films of BZT deposited on to borosilicate and quartz substrates using the pulsed laser deposition (PLD) technique under different oxygen mixing percentage (OMP) and preliminary studies on their structural and optical properties. The EDAX spectra show that the deposited films exhibit the composition of the target. As-deposited films, whether on a glass or quartz substrate, were found to be amorphous. The refractive index and energy bandgap of the films were found to be around 1.5 in the dispersion free region (500–1500 nm) and 5.2–5.5 eV, respectively. The Dynamic Force Microscopy (DFM) study of the BZT films exhibited columnar growth and films deposited at higher OMPs showed the smaller grain size.

Doped Ca(Ca1/4A2/4Ti1/4)O3 (A=Nb, Ta) Dielectrics for Microwave Telecommunication Applications

Ca(Ca1/4A2/4Ti1/4)O3 (A=Nb, Ta) dielectric resonator materials have been prepared by the solid‐state ceramic route. The effects of various amounts of di‐, tri‐, tetra‐, penta‐, and hexavalent impurities on the structure, microstructure, density, and microwave dielectric properties of the complex perovskites have been investigated. The structure of the parent materials remained unchanged while slight increase in density was observed with a small amount of certain dopants. An improvement in dielectric constant, quality factor, and temperature coefficient of resonant frequency was observed with the doping of small amounts of MgO, ZnO, NiO, CuO, Co3O4, Cr2O3, SnO2, and Sb2O5. A correlation between the microwave dielectric properties of Ca(Ca1/4A2/4Ti1/4)O3 (A=Nb, Ta) ceramics and ionic radius of the dopant has been observed. The reported ceramics are potential candidates for dielectric resonator applications in wireless communication devices operating in the S and C bands.

High Q dielectric resonator material with low dielectric constant for millimeter-wave applications

Al 2O 3 TiO 2 ceramics has great promise as a dielectric resonator material for millimeter-wave use. The Al 2O 3 TiO 2 MnO system provides low dielectric constant and high quality factor ( Q). TiO 2 and Al 2O 3 can compensate each other's temperature coefficient of resonant frequency. It is important to suppress the appearance of Al 2TiO 5 phase for obtaining high Q-value. In this study, dense Al 2O 3 TiO 2 mixed ceramics without Al 2TiO 5 phase was synthesized by lowering the sintering temperature. The addition of MnO decreases the sintering temperature from 1400 to 1300 °C. In this temperature range, Al 2TiO 5 phase is hardly formed. X-ray powder diffraction (XRD) patterns show that the ceramics is composed of Al 2O 3 and TiO 2 phases only. Dense and well dispersed mixture of Al 2O 3 and TiO 2 grains is observed by scanning electron microscopy (SEM). The 0.9Al 2O 3 0.1TiO 2 ceramics doped with 0.4 mol% of MnO has dielectric constant of 12.4, Q × f of 274,000 GHz at 76 GHz, and temperature coefficient of resonant frequency of +0.4 ppm/°C. The dielectric constant and the temperature coefficient of resonant frequency can be controlled by TiO 2 content. This ceramics is suitable for millimeter-wave applications because of its low dielectric constant, high Q-value, and small temperature coefficient of resonant frequency.

Tailoring the microwave dielectric properties of Ba(Mg 1/3Ta 2/3)O 3 ceramics

Ba(Mg 1/3Ta 2/3)O 3 (BMT) is a very important microwave dielectric resonator material with a high dielectric constant of about 25, high quality factor and small temperature variation of resonant frequency. The preparation temperature of BMT ceramics is relatively high, about 1650 °C. The microwave quality factor of BMT depends on the ordering of Mg–Ta–Ta ions on the perovskite B-site. In the present paper we report how one can tailor the properties of BMT ceramics by glass addition, slight non-stoichiometry and by dopant addition. (a) It is found that addition of small amount of glasses such as B 2O 3, ZnO–B 2O 3, ZnO–2B 2O 3, ZnO–B 2O 3–SiO 2 reduces the sintering temperature, increases density, order parameter and quality factor. (b) Slight Mg or Ba deficiency improves densification, order parameter and quality factor whereas excess Mg or Ba deteriorated the properties (c) Small amounts of dopants such as Sb 2O 5, MnCO 3, ZrO 2, WO 3, SnO 2 and ZnO improve the microwave dielectric properties. It is found that the quality factor is maximum when the ionic radii of the dopant ions are close to the weighted average ionic radii of B site ions (i.e. Mg 1/3Ta 2/3), which is 0.653 Å.

Temperature-compensated frequency discriminator based on dielectric resonator

A planar circuit realisation of the Pound-type frequency discriminator has been implemented with a dielectric resonator in a microstrip environment. By taking advantage of the nature of the planar geometry, the circuit is further simplified and the original performance is maintained. Various frequency discriminators with centre frequencies around 4.2 GHz have been constructed and tested. It is demonstrated with analytical models and substantiated by measurement results that the dielectric resonator, with its own temperature coefficient of the resonant frequency, offers a degree of freedom that proves to be effective for temperature compensation in the design of the frequency discriminator. A temperature coefficient of 3.6 ppm/°C for the centre frequency is achieved with readily available dielectric resonator and substrate material from commercial sources. Further improvement of the system thermal stability can be obtained by tailoring the thermal property of the dielectric resonator to the chosen microstrip substrate.

Recent progress on the dielectric properties of dielectric resonator materials with their applications from microwave to optical frequencies

The dielectric properties at microwave and millimeter-wave frequency are reported for practical dielectric resonator materials. The dielectric materials suitable for each application such as antenna duplexers for mobile phones, filters for cellular base station, millimeter-wave applications, and high temperature superconductors are introduced with their dielectric properties. Recently, valuable optical properties have been obtained by altering specific dielectric resonator materials.

Piezoelectrically tuned dielectric resonators

A simple technique for rapid tuning of a dielectric resonator using piezoelectric actuation is described. Results are presented for three dielectric resonator materials with relative permittivities of 9.5, 47 and 100 and dielectric Q-factors of 50000 (10 GHz), 9000 (5 GHz) and 16000 (3 GHz). The advantage of the proposed tuning method is that little degradation in the device Q-factor is observed even with tuning up to 2%.

電子材料 誘電体共振器の動向と移動体通信機用電子部品への応用

Since the 1970's, dielectric resonator materials have been developed and put into practical use for filters and oscillators in microwave frequency, miniaturizing these components and saving costs. The concentrated effort has been undertaken to decrease the dielectric loss of these materials. In this paper, the recent progress on the dielectric properties of dielectric resonator materials is reported with their practical applications. The dielectric materials suitable for each application such as the antenna duplexer for.handymobile phone, the filter for cellular base station, millimeter-wave application and high temperature superconductor are introduced with their dielectric properties.

New low loss microwave dielectric ceramics in the BaO-TiO2-Nb2O5Ta2O5 system

Microwave ceramic dielectric resonator materials in the BaO-TiO2-Nb2O5Ta2O5 system such as BaTiNb4O13, BaTiTa2Nb2O13, BaTiTa4O13, Ba3Ti4Nb4O21, Ba3Ti4Ta4O21, Ba3Ti5Nb6O28, Ba3Ti5Ta6O28 and Ba3Ti5Nb3Ta3O28 have been prepared by the conventional solid state ceramic route. They have relatively high dielectric constant and high quality factor. The resonator materials are characterized by X-ray diffraction and scanning electron microscopy (SEM) methods. The BaTiNb4O13Ba3Ti5Nb6O28 and Ba3Ti5Nb3Ta3O28 have small temperature variation of the resonant frequency and are possible microwave dielectric resonator materials for practical applications.