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This paper presents the study of a novel microwave electrothermal thruster with a dielectric resonator based approach for the plasma localization and propellant gas heating. The study is purely computational in a two-dimensional planar geometry and establishes the concept and demonstrates feasibility as an electric propulsion device. The resonant structure consists of a two cylindrical high dielectric constant (ɛr = 172.5) resonator enclosed within a plasma chamber that terminates at a convergent-divergent nozzle. The plasma chamber is irradiated by an incoming microwave that experiences a large wave electric field amplification of about 25 000 at a resonant frequency of 18.5 GHz. The field amplification results in breakdown and establishment of a steady plasma in a helium propellant in close vicinity to the nozzle. With a microwave power input of 40 W mm−1 (depth) at 1 atm. discharge pressure, the peak gas temperature is about 1300 K, with an electron number density of approximately 1020 m−3, resulting in a peak specific impulse of 245 s. The corresponding cold gas specific impulse is 150. The high specific impulse is attributed to the plasma hot zone being located in close vicinity of the nozzle, which effectively increases thrust. However, the thrust increase is accompanied by significant heat conduction losses, particularly as the dielectric gap size increases, underscoring the importance of thermal management in the system. [ABSTRACT FROM AUTHOR]

This paper studies innovative microwave resonators, utilizing special dispersive materials whose relative permittivity is inversely proportional to the frequency square. The "dispersive material" refers not only to natural or synthesized materials but also to equivalent materials achieved through advanced dispersion management techniques. The new resonator theory and analysis of the electromagnetic properties and eigenmode frequency of these new resonators are presented comprehensively and validated through a combination of analytical and numerical simulations using commercially available electromagnetic simulation software (CST Studio Suite). Detailed deduction and demonstration of wideband resonance characteristic, unloaded quality factor (Q), and new formulas are given. Several new types of resonators are introduced including rectangular waveguide cavity resonators and dielectric resonators. This inverse-square property of the special dispersive material provides the new resonators with wideband resonance characteristics. Besides, other dispersive materials whose relative permittivity is inversely proportional to the frequency by the power of n are also demonstrated to be useful for bandwidth enhancement. Moreover, the theory behind these dispersive materials and their equivalent approaches for achieving similar material characteristics through various techniques of dispersion management are also discussed in detail. Compared with the traditional resonator, the new resonator breaks the bandwidth limitation and offers the potential to a variety of new microwave devices and antennas such as bandwidth enhancement, stable radiation patterns, and other merits. This could make it useful for a variety of applications including 6G communication, broadband radar systems, and ultrahigh-speed data transfer. [ABSTRACT FROM AUTHOR]

Free‐standing and flexible Polyvinylidene fluoride‐trifluoroethylene (P(VDF‐TrFE))—Copper (II) oxide (CuO) nanocomposite films were synthesized using the solution casting method. CuO nanoparticle weight percentage varied as 0%, 10% and 20% in the P(VDF‐TrFE) matrix. X‐ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy were employed for phase confirmation. The morphological changes with the content of CuO nanofiller in the P(VDF‐TrFE) matrix was examined using Field Emission Scanning Electron Microscope (FESEM). The thermal stability of the free‐standing films were tested by the Differential Scanning Calorimeter (DSC). The dielectric permittivity and loss tangent of the films were measured at 10.156 GHz using a Split Post Dielectric Resonator (SPDR) method. The results were verified with the Cavity perturbation technique at 9.174 GHz and showed a decrease in the dielectric properties with a rise in the weight percentage of CuO up to 20%. The present study demonstrates the comparison of the two techniques and the dielectric tunability in microwave frequencies. [ABSTRACT FROM AUTHOR]

A pattern-reconfigurable, vertically polarized (VP), electrically small (ES), Huygens source antenna (HSA) is demonstrated. A custom-designed reconfigurable inverted-F structure is embedded in a hollowed-out cylindrical dielectric resonator (DR). It radiates VP electric dipole fields that excite the DR's HEM11δ mode, which in turn acts as an orthogonal magnetic dipole radiator. The HSA's unidirectional properties are thus formed. It becomes low-profile and electrically small through a significant lowering of its operational frequency band by loading the DR's top surface with a metallic disk. The entire 360° azimuth range is covered by each of the HSA's four 90° reconfigurable states, emitting a unidirectional wide beam. A prototype was fabricated and tested. The measured results, which are in good agreement with their simulated values, demonstrate that the developed wideband Huygens source antenna, with its 0.085 λL low profile and its 0.20 λL × 0.20 λL compact transverse dimensions, hence, electrically small size with ka = 0.89, exhibits a wide 14.1% fractional impedance bandwidth and a 6.1 dBi peak realized gain in all four of its pattern-reconfigurable states. [ABSTRACT FROM AUTHOR]

In this work, M-type hexagonal ferrite nanoparticles having the composition Ca0.25Ba0.75CrxFe12−2xO19, where x = (0.0, 0.05, 0.10, 0.15, 0.20) were fabricated by the sol–gel auto-combustion technique. The influence of chromium doping on structural, dielectric and magnetic characteristics was examined. XRD powder analysis revealed the geometry of single-phase hexaferrite with P63/mmc space group. The magnetoplumbite hexagonal structure was revealed by the X-ray diffraction analysis. Crystallite size, a & c lattice parameters, bulk density, X-ray density, cell volume and porosity were assessed. Crystallite size ranged from 39.54nm to 42.91nm. The X-ray density and bulk density were enhanced while porosity was decreased with the substitution of Cr3+cation. The morphology of the fabricated materials was inspected by the SEM analysis, which displays uniformly scattered particles with hexagonal platelet shape. The value of the dielectric constant is high in the low-frequency regime, and it decreases with increasing frequency. The dielectric constant decreased appreciably with the increase of Cr3+. Such observed dielectric and magnetic features are useful for different technological applications like microwave absorbers, voltage-controlled, dielectric resonators and recording media. [ABSTRACT FROM AUTHOR]

SQUID-embedded superconducting resonators are of great interest due to their potential for coupling highly scalable superconducting circuits with quantum memories based on solid-state spin ensembles. Such an application requires a high-Q, frequency-tunable resonator that is both resilient to magnetic field and able to operate at millikelvin temperatures. These requirements motivate the use of a higher H c metal such as niobium; however, the challenge then becomes to sufficiently reduce the operating temperature. We address this by presenting a monolithic Nb nanoSQUID-embedded resonator, where neon focused-ion-beam fabrication of the nanoSQUID results in a device displaying frequency tunability at T = 16 mK. In order to assess the applicability of the device for coupling to small spin clusters, we characterize the flux sensitivity as a function of microwave drive power and externally applied magnetic field and find that the noise is dominated by dielectric noise in the resonator. Finally, we discuss improvements to the device design that can dramatically improve the flux sensitivity, which highlights the promise of Nb SQUID-embedded resonators for hybrid superconductor-spin applications. [ABSTRACT FROM AUTHOR]

