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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]

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]

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]

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 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]

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]

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]

A high-tuning range frequency reconfigurable dual-band compact cylindrical Dielectric Resonator Antenna (DRA) for 5 G Sub 6 GHz applications is presented in the proposed work. The work presented here provides compactness, frequency reconfigurability (FR), and dual-band. FR is obtained through two PIN diode switches, which operate in ON-ON, ON-OFF, OFF-ON, and OFF-OFF configurations and offer a maximum wide tuning range and a total spectrum of 44.44% and 71.49%, respectively. In the cylindrical DRA, the ${\rm{HE}}{{\rm{M}}_{11{\rm{\delta }}}}$HEM11δ and ${\rm{HE}}{{\rm{M}}_{12{\rm{\delta }}}}$HEM12δ modes create dual-band, while the hybrid structure and higher order mode excitation yield compactness. [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]

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]

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]

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]

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]

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]

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]

In high-frequency electronics, optimizing RF oscillators performance is essential, especially as applications reach into wide frequency bands. This article describes proposed clock generators for UWB sensor systems based on oscillators with dielectric resonator (DRO). Evaluation boards with different sizes of microstrip conductors were developed and tested, based on which new versions of boards were created. Improvements were made to integrate the DRO into a shielded box to ensure minimal external interference. The final designs demonstrated stable operation with low phase noise λ (1 MHz) = -108.805 dBc at fc = 21.732 GHz, sufficient power (3.65 dBm) and low power consumption(56 mW). [ABSTRACT FROM AUTHOR]

This paper presents the design of a two-port dual-band dual-circularly-polarized dielectric resonator antenna (DRA). The proposed DRA is formed by stacking two dielectric resonators (DRs) of different shapes, including a hexagonal DR on top and a cross-shaped DR on the bottom. It is designed to resonate at two near-degenerate orthogonal modes of TE111 and TE113, and an aperture-coupled feeding through a cross-like slot is used to achieve dual-band impedance matching simultaneously for right- and left-handed circular polarizations. Tests were conducted on a prototype working in C-band to verify the design concept. The experiment results demonstrate that the proposed DRA has exceptional performance with measured −10 dB reflection bandwidths of 24.4% and 17.4%, 3 dB axial ratio bandwidths of 21.2% and 16.3%, and maximum gains of 5.64 and 8.13 dBic for the lower and upper bands, respectively. Moreover, the measured channel isolation is more than 15.8 dB. The results obtained from the experiments show good agreement with the simulation, and hence, it can be concluded that the proposed DRA is a promising solution that can be used for various wireless communication applications. [ABSTRACT FROM AUTHOR]

In this Paper, a low-profile circularly polarized (CP) chamfered rectangular dielectric resonator antenna (RDRA) is designed and investigated for radio frequency energy harvesting (RFEH) applications. The proposed modified RDRA comprises of dielectric resonator (DR) made up of Alumina material (εr = 9.9) mounted on the PEC ground plane. Dual unequal triangular-shaped vertical slits are engraved on the rectangular DR for generating the orthogonal modes with CP characteristics. The optimized antenna offers an impedance bandwidth (IBW) of 51.4% (2.25–3.81 GHz) and axial ratio bandwidth (ARBW) of 14.8% (3.25–3.77 GHz), respectively. The peak realized gain and maximum radiation efficiency are 7.18 dBi and 97.8% in desired frequency bands. Due to the wide impedance and AR bandwidths with realized gain and radiation efficiency, the optimized antenna is suitable for integration with a rectifier circuit for RF energy harvesting applications. A rectifier circuit with a single shunt diode topology is also designed for rectification purposes. The rectifier achieved 67.16% RF-DC power conversion efficiency (PCE) at 3.5 GHz and 5dBm input power. At 0dBm input power, the rectifier achieved 60.26% PCE. The effective input power range, during which the PCE maintains above 50%, is calculated to be 15.2 dBm from −3.5 to 11.7 dBm. [ABSTRACT FROM AUTHOR]

Designing and fabricating antennas that exhibit low losses and are compact, lightweight, and highly radiation efficient are challenging in the wireless‐communication field. In this study, we simulated and fabricated microstrip patch antennas using β‐CaSiO3 low‐temperature co‐fired ceramic (LTCC) as dielectric resonator substrate. Compact ceramics that show good microwave dielectric properties (a relative dielectric constant [εr] of 6.57, high‐quality factor [Q × f] of 35 086 GHz [@14.85 GHz], and temperature coefficient of frequency [τf] of −33.56 ppm °C−1 for the optimal composition) were obtained when Li2O–CaO–B2O3–CuO glass was added to β‐CaSiO3 and sintered at 950°C. The high‐frequency properties of these composite ceramics reveal that the dielectric constant and dielectric loss are stable in the 38−58 and 70−90 GHz ranges, respectively. Furthermore, a circularly polarized antenna fabricated using a CaSiO3‐based ceramic shows a high radiation efficiency (92.04%) and gain (3.35 dBi) at a center frequency of 2.5 GHz. These β‐CaSiO3 composite ceramics offer promising prospects for high‐frequency use as well as in mobile communication applications. This study provides insight for the development of innovative antennas with new LTCC materials. [ABSTRACT FROM AUTHOR]

