Nodal shift impedance measurements in periodic waveguides

Abstract

The nodal shift method of measuring the properties of a Coupling system connecting two transmission lines is a convenient and accurate method which does not require the existence of good terminations to match the lines. Using a generalized definition of impedance in a periodically loaded waveguide, such as is encountered in the Stanford linear accelerator or in traveling-wave tubes, this technique can be extended to determining the properties of a coupling system connected between a smooth waveguide and the periodic one, and when these are known, one can measure impedances in the periodic structure by observing those in the smooth guide. In addition, this impedance relation permits one to deduce the phase-shift constant of the structure at any frequency in the pass-band.