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Multiport Waveguide Junctions


Analysis and Design of Multiport Waveguide Junctions and Branchings With Improved Matching Characteristics

Tech Area / Field

  • PHY-RAW/Radiofrequency Waves/Physics
  • INF-ELE/Microelectronics and Optoelectronics/Information and Communications

8 Project completed

Registration date

Completion date

Senior Project Manager
Rybakova T A

Leading Institute
Georgian Technical University, Georgia, Tbilisi


  • Korea Maritime University, Korea, Busan\nKyushu University / Department of Computer Science and Communication Engineering, Japan, Fukuoka

Project summary

The objective of this Project is a systematic analysis of electromagnetic properties of multiport waveguide junctions with artificial inhomogeneities and creation of program package to optimise parameters of such the junctions for improving their matching properties.

The topicality of the Project objectives is defined by the modern trends in development of radio-electronic and communication systems that produce the increased claims to the effectiveness and electromagnetic compatibility (EMC) of these systems as a whole and of their constructive, transmitting and transforming elements as well. These claims, in a large extent, also concern of multiport (three and higher) waveguide junctions and branchings which compose the elemental base of many microwave radio-electronic and communication systems. In particular, they are widely used in microwave range as directional couplers, power piding circuits, multiplexers, duplexers, filters, phase shifters and other devices.

In order to increase effectiveness and electromagnetic compatibility of multiport waveguide junctions including in electronic and communication systems, first of all, it is needed o increase their carrying capacity and decrease the energy losses. Moreover, in brunching, piding or transforming of a signal energy in such the systems, it is necessary provide an acceptable matching of waveguide arms, i.e. to provide a high enough quality of delivering of the operating wave energy to a desired arm and its suppression in other arms. And at last, to support the steady operation of multiport waveguide junctions, it is necessary to provide the stable characteristics of these junctions in a wide frequency band

The existing multiport waveguide junctions with homogeneous internal filling do not totally satisfy the up-to-date requirements to their effectiveness and electromagnetic compatibility with other elements. Thus, the studies of homogeneous both three-port, T-junctions (waveguide tees) and forth–port, cruciform waveguide junctions in E- and H- planes show, that the practically applicable matching of waveguide arms can be achieved only in a narrow frequency band and for fixed cross-section size ratios of waveguide arms. Thereby, the task of the acceptable matching level of multiport waveguide junctions in a wide frequency band can not be solved without constructional modification of junction geometry. As such the constructional modifications, inclusion of artificial inhomogeneities in the junction construction may be applied.

Various types of artificial inhomogeneities (inductive pin, strip, aperture, dielectric layers and so on) are widely applied in waveguide technique as adjusting elements for matching waveguide sections with different properties Inclusion of these inhomogeneities or their combinations in construction of multiport waveguide junctions allows us to modify wave impedances of the main and branched arms. Hence, adjusting the geometrical and physical characteristics of theses inhomogeneities, we can achieve an acceptable for practical application matching of wave impedances in different arms of waveguide junctions and, therefore, solve the matching task in a wide frequency band.

Since the experimental manufacture of optimum dimensions and material characteristics of desired constructions is very expensive, multi-parameter investigation of electrodynamic characteristics should precede to the serial production of multiport waveguide junctions with improved characteristics. However, the existing electrodynamical approaches to the study of multiport waveguide junctions and branchings are intended only for the homogeneous filling of waveguide arms.

The current Project is aimed to fill up the existing gap in this area in the following directions:

– to carry out the rigorous (full-wave) electrodynamic analysis of multiport waveguide junctions in E- and H- planes with included artificial inhomogeneities of various types (inductive and capacity pin, strip, aperture, dielectric layers and their combination);

– to conduct a numerical simulation and physical analysis of the investigated constructions;
– to give the concrete recommendations for improving characteristics of multiport waveguide systems.