This paper proposes an idea of the use of Dielectric Resonators (DRs) as concentrators of alternating magnetic fields for plasma density control applications. The study involves numerical simulations using the Method of Auxiliary Sources (MAS) to analyze Dielectric Frequency Selective Surfaces (DFSS) composed of periodic dielectric elements. Materials with variable dielectric permittivities, including E-Glass, Plexiglass, Taconic CER-10, and Teflon are considered, and their resonance properties are investigated. Results indicate that DFSSs can create strong magnetic fields at resonance frequencies, which can be utilized for plasma density regulation in processes like thin film deposition. The results demonstrate that materials with lower dielectric permittivity, such as Plexiglass and Teflon, exhibit higher resonance quality factors, while higher permittivity materials like E-Glass and Taconic CER-10 show poorer quality factors. The study emphasizes the potential of DFSSs in enhancing plasma density and improving industrial applications, highlighting the importance of precise geometric configurations and material properties in designing effective dielectric resonators.

Hybrid metasurfaces are made of metals and dielectrics in which dielectrics (metals) are sandwiched between metals (dielectrics) to control the reflection and transmission of light. The existing designs have low sensitivity, little color coverage, and a lack of flexibility. Here, a new structural color design is proposed in which metals and dielectric resonators are arranged spatially in 2D to form a lateral hybrid system, instead of being placed as layers. Such a design exhibits a high level of sensitivity to mechanical forces because it works via 2D optical coupling and light confinement between adjacent resonators. Our study shows that in-planar coupling of two dissimilar resonators can enhance sensitivity by an order of magnitude in comparison to stacking them. Metasurfaces with our design would have unprecedented mechanical tunability without compromising either the materials choice or processing. Using the proposed hybrid system, we demonstrate large tunability across the full range of colors with only a 10% change in the size of the lattice, which further proves its superiority over existing designs. This concept could find application in wearable devices that require high sensitivity to small mechanical fluctuations. [ABSTRACT FROM AUTHOR]

The coherent perfect absorption (CPA) occurring in the graphene sheet suspended in air can be utilized to develop an ultrathin, ultra-broadband absorber working in the frequency range from a few hertz (Hz) to terahertz (THz) with perfect absorption. A graphene sheet is studied to induce the CPA to cover radio, microwave and lower THz frequency ranges. A graphene resonator able to provide the surface plasmon resonance (SPR) is combined with the graphene sheet to provide CPA at either side of a thin dielectric layer forms metamaterial structure with the cavity and enhances the absorption bandwidth in the THz region by creating a resonance near quasi-CPA frequency. A dielectric silicon resonator is embedded in the structure, which creates dipolar resonances between the resonances obtained by the formed cavity between the graphene sheet and resonator. This enhances the absorption level in the THz region. The absorption bandwidth is further enhanced to 7 THz by including a graphene disc at the top of the silicon resonator. Thus, the multiple multi-order resonances occurring in the silicon dielectric and SPR of graphene resonators are merged with the phenomena of CPA occurring in the graphene sheets to extend the CPA bandwidth in the THz regime. The doping level of graphene or its tunable Fermi energy based on the applied DC electric field provides the tunability in the total obtained absorption bandwidth. The symmetric structure provides polarization-insensitive behavior with an allowed incident angle of more than 45° with more than 90% absorption. [ABSTRACT FROM AUTHOR]

Physical features of spatial-energy characteristics of linearly polarized THz laser beams at sharp and moderate focusing in free space are analyzed both theoretically and experimentally. The Rayleigh-Sommerfeld vector theory is used to model propagation of laser beams excited by quasi-optical waveguide resonator modes in free space. Well-known methods of measuring spatial-energy characteristics of laser beams in the THz range are used in the experimental study. It is shown that the intensity of the total electric field of both combined TE0n + EH2n and EН-1n + EH3n modes (n = 1, 2, 3) in the focal region is defined by all three components and has a dip on the axis for both focusing types. The central maxima of the field of these modes become significantly shifted from the geometric foci of the lenses used as the order n of these modes increases. The EН-11 + EH31 mode has the smallest diameter (2.94λ) of the focal spot in the maximum intensity region at sharp focusing. The TE01 + EH21 mode has the smallest diameter (13.65λ) of the focal spot at moderate focusing. [ABSTRACT FROM AUTHOR]

