Generalized Transmission Line Theory Research Articles

A study on the effect of metal skeleton auxiliary heating device on microwave heating efficiency of batch Al2O3 ceramics

In order to improve the microwave heating efficiency of the batch Al2O3 ceramics, according to generalized transmission line theory in this paper, the relationship between the amplitude and phase of the electromagnetic field in the microwave resonant cavity was deduced by using the distribution relationship of voltage and current on the transmission line. SiC auxiliary heating plate was used as the auxiliary heating device. Based on the reflection principle of metal material to electromagnetic wave, the metal skeleton was added to SiC auxiliary heating plate. The COMSOL multi-physics field simulation software was used for simulation. The results showed that the addition of metal materials could change the intensity and distribution of the electromagnetic field on SiC auxiliary heating plate and Al2O3 ceramic blocks, so as to affect the microwave energy utilization rate of heating area and the heating efficiency of Al2O3 ceramic blocks. The numerical simulation results showed that the microwave energy utilization rate of the heating area could be improved by adding the metal skeleton in the SiC auxiliary heating plate and employing a reasonable design, so as to improve the overall heating efficiency of the Al2O3 ceramic blocks. Compared with the traditional SiC auxiliary heating device, the heating efficiency of Al2O3 ceramic blocks was improved by 26.4%, and the overall temperature uniformity was improved by 12.5%.

Analysis and Design of the Resonator in a 110 GHz Gyrotron Oscillator

Gyrotron oscillators are powerful millimeter, sub-millimeter and even potential THz wave sources, capable of reaching megawatt power levels. They are widely studied today to use for electron cyclotron resonance heating, current drive, stability control and active diagnostics of magnetically confined fusion plasmas. To suppress the parasitic modes and improve the efficiency of the over-mode resonator is a important object for the design of high power gyrotrons. On the basis of electron cyclotron resonance maser theory and generalized transmission line theory, we compiled programs to analyze the resonant cavity in a 110 GHz gyrotron. The results shows that the coupling coefficient to parasitic modes of gradually tapered cavity is obviously less than line-joint cavity. By calculating and studying different gradual-varying and line-joint resonant cavities, we designed a gradually tapered resonator for a 110 GHz gyrotron, which is good at suppressing the parasitic modes, improving the purity of the operating mode and the efficiency of the beam–wave interaction.

Some limiting aspects of transmission line theory and possible improvements

Wiring still supports most of electric power fluxes as well as data transmission in various infrastructures and transport systems. Hopefully, transmission line theory is a very helpful approximation to estimate interference propagation among cable harnesses. This is definitely a useful tool for engineers, since it enables anticipating the probability of failure of equipment they are connected to. Everything has been written from the initial roots of transmission line derivation, dated from the ancient telegraphist's equations established by O. Heaviside back to...1880! until the last developments of sophisticated and off-the-shelf transmission line solvers for complex arrangements of cable networks. The fact is, that these tools are so familiar to many EMC engineers that it might come with some misunderstanding of some results. In this paper, we take a look at the root assumptions of this approximate theory and examine some of its potential weaknesses, through simple examples. Then, we investigate the question of the possible improvement of the classical transmission line theory (when and if required). In principle, this would require the derivation of some kind of generalized transmission line theory or even the examination of the super theory of transmission lines. We rather show that a much more simple modification of transmission line equations is possible for a better approximation of the experimental observations.

Generalized transmission line theory as an antenna theory for EMC analysis

This contribution exhibits the equivalence between generalized transmission line theory and antenna theory, as applied to thin-wire structures. While in antenna theory focus is put on the direct solution of appropriate field integral equations, in the derivation of generalized transmission line theory the relevant field integral equations are first transformed into equivalent generalized Telegrapher equations and eventually solved by methods which are tailored to transmission line theory. This is illustrated by two examples that exemplify the use of generalized transmission line theory in EMC analysis for the investigation of radiating transmission line systems.

