Dielectric Wedge Research Articles

A high-performance microwave plasma source employing dielectric wedges

A high-performance microwave plasma source employing dielectric wedges

Flexible and efficient direct-insertion microwave heating with a dielectric wedge

Traditional microwave heating requires the heated object to be placed in a metal cavity, which limits its flexibility. Moreover, the microwave heating efficiency is affected by the shape, size, and permittivity of the load. This paper proposes a direct-insertion microwave heating device based on a dielectric wedge. It offers flexible and efficient heating for different loads. Firstly, a dielectric wedge with a gradient refractive index was designed, which can convert electromagnetic waves into surface waves propagating along the dielectric. Secondly, efficient heating of materials with permittivity ranging from 10 to 80, regardless of their shape, is achieved by inserting the dielectric wedge into the load. Microwave heating efficiencies above 90 % were consistently observed in heating tests with beverages, mashed potatoes, and minced fish of varying shapes. Finally, A high-power continuous flow heating scheme was introduced, utilizing the device as a heating module and scaling up by adding more modules to boost microwave power. Multi-physics simulations confirmed the device's efficiency and versatility in microwave continuous flow heating, with minimal energy interference between microwave sources.

Efficient Microwave Heating of Arbitrary Loads in Multimode Cavities Employing Transformation Optics-Designed Dielectric Wedges

Efficient Microwave Heating of Arbitrary Loads in Multimode Cavities Employing Transformation Optics-Designed Dielectric Wedges

Antenna Systems with Wide-Angle Mechanoelectrical Beam Steering

Introduction. The active development of satellite communication networks determines the need for new antenna systems for ground terminals. The Sphere Federal program implies the commissioning of new satellite constellations for communication and remote sensing of the Earth. The Skif (providing broadband Internet access) and Express-RV (providing the Internet and communications for Arctic) satellite constellations are not geostationary, thus requiring constant satellite tracking even for stationary terminals. Deflecting structures operating on the principle of quasi-optical beam control make it possible to develop scanning antenna systems for organizing continuous satellite communications. Aim. Investigation of various types of dielectric structures for radiation pattern deflection and scanning antenna systems on their basis, as well as identification of a configuration with improved characteristics compared to the ideal structure in the shape of a dielectric wedge. Materials and methods. Mathematical modeling, electrodynamic modeling using CAD by the finite element method and the finite integration method, as well as an experimental study of an antenna system prototype in an anechoicchamber by measuring methods in the far-field and near-field of the antenna. Results. Electrodynamic simulation was carried out for three types of dielectric structures, analogues of a dielectric wedge, including a structure assembled from various dielectrics of fixed sizes with different dielectric constants; a structure of triangular dielectric plates; and a perforated dielectric structure. In addition, scanning antenna systems based on the presented configurations were analyzed. Radiation patterns were obtained for all structural types for various rotation angles of the deflecting systems. The structure assembled from various dielectrics of fixed sizes with different dielectric constants was found to possess the most optimal characteristics. This structure was used to develop a model for experimental confirmation of the conducted electrodynamic simulation. The maximum tilt angle of the radiation pattern was about 60°, the decrease in the directivity relative to the maximum value was 6 dB; for tilt angles up to 55°, the directivity degradation did not exceed 4 dB, the level of the side lobes did not exceed –12 dB (calculated) and –14 dB (measured). Conclusion. The results of studies into various types of structures for quasi-optical beam control of the radiation pattern show the possibility of using these configurations when creating low-profile antenna systems with wide-angle mechanoelectric scanning for organizing satellite communications for both mobile and stationary consumers using medium earth orbit spacecrafts.

E-Plane-Focused Partial Maxwell Fish-Eye Lens Antenna for Multibeam Wide-Angle Scanning

This letter presents a multi-beam wide-angle scanning antenna based on the E-plane-focused partial Maxwell fish-eye (PMFE) lens operating in Ka-band. The gradient equivalent refractive index distribution of the lens is realized by the parallel plate waveguide (PPW) partially filled with dielectric material, which can support the E-plane focus. The lens is fed by a series of rectangular waveguides arranged along the straight cut line to realize the multiple beams. To improve the impedance matching, the dielectric wedges are loaded in the interface between the feeders and the lens. The E-plane broadening of waveguide feeding ports effectively alleviates the gain drop of wide-angle scanning. The measured results of the prototype show a beam scanning range more than ±90° with the aperture efficiencies between 57% and 85.7%. The good impedance matching is also obtained in the operating band. The proposed PMFE lens antenna has the application potential in the low-cost millimeter wave (MMW) multi-beam systems.

