Dielectric Elements Research Articles

On the τf measurement of microwave dielectric ceramics

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

Monolithically integrated wide field-of-view metalens by angular dispersionless metasurface

Meta-lenses, which are made by sub-wavelength metallic or dielectric elements, have attracted widespread attentions due to its unprecedented electromagnetic wave manipulation abilities and novel applications. Dissimilar to previous metalens doublet by all-dielectric metasurfaces in the optical band, an innovative and more robust approach by angular dispersionless meta-atom to directly eliminate aberrations in low spectrum is proposed. As a proof of concept, an elaborately selected singlet metallic resonator for simultaneously high transmission, full phase coverage and the ignored angular dispersion is presented in the microwave. The designed metalens with only one single phase gradient profile can focus wide field-of-view (FOV) incident waves of ± 40° with both a large numerical aperture of 0.56 (NA = 0.56) and high focusing efficiency of 53 % on average at microwave regime. The metalens is also fabricated by a single-step printed circuit board technique and the measured high-performance focusing are also achieved for the entire FOV. The presented on-chip and integrated wide FOV metalens provides a simple yet cost-effective method to develop wide-angle metalenses especially in low frequency band where plasmonic metasurfaces are commonly adopted. Besides, its excellent wide-angle focusing performances can satisfy diverse applications in modern radar engineering such as imaging, sensing, communications and detection, etc.

Numerical optimization of dielectric properties to achieve process uniformity in capacitively coupled plasma reactors

This paper presents the results of our numerical analysis to optimize the dielectric properties to achieve process uniformity in the thin film deposition process using capacitively coupled plasma. The difference in the plasma density distribution was analyzed by changing the wafer material from silicon to quartz (or Teflon). Similarly, aluminum was compared with aluminum nitride as the electrode material, and the sidewall material was varied from quartz to a perfect dielectric to study the effect on the plasma characteristics. A two-dimensional self-consistent fluid model was used to analyze the spatial distribution of the plasma parameters. In terms of the process conditions, the gas pressure was set to 400 Pa, the input power was fixed to 100 W, and a radio frequency of 13.56 MHz was used. SiH4/Ar was used as the gas mixture, and these conditions were used as input for numerical simulations of the deposition state of the hydrogenated amorphous silicon layer. The radial spatial distribution of plasma parameters was confirmed to be modified by dielectric elements with low dielectric constants regardless of the type of element. Despite the thin wafer thickness, the use of a wafer with low permittivity weakens the electric field near the electrode edge due to the stronger surface charging effect. Additionally, by changing the material of the sidewall to a perfect dielectric, a more uniform distribution of plasma could be obtained. This is achieved as the peak values of the plasma parameters are located away from the wafer edge. Interestingly, the case in which half of the sidewall was specified as comprising a perfect dielectric and the other half quartz had a more uniform distribution than the case in which the sidewalls consisted entirely of a perfect dielectric.

Fractal Cross-Slot-Coupled Antenna with Dielectric Resonator Elements having Circular Polarization

This article presents the design and analysis of an “ultra-wideband (UWB)” Fractal Cross-slot-Coupled Antenna with “Dielectric Resonator Elements (DREs)” exhibiting circular polarization and band-notched characteristics. The proposed antenna aims to reject the frequency range of 5.1 GHz to 5.9 GHz while maintaining high impedance bandwidth and radiation efficiency. A coplanar waveguide feeds the planar UWB antenna, featuring a narrow slot on the radiating element and a dielectric resonator mounted on top. Simulation results demonstrate excellent performance in terms of impedance bandwidth and radiation efficiency. To further improve the design for wireless applications, Fractal-slot-aperture coupled DRE antennas are employed. The proposed configuration takes into account the radiative efficiency and concomitant excitation of the rectangular DRE by a “Circularly Polarized Dielectric Resonator Antenna (CPDRA)” coupled through a fractal cross-slot. By appropriately adjusting the fractal cross-slot size, a wider “axial ratio (AR)” bandwidth is achieved through the combination of its resonance with the dielectric resonator. The antenna is designed utilizing the proposed fractal cross-slot-coupled CPDRA, with its architecture and efficiencies thoroughly investigated. The performance of the proposed antenna demonstrates its potential for various wireless communication applications, highlighting the advantages of integrating Fractal Cross-slot-coupled DREs in antenna design.

