QUASI-ANALYTICAL CALCULATION OF THE ATTENUATION COEFFICIENT IN METAL WALLS OF LUNAR WAVEGUIDE

An expression for quasi-analytical calculation of the attenuation coefficient, due to losses in metal walls of a lunar waveguide with homogeneous dielectric filling is obtained. The results of quasi-analytical calculation of the attenuation coefficient in metal walls of hollow lunar waveguide at different values of its geometrical sizes and operating wavelength, which can be useful in synthesis of microwave devices for various applications, based on the considered guide system, are represented.

Photonic Band Gaps and Resonance Modes in 2D Twisted Moiré Photonic Crystal

The study of twisted bilayer 2D materials has revealed many interesting physics properties. A twisted moiré photonic crystal is an optical analog of twisted bilayer 2D materials. The optical properties in twisted photonic crystals have not yet been fully elucidated. In this paper, we generate 2D twisted moiré photonic crystals without physical rotation and simulate their photonic band gaps in photonic crystals formed at different twisted angles, different gradient levels, and different dielectric filling factors. At certain gradient levels, interface modes appear within the photonic band gap. The simulation reveals “tic tac toe”-like and “traffic circle”-like modes as well as ring resonance modes. These interesting discoveries in 2D twisted moiré photonic crystal may lead toward its application in integrated photonics.

Numerical simulation of characteristics of propagation of symmetric waves in microwave circular shielded waveguide with a radially inhomogeneous dielectric filling

The paper presents a numerical simulation of the propagation characteristics of symmetric E-type and H-type waves in microwave circular shielded waveguide with radially inhomogeneous dielectric filling. Using the modified Galerkin method, the calculation of a circular two-layer shielded waveguide was carried out, as a result of which the distribution of the electromagnetic field of the waveguide with linear and parabolic distribution of permeability was determined. The results obtained using the modified Galerkin method were compared with the results obtained using the classical partial domain method, which agree well enough.

STUDY OF PHASED ARRAYS OF SLOTTED WAVEGUIDE ANTENNAS WITH DIELECTRIC FILLING

The article describes the computer simulation of phased antenna arrays consisting of slotted waveguide antennas with air and dielectric filling. It is shown that inser-tion of a thin dielectric layer shifts the operating frequency range of phased anten-na arrays by 1 GHz or more down in frequency while maintaining directional char-acteristics.

Planar slotted ridged waveguide antenna arrays with dielectric layer

The paper simulates the options available to move operating range of slotted waveguide antennas downward in frequency without changing the waveguide cross-section, and suggests the ways for designing linear waveguide-slotted elements based on rectangular and ridge waveguides with air and partial dielectric filling. The critical frequency of the fundamental mode of a 16x8 mm rectangular waveguide moves by ridging from 9.5 to 6.5 GHz. Partial dielectric filling of the cavity of the ridge waveguide makes it possible to additionally shift the operating range downward in frequency by 6-10% without making changes to antenna design. The antenna characteristics of linear arrays based on a dielectric-filled ridge slotted waveguide have been compared in terms of gain and voltage standing wave ratio to similar designs of arrays on rectangular and air-filled analogues. Based on the obtained structures of linear elements, simulation models of planar arrays have been constructed so that they have the similar area of total surface. Simulated frequency dependence of the realized gain for planar arrays has demonstrated a shift of the operating range downward in frequency. The analysis of the directivity characteristics of planar arrays for various phase shifts between the linear elements has been carried out. The simulation results have shown that the use of a dielectric-filled ridge waveguide gives an advantage in phase scan angle of the main beam of the radiation pattern. With the same phase shift, in planar arrays of dielectric-filled ridge waveguides, the main beam scans for a larger angle while keeping side lobes at low level. Thus, the use of a ridge slotted waveguide with a dielectric layer inside makes it possible to expand the phase scan angle.

Broadband Metal-Dielectric Waveguide Path with Low Losses in the EHF Range

. The present paper is devoted to the design of a new shielded metal-dielectric waveguide with low losses (less than 0.5 dB/m) and wide bandwidth for the 90–100 GHz frequency range. Various types of waveguide structures were analyzed, such as metal waveguides, oversized metal waveguides, dielectric waveguides, dielectric waveguides with a metal shield and various designs of the dielectric filling element. Estimates of loss per unit length in them are obtained. The design of a waveguide containing an oversized round metal screen and a dielectric element consisting of a plate and a rod, located in the center of symmetry of the device, is proposed. The task of creating a transition from the investigated waveguide to a standard rectangular metal waveguide is considered. It is a horn transition from a circular cross-section to a rectangular one with a length of more than 25 wavelengths with a dielectric structure continuing the dielectric element of the waveguide path. As a result of the work, the ratios of the dimensions of the structural elements of the waveguide path and the materials used were obtained that satisfy the required losses.

Slotted ridged waveguide antennas with partial dielectric filling

Slotted single-ridge waveguide antenna with dielectric filling has been simulated. Dielectric material has been used to fill the slots, and to form a thin layer directly under the slotted broad wall. The specific pairs of ridge dimensions have been found that provide the same cut-off frequency for an air-filled ridged waveguide as it is for a broader air-filled rectangular waveguide. It has been shown that waveguide ridging followed by insertion of a thin dielectric layer under the slotted wall shift consecutively the antenna operating band down to lower frequencies. The specific values of thickness and permittivity of the dielectric layer suitable for frequency shifting have been found. The simulated characteristics of a 20-element dielectrically filled slotted single-ridge waveguide antenna have been presented. Resultantly, the efficient method of shifting the operating interval of a slotted-waveguide antenna down to lower frequencies has been proposed. The method does not require a broader waveguide, and therefore is effective with respect to low frequency – mass/dimension trade-off.