The transition two-port (TT) for VHF transmission lines, as is known, transforms the wave type, frequently the TEM line wave mode into TE waveguide mode, and vice versa. In TT structure the most important is line junction-element (exciter) type (vibrator, coil, a. o.), and also reactance type for TT tuning. Thus it is possible to present the TT structure as the junction-three-port (JT), whose one port is by tuning reactance loaded.
As an example in the paper is a TT with vibrator junction-element for coaxial line and rectangular waveguide considered. The tuning reactance here is a section of shorted waveguide. Main characteristic quantity for TT device is the wavelength-band width, and corresponding value of reflection coefficient. Usually for TT device the middle wavelength of band-width is given. At the designing of TT device it is necessary all efforts for wavelength-band widening to made. Such the optimization problem for geometrical sizes of TT structure elements arise.
The proposed here TT synthesis algorithm is on results of junction-element (exciter) electrodynamics’ analysis based. These results are in analytical part of synthesis algorithm used. For that calculation the VHF circuit theory is applied. In high regret, the electrodynamics’ analysis results we get from none closed expressions in numerical form. Therefore we are forced the numerical synthesis to realize, for which geometrical sizes of junction-element structure must be given. In our case by electrodynamics’ analysis we get the value of input impedance and argument of transmission coefficient between coaxial line and waveguide JT ports. These numerical values serve for scattering matrix elements of JT calculations, use the equations for loss free structure. By aid of one contour signal flow graph reflection coefficient from TT input, and corresponding wave-band width is determined.
The mentioned above numerical synthesis algorithm expects the zero value of reflection coefficient from TT input at the middle wavelength, and correspondingly narrow wavelength-band width. The line wave-resistance value can be for that calculation sufficient low accepted. For wavelength-band widening it is possible the optimization of arbitrary geometric size of TT structure to apply. Here for that purpose is choosing of coaxial line wave-resistance used. The enlargement of that resistance disturbs the TT structure. Then at the middle wavelength arise the reflection, and simultaneously appears greater wavelength-band width.
It is to emphasize, that up today in technical literature the TT synthesis problem is not considered. Only the electrodynamics’ analysis of junction-element (exciter) is today into considerations taken. Thus we have the evidence, that the TT synthesis is by costly experimental methods realized. The presented numerical synthesis of TT structure provide the possibility for optimization, and cheaper the designing process of TT structure.