Author details

From the figure, one can see that moving the plunge from the surface of the flat mirror (m ¼ 0) along the waveguide up to four waveguide half waves (m ¼ 4), increase of the losses is observed (Г<sup>r</sup> growth from 0.257 till 0.322). This apparently could be explained by transformation of the Gaussian beam into the waveguide wave. At further increasing of the waveguide segment length up to m ¼ 8, there is insignificant growth of loss is caused by ohmic losses in the waveguide segment. If m is increased further, then, Г<sup>r</sup> is almost without any change.

50 Emerging Microwave Technologies in Industrial, Agricultural, Medical and Food Processing

Considered here resonant system will be the most promising at the analysis of biological liquids and food stuffs, the basic element of which is water (wines, juices, drinks). For carrying out measurements, a pipe made of the material of lower permittivity than that of a sample is placed into the oversized rectangular waveguide parallel to the vector of electric field intensity of the ТЕ<sup>10</sup> mode. For reduction of losses inserted to the resonant system, it can be displaced to

The cavity with the dielectric layer, being an electrodynamic model of the hemispherical ОR with the segment of the oversized circular waveguide and dielectric bead, is considered in this chapter. As a result of the carried out theoretical analysis, it is shown that dependence of the frequency upon the thickness of the dielectric bead, located on the bottom of the cavity cylindrical part, has a quasi-periodic behavior. Such behavior is related to the amplitude distribution of Е<sup>φ</sup> - component of the axial-symmetric mode at the top of the sample. The weak dependence of frequency on the bead thickness takes place when near to the sample top the node of the electric field component of the standing wave in the resonator is located. If in the area of the sample top, there is an antinode of the electric field component of the standing wave in the resonator, and the frequency dependence on the sample thickness is strong. Measurement of the permittivity and the tangent losses of beads, made of Teflon and Plexiglas at the various thickness, using the ОR with the segment of the oversized circular waveguide,

authors. In such a way, the proposed resonant system can be applied for measurement of electromagnetic parameters of substances in the short wave part of the millimeter and sub-

The hemispherical ОR, with the segment of the rectangular oversized waveguide located in the center of the flat mirror, has been considered in this chapter as well. As a result of the carried out theoretical analysis, it was demonstrated that efficiency of the ТЕ<sup>10</sup> mode excitation in such waveguide by means of the resonator fundamental mode ТЕМ00q can reach the value ~90% at cross-section sizes <sup>~</sup><sup>a</sup> <sup>¼</sup> 2.844 and <sup>~</sup><sup>b</sup> <sup>¼</sup> 1.98. The experimental researches carried out by the authors made it possible to establish that the resonator with the segment of the rectangular oversized waveguide possesses selective properties in the wide band of frequencies. Presence of the rectangular waveguide segment does not result in an abrupt increase of the ohmic losses. These circumstances are advantageous for application of such resonator for research of dielectric substances. Considered resonant system will be the most promising for the analysis

<sup>2</sup> and tanδ are in agreement with the data of the other

one of the side walls of the waveguide.

have been carried out. Obtained values ε<sup>0</sup>

millimeter ranges, both with high and with low losses.

5. Conclusions

Kuzmichev Igor K.\* and Popkov Aleksey Yu.

\*Address all correspondence to: kuzmichev.igr@i.ua

The A.Ya. Usikov's Institute for Radio Physics and Electronics of the NAS of Ukraine, Kharkiv, Ukraine
