Dielectric Resonator Research Articles

A Wide-Band Circularly Polarized Euler Spiral Dielectric Resonator Antenna for X/Ku-Band Applications

This paper puts forward a low-profile, circularly polarized (CP), wideband Euler’s Spiral Dielectric Resonator Antenna (ES-DRA) having a footprint of 0.68 λ × 0.68 λ × 0.096 λ and operating in X and Ku-band (8.26–14 GHz). A cross-shaped aperture is used to couple the power from 50 Ω walking stick-shaped microstrip line to the ES-DRA. The antenna generates circular polarization radiation in the frequency band 10.47–11.69 GHz and has a peak gain of 8.1 dBic. There is a good matching between radiation and total efficiency in the operating band. The antenna can be put to use in weather mapping and detecting, long-range tracking radar and missile applications. The prototype has been fabricated and tested for experimental validation and the results are in good coherence with the simulated ones.

Role of charge-compensation process on the structural, microstructure and electrical properties of pure and Nb-doped Sr2SnO4

This article explores the charge compensation method by synthesising Sr2SnO4, Sr2Sn0.99Nb0.01O4, and Sr1.995Sn0.99Nb0.01O4. The synthesis of a monophasic, tetragonal sample was achieved using a typical ceramic approach and high-temperature heat treatment. The XRD followed by Rietveld refinement, confirmed the crystallization of material under the space group I4/mmm. The crystallite sizes for all samples determined to be less than 50 nm, while the micro-strain falls within the range of (1.78–2.93) × 10–3. The microstructure exhibits a cuboidal shape for all samples, and the grain size is observed to decrease with the addition of Nb. The dielectric characteristics of the samples indicate the existence of Maxwell-Wagner and Orientational polarization in the sample. The sample Sr2Sn0.99Nb0.01O4 demonstrates a greater conductivity value compared to Sr1.995Sn0.99Nb0.01O4. This is attributed to the presence of excess electrons that compensate for the overall charge, as opposed to Sr1.995Sn0.99Nb0.01O4 where the extra charge is compensated by a cationic vacancy VSr″. The time-temperature-superposition principle (TTSP) is applicable to all compositions and indicates that similar sources are responsible for both conduction and relaxation processes. The dielectric permittivity and dissipation factor are found to be in the range of 150 to 175 and 0.2 to 0.5, respectively. This suggests that they have potential for future use in millimeter-wave communication with dielectric resonator antennas (DRAs). Due to the presence of oxygen ions and the ability to conduct both ions and electrons, at temperatures above 400 °C, it is a suitable choice for electrode materials in the application of intermediate temperature solid oxide fuel cell (IT-SOFCs). Exploring the manipulation of defects using electrical and ionic charge compensation methods shows potential for enhancing materials in semiconductor technology.

Infrared imaging with nonlinear silicon resonator governed by high-Q quasi-BIC states

Nonlinear light-matter interactions have emerged as a promising platform for various applications, including imaging, nanolasing, background-free sensing, etc. Subwavelength dielectric resonators offer unique opportunities for manipulating light at the nanoscale and miniturising optical elements. Here, we explore the resonantly enhanced four-wave mixing (FWM) process from individual silicon resonators and propose an innovative FWM-enabled infrared imaging technique that leverages the capabilities of these subwavelength resonators. Specifically, we designed high-Q silicon resonators hosting dual quasi-bound states in the continuum at both the input pump and signal beams, enabling efficient conversion of infrared light to visible radiation. Moreover, by employing a point-scanning imaging technique, we achieve infrared imaging conversion while minimising the dependence on high-power input sources. This combination of resonant enhancement and point-scanning imaging opens up new possibilities for nonlinear imaging using individual resonators and shows potential in advancing infrared imaging techniques for high-resolution imaging, sensing, and optical communications.