Rubidium zinc trioxide perovskite materials for photovoltaic solar cell applications: A first principle calculations

Perovskite materials are the well-known of solar cell applications and have excellent characteristics to study and explain the photocatalytic research. Exchange generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof-PBE correlation functionals and density functional theory (DFT)-based Cambridge Serial Total Energy Package (CASTEP) software are used to inspect the structural, electrical, mechanical, and the optical aspects of Zinc-based cubic perovskite RbZnO3. The compound is found to be in a stable cubic phase according to our study. The predicted elastic characteristics also satisfy the mechanical criterion for stability. Pugh's criterion indicates that RbZnO3 is brittle. The examination shows that the electronic band structure, RbZnO3 possesses an indirect bandgap (BG) that has 4.23eV. Findings of BG analysis agree with currently available evidence. Total and partial density of states (DOS) are used in the confirmation of degree of a localized electrons in special band. Optical transitions in compound are evaluated by adjusting damping ratio for the appropriate peaks of the notional dielectric functions. On one hand, the material is a semiconductor at absolute zero. On the other hand, the dielectric function's fictitious element dispersion illustrates the wide range of values for energy transparency. This substance might therefore be used in a solar cell to capture ultraviolet light.

High‐gain wideband all‐dielectric digital metasurface reflectarray antenna for millimeter‐wave applications

AbstractThis paper presents an additive manufacturing technique to design and prototype a reflective metasurface antenna for Ka‐band applications. The dielectric cuboidal element with an air‐filled void is designed to act as a unit cell for designing a three‐dimensional (3D)‐printed phase‐graded metasurface reflector. The designed phase‐graded metasurface reflector is a 3‐bit quantized highly reflective surface, designed by rigorous unit cell optimizations. The quantized unit cells are distributed to provide a 45° phase gradient and wideband reflections operating from 24 to 38 GHz. The designed reflector is excited by a wideband 3D‐printed horn antenna placed at the optimized focal point. The simulated and measured results indicate the designed antenna achieves a maximum gain of 23.66 dBi with a gain enhancement of 60%. The designed antenna is found to have a 1 dB stable gain bandwidth of 4 GHz, from 28 to 32 GHz with a maximum gain of 23.66 dBi at 30 GHz.

Microstrip dual band hybrid directional resonator antenna with volume reduction

This paper presents a novel design of a single-layer, horizontally polarized, dual-band, omni- and multi-directional hybrid dielectric resonator antenna (DRA) feeding through a 50 Ω coaxial connector. The proposed antenna consists of an FR4 substrate, a regular ground plane and a cross-shaped patch. The connector is placed at the middle point of the square ground plane. Above the microstrip patch, four similar solid dielectric resonator elements are placed diagonally. These DRA structures generate the TE111, hybrid HEM22δ modes and put up an ideal magnetic dipole and an electric quadrupole far-field radiation pattern. To verify the idea, an optimized antenna model is fabricated and tested. A reasonable agreement between the measured and simulated results is obtained. The measured impedance bandwidths of the TE111 and HEM22δ modes are 4.26 % (2.9–3.2 GHz) and 4.34 % (4.4–4.6 GHz), respectively. The proposed antenna has a stable omnidirectional radiation pattern at the first resonance frequency and a directional radiation pattern at the second resonance frequency and provides volume reduction.

