Automatic Dispersion Measurements of Helical Slow- Wave Structure

Abstract

An experimental setup for computer-controlled automatic measurement of dispersion characteristi 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. NOMENCLATURE very little dispersion over a wide bandwidth, is/ ideal for these tubes. A helix SWS is characterised by its dispersion behaviour, i.e., variation of phase velocity with fequency ( ro -fJ characteristics ). The interaction impedance and characteristic impedance of the dispersion behaviour of helix SWSs can be analysed either using an equivalent circuit approach or carrying out field analysis of the structure. However, there is need for a simple, efficient, fast and accurate technique for studying the dispersion characteristics of the practical SWSs due to difference in theoretical prediction and actual values owing to certain assumptions / made' in the theory and certain imperfections in,the assembly of actual SWSs. a am /3