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The main characteristic of the converter element in resonant microwave sensors that determines the sensitivity of the conversion is the quality factor of the resonance line. In structures with periodic inhomogeneity of the classical topology, the quality factor of the circuit at high values of the signal-to-noise ratio may turn out to be low, which entails the emergence of restrictions on the maximum achievable conversion parameters. One of the ways to increase both the Q factor and the modification of other properties of the microwave structure that affect the overall efficiency of the converter element is the use of quasiperiodic elements. The coaxial cable, where the holes in the dielectric act as inhomogeneity, is presented, forming structure with phase shift. Using the method of flow graphs, we obtained the analytical dependence of the reflection coefficient for this structure. The analysis of the frequency response of the microwave reflection coefficient was carried out for different values of the phase shift and the location of the phase shift section along the length of the cable. A numerical and physical experiments were carried out to determine the frequency dependence of the microwave reflection coefficient with a π-phase shift for various values of the automobile fuel permittivity introduced into the cells.

Bragg microwave structures in a coaxial line have found application as converting elements in devices for dielectric control of liquid and bulk medias. A feature of the measuring conversion of the complex dielectric constant in coaxial structures is the introduction of the substance under study into the inner space of the line. The latter circumstance imposes certain restrictions on the design of the external conductor for express control. In this regard, the consideration of half-open coaxial lines based on an external conductor in the form of longitudinal conducting rods is an urgent problem. The article proposes a method for calculating the wave impedance of a half-open coaxial line using a numerical calculation of electromagnetic fields. Based on the results of modeling Bragg microwave structures in a half-open coaxial line, recommendations are made for the construction of conversion elements based on them.

Журнал зарегистрирован в Управлении Федеральной службы по надзору в сфере связи, информационных технологий и массовых коммуникаций ПИ № ФС77-41672 от 13 августа 2010г.Журнал размещен в открытом бесплатном доступе на сайте www.ntvp.ru, и в Научной электронной библиотеке (участвует в программе по формированию РИНЦ).Журнал включен ВАК РФ в перечень научных журналов, в которых должны быть опубликованы основные научные результаты диссертаций на соискание ученых степеней доктора и кандидата наук.Подписной индекс в объединенном каталоге «Пресса России» № 12025.