A novel approach for approximating the average field diffracted from a double-layered dielectric wedge with Gaussian rough inner wedge face

This article studies the phenomenon of diffraction from a double-layered dielectric wedge that has roughness on the inner wedge face. For realizing the practical significance of this study, a hilly terrain may be imagined where the hills act as obstacles in the path of radiowave propagation and they are covered with snow or forest. Since generally, the hill surfaces are rough, these snow or forest covered hills can be approximated by double-layered dielectric wedges with a rough inner wedge face. Hence, this novel approach for approximating the average field diffracted from such wedges will be helpful to those involved in propagation channel modeling, especially for hilly and mountainous terrain.

EM response of right angle dielectric wedge for normal incidence

EM response of right angle dielectric wedge for normal incidence

Gordon Coupler with Inductive or Capacitive Iris for Small EPR Resonators for Aqueous Samples.

The Gordon coupler was introduced for use in EPR experiments at liquid helium temperatures. It provides an evanescent wave incident on the iris of a microwave resonator. Match of power incident on the coupler to the resonator is obtained by variation of the amplitude of an evanescent wave that arises from displacement of a dielectric wedge in a tapered waveguide. Reduced microphonics from helium bubbling was reported. The Gordon coupler was subsequently extended from cavity resonators to loop-gap resonators, initially at helium temperatures but later for aqueous samples. Plastics with low dielectric constants, usually Teflon, were used. Here, we extend the Gordon coupler for application in X-band five-loop-four-gap resonators using fused quartz, sapphire, or rutile dielectrics, noting that the size of the coupler can then be commensurate with dimensions of dielectric loop-gap resonators as well as dielectric tube resonators. Finite element modeling of electromagnetic fields has been carried out, and use of a capacitive iris that interfaces with the Gordon coupler reduces pulling of the resonant frequency when matching the resonator.

A heuristic method to calculate the field diffracted from a double-layered dielectric wedge

Double-layered dielectric wedges (e.g. forest or snow-covered hills, building corners with vertical gardens) are quite common obstacles that appear in radio-wave propagation channels. This article presents a heuristic method to obtain the field diffracted from a double-layered dielectric wedge. Though it uses a framework that appeared in an earlier publication, it improves upon the issue of complexity. The method proposed here reduces the requirement of solving nonlinear equations to half and makes the process substantially less time-consuming without compromising the accuracy. Hence this improvement makes the method more useful for real-time usage in emergency situations. Apart from this advantage on time consumption, this method also improves upon the memory consumption and limit of validity.

A new time-domain heuristic diffraction coefficient for characterization of diffracted and transmitted field with UWB applications

In this paper, a novel heuristic diffraction coefficient in the frequency-domain (FD) for non-perfectly conducting wedges and buildings is proposed. The six-terms diffraction coefficient which is an extension of the four-terms UTD coefficient is proposed to include the effect of transmitted ray for a lossy dielectric wedge with arbitrary low wedge angle, thus, attaining the continuity of the total field all around the structure. This new six-terms UTD diffraction coefficient is verified with the earlier available finite-difference time-domain (FDTD) result. Further, the time-domain (TD) solution based on the classical frequency domain result is proposed for UWB applications in indoor environments. Finally, a case of double diffraction for two consecutive buildings scenario is presented based on slope diffraction and their corresponding TD solution is also presented. The different input pulses and building materials are considered to test the overall behavior of the TD model. All the TD results are verified with inverse fast Fourier transform (IFFT) of the FD results in both the soft and hard polarization and the results are found to be in very good agreement. The channel impulse response is also presented to determine the distortion on the input pulse. The computational efficiency of the proposed TD solutions is demonstrated by comparing them with IFFT-FD solutions.