A novel method is proposed to achieve a low-profile miniaturized dual-band dielectric resonator antenna (DRA) for wireless communication applications. The cylindrical dielectric resonator (DR) is fed by a microstrip loop on the top surface of the substrate and a mountain shaped ground on the bottom surface of the substrate. This structure not only effectively transfers energy to the DR but also plays a pivotal role in establishing a lower resonance frequency of 1.73 GHz, achieving this with a compact structure (0.21λ0 × 0.18λ0 × 0.02λ0, and λ0 is the free-space wavelength at 1.73 GHz). HEM11δ mode of the cylindrical DR is employed to cover the upper frequency band of 2.8 GHz. Ultimately, the effectiveness of our suggested approach and the antenna's performance are confirmed through the measurement. [ABSTRACT FROM AUTHOR]

A balanced dielectric resonator filtering power divider with isolation performance is proposed. By using the coupling of the T E 111 y modes between three rectangle dielectric resonators, combined with balanced feed structures, the differential-mode filtering and power dividing functions, as well as the common-mode suppression were achieved effectively. Additionally, by technically utilizing the hollow structure of the stacked substrates, isolation resistor structures are introduced at the two output ports to improve the isolation level of the power divider. It can solve the problem of traditional metal-cavity dielectric resonator filter power dividers being unable to add isolation structures due to structural reasons. Compared with the reported dielectric resonator filtering power dividers, the proposed one has the characters of a lower profile and high isolation. For demonstration, one dielectric resonator filtering power divider was fabricated and measured at 11.65 GHz with the profile of 0.66 λg and an isolation higher than 15 dB. The simulation results are in good agreement with the measured results. [ABSTRACT FROM AUTHOR]

A novel compact low-profile Conformal Dielectric Resonator Antenna (CDRA) for wideband applications is proposed. By employing a specially designed dielectric resonator in conjunction with an inverted-trapezoidal patch for feeding, an extensive Impedance Bandwidth (IB) around 51.5% is realized. The resonant frequencies of 6 GHz and 7.5 GHz correspond to the observation of the TE21δ mode and the second higher-order TE23δ mode, respectively. Moreover, a realized peak gain of 7.2 dBi is attained at 7.4 GHz. The proposed DRA offers a wide IB with more than 90% radiation efficiency throughout the bandwidth. Additionally, a good alignment is observed between the measured and simulated results. The proposed DRA is compact and has a low profile of 0.1λg, where λg represents the wavelength at the lower cut-off frequency. A CDRA with a conformal feed is an innovative design tailored for wireless communication systems operating within the frequency range from 5.2 GHz to 8.8 GHz. This antenna configuration is specifically engineered to exhibit conformal properties, enabling it for applications such as the exteriors of vehicles, aircraft, or other non-planar structures. [ABSTRACT FROM AUTHOR]

In this paper, a tunable and ultra-broadband terahertz (THz) absorber is proposed. The absorber, which is built upon the conventional metal–dielectric–metal tri-layer configuration, incorporates a KCl thin film within the dielectric gap situated between the top resonator and the middle dielectric layer. The simulation indicates that the absorber effectively captures more than 90% of terahertz waves between 3.6 and 7.3 THz, achieving absorption of over 99% within the 5.8–6.9 THz range. This unique broadband absorber is enabled by the interaction of plasmon and epsilon-near-zero (ENZ) modes. Additionally, due to the utilization of VO2 in the top resonator, the designed absorber holds potential to function as a thermally controlled radiation emitter, exhibiting a high emissivity of 90.5% at high temperatures while maintaining a low emissivity of 8.2% at low temperatures. The absorber is uncomplicated and adjustable, offering great potential for use in thermal management, terahertz camouflage, and engineering insulation. [ABSTRACT FROM AUTHOR]

The BaNb2V2O11 microwave dielectric material, synthesized using a solid-state process, was proposed for utilization as a temperature compensator in LTCC applications. XRD analysis indicated that all samples revealed a trigonal structure of the BaNb2V2O11 phase with the R3̅m (166) space group. Influence of lattice energy and bond energy on the dielectric characteristics were investigated. Correlation between the Full Width at Half Maximum (FWHM) of the primary Raman peak at 917 cm⁻1 and the Q × f value was also analyzed. The sample sintered at 860 °C exhibited remarkable microwave dielectric properties, including a high relative permittivity (εr) of 88.7, a high Q × f value of 2100 GHz, and a significantly positive temperature coefficient of resonant frequency (τf) of + 602.4 ppm/°C. This notably large positive τf value makes it an effective τf compensator. Furthermore, the high εr value indicates its suitability for use in decoupling devices or as dielectric resonators in 5G base stations. [ABSTRACT FROM AUTHOR]

Masers—the microwave analog of lasers—are coherent microwave sources that can act as oscillators or quantum-limited amplifiers. Masers have historically required high vacuum and cryogenic temperatures to operate, but recently, masers based on diamond have been demonstrated to operate at room temperature and pressure, opening a route to new applications as ultra-low noise microwave amplifiers. For these new applications to become feasible at a mass scale, it is important to optimize diamond masers by minimizing their size and maximizing the power of signals that can be amplified. Here, we develop and numerically solve an extended rate equation model to present a detailed phenomenology of masing dynamics and determine the optimal properties required for the copper cavity, dielectric resonator, and gain medium in order to develop portable maser devices. We conclude by suggesting how the material parameters of the diamond gain media and dielectric resonators used in diamond masers can be optimized, and how rate equation models could be further developed to incorporate the effects of temperature and nitrogen concentration on spin lifetimes. [ABSTRACT FROM AUTHOR]

The hybrid system consisting of microwave photons and ferromagnetic magnons has been studied in the context of quantum sensing and quantum manipulation of magnons. We demonstrate a strong coupling between magnons and photons in a dielectric resonator with a large dielectric constant and high quality factor. The coupling rate between magnons and photons amounts to g / 2 π = 126 MHz, and the corresponding cooperativity reaches C = 1.09 × 10 6 at cryogenic temperature. The high cooperativity is mainly due to the small internal decay rate of the resonator, which is advantageous for various quantum magnonics experiments. [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, a rectangular dielectric resonator (DR) based multiple input multiple output (MIMO) hybrid antenna with a machine learning (ML) optimization approach for 5G New Radio (NR), WiMAX, WLAN, Wi‐Fi 6, Vehicle to Everything (V2X), and C‐band uplink applications are presented. The proposed antenna provides a triple band. It covers n1, n2, and n39 5G NR at a lower frequency (1.59–2.26 GHz), n48 5G NR at the middle frequency (3.1–3.87 GHz), and n46, n47, n96, WiMAX, WLAN, and C‐band uplink at higher frequency (5.25–6.91 GHz). It achieved more than 20% impedance bandwidth and 20 dB isolation in all frequency bands. The maximum gain of the proposed antenna is 15 dBi. The calculated MIMO parameters are within the accepted range. It is optimized through various ML algorithms, including random forest (RF), K‐nearest neighbor (KNN), artificial neural network (ANN), extreme gradient boosting (XGB) and decision tree (DT). The RF ML algorithm gives 98.09% accuracy compared to other ML algorithms for S parameter prediction. [ABSTRACT FROM AUTHOR]