A comprehensive study on crystal structure, phase compositions of the BiVO4-LaVO4 binary dielectric ceramic system and a typical design of dielectric resonator antenna for C-band applications

Novel multi-component (Bi1-xLax)VO4 (BLVOx) (0.05 ≤ x ≤ 0.9) solid-solution/composite ceramics crystal structures, phase compositions as well as its applications in the C-band dielectric resonator antenna have been designed and investigated. With the increased substitution of La3+, phase transitions among the monoclinic scheelite (mBiVO4), tetragonal zircon (zt(La,Bi)VO4) and monoclinic monazite (mLaVO4), driven by the compositional changes, were detected. La3+ played an essential role in the optimization of the dielectric properties of BLVOx. The measured Q × f values at the microwave band are considerably larger around the range of compositions forming the zircon phase and reached the maximum value (12,800 GHz) at pure zircon phase (x = 0.5), demonstrating that the impact of zircon structure on the intrinsic loss should not be disregarded and is beneficial for low dielectric loss. Meanwhile, the εr and TCF values could be tuned by regulating the concentration ratio of Bi3+/La3+ to obtain composites or solid-solutions with appropriate εr and near-zero TCF values. Additionally, a cylindrical dielectric resonator antenna (CDRA) of BVLO0.5 ceramic was designed with high simulated radiation efficiency (99.8%) and gain (4.58 dBi) at the center frequency (6.73 GHz), indicating its potential application in C-band because of its tunable permittivity and low-loss.

A Two-Port Dual-Band Dual-Circularly-Polarized Dielectric Resonator Antenna

A Two-Port Dual-Band Dual-Circularly-Polarized Dielectric Resonator Antenna

Two port high gain and low mutual coupling dielectric resonator based array antenna for 5G mm-wave applications

In this communication, a two-port ceramic based array radiator at mm-wave frequency range is structured and analysed. 3-dB power divider based microstrip feed line is utilised to excite the rectangular aperture. The same aperture is used to feed the ceramic, which creates fundamental hybrid mode (HEM11δ ) inside the dielectric resonator. Feeding structure is designed on RT Duroid substrate having thickness 0.254 mm and permittivity 2.2. The length and width of the substrate is 60.0 mm and 30.0 mm respectively. Alumina material is used to design the ceramic having permittivity 9.8. The exclusive feature of the proposed antenna design is to get highly directional pattern along with high gain (more than 13.5 dBi) in mm-wave frequency range with the assistance of 1*4 array structure. Orthogonal orientation of antenna ports adds the polarization diversity concept, which in turns improve the isolation level more than 50 dB. Measured results confirm that the designed antenna works effectively in between 31.5–32.8 GHz. Broadside radiation pattern and good value of Envelop correlation coefficient (less than 0.1)/Diversity gain (10.0 dB) make the designed antenna employable for n257 frequency band of 5G mm-wave applications.

Strontium tantalate ceramics for dielectric resonator and antenna applications

Bulk SrTa2O6 ceramics were produced via solid-state reactive sintering, characterized by x-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy, and their dielectric properties determined via resonant cavity in the 5G frequency domain. Two polymorphs were obtained. Orthogonal β phase ceramics, obtaining much lower relative densities, achieved, at ∼5 GHz, an effective permittivity (εeff) of ∼22, dielectric losses (tanδ) around 1 × 10−2 and temperature coefficient of resonant frequency (τf) of around 250 ppm/°. Tetragonal tungsten bronze β′ phase ceramics achieved relative densities of ∼87 %, and at ∼2.8 GHz a higher 'εeff' between 79 and 85, lower ‘tanδ’ around 5 × 10−3, and a ‘τf’ of about 300 ppm/° at 90 °C. Both phases are found to be Sr-deficient, which may have caused a liquid-phase sintering in the powder bed configuration used for these ceramics. The performance of a prototype dielectric resonator antenna incorporating a β′ ceramic was demonstrated to validate the measured dielectric properties.