Asymmetric Metal-Dielectric Metacylinders and Their Potential Applications From Engineering Scattering Patterns to Spatial Optical Signal Processing

We propose a novel type of bi-anisotropic hybrid metal-dielectric structure comprising dielectric and metallic cylindrical wedges wherein the composite meta-cylinder enables advanced control of electric, magnetic and magnetoelectric resonances. We establish a theoretical framework in which the electromagnetic response of this meta-atom is described through the electric and magneticmultipole moments. The complete dynamic polarizability tensor, expressed in a compact form, is derived as a function of the Mie scattering coefficients. Flexibility in the design makes the proposed meta-cylinder a viable candidate for various applications in the microscopic (single meta-atom) and macroscopic (metasurface) levels. We show that the highly versatile bi-anisotropic meta-atom is amenable to being designed for the desired electromagnetic response, such as electric dipole-free and zero/near-zero (backward and forward) scattering at the microscopic level. In addition, we show that the azimuthal asymmetry gives rise to normal polarizability components which are vital elements in synthesizing asymmetric Optical Transfer Function (OTF) at the macroscopic level.We conduct a precise inspection, from the microscopic to the macroscopic level, of the metasurface synthesis for emphasizing on the role of normal polarizability components for spatial optical signal processing. It is shown that this simple two-dimensional asymmetric meta-atom can perform first-order differentiation and edge detection at normal illumination.The results reported herein contribute toward improving the physical understanding of wave interaction with artificial materials composed of asymmetric elongated metal-dielectric inclusions and open the potential of its application in spatial signal and image processing.

Heuristic UTD Diffraction Coefficient for Three-Dimensional Dielectric Wedges

This article presents a heuristic diffraction coefficient for 3-D dielectric wedges of arbitrary angles. First, the proposed diffraction coefficient is derived for 2-D wedges with soft and hard polarization, by enforcing continuity of the total field at every shadow boundary associated with the multiply reflected fields inside the wedge. The accuracy of the proposed heuristic 2-D solution is verified comparing with the UTD solution derived from Maliuzhinets' exact integration. Then, it is extended to 3-D wedges for arbitrary polarizations and incident/scattered directions by transforming ray-fixed to edge-fixed coordinate systems. The total field predicted using the proposed heuristic diffraction coefficient is continuous for arbitrary angle 3-D dielectric wedges, including interior wedges, and is close to the geometrical optics field far from the shadow boundaries. The proposed method is validated against a Method-of-Moment solution. Finally, we show the method can significantly improve the accuracy of ray-tracing modeling of wave propagation in arched tunnels.

Analytical Explanation of Electromagnetic Diffraction From Double-layered Dielectric Wedge

This article explains the phenomenon of electromagnetic diffraction from a double-layered dielectric wedge analytically. Mountain ridges with forest or snow cover, concrete building with wooden interior wall decoration or vertical garden, et cetera are good examples of double-layered dielectric wedges that often appear in indoor and outdoor propagation channel models. The analytical model presented here considers the contributions from the inner and outer wedges individually. Then the total diffracted field is calculated by superimposing one upon another. The problem becomes complex because the field diffracted from the inner wedge has a cylindrical wavefront, which gets the chance to reach air only after transmitting through the outer wedge’s dielectric material. Moreover, since the interface between air and the outer wedge dielectric is not planar, it adds to the complexity of the problem. The proposed analytical model has been validated by comparing its results with the results from finite-difference time-domain (FDTD) simulations.

Dielectric-Boosted Sensitivity to Cylindrical Azimuthally Varying Transverse-Magnetic Resonant Modes in an Axion Haloscope

Axions are a popular dark matter candidate which are often searched for in experiments known as ``haloscopes" which exploit a putative axion-photon coupling. These experiments typically rely on Transverse Magnetic (TM) modes in resonant cavities to capture and detect photons generated via axion conversion. We present a study of a resonant cavity design for application in haloscope searches, of particular use in the push to higher mass axion searches (above $\sim$60$\,\mu$eV). In particular, we take advantage of azimuthally varying TM$_{m10}$ modes which, whilst typically insensitive to axions due to field non-uniformity, can be made axion-sensitive (and frequency tunable) through strategic placement of dielectric wedges, becoming a type of resonator known as a Dielectric Boosted Axion Sensitivity (DBAS) resonator. Results from finite-element modelling are presented, and compared with a simple proof-of-concept experiment. The results show a significant increase in axion sensitivity for these DBAS resonators over their empty cavity counterparts, and high potential for application in high mass axion searches when benchmarked against simpler, more traditional designs relying on fundamental TM modes.