This article presents the design, development, and testing of a two-port microstrip-fed dielectric resonator antenna (DRA) with a defective ground structure (DGS) for future smart phones. The proposed DRA array is fabricated on an FR-4 substrate with dimensions of 23 × 54 × 1.57 mm³. The top layer of the substrate consists of two inverted L-shaped alumina dielectric resonators, energized by a pair of L-shaped microstrip feed lines. The bottom layer of the substrate features two airplane-shaped structures to form the reduced ground DGS. Initially, a single-input single-output (SISO) rectangular dielectric resonator (DR) made of alumina material is placed over the feed network. This is later modified into an inverted L-shaped DR to enhance the antenna's bandwidth. Subsequently, a 2 × 2 array is devised from the proposed SISO, and two airplane-shaped DGS structures were introduced on the surface of the ground plane to achieve the desired impedance bandwidth of 6.3–12.6 GHz. This configuration provides a maximum gain of 4.5 dB at a frequency of 7.6 GHz with a high isolation value (S21 ≤ − 22.5 dB).The performance of the proposed DRA prototype in MIMO systems is validated by measuring various diversity parameters, such as a low envelope correlation coefficient (ECC), high diversity gain (DG), high mean effective gain (MEG), and better multiplexing efficiency, all within acceptable limits. [ABSTRACT FROM AUTHOR]

A novel wide-band circularly polarized (CP) antenna with a step-like dielectric resonator (DR) is proposed, which features a two-order step-like dielectric resonator (TSDR) and fed by a Microstrip-slot structure. The parameter values of the TSDR are adjusted and the return loss (S11), axial ratio (AR), gain and radiation pattern are estimated by using HFSS. Results show that the new antenna has 10 dB S11 bandwidth of 56.3% (3.7 GHz-6.6 GHz), 3 dB AR bandwidth of 52.2% (3.78 GHz-6.45 GHz), and gain of 2 dBic-4.4 dBic, respectively. The usable bandwidth and peak gain are increased by 15% and 13%, respectively. [ABSTRACT FROM AUTHOR]

A substrate-integrated cylindrical cavity (SICC) fed polarization flexible cylindrical dielectric resonator antenna (CDRA) is presented in this literature. To excite the CDRA, a unique and simple feeding approach based on substrate-integrated waveguide (SIW) technology is demonstrated. This SICC is fed by two 50Ω microstrip lines, oriented orthogonally to each other. The SICC with a cross slot on its top metalized surface and the TM110 mode excites inside it act together to couple energy efficiently to the CDRA. Applying different phase combinations signals at the two input ports of the SICC, the CDRA can radiate in four different orientations linear polarization (LP) (along φ = 0°, 45°, −45°, and 90°), left-handed circular polarization (LHCP), and right-handed circular polarization (RHCP). A conventional cylindrical dielectric resonator having relative permittivity ϵd = 10 is preferred. Its diameter, height, and cross-slot dimensions are optimized to operate the CDRA over Ku-band with 12% impedance bandwidth, 2-dB axial ratio (AR) bandwidth of 11%, and 3-dB gain bandwidth of 12%. In this operating band, CDRA resonates at three different higher-order modes (HEM32δ, HEM113, and HEM12δ+2) with 8 ± 1.6 dBi/dBic gain for all the polarization states. The measurements of this antenna are conducted using two external phase shifters and one power divider. [ABSTRACT FROM AUTHOR]

In this paper, a compact 2 × 1 dielectric resonator antenna (DRA) array with circular polarization (CP) agility array is presented. The array is formed of two novel resonating elements, and each is composed of a pentagonal slot (PS) coupling a rectangular dielectric resonator (RDR). The proposed resonating element emits two degenerate orthogonal modes TExd 11 and TEy d21, confirming the CP radiation performance. The proposed resonator is utilized to portray a 2×1 sequentially rotated (SR) array with the ability to alter the CP polarization orientation. The signal at the feeding network input splits into two paths with equal magnitudes and phase progression phase by means of Wilkinson power divider (WPD). To obtain the 90 phase shifting between the WPD output signals, a single branchline coupler (BLC) is utilized. Considering the fact that the shifting orientation of the BLC output depends on which of the two BLCs is used as in input, the signal phase at the BLC can be controlled to yield a right hand circular polarization (RHCP) or left hand circular polarization (LHCP). To control the switching between the BLC output ports phase state, two PIN diodes are used at the BLC input ports. The 50 × 50 mm2 archetype achieves a bandwidth of 5.17% with a maximum realized gain of 7 dBic and a polarization purity of 4.4%. The findings of the proposed array make it a decent candidate for application using a 5.8 GHz band. [ABSTRACT FROM AUTHOR]

Confining light in nanoscale air voids can enable new photonic applications by eliminating the requirement of low loss in traditional dielectric resonators. Van der Waals materials are uniquely suited for this purpose as they offer a tailored assembly of different materials and the ability to fully enclose air voids through transfer techniques. Here, highly lossy van der Waals materials are leveraged to demonstrate optical resonances that confine light in encapsulated air voids. Void resonances are theoretically designed in the visible spectrum and resonant modes supported by void arrays are identified. Experimentally, void arrays are fabricated in tungsten diselenide and the confined resonances are characterized using far‐field reflectance measurements and scanning near‐field optical microscopy. Using van der Waals heterostructure assembly, the voids are encapsulated with hexagonal boron nitride and tungsten diselenide, which substantially reduces the void volume causing a large spectral blue shift of the void resonance exceeding 150 nm. The work demonstrates a versatile optical platform for lossy materials, opening a new regime of material space for photonic devices. [ABSTRACT FROM AUTHOR]

The homogeneity of the microwave magnetic field is essential in controlling a large volume of ensemble spins, for example, in the case of sensitive magnetometry with nitrogen-vacancy (NV) centers in diamond. This is particularly important for pulsed measurement, where the fidelity of control pulses plays a crucial role in its sensitivity. So far, several magnetic field-forming systems have been proposed, but no detailed comparison has been made. Here, we numerically study the homogeneity of five different systems, including a planar antenna, a dielectric resonator, a cylindrical inductor, a barrel-shaped coil, and a nested barrel-shaped coil. The results of the simulation allowed us to optimize the design parameters of the barrel-shaped field-forming system, which led to significantly improved magnetic field uniformity. To measure this effect, we experimentally compared the homogeneity of a field-forming system having a barrel shape with that of a planar field-forming system by measuring Rabi oscillations of an ensemble of NV centers with them. Significant improvements in inhomogeneity were confirmed in the barrel-shaped coil. [ABSTRACT FROM AUTHOR]