A high gain D‐band hybrid integrated on‐chip antenna (OCA) based on a low‐cost printed circuit board (PCB) packaging technology is analyzed and designed in a standard 40‐nm CMOS process in this paper. The proposed OCA is a hybrid structure of a slotted patch OCA with off‐chip PCB ground and off‐chip dielectric resonator (DR). The proposed OCA exhibits a simulated gain of 3.5 dBi and 53% radiation efficiency at 150 GHz. The simulated impedance bandwidth is 20 GHz. The radiation performance and impedance bandwidth of the OCA are observably improved with the proposed techniques. The proposed OCA occupies 0.52 × 0.56 mm2, and addresses the highly desirable yet challenging overall design of future low‐cost integrated millimeter‐wave (mm‐Wave) and terahertz (THz) systems, which hit the mark on cost and compatibility. [ABSTRACT FROM AUTHOR]

The design of three‐dimensional (3D)‐printed heterogeneous ceramics exhibiting isotropic and anisotropic dielectric permittivities at microwave frequencies is studied for dielectric resonator antenna (DRA) applications. The heterogeneous ceramics are engineered by using periodic structures made up of subwavelength unit cells filled with zirconia ceramic and air. Ceramic stereolithography (CSLA) allows the 3D printing of a one‐piece ceramic block mixing isotropic and anisotropic dielectric regions. In order to demonstrate the possibility of exploiting such 3D‐printed ceramics, a singly fed dual‐band circularly polarised DRA is presented. To achieve circular polarisation at both bands, the relative permittivity of the dielectric resonator is locally controlled by introducing anisotropic dielectric regions. The 3D‐printed DRA is finally measured, and its results agree well with the simulations. [ABSTRACT FROM AUTHOR]

Summary: In this communication, a dielectric resonator based dual‐port radiator is designed. Loading of meta‐surface over the dual‐port antenna creates two important features that make it unique to the proposed design: (i) conversion of the linear polarized plane waves into circularly polarized plane wave (ii) improve the isolation between the antenna port by more than 30 dB. Experimental measurement confirms that proposed design is working in the frequency range 5.14–5.55 GHz, and a 3‐dB axial ratio is produced from 5.36 to 5.45 GHz. Stable radiation pattern and good value of diversity performance are also achieved in the proposed radiator. All of these characteristics make the developed radiator appropriate for WLAN (5.4 GHz) applications. [ABSTRACT FROM AUTHOR]

Symmetry breaking plays a crucial role in understanding the fundamental physics underlying numerous physical phenomena, including the electromagnetic response in resonators, giving rise to intriguing effects such as directional light scattering, supercavity lasing, and topologically protected states. This work demonstrates that adding a small fraction of lossy metal (as low as 1 × 10−6 in volume) to a lossless dielectric resonator breaks inversion symmetry (IS), thereby lifting its degeneracy, leading to a strong bianisotropic response. In the case of the metasurface composed of such resonators, this effect leads to unidirectional perfect absorption while maintaining nearly perfect reflection from the opposite direction. It has developed more general Onsager‐Casimir relations for the polarizabilities of particle arrays, taking into account the contributions of quadrupoles, which shows that bianisotropy is not solely due to dipoles, but also involves high‐order multipoles. The experimental validation demonstrates an extremely thin terahertz‐perfect absorber with a wavelength‐to‐thickness ratio of up to 25,000, where the material thickness is only 2% of the theoretical minimum thickness dictated by the fundamental limit. The findings can pave a new route to design devices for applications involving optical‐to‐heat conversion processes. [ABSTRACT FROM AUTHOR]

This work proposes a complementary concentric open-ring microwave resonator sensor for accurate sensing of the electrical properties of soil and its moisture content. The device operation for microwave S-band at 3.1 GHz allows lower phase-dependent measurements for the accurate estimation of the dielectric constant. The device is fabricated on an RO48350B substrate of $ {\varepsilon _r} = 3.48 $ ε r = 3.48 and the corresponding results were found to close match the electromagnetic simulation data. Silt soil and red soil were tested and analysed up to 21% percentage of the moisture level. Transmission coefficient ( $ \mathrm{\Gamma } $ Γ )-based numerical technique was used to extract the dielectric constant of different soil samples. The proposed sensor design is also tested for on-field measurements of soil and moisture level from different soil surface depth has been extracted. [ABSTRACT FROM AUTHOR]