Transparent ionic liquid antenna based on multi-modes using multiple feeding structures

With the rapid development of modern wireless communication technology, there is an increasing demand for the functionality of the communication system carried by a single platform. To improve the utilization of the antenna, a multimode liquid antenna is proposed in this paper. The antenna is fabricated using 3D printing technology and mainly consists of a cylindrical dielectric resonator, a coaxial feeding structure, and a slot-coupling feeding structure. By hollowing out the middle of a resin container and filling it with low-loss ionic liquid with stable dielectric properties, a liquid dielectric resonator antenna (DRA) is formed. The various resonant modes (slot mode, HEM11δ, TM11δ, TM21δ, and TM31δ modes) can be excited by introducing different feeding structures. The operating frequencies and radiation patterns can be modulated by mode switching. Simulated and measured results show that the antenna operates in the frequency bands of 2.25–2.76 GHz (20.4 %) and 4.82–5.73 GHz (17.3 %), and the maximum gain can be up to 10.3 dBi. The proposed antenna structure avoids the complex RF control circuit design, which has various applications including 5G/6G communications, transparent electronic devices, and Internet of Things.

Integrated Dielectric Resonator Antenna to Traditional Antenna for Better Bandwidth and Gain

Integrated Dielectric Resonator Antenna to Traditional Antenna for Better Bandwidth and Gain

Endfire Substrate Integrated Dielectric Resonator Antenna With Dual-Beam Radiation for Millimeter-Wave Application

Endfire Substrate Integrated Dielectric Resonator Antenna With Dual-Beam Radiation for Millimeter-Wave Application

Investigating a Cylindrical Dielectric Resonator Antenna Fabricated with Li3MgNbO5 Microwave Dielectric Ceramic

This work aims to fabricate a single-feed line Cylindrical Dielectric Resonator Antenna (CDRA) using low-temperature sintered Li3MgNbO5 microwave dielectric ceramic as a resonator, excited in HEM11δ mode. The ceramic synthesized using the conventional solid-state route resulted in a single-phase material exhibiting a cubic structure with an Fm-3m space group. The densely packed cylindrical disk of the ceramic was subsequently characterized for its microwave dielectric behaviour in TE01δ mode using the Hakki-Coleman method. The dielectric permittivity (ε r) measures 14.4, with a loss factor (tan δ) nearly equal to 4.01 × 10−4 and a temperature coefficient (τf) of −50.9 ppm °C−1. The antenna design was executed using the high-frequency structure simulator design software, utilizing the dielectric ceramic as the resonator, Cu strip as the feedline, and FR4 as the substrate. The maximum energy was coupled to the antenna when the resonator was placed at 11.75 mm on the substrate. The fabricated CDRA, using appropriate simulated parameters, resonated at 7.67 GHz, offering a return loss (S11) of −32.64 dB and an impedance bandwidth of 10.73%. Furthermore, the CDRA displayed a voltage standing wave ratio of 1.04, ensuring a nearby ideal impedance match and a bandwidth of 810 MHz to support high-speed data transmission.

On the τf measurement of microwave dielectric ceramics

As a key parameter of microwave dielectric ceramics, the temperature coefficient of resonant frequency (τf) determines the temperature stability of microwave dielectric ceramics and relevant microwave devices. The τf of a microwave dielectric ceramic is typically calculated from the measured resonant frequencies of the system, consisting of the ceramic sample plus other dielectric elements, at two temperatures ∼60 – 70 °C apart. This measurement process assumes that τf is a constant; however, it is generally temperature-dependent based on both theoretical and experimental results. Furthermore, the as-measured τf is actually the τf of the dielectric resonator system, which is different from that of the sample itself. In this paper, these two overlooked problems during τf measurement are discussed in detail, and suggestions are given to avoid their possible misleading consequences and thus ensure the reliability of τf measurements.

Microstructural and dielectric properties of civil construction ceramic waste sintered at various temperatures

This study investigates the dielectric properties of ceramic waste derived from roof tiles and bricks commonly used in civil construction. The materials were analyzed by grinding them into a fine powder, followed by producing of cylindrical samples through uniaxial pressing on a steel matrix. The samples were sintered at temperatures of 1000 °C, 1050 °C, and 1100 °C to analyze the effect of temperature on the electrical characteristics of the ceramics. XRD and SEM analyses were performed to evaluate microstructural parameters and coalescence behavior. The dielectric characterization aimed to obtain the real relative electrical permittivity with average values of 2.85, 3.56, and 3.65, correlated with apparent porosity levels of 30.74 %, 20.54 %, and 9.11 %, and the loss tangent of 7.5 × 10−5, 3.9 × 10−5, and 12 × 10−5, respectively. The loss tangent values are lower than those obtained in commercial dielectrics from 1 to 6 GHz frequency range. The dielectric characteristics of samples manufactured from ceramic waste from bricks and tiles can serve as sustainable alternatives to produce dielectric resonator antennas (DRA), applicable to fifth-generation wireless communication devices in the sub-6GHz band.