A low-cost microwave resonator sensor for angular displacement detection is proposed. The sensor uses a strip-loaded dielectric resonator (SLDR) as the key element. The sensor operates in the reflection mode, i.e. by producing a variation in the reflection coefficient (S11) according to the angular position of the SLDR relative to a microstrip transmission line. The primary advantage of the proposed strategy is its fixed-frequency operation enabling the S11 measurement with a low-cost reflectometer, thereby avoiding the costly vector network analyzer (VNA). Design modelling and initial analysis of the sensor are performed with ANSYS HFSS software. To demonstrate proof of concept, a sensor prototype is fabricated and experimentally characterized with a custom-made reflectometer. Results are compared against VNA-based measurements to be in decent agreement. The proposed sensor exhibits 0.43 dB/0 sensitivity over the dynamic range of 00–900. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this work, a cylindrical-shaped dielectric resonator antenna (DRA) with four elements is designed and presented at 28 GHz for millimeter-wave applications. The microstrip line is designed to excite the dielectric resonator (DR) with a relative permittivity of 8.3, and then the proposed single cylindrical DR antenna has been mounted on a FR4-Epoxy substrate with a relative permittivity of 4.4 and a thickness of 1.8 mm. However, the optimized single element was used to create a particular array for improving the gain and achieving the required antenna performance. The resulting antenna enabled a response range for the reflection coefficient from 26.8 GHz to 30.6 GHz, which covers the operational frequency. This allows for a maximum gain of 19.07 dB, an impedance bandwidth of 3.8 GHz, and a total efficiency of 80.62%, meeting the requirements for millimeter-wave and fifth-generation applications. [ABSTRACT FROM AUTHOR]

Summary: This article explains the design and implementation of a multiple input multiple output (two‐port) antenna, based on dielectric resonators. The antenna design not only demonstrates high isolation between its ports but also showcases robust diversity performance. The initial step introduces an asymmetrical ground plane radiating stub microstrip feed for circular polarization generation in a single‐port cylindrical dielectric resonator antenna (CDRA). This approach utilizes an asymmetrical ground plane and incorporates three radiating stubs connected to a microstrip feed line to generate HEM11δ modes in a cylindrical DRA. The proposed dual‐port CDRA offers high impedance bandwidth of 29.73% (2.95–3.98 GHz) and the axial ratio falls below 3 dB specifically from 3.01–3.35 GHz. The antenna demonstrates left‐handed circularly polarized fields with an average gain of 4.95 dBi and a radiation efficiency of 90.56%. All of these characteristics make the developed radiator appropriate for WiMAX (3.3–3.5 GHz) applications. [ABSTRACT FROM AUTHOR]

Quantum electronics operating in the microwave domain are burgeoning and becoming essential building blocks of quantum computers, sensors, and communication devices. However, the field of microwave quantum electronics has long been dominated by the need for cryogenic conditions to maintain delicate quantum characteristics. Here, a solid‐state hybrid system, constituted by a photo‐excited pentacene triplet spin ensemble coupled to a dielectric resonator, is reported for the first time capable of both coherent microwave quantum amplification and oscillation at X band via the masing process at room temperature. By incorporating external driving and active dissipation control into the hybrid system, efficient tuning of the maser emission characteristics at ≈9.4 GHz is achieved, which is key to optimizing the performance of the maser device. The work not only pushes the boundaries of the operating frequency and functionality of the existing pentacene masers but also demonstrates a universal route for controlling the masing process at room temperature, highlighting opportunities for optimizing emerging solid‐state masers for quantum information processing and communication. [ABSTRACT FROM AUTHOR]

Rapid technological advancements in recent years have opened the door to innovative solutions in the field of telecommunications and wireless systems; thus, new materials and manufacturing methods have been explored to satisfy this demand. This paper aims to explore the application of low-cost, commercially available 3D-printed ceramic/polymer composite filaments to design dielectric resonators (DRs) and check their suitability for use in high-frequency applications. Three-dimensional printing was used to fabricate the three-dimensional dielectric resonant prototypes. The filaments were characterized in terms of their thermal and mechanical properties and quality of printability. Additionally, the filaments' dielectric properties were analyzed, and the prototypes were designed and simulated for a target frequency of ~2.45 GHz. Afterward, the DRs were successfully manufactured using the 3D printing technique, and no post-processing techniques were used in this study. A simple and efficient feeding method was used to finalize the devices, while the printed DRs' reflection coefficient (S11) was measured. Results on prototype size, manufacture ease, printability, cost per volume, and bandwidth (BW) were used to evaluate the materials' suitability for high-frequency applications. This research presents an easy and low-cost manufacturing process for DRs, opening a wide range of new applications and revolutionizing the manufacturing of 3D-printed high-frequency devices. [ABSTRACT FROM AUTHOR]

Summary: In this article, a dual port Multiple Input Multiple Output (MIMO) cylindrical Dielectric Resonator (DR)‐based frequency tunable antenna with a machine learning (ML) approach for a 5G New Radio (NR) application is presented. According to the author's best knowledge, it is the first time‐frequency tunable MIMO hybrid DR with ML is reported. A dual port MIMO DRA is placed in the orthogonal configuration with the connected ground to obtain higher isolation S12<−19dB in the entire frequency range. The proposed dual port antenna provides a total spectrum (TS) and tuning range (TR) of 98.99% and 80.93%, respectively. The different MIMO parameters, Envelope Correlation Coefficient (ECC), Total Active Reflection Coefficient (TARC), and Diversity Gain (DG) are investigated and found within the acceptable limits. The optimization of the proposed dual port tunable antenna is done through the various ML algorithms, including Artificial Neural Network (ANN), K‐Nearest Neighbor (KNN), Decision Tree (DT), Random Forest (RF), and Extreme Gradient Boosting (XGB). The KNN ML algorithm provides more than 98% accuracy for predicting the S‐parameters in all configurations. Hence, the proposed antenna is suitable for 5G NR applications. [ABSTRACT FROM AUTHOR]

Hyperthermia, utilizing various types of energy sources such as microwaves, holds great promise for cancer treatment. The intense interaction between microwaves and substances during hyperthermia can produce heat efficiently, leading to the inactivation of cancer cells. Mie‐type resonance is widely studied in the regulation of electromagnetic waves, offering a new perspective for microwave hyperthermia. In this study, a Mie‐type dielectric resonator is reported for microwave hyperthermia using high‐permittivity and temperature‐stable ceramic. The proposed dielectric particles have the characteristics of compact size, low cost, and excellent biocompatibility. The resonant frequency of the system can be finely tuned through material design and arrangement, thus expanding its potential application scenarios. The dielectric particles can be rapidly heated under microwave irradiation, thereby enabling effective hyperthermia to eliminate cancer cells. This work demonstrates the potential of a safe and tunable Mie‐type dielectric resonator in microwave hyperthermia, which is expected to promote further research on Mie‐type resonance in the biomedical field. [ABSTRACT FROM AUTHOR]

