NONRESONANT PERTURBATION MEASUREMENT ON DISPERSION CHARACTERISTICS OFA FAST-WAVE CYLINDRICAL WAVE-GUIDE

A nonresonant perturbation technique (NRP), normally used for the expe rimental evaluation of the dispersion characteristics of a helical slo w-wave structure in a TWT, is extended to the characterization of the fast-wave cylindrical waveguide that can be used as an interaction str ucture of a gyro-TWT. An experiment is conducted to record how the pha se of the reflection coefficient at the measurement port varies as a p erturber is moved down a cylindrical waveguide excited in the dominant (TE11) mode. This pahse variation is interpreted to obtain the omega- beta plot, which is found to agree closely with that obtained by the c onventional resonant perturbation (RP) technique. The NRP and RP measu rement values of beta lie within 6% and 12%, respectively, of theoreti cal predictions. (C) 1997 John Wiley & Sons, Inc.