A modified two dimensional Maliuzhinets' diffraction coefficient for modeling snow or vegetation covered dielectric wedges

AbstractA new diffraction coefficient, obtained by modifying the Maliuzhinets' diffraction coefficient, has been proposed here in this article for a double‐layered dielectric wedge which can be considered as an approximated version of a snow or vegetation‐covered dielectric wedge in a practical propagation channel modeling scenario. An experiment was conducted with an artificially created double‐layered wedge for validating the response from the proposed coefficient in a real‐life scenario. The same environment was modeled and simulated using gprMax simulator, which further verified the experimental result and the effectiveness of the newly developed coefficient.

Useful Solutions for the Plane Wave Diffraction by a Configuration of Dielectric and Metallic Acute-Angled Wedges

Useful Solutions for the Plane Wave Diffraction by a Configuration of Dielectric and Metallic Acute-Angled Wedges

Beam-Scanning Antenna Based on Near-Electric Field Phase Transformation and Refraction of Electromagnetic Wave Through Dielectric Structures

An elegant combination of electric near-field phase transformation technique and electromagnetic-wave refraction, implemented through a pair of 3D printed dielectric structures, has been used to demonstrate a Ka-band beam-scanning antenna system. The system comprises a resonant-cavity antenna (RCA), which is used as a base antenna, a stepped dielectric (SD), and a dielectric wedge (DW). The SD is suspended above RCA in the near-field region to focus its broadside beam at an offset angle of 20°. The DW is placed above the SD and its two opening angles are selected such that the offset-angle focused beam tilts further and moves back to the broadside when the DW is co- and counter-aligned with the SD, respectively. The total height of the antenna system is 8.1λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength at the operating frequency of 30 GHz. The total cost of the material used for printing the two dielectric structures in prototyping is only 6 USD. It has been demonstrated through measurements of the prototype that by rotating the DW around its own axis, the antenna beam can be scanned in both azimuth and elevation planes. The measured results indicate that antenna beam can effectively be scanned to any arbitrary angular position within a conical region having an apex angle of 68°, while maintaining peak-gain value within the 3 dB limit of the maximum gain of 16 dBi.

X-Ray Transmission through Infinite Dielectric Wedge-Shaped Objects

The problem of transmission and reflection of X-rays (0.1 A ≤ λ ≤ 10 A) from an infinite amorphous homogeneous wedge-shaped dielectric plate has been analytically solved. The obtained solution is a “zero” step in solving the problem of X-ray diffraction on a semi-infinite amorphous homogeneous dielectric wedge within the heuristic geometric diffraction theory.

A note on the two-dimensional electrostatic field produced by a line charge near a dielectric wedge

Summary We shall consider the problem of determining the correct electrostatic field produced when an infinite two-dimensional line source is influenced by an adjacent infinite dielectric wedge. This result corrects a number of previous attempts at this problem, which are shown to be in error. The method avoids using the Mellin transform which has lead to some of these earlier errors. The method is used to solve a more general problem of the electrostatic field produced by an arbitrary number of line sources located in an arbitrary number of contiguous dielectric wedges.

Plane Wave Diffraction by Arbitrary-Angled Lossless Wedges: High-Frequency and Time-Domain Solutions

This paper concerns the diffraction phenomenon originated by a uniform plane wave impacting an arbitrary-angled lossless dielectric wedge with planar surfaces. The high-frequency diffraction coefficients are obtained by performing uniform asymptotic evaluations of the radiation integrals resulting from the physical optics approximation of the electric and magnetic equivalent surface currents located on the inner and outer faces of the wedge. The final expressions are in closed form and contain the standard transition function of the uniform theory of diffraction and the Fresnel reflection and transmission coefficients related to the geometrical optics propagation mechanisms. Moreover, they allow a simple physical interpretation of each contribution and they are easy to use and to implement in a computer code. The knowledge of such diffraction coefficients in the frequency domain permits to apply the inverse Laplace transform to obtain the time-domain counterparts, which enable the evaluation of the transient diffracted field originated by an arbitrary function plane wave.