We propose a structure utilizing a double-layer aluminum ring resonator embedded in a dielectric layer of metamaterial to demonstrate the appearances of unidirectional reflectionlessness, asymmetric reflection, and asymmetric transmission for the incident linear and circular polarizations. A significant feature of this structure is that it allows multiple functions to be implemented in the same structure without changing any structure parameters. For the vertical incident x- and y-polarizations, not only significant unidirectional reflectionlessness and asymmetric reflection effects are verified but also the strong linear to circular polarization conversions are illustrated in both transmission and reflection modes. For the vertical incidences of right-handed and left-handed circular polarizations, unidirectional reflectionlessness and asymmetric reflection are also demonstrated in detail. In addition, when linearly or circularly polarized waves are incident obliquely, the structure exhibits a stable asymmetric transmission phenomenon within a wide incident angle range. Furthermore, it also supports the occurrences of unidirectional reflectionlessness and asymmetric reflection stably within wide ranges of incident angle, resonator spacing, and rotation angle of the upper aluminum ring. [ABSTRACT FROM AUTHOR]

We report on temperature-dependent dielectric behavior of disordered ternary A6B2O17 (A = Zr, Hf; B = Nb, Ta)-form oxides in the GHz frequency range. The microwave dielectric properties including relative permittivity, dielectric loss, and temperature-dependent relative permittivity were characterized using cylindrical dielectric resonators using a resonant post measurement technique. Dielectric measurements through the resonant post method approach generally agree with dielectric measurements of A6B2O17 bulk ceramics measured through standard resonant post techniques. Coefficients describing the temperature-dependent relative permittivity for ternary A6B2O17 phases are strongly positive, suggesting contributions to polarizability arising from long-range mechanisms potentially associated with structural disorder. These observations support the working hypothesis that material functionality can be engineered by the chemical diversity and structural disorder possible in high configurational entropy A6B2O17 phases. [ABSTRACT FROM AUTHOR]

Edge scanning reflectometry (ESRL) on the SPARC tokamak aims to measure the electron density profile from the far scrape-off layer to the top of the typical H-mode pedestal and provide real-time data for plasma control. ESRL uses a standard frequency-modulated continuous wave technique from 18 to 90 GHz. By implementing both the O-mode and left-hand-cutoff X-mode, it covers densities from ∼4 × 1018 to ∼4 × 1020 m−3 at B0 ∼12 T. A voltage-controlled oscillator acts as the frequency sweep source. Phase-locked dielectric resonator oscillators and bandpass filters generate base signals ∼9–15 GHz. The signals are then frequency multiplied and amplified to reach the K (18–26 GHz), Ka (26–40 GHz), U (40–60 GHz), and E (60–90 GHz) bands. Multi-band signals are combined via the quasi-optical technique. ESRL plans to use oversized waveguides (∼20 m one-way) and a bi-static arrangement to minimize signal losses and distortions while allowing system flexibility. A COMSOL Multiphysics RF model in 2D has been set up to simulate the reflectometry process and help decide the layout of the horn antennas. Engineering analyses of the key parts of the system have been carried out in support of its preliminary design. [ABSTRACT FROM AUTHOR]

This paper proposes a high-sensitivity microstrip differential sensor for measuring the complex permittivity of liquids. The prototype of the differential sensor was formed by cascading two LC resonators on a microstrip transmission line based on stepped impedance. A strong electric field was found to be distributed in the circular patch of the LC resonator; therefore, a cylindrical micropore was set in the center of the circular LC resonator to measure the dielectric sample, which maximized the disturbance of the dielectric sample on the sensor. By optimizing the size of the circular LC resonator, a high-sensitivity sensor circuit was designed and manufactured. The complex permittivity of the test sample was calculated by measuring the transmission coefficient of different molar concentrations of ethanol–water solutions. The experimental results show that the designed differential sensor can accurately measure the complex permittivity of liquid materials with an average sensitivity of 0.76%. [ABSTRACT FROM AUTHOR]

This investigation introduces a MIMO antenna using cylindrical shaped dielectric resonators and discusses both the design and implementation approaches. The proposed antenna design employs a CSRR structure and L-shaped metallic reflectors to improve isolation across many frequency bands. The typology operates at five different frequency ranges: 2.48, 3.92, 5.36, 7.4, and 8.56 GHz. It provides isolation levels of 39, 52.5, 33.8, 42.9, and 37.2 dB, respectively. The semi-circular tapered feed enables for circular polarization between 5.3 and 5.75 GHz. The simulated results indicate that the specified antenna is appropriate for usage in five frequency ranges: 2.1–2.6, 2.7–4.4, 4.9–5.8, 6.9–7.8, and 8.1–9.1 GHz. In a multiple-input multiple-output configuration, antenna performance is evaluated using a variety of diversity indicators, including the envelope correlation coefficient, mean effective gain, diversity gain, channel capacity loss, and total active reflection coefficient. Both simulations and measurements reveal that the proposed antenna can handle Wi-Fi 6, Wi-Max, and W-LAN services, including X-band. [ABSTRACT FROM AUTHOR]

Dielectric resonator antennas (DRAs) use dielectric material as a resonator to accomplish high radiation efficiency and avoid severe conductor loss. The dielectric material that behaves as a resonator is plagued by a number of limitations, including strong cross-polarised (XP) radiation and difficulties integrating with any development platform. Yet, it also offers a lot of benefits, including compact size, lightweight, affordable price, and diversity in form, including cylindrical, rectangular, conical, and ring. A discussion of DRAs, covering DRA propagation modes, geometries, feeding mechanisms, and different bandwidth augmentation approaches, is presented. A stacked arrangement with two or more DRs has achieved the widest impedance bandwidth (BW). The perforated topology is a straightforward alternative for increasing the DRA's bandwidth while maintaining a small, discrete size. [ABSTRACT FROM AUTHOR]

