Measurement of phase velocity of electromagnetic wave and interaction impedance in helical slow-wave structures

Phase velocity and interaction impedance measurements on slow wave structures are especially important in the microwave tubes industry. Among the methods available for measuring the phase velocity and interaction impedance, non-resonant perturbation method is simple yet accurate and applicable. In this paper, the correctness of this method for helical slow wave structure is investigated with simulation and analytical methods and based on it, a device is built that has the precision needed to move the perturber inside a slow wave structure. The results and measurement capabilities of this device have been demonstrated using simulations in CST software and analytical relationships.