INSULATED CYLINDRICAL ANTENNA IN A COLD MAGNETOPLASMA

A study is made of the characteristics of a perfectly conducting cylindrical antenna insulated from the surrounding cold collisionless magnetoplasma by an isotropic coaxial cylindrical sheath for the case where the antenna is aligned with an external magnetic field and is excited by means of a delta-function voltage generator. A rigorous representation is obtained for the current distribution on an infinitely long antenna. It is shown that in the whistler frequency range, the current distribution of a sufficiently thin antenna is determined mainly by the eigenmode whose guided propagation is found to be supported along the antenna. Based on the results obtained for an infinitely long antenna, a generalized transmission-line theory is developed for determining the current distribution and the input impedance of an insulated antenna of finite length located in a resonant magnetoplasma. The influence of the sheath parameters on the antenna characteristics is analyzed.

Generalized Transmission Line Theory for Parallel Planar Transmission Lines

The frequency-domain transmission-line equations for parallel planar transmission lines are derived in this paper. Such a general formula is very useful in order to analyze the characteristics of arbitrary transmission lines. And the hypothesis, i.e., the existence of non-zero diagonal parameters in the parameter matrix, made by Haase and Mei is validated through a sound theoretic derivation. The non-zero parameter takes into account the effects of discontinuity, radiation and higher modes of the lines.

Analysis of a Double Folded Stub Microstrip Structure using Generalized Transmission Line Equations Method

This paper presents a generalized transmission-line theory which is useful to describe the local radiation effect along almost arbitrary three-dimensional wire structures. For the generalized transmission-line theory, the mathematical structure of the classical telegrapher equation is preserved, while the coefficients (the per-unit-length parameters) are generalized in order to represent the intrinsic behavior of the wire structure. Essentially, the generalized transmission line equations (GTLEs) is a novel kind of telegrapher equation. The equation coefficients of the generalized transmission line equations (GTLEs) are determined from full-wave numerical solutions in this paper. In comparison with the conventional telegrapher equation, the GTLEs has two additional terms — dependent series voltage and shunt current sources — which represent local radiation effect from discontinuities of the nonuniform transmission-line itself. For the double folded stub microstrip structure, the novel 1D-GTLEs whose coefficients are determined by dynamic numerical methods can have broadband frequency characteristics. To the investigated microstrip structure as a band stop filter, the S parameters for a frequency band from 3 GHz to 18 GHz can be calculated by using only one group of the 1D-GTLEs at a frequency of 12 GHz, while 1D-GTLEs is only established on the central transmission line rather than on the whole structure with the stubs. Furthermore, the 2D-GTLEs developed from the 1D-GTLEs is sought for the whole structure with stubs and the model of 2D-GTLEs is validated to be more accurate than that of 1D-GTLEs through numerical experiments in this paper

Generalized transmission-line theory for the treatment of nonuniform multiconductor transmission lines

This paper presents a generalized transmission-line theory which is useful to describe the wave propagation along almost arbitrary three-dimensional wire structures. In contrast to the classical transmission-line theory this new approach is an approximate full-wave description based on generalized telegrapher's equations. Whereas the mathematical structure of the classical telegrapher's equations is preserved, the coefficients (the per-unit-length parameters) are generalized in order to represent the intrinsic behavior of the wire structure. MoM simulations were performed to validate the predicted data.

The mode matching technique for electromagnetic scattering by cylindrical waveguides with canonical terminations

The Mode Matching Technique is employed for the evaluation of the Radar Cross-Section (RCS) of cylindrical inlets terminated by a perfectly conducting cylindrical hub or a cylindrical array of grooves that may be straight or curved. In the case of curved grooves, the geometry is analyzed via the generalized transmission line theory and a closed form solution is given for the first time. The method is formally exact, and yields accurate RCS patterns for geometries that have not been previously investigated. Analytical expressions are derived for the coupling factors between the various modes and RCS results are presented which may be used as a reference in validating other, more general numerical techniques.