A wideband dual-beam dielectric resonator antenna (DRA) with substrate integration capability was proposed for millimeter-wave (mm-wave) applications. The four rows of air vias along the x-direction and two extended rectangular patches could shift the undesirable radiation mode upward and move the conical-beam radiation mode downward, respectively. Thus, the TE211 mode and the TE411 mode of the patch-loaded perforated rectangular substrate integrated dielectric resonator (SIDR) supporting the dual-beam radiation can be retained in the operating band, and their radiation can be improved by the air vias along the y-direction. The T-shaped line coupled dual-slot structure could excite the above two modes, and a dual-slot mode supporting dual-beam radiation could also work. Then, a wideband DRA with a stable dual-beam radiation angle can be achieved, and its impedance matching can be improved by two air slots on two sides. Compared with the state-of-the-art dual-beam antennas, the proposed antenna shows a wider bandwidth, a higher radiation efficiency, and the substrate integration capability of DRA, making it more suitable for mm-wave applications. For demonstration, a 1 × 4 array was designed with the 10 dB impedance matching bandwidth of 41.2% and the directions of the dual beams between ±30° and ±35°. [ABSTRACT FROM AUTHOR]

Bound states in the continuum (BICs), which are characterized by their high-quality factor, have become a focal point in modern optical research. This study investigates BICs within a periodic array of dielectric resonators, specifically composed of a silicon rectangular bar coupled with four silicon rectangular blocks. Through the analysis of mode coupling, we demonstrate that the interaction between the blocks significantly modulates the eigenmodes of the bar, causing a redshift in all modes and enabling the formation of electromagnetically induced transparency based on BICs (EIT-BIC). Unlike typical EIT mechanisms, this EIT-BIC arises from the coupling of "bright" and "dark" modes both from the rectangular bar, offering novel insights for nanophotonic and photonic device design. Further, our systematic exploration of BIC formation mechanisms and their sensing properties by breaking structural symmetries and changing environmental refractive indices has shed light on the underlying physics. This research not only consolidates a robust theoretical framework for understanding BIC behavior but also paves the way for high-quality factor resonator and sensor development, as well as the precise control of photonic states. The findings significantly deepen our understanding of these phenomena and hold substantial promise for future photonic applications. [ABSTRACT FROM AUTHOR]

Wave characteristics of vortex laser beams during their tight focusing have been theoretically studied. The Rayleigh-Sommerfeld theory was used to describe propagation in free space of laser beams excited by the modes of a waveguide dielectric resonator. It is shown that at the topological charge of the spiral phase plate n = 0, the studied EH11 mode has a maximum of radiation intensity on the axis. Introduction of a topological charge leads to the appearance of a minimum of radiation intensity on the axis as well as to the increase in the size of the focal spot. However, for the TE01 mode with the topological charges n = 0 and n = 2, the intensity distribution retains a ring shape, while at n = 1 the beam profile turns into the Gaussian-like one. The wave front in the focal region of the lens for the components of the EH11 and TE01 modes transforms from spherical to spiral one with increasing the topological charge. [ABSTRACT FROM AUTHOR]

A wideband circularly polarized (CP) stacked rectangular dielectric resonator antenna (RDRA) is proposed in this article. The 3 dB axial ratio (AR) and 10 dB impedance bandwidth overlap of more than 66% is obtained. For increased bandwidth, the antenna comprises two dielectric resonators separated by an air gap. The upper dielectric layer is rotated at ∠45∘ $\angle 4{5}^{\circ }$ relative to the lower layer to obtain orthogonal modes for CP Both layers have dielectric constant εr=9.8 ${\varepsilon }_{r}=9.8$. The rotation aids excitation of orthogonal modes TEδ11x∕TE1δ1y,TEδ31x∕TE3δ1y $T{E}_{\delta 11}^{x}\unicode{x02215}T{E}_{1\delta 1}^{y},T{E}_{\delta 31}^{x}\unicode{x02215}T{E}_{3\delta 1}^{y}$, and TEδ21x∕TE1δ2y $T{E}_{\delta 21}^{x}\unicode{x02215}T{E}_{1\delta 2}^{y}$ in RDRA. The higher‐order modes generate left‐hand circular polarization at frequencies 6.75, 7.8, and 10.7 GHz, respectively. The upper layer consists of three holes giving a 10 dB impedance bandwidth of 66.7% from 6.52 to 11.02 GHz. The CP gain of 8.7, 6.8, and 6.4 dBi for 6.75, 7.8, and 10.7 GHz, respectively, is measured. The conformal orthogonal feeds enable a 72% $ \% $ 3 dB AR bandwidth across the entire frequency band. The radiation efficiency is observed above 89% $ \% $ in the entire band (6.5–11 GHz). This work demonstrates a 66.7% $ \% $ overlap of 10 dB impedance and 3 dB AR bandwidth along with high gain in a single design which is suitable for 5G applications in C‐band as well as other X‐band applications. [ABSTRACT FROM AUTHOR]

The recent breakthrough in integrating single quantum emitters to dielectric metasurfaces opens up avenues in quantum technologies with the possibility to obtain on‐demand single photon sources and efficient spin–photon interface. All‐dielectric metasurfaces with unprecedented possibilities of generating directional light scattering instigated a novel concept of the Kerker effect that led to applications in nanophotonics. Here, an all‐dielectric metasurface consisting of silicon‐like nanodisks with square lattice symmetry that exhibits Kerker condition governed by constructive interference of multipoles optimized for the zero‐phonon line (ZPL) of negatively charged nitrogen‐vacancy (NV‐) center at a wavelength of 640 nm is discussed. The phase and amplitude of excited multipolar moments are manipulated by varying the geometrical parameters of the metasurfaces. The constructive interference between multipolar moments generates a Kerker condition, which is tunable by varying the diameter, thickness, refractive index of nanodisks, and substrate refractive index. The Kerker condition is further used to control the emission from a single NV‐ center and a Purcell enhancement of 300 times is achieved at 640 nm. The study profoundly explores new insights into quantum metasurfaces and paves a new way to utilize dielectric resonators with emitters as on‐chip quantum light sources at Kerker condition. [ABSTRACT FROM AUTHOR]

