Double slot aerosol jet printed antenna for X-band applications

A double slot antenna for X-band applications was designed and aerosol jet printing technology was used to fabricate the prototype with silver nano-ink on a flexible polyimide substrate. We investigated the microwave losses of printed antennas in the range from 100 kHz to 27 GHz, obtained at sintering temperatures of 200 °C and 250 °C. Double slot X-band antennas have been calculated and measured. It was found that an operating bandwidth of the printed antenna is 10% in the region of the central frequency of 10.5 GHz. Thus, the possibility of forming antennas on flexible polymer substrates with high functional characteristics by aerosol jet printing method has been demonstrated.

Transmission, Reflection and Dissipation of Microwaves in Magnetic Composites with Nanocrystalline Finemet-Type Flakes

The microwave properties of a composite material containing flakes of finemet-type nanocrystalline alloy placed in the epoxy matrix have been investigated. Two compositions have been studied: with 15% and 30% flakes. Frequency dependences of transmission and reflection coefficients are measured in the frequency range from 12 to 38 GHz. The dielectric permittivity and magnetic permeability are obtained, and the microwave losses are calculated. The dependences of transmission and reflection coefficients have been drawn as functions of wave frequency and thickness of the composite material, taking into account the frequency dependences of permittivity and permeability. The regions of maximal and minimal microwave absorption have been defined. The influence of wave interference on the frequency dependence of microwave absorption is studied.

Microwave resonance method for measuring microliter volumes of free moisture in aviation fuels

One of the conditions for ensuring the safety of air transport operation is the quality of aviation fuel refueled in aircraft. Fuel quality control is a multi-parameter task that includes monitoring the free moisture content. Regulatory documents establish the content of free water no more than 0.0015% by weight. It is developed a direct electrometric microwave resonance method for controlling free moisture in aviation fuels, which consists in changing the shape of the water drops by pressing them on a solid surface inside a cylindrical cavity resonator. This can dramatically increase dielectric losses. Analytical and experimental analysis of the proposed method is carried out. The control range from 0,5 to 30 μl of absolute volume of moisture in aviation fuels with a maximum error of not morethan 25 % is justified. The sensitivity of the proposed method for monitoring microwave losses in free moisture drops transformed into a thin layer by pressing is an order of magnitude greater than the sensitivity of the method for monitoring microwave losses in moisture drops on a solid surface in a resonator. The proposed method can be used as a basis for the development of devices for monitoring the free moisture of aviation fuels in the conditions of the airfield and laboratory. The direction of development of the method is shown.

To the Phenomenological theory of Avalanche-Like Effect in Dc-Biased Microwave Nonlinear HTS Transmission Line

A phenomenological model has been proposed to describe the avalanche-like transition of a microwave nonlinear HTSC-based transmission line into a dissipative state. This effect was observed by the authors in a dc-biased transmission line. The proposed model generalizes the well-known phenomenological model for the nonlinear HTSC-based transmission line under the action of a direct current. The character of the dependences obtained for microwave losses allows the jump-like changes in the properties of the nonlinear HTSC-based transmission line to be regarded as a fold-type catastrophe and the methodological and mathematical apparatus of the theory of catastrophes to be used in order to explain the results obtained and predict new ones.

INVESTIGATION OF LOSSES IN SILICON AT MICROWAVE FREQUENCIES

In this work basic mechanisms of microwave losses in silicon substrate and at the interfacial Si/heterostructure AlGaN/GaN for HEMTs and MMIC were investigated. Methods for reducing of losses were proposed. Requirements to resistivity of silicon substrate taking into account the characteristics of growth AlGaN/GaN heterostructure were defined.

Microwave losses of nanostructure Li-Ni ferrites in X-band and Ku-band

The molar ratio(x) of Li-Ni ferrites in the formula Li0.5-0.5xNixFe2.5-0.5xO4 was varied in range 0.1-1.0 by hydrothermal process. TheXRD, SEM, and TEM tests were conducted to examine the samplescrystalline phase and to characterize the particles shapes and sizes.The high purity spinel structure was obtained at med and high xvalues. SEM and TEM images showed the existence of differentferrite particles shapes like nanospheres and nanorods. Themaximum particle size is around (20nm). These size encourageoccurrence of super paramagnetic state. The reflection loss andinsertion loss as microwave losses of Li-Ni ferrite-epoxy compositeof 1mm thickness and mixing ratio 39.4 wt was investigated. Theminimum reflection loss in x-band and in Ku band was about -8dBaround 10GHz and lower than -18dB respectively. The insertion lossexceeded -6dB in the two band for some samples.

Electromagnetic Fields in Technology of Processing of Polymeric Materials

The issues related to the implementation of the process of depolymerizing of waste polymers, initiated by thermal action of an intense electromagnetic microwave field, are considered. The reactions considered are distinguished by the possibility of reducing the initial monomers or oligomers. The required reaction temperatures are achieved by indirect heating due to the presence of carbon thermal converters in the mixture or the use of liquid reagents characterized by high microwave losses. The results of the study of two different mechanisms of depolymerizing, namely the decomposition of the polymer in a glycol medium and thermal decomposition, are shown. The methods of mathematical modeling of the joint problem of electrodynamics and heat conduction are analyzed to estimate the temperature regimes of the processes of thermal decomposition of polymers. Experimental studies are illustrated by examples of the depolymerizing of polyethylene terephthalate, polystyrene and polymethyl methacrylate, the destruction products of which were esters of terephthalic acid, styrene and methyl methacrylate.