Wideband Millimeter-Wave Perforated Hemispherical Dielectric Resonator Antenna

This paper presents a novel wideband circularly polarized millimeter-wave (mmWave) hemispherical dielectric resonator antenna (HDRA). Two distinct configurations of alumina dielectric resonator antennas (DRAs) are investigated, each featuring a different coating: the first configuration incorporates a polyimide layer, while the second involves a perforated alumina. Both configurations demonstrate promising characteristics, including impedance and axial ratio (AR) bandwidths of 58% and 17.7%, respectively, alongside a maximum gain of 10 dBic at 28 GHz. Leveraging additive manufacturing technology, the HDRA with the perforated coating layer is fabricated, simplifying assembly and eliminating potential air gaps between layers, thereby enhancing the overall performance. This innovative approach yields a circularly polarized (CP) HDRA suitable for Beyond 5G (B5G) communication systems. Agreement between measurements and simulations validates the efficacy of the proposed design, affirming its potential in practical applications.

Bulk glass-ceramic composites and ULTCC substrates for microwave and millimetre-wave applications

In this study, a new ultra-low-temperature co-fired ceramic (ULTCC) glass-ZnO-SiO2-B2O3CeO2−MgO-Al2O3 composite was developed and its applicability as a dielectric substrate in emerging high-performance communication technologies in the microwave and millimetre-wave frequency ranges was investigated. The novel material composition enables achieving good sinterability at a low fabrication temperature of 470 °C. Extensive studies have been conducted on the microstructure, porosity, water absorption, surface roughness, and thermal expansion coefficient. Following this analysis, the dielectric properties of the bulk glass-ceramic composites and the final ULTCC substrates were characterised. These measurements were conducted within a broad frequency range of 5 GHz–1.1 THz using split-post dielectric resonators, a Fabry-Perot open resonator, and a time-domain spectrometer, resulting in quasi-continuous frequency characteristics of the complex permittivity. Furthermore, the fabricated ULTCC substrates were subjected to surface-wise measurements, which provided 2D maps of the dielectric properties as qualitative and quantitative measures of the uniformity and quality of the material.

Surface dielectric resonator for in vivo EPR measurements

This research report describes a novel surface dielectric resonator (SDR) with a flexible connector for in vivo electron paramagnetic resonance (EPR) spectroscopy. Contrary to the conventional cavity or surface loop-gap resonators, the newly developed SDR is constructed from a ceramic dielectric material, and it is tuned to operate at the L-band frequency band (1.15 GHz) in continuous-wave mode. The SDR is designed to be critically coupled and capable of working with both very lossy samples, such as biological tissues, and non-lossy materials. The SDR was characterized using electromagnetic field simulations, assessed for sensitivity with a B1 field-perturbation method, and validated with tissue phantoms using EPR measurements. The results showed remarkably higher sensitivity in lossy tissue phantoms than the previously reported multisegment surface-loop resonators. The new SDR can provide potential new insights for advancements in the application of in vivo EPR spectroscopy for biological measurements, including clinical oximetry.