The Project participants have a prolonged and productive experience in investigation of both homogeneous waveguide junctions and branchings, and artificial inhomogeneities as well. These researches were carried out in frame of activity of the char of Radio Engineering and chair of General Physics of Georgian Technical University. Resulting from these investigations, the Project participants have published more than 15 scientific works were defended 3 candidate, PhD (1983, 1986, 1995) and 1 Doctoral (1994) dissertations. Based on the published works, two Project participants, including the Project manager, Prof. G.Sh. Kevanishvili, were many times awarded by Republic and International grants. Six candidate (1996, 1997, 1998, 1999, 2001, 2002) and 1 Doctoral (1998) dissertations were defended under the supervisor of Prof. G.V. Jandieri. During period 1998–2001 Prof. G. Jandieri published 23 papers concerning to electromagnetic and pulse signal propagation in different inhomogeneous media, participated in several international symposiums and was awarded by Republic and International grants.

Thus, the Project participants reveal all the necessary qualities and possess the needed competence to successfully perform the tasks of the supposed Project. The base of this project is the original works, as well as scientific, methodical and personal potential of the supposed participants of the Project.

The Expected Results of this project are the following:

– development of rigorous electrodynamical theory and methods for analysis of multiport waveguide junctions and branchings with both single and combined artificial inhomogeneities;

– providing the possibilities for substantial improvement of matching properties of multiport waveguide junctions and branchings at the expense of application of adjusting elements (artificial inhomogeneities);
– creation of the program complex with developed interface for optimization of parameters of such the junctions;
– elaboration of specific recommendations for improvement of matching properties of multiport waveguide junctions and branchings by means of optimal selection of: the type, arrangement, geometrical and physical parameters of adjusting elements.

The scientific and commercial significance of expected results of the project consists in the following:

– development of the effective methods for rigorous electrodynamic calculation and analysis of complicated microwave circuits;

– creation of commercial product for optimization of construction of multiport waveguide systems with adjusting elements;
– giving the concrete recommendations for the serial (industrial) manufacture of new microwave components with improved matching characteristics.

The Project activity implies performing the following Scope of Activities:

– solution of theoretical problems of electrodynamic study of multiport waveguide junctions with various classes of artificial inhomogeneities;

– elaboration, realization, testing and verification of computational programs for calculating electro- dynamical characteristics of the structures to be investigated;
– creation of visualisation elements and interface of the program complex for providing of properly inputting geometry and parameters of construction, as well as for calculating and visualising the computation results;
– electrodynamical analysis of investigated structures in a wide range of parameters;
– giving recommendations on optimisation of parameters of investigated structures.

This activity will be performed in the frame of 4 main tasks, each of which will be subpide into a few separate stages.

To meet the Project Objectives, a rigorous theoretical approach will be used which is based on utilization of Fourier transform technique, residue theory, method of mirror image, moment method and original techniques for transformation of multipole and spatial (modal) spectra.

Above all, using the method of mirror image, the initial problems will be transformed to the equivalent multi-element periodic gratings with corresponding filling of grating spacing and boundary conditions. Further, using Fourier analysis technique and original techniques for the transformation of multipole and diffraction (modal) spectra, the corresponding functional (integral-adder) sets of equations for unknow amplitudes of discrete and continuous Fourier spectra of scattered fields will be obtained. After determining the adequate sets of basis functions in moment method, these sets will be transformed to the infinite systems of Fredholm–type algebraic equations.

Further, effective algorithms and computational programs for obtaining the problem solution will be compiled, tested and verified; numerical simulation of characteristics of the investigated structures will be carried out; the program complex for optimization of their matching properties will be created; the recommendations for optimization of parameters of these structures will be given.. Finally, the Final Report for the Center will be prepared.

The Project activity will be carried out in collaboration with the foreign collaborators, the role of whom in the Project consists in the following:

– exchange of scientific information;

– joint scientific consultations;
– joint consideration of the Annual and Final reports;
– joint attendance to scientific conferences;
– trip of one of participants to the organization of foreign collaborator;
– joint scientific publications.

The supposed Project is an alternative of the previous defence activity of the Project participants and meet the following ISTC goals:

– providing weapons scientists and engineering in the CIS opportunities to redirect their talents to peaceful activities;

– promoting integration of scientists of CIS stated into the international scientific community;
– supporting basic and applied research and technology development for peaceful purposes;
– contribution to the solution of national or international technical problems.