| || Plasma Frequency Reduction Factor
Author : Datta, S.K.;Kumar, Lalit
Source : Defence Science Journal ; Vol:58(6) ; 2008 ; pp 768-770
Subject : 621.38 Electronics
Keywords : Artificial neural network;Plasma oscillation;Plasma frequency reduction factor;Solid electron beam;Metallic tunnel
Abstract : A simple formula for plasma frequency reduction factor for a solid cylindrical electron beam in a metallic tunnel has been developed by means of a 3-D curve fitting to the standard results of Branch and Mihran with accuracy > 1.7 per cent, over the parametric regime of normalised beam-radius and beam-filling factor applicable for linear-beam microwave tubes. An artificial neural network algorithm was used for the curve-fitting following the approach of universal approximation. The formula is simple and amenable to easy computation, even using a scientific calculator.
| || Automatic Dispersion Measurements of Helical Slow Wave Structure
Author : Rao, S.J.;Subramanian, S.K.;Datta, S.K.;Seshadri, R.
Source : Defence Science Journal ; Vol:50(1) ; 2000 ; pp 83-86
Subject : 681.2 Instrumentation;537-962 Microwaves
Keywords : Dispersion characteristics;Slow wave structures;Perturbation techniques
Abstract : An experimental setup for computer-controlled automatic measurement of dispersion characteristics of helical slow-wave structures (SWSs) has been described. A non-resonant perturbation technique was employed for this purpose. The dispersion characteristics of a practical X-Ku band helical SWS were studied using this experimental setup. The experimental results have shown good agreement with analytical results obtained using an equivalent circuit approach for an X-Ku band helix SWS.
| || Backward-Wave Oscillation Criterion in a Step-Tapered Helix Travelling-Wave Tube
Author : Datta, S.K.;Sinha, S.;Rao, P. Raja Ramana;Reddy, S.U.M.;Kumar, Lalit
Source : Defence Science Journal ; Vol:59(1) ; 2009 ; pp 49-54
Subject : 53 Applied Physics
Keywords : Backward-wave oscillation;Helix travelling-wave tube;Slow-wave structure;Step-taper circuit;TWT;Amplifier design;Travelling-wave tube
Abstract : Analysis of backward-wave oscillation criterion is one of the essential steps for designing a broadband travelling-wave tube (TWT) amplifier. In this paper, a methodology for the analysis of the backward-wave oscillation criterion in a helix travelling-wave tube has been proposed with emphasis on its usage as a design tool. The analysis is also extended for a slow-wave structure having distributed RF loss and a closed-form equation has been proposed for calculating the critical interaction length. The analysis is further extended for a step-tapered TWT with distributed circuit loss included in the analysis. The method is finally applied to design a typical slow-wave structure used in an X-Ku band TWT having a step-tapered output circuit.