In this paper, a slotted frustum-shaped $ 4\times 4 $ 4 × 4 multiple-input multiple-output (MIMO) dielectric resonator antenna (DRA) is designed and developed for portable 5G Wi-Fi ( $ 5.15{-}5.85\, {\rm GHz} $ 5.15 − 5.85 GHz ) applications. The DRA is excited by $ HEM_{11\delta } $ HE M 11 δ and $ HEM_{21\delta } $ HE M 21 δ modes. A slotted right-angle frustum-shaped (SRFS) structure of alumina material as a dielectric resonator (DR) is positioned on the ground plane of the FR4 substrate to design a DRA. Based on the designed DRA, a compact ( $ 2.57\, \lambda _g\times 2.57 \,\lambda _g $ 2.57 λ g × 2.57 λ g , where $ \lambda _g $ λ g is guided wavelength and calculated at a lower cut-off frequency, $ 5.0\, {\rm GHz} $ 5.0 GHz , for $ \epsilon _f $ ϵ f of $ 4.4 $ 4.4) $ 4\times 4 $ 4 × 4 MIMO antenna with high isolation of greater than $ 27.13\, {\rm dB} $ 27.13 dB (from $ 5.0 $ 5.0 to $ 6.1\, {\rm GHz} $ 6.1 GHz ) and $ 24.3\, {\rm dB} $ 24.3 dB (from $ 6.1 $ 6.1 to $ 6.25\, {\rm GHz} $ 6.25 GHz ) is proposed. The developed MIMO antenna's measured working frequency ranges from $ 5.0 $ 5.0 to $ 6.25\, {\rm GHz} $ 6.25 GHz , with an impedance bandwidth, $ BW_i $ B W i of $ 22.22\% $ 22.22 % , peak gain, $ G_P $ G P of $ 5.85\, {\rm dBi} $ 5.85 dBi and an average peak gain, $ G_{av} $ G av of $ 5.25\, {\rm dBi} $ 5.25 dBi . The calculated MIMO antenna's diversity performance parameters, channel capacity loss $ (C_{CL}^{ij}) $ (C CL ij) , diversity gain $ (D_G^{ij}) $ (D G ij) , envelop correlation coefficient $ (E_{CC}^{ij}) $ (E CC ij) , mean effective gain $ (M_{EG}^i) $ (M EG i) , total active reflection coefficient $ (T_{ARC}) $ (T ARC) , and channel capacity $ (C_C) $ (C C) are obtained as $ { \lt }0.17\, {\rm bits}/{\rm sec}/{\rm Hz} $ < 0.17 bits / sec / Hz , $ { \gt }9.99 \, {\rm dB} $ > 9.99 dB , $ { \lt }0.0301 $ < 0.0301 , $ { \lt }-6.06\, {\rm dB} $ < − 6.06 dB , $ { \lt }-12.5\, {\rm dB} $ < − 12.5 dB , and $ { \lt }21.6\, {\rm bits}/{\rm sec}/{\rm Hz} $ < 21.6 bits / sec / Hz , respectively. The agreement between the simulation and measurement results is found to be remarkably consistent. [ABSTRACT FROM AUTHOR]

In the design of circularly polarized (CP) dielectric resonator antenna (DRA) arrays, the regular-shaped DRAs with simple feeding configurations are mostly used as array elements to make the design procedure more efficient. However, such an array element DRA usually achieves only about 6% axial ratio (AR) bandwidth. In this design, a CP DRA element coupled by a fractal cross-slot which can radiate efficiently and excite the rectangular DRA simultaneously is considered. By adjusting the dimensions of the fractal cross-slot properly, the resonances of the fractal cross-slot and the dielectric resonator can be merged to obtain a wider AR bandwidth. Based on the proposed fractal cross-slot-coupled CP DRA element, three different CP DRA arrays are designed: a 4 coupled DRA array of parallel power divider without T-bend, a 4 coupled DRA array of parallel power divider with Miter bend and a 4 coupled DRA array of 2 set power divider with Miter bend. The designed DRA arrays are fabricated and measured, and structures and performances of the arrays are presented and discussed. [ABSTRACT FROM AUTHOR]

The integration of dielectric resonator antennas (DRAs) with conventional antennas appears to be a suitable technique for enhancing bandwidth and gain in present day communication systems. The dielectric resonators themselves are low loss materials in the microwave frequency range, possessing properties which improve the performance of antennas. Combined with a more traditional antenna, the patch or dipole, for instance, the capability of the two antennas together simply enhances the features of the two separate sources. DRAs can enhance efficiency, yield wider bandwidth, and optimize radiation patterns compared to conventional antennas, which offer tested structures of consistently performing their tasks. This combination makes it possible to design smallsized, high-gain efficient antennas, mainly suitable for applications, which demand a wide operating frequency range, including the 5G, satellite communication technologies, radars, etc. Further, DRAs enable reduction of conductor losses while improving gain and efficiency, especially when operating at higher frequencies. It also provides a higher degree of freedom in designing the antenna, because the performance can be optimized to meet certain needs like compact size or being multiband. As the requirements for new generation of complex communication systems with high-gain and wideband antennas continue to increase, this research creates a new concept to integrate the dielectric resonators and conventional antennas. [ABSTRACT FROM AUTHOR]

Machine to Machine communication or Internet of things are emerging fields of communication. To support such technologies advanced electronics like wearable devices are popular field of research. The proposed Button shaped wearable Cylindrical Dielectric Resonator Antenna (CDRA) is specially designed to support IoT applications at 2.4 GHz band. The planer section of the DR antenna is developed over FR4 substrate and Dielectric resonator consists of Alumina material. An Aperture coupled feed is used to excite the antenna. There are two holes arranged on the structure such that it can be easily placed over any upper outfit like jacket or coat. To investigate the performance of the proposed wearable DRA over the body and to identify the best portion of the body where the antenna can be worn, the simulation has been done on three different phantoms of different age groups and gender on CST voxel phantom models. To analyse the performance four important parameters reflection coefficient, gain, radiation pattern, and bandwidth are selected. It is discovered that the button-shaped wearable CDRA well satisfies the performance requirements for IoT applications at 2.4 GHz band. Finally, the proposed antenna is developed and its performance has been measured. The measured output and the simulated results have been found to be in good agreement. [ABSTRACT FROM AUTHOR]

High-radio-frequency (RF) conductivity is required in advanced electronic materials to reduce the electromagnetic loss and power dissipation of electronic devices. Graphene/copper (Gr/Cu) multilayers possess higher conductivity than silver under direct current conditions. However, their RF conductivity and detailed mechanisms have rarely been evaluated at the micro scale. In this work, the RF conductivity of copper–copper (P-Cu), monolayer-graphene/copper (S-Gr/Cu), and multilayer-graphene/copper (M-Gr/Cu) multilayer structures were evaluated using scanning microwave impedance microscopy (SMIM) and dielectric resonator technique. The results indicated that the order of RF conductivity was M-Gr/Cu < P-Cu < S-Gr/Cu at 3 GHz, contrasting with P-Cu < M-Gr/Cu < S-Gr/Cu at DC condition. Meanwhile, the same trend of M-Gr/Cu < P-Cu < S-Gr/Cu was also observed using the dielectric resonator technique. Based on the conductivity-related Drude model and scattering theory, we believe that the microwave radiation can induce a thermal effect at S-Gr/Cu interfaces, leading to an increasing carrier concentration in S-Gr. In contrast, the intrinsic defects in M-Gr introduce additional carrier scattering, thereby reducing the RF conductivity in M-Gr/Cu. Our research offers a practical foundation for investigating conductive materials under RF conditions. [ABSTRACT FROM AUTHOR]

