WAVEGUIDES USED IN THE TERAHERTZ RANGE

Abstract

Waveguide types mostly used in the terahertz range are considered. The main electrical characteristics of dielectrical, metal and metal-dielectrical waveguides are studied. The sphere of usage of each waveguide is shown. The comparative analysis of electrical and mechanical characteristics of each waveguide is carried out. The optimal solution is considered. As it is known, the most important charachteristics of waveguides are uniform frequency and linear phase characteristics, the pursuit of loss and the maximum transmit power level. Two main factors obstruct to the wide application of the metalic waveguides in the terahertz range. Firstly, the production of a metalic single-mode waveguide is impossible because of its microscopic size. The values of loss in this type of waveguides exceed the acceptable norms because of the skin-effect. Secondly, the use of the oversized metalic waveguide is limited to multiwavelength. The main means of overcoming the multiwavelength is self-filtering. But metallic waveguides do not have the mentioned property. Dielectric waveguides belong to the open-type class. The main drawback of the open-type waveguide is the presence of radiation losses. This property is crucial and can not create the functional elements for the implementation of schemes for different purposes in the terahertz range. In this paper, it is theoretically and experimentally shown that metal-dielectric waveguides have the best electrical characteristics. This waveguide belongs to the oversized waveguides. The dielectric cоver on the walls of the waveguide, on the one hand, leads to a considerable reduction of longitudinal currents on the metal walls of the waveguide, on the other hand, provides self-filtering of higher types of waves that can occur on the non-uniformities. These properties of the metal-dielectric waveguide allow to create virtually all the waveguide elements on which it is possible to implement high-frequency circuits for various applications.