A dielectric‐loaded slot antenna with the characteristic of broadband, low profile, and low cross‐polarization is presented. The antenna incorporating a low permittivity (εl=4.1 ${\varepsilon }_{l}=4.1$) and multiple high permittivity (εh=22 ${\varepsilon }_{h}=22$) rectangle dielectric is fed by two rectangle slot, which generates three slot modes and achieves measured 10 dB impedance bandwidth of 88% $ \% $ from 1.57 to 4.04 GHz covering the long term evolution (1.71–2.69 GHz) and sub‐6G (3.3–3.6 GHz). Furthermore, the presented slot antenna with a footprint of 0.81 × 0.56λ02 ${\lambda }_{0}^{2}$ and a low profile of 0.09λ0 ${\lambda }_{0}$ (λ0 ${\lambda }_{0}$ is the wavelength in the air region at the center frequency) appears the performance of measured peak gain of 9 dB without using any dielectric resonator mode. On the basis of the single‐polarized design, the dual‐polarized design with a profile of 0.09λ0 ${\lambda }_{0}$ is investigated and fabricated. According to the measured results, the dual‐polarized prototype achieves a 10‐dB impedance of 60% $ \% $ from 1.6 to 3 GHz. [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.

Perfect magnetic mirrors are important optical devices for the development of novel optical detectors, solar cells, and imaging devices. They have the property of only reversing the magnetic field of a light wave upon reflection, for instance, in functional optical metasurfaces. To design an optical magnetic mirror, high-refractive-index dielectric nanostructures that support strong magnetic dipole (MD) response in the optical wavelength range are used. However, the spectral overlap between the MD and electric dipole in dielectric resonators degrades the magnetic mirror reflection. Here, we propose and demonstrate a perfect optical magnetic mirror metasurface that totally reflects an incident wave without electric field phase change. In this perfect magnetic mirror, the electric dipole radiation is completely suppressed by the radiation of the anapole mode in the spectral range where the destructive interference between the electric dipole and toroidal dipole occurs. By fine-tuning the size parameters of the dielectric resonators, we show near-perfect MD scattering as a result of the spectral overlap between MD resonance and anapole mode. The optical magnetic mirror can be tuned from the visible to near-infrared range by scaling the sizes of the resonators. The MD scattering resonators promote the perfect magnetic mirror, a promising platform for designing photodetectors, biological sensors, and reflected waveplates. [ABSTRACT FROM AUTHOR]

High-contrast gratings (HCGs) based spoof surface plasmon polaritons (SSPPs), as a new kind of SSPPs, have been proposed recently. Here, we study their particular mechanism and characteristics by comparing them with traditional metal-type SSPPs. The different fundamental dielectric resonator modes decided by the height–length ratio R of the dielectric element are found to be the key factor of the mechanism, leading to new characteristics and providing more working modes. In low R mode, HCG-based SSPPs can work under deep-subwavelength thickness and can be easily excited by free space wave and, thus, are considered to be applied to all-dielectric metamaterial absorbers (ADMMAs). Simulations and analysis confirm the microwave absorption effect of HCG-based SSPPs as a new mechanism of ADMMAs. Based on this, a carbon black based ADMMA is designed and the simulation and experimental results verify the important role of HCG-based SSPPs in broadband absorption. It is expected that this work can give rise to further and wider studies on the characteristics and applications of HCG-based SSPPs. [ABSTRACT FROM AUTHOR]

In this study, several performance analyses are conducted on all-dielectric absorbers composed of cylindrical-, elliptical-, square-, rectangular-, hexagonal-, and octagonal-shaped dielectric resonators. These performance analyses include the numerical investigation of the change in the resonance frequency and the absorption peak level with respect to the changes in dielectric constant and loss tangent, respectively, in the WR-284 rectangular waveguide setup. In addition, the designed structures are also analyzed in a free-space simulation setup to present the differences that come from using different boundary conditions and excitations. The analyses reveal that the absorption spectra behaviors are similar in response to changes in dielectric constants and loss tangents among the studied geometries. Absorption peak levels of the observed higher-order resonance modes are highly dependent on the resonator geometry. On the other hand, the free-space simulation results reveal that the designed structures have negligible cross-polarization components, hence they do not practically contribute to the absorption spectra. Moreover, absorption, reflection, and transmission spectra are highly affected by differences in the simulation setup and accordingly by the excitation signal for all resonator geometries. In addition, the behavior of the absorption spectra for all the dielectric resonator geometries is investigated under the oblique incident wave for TE and TM modes. It has been noticed that the absorption spectra are nearly independent of the angle at lower incident angle values. It is believed that these analyses will contribute to the sensor studies based on all-dielectric absorber designs. [ABSTRACT FROM AUTHOR]

The method of evaluating the resonant frequencies of multilayered resonator containing demagnetized ferrites is presented. The detailed solution of Maxwell's equations for such a structure by means of the radial modes matching method for TE0mn modes is given. The results of calculations using developed and launched computer program are given. Results of calculations are compared with those obtained by other method using CST simulator. These results are in close agreement, which proves the correctness of the method. The developed solution, and the software program can be used to measure the initial permeability of ferrites. [ABSTRACT FROM AUTHOR]