We demonstrate a low-loss dielectric microwave resonator with an internal quality factor of 2.30 × 10 4 while accommodating optical apertures with a diameter of 8 mm. The two seemingly conflicting requirements, high quality factor and large optical apertures, are satisfied, thanks to the large dielectric constant of rutile ( TiO 2 ). The quality factor is limited by radiation loss, and we confirmed by numerical simulation that this radiation loss can be suppressed by extending the enclosure height of the resonator; the resonator can potentially achieve a dielectric loss-limited quality factor, exceeding 106. Using this resonator, we performed both continuous-wave (cw) and pulse electron spin resonance (ESR) spectroscopy on 2,2-diphenyl-1-picrylhydrazyl (DPPH) crystalline powder and P1 centers in a diamond crystal in a dilution refrigerator. The cw ESR spectroscopy demonstrated high-cooperativity and strong spin-resonator coupling with the DPPH and P1 centers, respectively, while the pulse ESR spectroscopy successfully measured longitudinal and transverse relaxation times. This optically accessible low-loss microwave resonator enables the implementation of a spin-based quantum device, such as a microwave-optical photon transducer. [ABSTRACT FROM AUTHOR]

Summary: This study introduces a novel sensor for glucose measurement based on a rectangular dielectric resonator (RDR) excited by a rectangular slot fed by a 50‐Ω microstrip line. The RDR operates at 6 GHz and incorporates a cubic portion section for accommodating a finger or container containing the test sample. By utilizing the distinctive resonant frequencies associated with varying dielectric permittivity of different glucose concentrations, the proposed RDR functions as a reliable sensor. The sensor's performance is evaluated through a 3D electromagnetic model of the human thumb and the application of the Cole‐Cole method for modeling the blood layer. Experimental validation is conducted using three alternatives (water, glucose, and alcohol) and a range of glucose concentrations (70 to 2000 mg/dL) in simulation. During experimental verification, an invasive glucometer is employed as a reference for blood sugar levels. Results demonstrate that the proposed RDR sensor exhibits higher sensitivity (36.86 MHz/(mg/dL)) than other sensor counterparts. The experimental outcomes confirm the resonance frequency alignment between the manufactured sensor and the simulated projections. Considering its economic viability and applicability, this sensor represents a promising alternative biosensor for monitoring blood glucose levels. [ABSTRACT FROM AUTHOR]

With the emergence of 5G–6G communication technology, the miniaturization and integration of electronic components are crucial. Ba3Ti4Nb4O21 (BTN) ceramics with hexagonal structures have attracted special attention due to their high dielectric constant, which shows greater application potential in communication base stations and dielectric resonators. However, its high sintering temperature and low‐quality factors also greatly limit the application field. In this paper, boric acid (H3BO3) as a dopant, was used to investigate the influence on the structure, microstructure, Raman spectrum, and microwave properties for Ba2.92Cu0.08(Zn1/3Nb2/3)2Ti2Nb4O21 (BCZTN)‐xHB (0.25≤x≤1.25 wt%) ceramics. The results reflected that H3BO3 was an effective additive, which could promote ceramic densification, accelerate grain growth and uniform distribution, and enhance its microwave performance. Among them, high densification was 93.92 ± 0.35%, and the Q × f value ∼16981 ± 340 GHz at x = 0.75, was more than 2∼3 times higher than other BTN‐based ceramics. Superior microwave dielectric properties were achieved for 0.75 wt% H3BO3‐doped BCZTN ceramic sintered at 900°C: εr∼42.35 ± 0.48, Q×f∼16981 ± 340 GHz, and τf∼40.02 ± 1.43 ppm/°C. More encouragingly, BCZTN‐0.75HB ceramic did not chemically react with Ag, which suggested that it had the potential to be a candidate material for low‐temperature co‐fired ceramics base station communication devices. [ABSTRACT FROM AUTHOR]

This paper presents a compact multiple-input multiple-output (MIMO) two-element dielectric resonator antenna (DRA) for wideband (WB) and ultra-wideband (UWB) operations. The dielectric resonators (DRs) are fabricated on the top side of the low-cost substrate (FR4) and the etched ground plane on the bottom of the substrate. Featuring two compact U-shaped DRs with a U-shaped defective ground surface (DGS) it has a wide impedance bandwidth of 112.84% (3.02–10.88 GHz). When the diode is connected between U-shaped metallic parasitic strips and the feedline edge, it provides a wide impedance bandwidth of 23.62% (5.6–7.1 GHz). Two parasitic metal elements are placed on the upper surface of the DR to improve the transmission coefficient better than −22 dB between the two ports. This compact antenna has a total volume of 4704.55 mm3 (29 × 29 × 5.594). The proposed MIMO DRA has WB and UWB features, making it easy to monitor and detect signals in the environment. [ABSTRACT FROM AUTHOR]

A novel dual band tunable terahertz (THz) circularly polarized dielectric resonator antenna (CPDRA) is designed and numerically studied. Hybrid Silicon-Graphene materials are employed as radiator with cross-slot shaped aperture coupled feed, enabling tunable linearly and circularly polarized radiation. Silicon is a good material as dielectric resonator with its operation in the THz regime due to lack of absorption, cheaper to grow and machine. Cross shaped slots of appropriate dimensions are engraved in the centre of the ground plane to split the fundamental mode of the rectangular DR into two near degenerate orthogonal modes having quadrature phase difference. As a result, circular polarization is obtained in the upper passband. Introducing cross slot also helped to improve the impedance matching and dual band operation is achieved with linearly polarized response in lower band and circularly polarized response in the upper band. By adjusting the chemical potential of graphene, frequency tunability in the both the operating bands is obtained, without changing the physical geometry of the antenna. The proposed antenna operates with 10 dB impedance bandwidth of 4.24 \% (2.31–2.41 THz) and 12.1 \% (3.11–3.51 THz) and 3 dB axial ratio bandwidth of 3.54 \% (3.33–3.45 THz). The antenna parameters are calculated and gain of 6.11 dBi and 5.8 dBiC in lower and upper band, respectively and radiation efficiency of 96.5 \% in both operating bands is obtained. This hybrid radiator-based THz CPDRA shows great potential in the development of tunable THz devices and could pave a path for new researchers. [ABSTRACT FROM AUTHOR]

The application of ceramic for a circularly polarized (CP) filtering antenna is studied in this paper. The dielectric resonator (DR) of sintered aluminum oxide (Al 2 O 3) ceramic has a dielectric constant of 9.5 and low dielectric loss of 0.003, and excellent mechanical properties. The dielectric resonator antenna (DRA) consists of two parts, the upper part is a DR, and the lower part uses a feeding network containing two hairpin bandpass filters. The measured | S 11 | of the DRA is 48.0 % and the axial ratio (AR) bandwidth is 33.5 %. Meanwhile, the peak gain of the DRA is 6.13 dBi, and the suppression level across the stopband exceeds 15.2 dB. The DRA uses the hairpin bandpass filters to improve the filtering characteristics of the antenna and uses the corner-cutting processing of the DR to improve the AR, which can be implemented to reduce the cost of fifth-generation (5 G) communication. [ABSTRACT FROM AUTHOR]