3D-printed wideband reflectarray antennas with mechanical beam-steering

Abstract This paper investigates the performance of 3D-printed dielectric reflectarray antennas (RAs) with wideband behavior and beam-steering capabilities. The designed unit cell consists of a single-layer dielectric element perforated with a square hole, whose side is used to control the local variation of the reflection coefficient. The numerical analysis of the unit cell and of first $52\times52$ reflectarray working in Ka-band, whose scanning capabilities are tested just moving the feed along an arc, confirms that the unit cell has a stable behavior with respect to both the frequency and the direction of arrival of the incident field. In view of these promising capabilities, the proposed unit cell is used to design a bifocal reflectarray with the same size and working in the same frequency band of the first one. Its numerical characterization and the measurements of a prototype prove that the RA is able to provide less than 0.8 dB of gain losses over a scanning range of ±40∘ in the vertical plane, while the bandwidth varies between 13.5% and 28%, depending on the pointing direction. The obtained results demonstrate the effectiveness of the proposed approach and highlight the potential of 3D-printing technology for producing high performance, cost-effective RAs with wideband behavior and excellent beam-steering features.

Remote Reconfiguration of Microwave Filters Using Dielectric Tuners

The objective of this article is to explore the use of dielectrics to reconfigure remotely microwave filters in rectangular waveguide. To start, we study experimentally the phase shift that is achievable using dielectric tuning elements in a rectangular waveguide. We then compare the results obtained with the performance of standard metallic tuning cylinders and screws. Next, the passive intermodulation (PIM) behavior of dielectric tuning elements is investigated experimentally. The PIM results obtained using dielectrics are then compared with the ones of metallic tuning elements. After that, the measured results for a filter tuned with a number of different dielectric tuning elements are discussed to identify the required relation between cavity size, dielectric constant, and tuner diameter. As a proof of concept, we then design, manufacture, and test two filters, one in WR75 and the other in WR90. Both simulated and measured results are then presented clearly demonstrating that the structures discussed can indeed be reconfigured (or tuned) both in terms of filter center frequency and bandwidth. Finally, computer-driven linear actuators are connected to the dielectric tuners, and the remote tuning capability is successfully demonstrated.

On the use of dielectric elements in axion searches with microwave resonant cavities

This study explores the primary effects of dielectric materials in a resonant cavity-based search for axion dark matter. While dielectrics prove beneficial in numerous cases, their incorporation may lead to less-than-optimal performance, especially for the lowest TM mode. Additionally, the stronger confinement of the electric field inside the dielectrics can exacerbate mode mixings, in particular for higher-order modes. Case studies have been carried out using a combination of analytical solutions and numerical simulations. The findings indicate dielectric cavities employing the TM010 mode experience a significant reduction in sensitivity when compared to a similar search conducted in a cavity at equivalent frequency using no dielectrics.

Wide gamut dynamic color manipulation based on dielectric metasurface on a stretchable substrate

Dynamic color adjustment technology has broad prospects in invisibility, anti-counterfeiting, and display, and is an important research direction in structural color. This study investigates the excitation of magnetic dipole resonances in the visible region by titanium dioxide (TiO2) metasurfaces using elastic dielectric polydimethylsiloxane (PDMS) and applied to dynamic color modulation. The near-field interaction between the resonant dielectric elements can be modulated using the mechanical strain of the PDMS substrate, enabling the advection of the resonance peak of the structure throughout the visible range, thereby achieving a wide color gamut. The color structure of TiO2 metasurface is sensitive to the refractive index of the surrounding medium. Moreover, active switching between the “ON” state (highly reflective at a selected wavelength) and the “OFF” state (transparent) can be achieved through the deformation of the flexible PDMS substrate. The proposed method can be applied to fields such as sensor displays and spectroscopy and for studying stretchable and wearable photonics.

Novel corrugated rectangular dielectric resonator antenna with wide half power beam width

ABSTRACT In this work, a dielectric resonator antenna element is corrugated in a specific way, which led to increase its half power beam width (HPBW). The HPBW of the antenna is investigated for different values of corrugation depth and it has been concluded that HPBW can be increased by increasing this depth. By embedding periodic grooves in the DRA walls, it is possible to adjust the radiation intensity ratio of the upper wall to the side walls. By increasing this ratio, the HPBW of the antenna can be increased. To confirm the concept of beam widening method, a prototype of the corrugated DRA is fabricated and measured. Measured results show an impedance bandwidth of 23% (3.8–4.8 GHz). The measured E- and H-plane HPBWs at 4.1 GHz are 137° and 123°, respectively. Measured and simulated results are in a good agreement.