Design of tunable THz dielectric resonator antenna with cross-slot for circular polarization

Design of tunable THz dielectric resonator antenna with cross-slot for circular polarization

Innovative synthesis technique for high-performance dielectric resonator antennas: laser-induced shockwave sintering of potassium sodium niobate (KNN)

This study explored the synthesis and sintering of potassium sodium niobate (KNN) nanoparticles, emphasizing morphology, crystal structure, and sintering methods. The as-synthesized KNN nanoparticles exhibited a spherical morphology below 200 nm. Solid state sintering (SSS) and laser-induced shockwave sintering (LISWS) were compared, with LISWS producing denser microstructures and improved grain growth. Raman spectroscopy and x-ray diffraction confirmed KNN perovskite structure, with LISWS demonstrating higher purity. High-resolution x-ray photoelectron spectroscopy spectra indicated increased binding energies in LISWS, reflecting enhanced density and crystallinity. Dielectric and loss tangent analyses showed temperature-dependent behavior, with LISWS-3 exhibiting superior properties. Antenna performance assessments revealed LISWS-3’s improved directivity and reduced sidelobe radiation compared to SSS, attributed to its denser microstructure. Overall, LISWS proved advantageous for enhancing KNN ceramics, particularly in antenna applications.

A droplet-shape inspired wideband bow-tie dielectric resonator antenna for sub-6 GHz and IoT applications

In this article, an approach to realizing a dielectric resonator based bow-tie shaped antenna for the sub-6 GHz, 5G and IoT applications is discussed that utilizes droplet-shaped radiators for its two arms. The droplet-shaped radiating element is systematically derived to obtain a wider bandwidth response by truncating the sides of an aperture-coupled cylindrical DRA operating at HE11δ mode. The proposed bow-tie dielectric resonator antenna (DRA) is a modified dipole structure that uses a balanced line to differentially feed the two radiating segments to attain an overall wideband characteristics. A wideband matching balun circuit facilitates the antenna feeding which produces equal amplitude signals with 180° phase difference at its two output ports throughout the band of interest. The measurement of the proposed antenna confirms that it can serve several 5G bands like n77 (3300–4200 MHz), n78 (3300–3800 MHz), n48 (3550–3700 MHz) and n79 (4400–5000 MHz) with an overall wide bandwidth of 42.7% in the sub-6 GHz range. This planar configuration has a realized gain value ≥7.5 dBi within 3.37–3.91 GHz and it remains higher than 6 dBi almost throughout the working bandwidth of 3.18–4.91 GHz with considerably wide beamwidth. This broadband DRA has a consistent broadsided radiation pattern with cross-polarization discrimination (XPD)> 20 dB and its radiation efficiency varies between 60%–70% within 3.2–4.8 GHz. The antenna occupies a volume 1.2λ×1.2λ×0.1λ corresponding to its lower frequency of operation and it can support many more significant applications including WiMAX (3.3–3.8 GHz), Citizens Broadband Radio Service (CBRS) (3.55–3.7 GHz) and LTE (3.41–3.5 GHz uplink/3.51–3.6 GHz downlink). All these characteristics make this antenna a suitable candidate for use in transceiver modules for indoor communication, base stations, and vehicular communication.

Compact quad element dual band high gain MIMO rectangular dielectric resonators antenna for 5G millimeter wave application

In this article, a compact dual-band quad-port Multiple Input Multiple Output (MIMO) Rectangular Dielectric Resonator Antenna (RDRA) with a defected connected ground Geometry (DCGG) for 5G millimeter-wave (mm-wave) application is presented. The antenna is operating at 24 GHz to 32 GHz frequency range. The antenna configuration comprises four identical rectangular microstrip radiators mounted on an RT Duroid 5880 substrate (20 × 20 × 0.254) mm3. To enhance bandwidth, each radiator is equipped with both rectangular and circular-shaped ring slots. To improve the performance of the 4 port MIMO antenna, RDRAs are placed over each radiator and optimized. The MIMO RDRs exhibit dual-band with 4.24 GHz and 0.46 GHz bandwidths. The MIMO RDRA achieves exceptional isolation (>27 dB), high gain (8.24 dB), and more than 94 % radiation efficiency. The diversity parameters exhibit a low Envelope Correlation Coefficient (ECC) of 0.0006, and a high Diversity Gain (DG) of 9.97 dB is achieved, highlighting the effectiveness of the antenna system in providing diversity reception and improving communication reliability in challenging environments. Hence, the proposed MIMO antenna is compact, making it suitable for integration into small 5G devices or systems where space is limited, such as IoT devices, mobile phones, or small base stations at mm-wave frequency bands.