Calculation of nonconverting taper structure for TE/sub 01/ modes in gyrotron
Calculations and analysis of nonconverting taper for circular waveguide with operating TE/sub 01/ mode are presented. Calculations are carried out on the basis of discretely defined T-functions. The results obtained were checked by alternative method of finite elements which is incorporated in widely spread program.
Theoretical Evaluation of Nonlinear Tapers for a High-Power Gyrotron
In this paper the theoretical performance of two nonlinear circular waveguide tapers constructed for a LO GHz, 30 Mw amplifier utilizing the lowest circular electric mode is evaluated. Mode coupling is estimated with a code that solves the generalized telegraphist's equa- tions numerically and is compared with the results of a cascaded scattering matrix code. It is found that assuming a sufficiently lossy conducting boundary allows evaluation of modes that pass through cutoff and that consideration of backward modes usually results in small changes in the forward modes that reconcile the two numerical procedures. A comparison of the raised cosine profile with other taper shapes is made.
Computer-aided analysis and design of circular waveguide tapers
Two computer programs have been developed for the rigorous performance analysis of circular waveguide tapers. They are based on the direct integration of the coupled wave equations and on a mode-matching procedure applied to a step-ladder equivalent of the taper, respectively. Close agreement has been obtained between the predictions of these two approaches. The computer programs are utilized to examine the usefulness of existing taper design procedures. It has been found that a Dolph-Chebychev design is actually capable of predicting the level of the first unwanted mode, provided that the operational frequency is far above its cutoff. The spurious mode excitation can still be improved by taking into account the reconversion of power from the unwanted into the wanted modes. It has been verified by the computer analysis that the above design procedures are applicable even for frequencies near cutoff of the dominant spurious mode; however, that is at the expense of a certain degradation of the input reflection of the incident mode. A further improvement of the performance is possible only by direct computer optimization of the taper. >