Laser Damage Performance Study of Fundamental Frequency Dielectric Film Optical Elements

In laser application systems, the optical film is one of the most important parts of the system, as well as its weakest link. Its damage performance determines the output characteristics and safety performance of the laser system. This paper focuses on the fundamental frequency reflection of dielectric films used in large high-powered laser devices. The study of the dielectric film’s initial laser damage performance and laser damage growth performance is carried out through laser damage testing and microscopic morphology testing of the damage. The results show two different damage morphologies: type 1 damage (film discoloration damage) and type 2 damage (cratered damage), and the damage growth behavior between the two is very different, with type 1 damage not growing and type 2 damage growing rapidly under subsequent episodes that trigger their damage fluxes. The difference in the growth behavior is well explained by the micro-zone surface shape of the damage location. The results of this paper help to deepen the understanding of the dielectric membrane element processing process and the damage growth behavior.

Tunable ultraviolet polarized light switch based on all-dielectric metasurfaces on a stretchable substrate.

Most ultraviolet (UV) passive optics are currently non-tunable and lack external modulation methods because of the poor tunability of wide-bandgap semiconductor materials in UV working media. This study investigates the excitation of magnetic dipole resonances in the solar-blind UV region by hafnium oxide metasurfaces using elastic dielectric polydimethylsiloxane (PDMS). The near-field interactions between the resonant dielectric elements can be modulated by the mechanical strain of the PDMS substrate, which can flatten the structure's resonant peak beyond the solar-blind UV wavelength range, thereby turning on or off the optical switch in the solar-blind UV region. The device has a facile design and can be used in various applications, such as UV polarization modulation, optical communications, and spectroscopy.

Effective Constitutive Parameters Extraction of Bianisotropic Metamaterials Using Bloch Modes

In this article, a method is proposed to extract the effective constitutive parameters of bianisotropic metamaterials using Bloch modes. We consider 3-D structures that are realized by stacking identical unit layers, where each unit layer is a 2-D periodic array of metallic or dielectric elements of arbitrary shape embedded in a background dielectric medium. Bianisotropic metamaterials do not satisfy the condition of reflection symmetry of unit layers considered in previous studies. The eigenvectors and eigenvalues of the generalized transfer matrix of a unit layer are related to the Bloch modes of the structure. When only two dominant Bloch modes exist, closed-form expressions are found for effective permittivity, permeability, and magnetoelectric tensors of the medium. The effects of nondominant Bloch modes are taken into account as interface surface impedance matrices. The calculated scattering parameters of a slab of bianisotropic metamaterial are shown to be in good agreement with the results obtained from full-wave electromagnetic simulations using commercial solvers.

Photosensitivity of Nanostructured Schottky Barriers Based on GaP for Solar Energy Applications

This work investigates the surface-barrier photoelectric properties of Au-palladium-n-GaP structures. Research into the visible spectrum region, under the action of both linearly polarized and natural radiation, provides us with new information about the height of the barrier, the interface m-s section, and the GaP band structure. SBs based on GaP (p- and n-type) are helpful for researchers in developing advantageous structures for creating various photovoltaic devices—photodetectors for fiber-optic control of energy systems or possible structures for solar energy. Despite many years of research, issues concerning the band structure of semiconductors based on the phenomenon of photoelectroactive absorption in such surface-barrier structures’ m-s remain urgent in the creation of new high-performance devices. Such structures may also be interesting for creating solar energy systems. They create a thin insulating dielectric layer (usually an oxide layer) in solar cells on SBs between the m and the semiconductor substrate. The advantage of solar cells based on m dielectric semiconductor structures is the strong electric field near the surface of the semiconductor that usually has a direction favoring the collection of carriers created by short-wavelength light. Diffusion of impurities usually results in crystal defects in the active region. There are no such defects in the studied elements. This is also the difference between solar cells on m dielectric structures and elements with diffusion in p-n junctions. We studied the PS of Au-Pd-n-GaP nanostructures to determine the height of the potential barrier qφBo and obtained accurate data on the zone structure of the n-GaP. The PS of nanostructured Au-Pd-n-GaP structures was studied in the visible region of the spectrum. Essential information about the semiconductor’s potential barrier parameters and band structure was obtained. The intermediate Pd nanolayer between Au and GaP has specific effects on the Au-Pd-n-GaP nanostructure, which are of considerable practical and scientific significance for future needs.

Damping characteristics of helicon and Trivelpiece–Gould waves in high density and low magnetic field helicon plasma

By employing a warm plasma model and considering a cyclotron harmonic effect in dielectric tensor elements, the power deposition properties of the azimuthally symmetric mode of the helicon and Trivelpiece–Gould (TG) waves due to collisional and kinetic damping in high density (∼1 × 1013 cm−3), low magnetic fields (∼30–50 G), and low to moderate neutral gas pressure (∼0.5–10 mTorr) helicon plasma are investigated. Theoretical calculations indicate that the magnetic field imposed a significant influence on the mode coupling surface properties between the helicon and TG waves; in a typical helicon plasma electron temperature range, Te ∈ (3, 5) eV, there exists the critical neutral gas pressure, below or above which different waves due to different damping mechanisms play the dominant role in the power deposition; meanwhile, in low neutral gas pressure (∼0.5 mTorr) circumstances, TG waves due to Landau damping dominate the power deposition and this dominance gradually becomes intensified as the magnetic field increases.

The Application of the Hybrid Projection Method for the Analysis

The problem of scattering of a plane electromagnetic wave by a 2D periodic structure formed by absorbing spherical radially inhomogeneous dielectric elements is considered. The elements have the type of electromagnetic black holes located on a semi-infinite substrate. The numerical algorithm of the solution is developed. The algorithm is based on the hybrid projection method and takes into account the peculiarities of the black hole construction. The algorithm is generalized to the case, when black holes are situated on aperfectly conducting screen. New expressions for calculating the power absorbed by the structure elements are derived. The numerical results characterizing the efficiency of the structure absorption are presented.

Wide‐beam bent cross‐shaped DRA antenna for wide‐angle beam‐scanning phased array

AbstractIn the paper, a bent cross‐shaped dielectric resonator antenna element with wide half‐power beamwidth of 224.9° is proposed and applied for designing a 1 × 8 wide‐angle beam‐scanning linear phased array. To obtain small gain drop and reduce the mutual coupling of the scanning array, the dielectric wall loaded rectangular truncated slots are inserted. For validation, a prototype operating at 5.8 GHz is designed. Measurement results indicate that the main beam of the designed phased array can scan from −70° to +70° GHz with a gain drop of less than 1.75 dB and a sidelobe level of less than −5.08 dB.

Design of high-gain wideband substrate integrated waveguide dielectric resonator antenna for D-band applications

The emerging mobile broadband applications and services demand high-performance networks operating at high frequencies. There is need for high gain and wideband antennas for mobile equipment to support high-speed communications in the millimeter (mm) wave and terahertz (THz) frequencies. In this paper, we propose a wideband substrate integrated waveguide (SIW) fed dielectric resonator antenna (DRA) for D-band applications. A rectangular dielectric resonator element is designed to operate in higher order modes. Wideband operation is achieved by merging adjacent resonances of the different modes. We present a systematic and sequential application of impedance matching techniques to merge the passbands of a multi-mode dual-band DRA, to achieve a wideband response. The proposed design operates between 123.97 GHz and 152.13 GHz. This represents a -10 dB bandwidth of 20.39% at the center frequency of 138.05 GHz. The proposed antenna design has stable broadside radiation patterns, exhibiting a high gain of 11.67 dBi, directivity of 13.36 dBi and maximum total efficiency of 79% . The proposed design is suitable for future generation wireless communication in the terahertz band.