Investigation of Abnormal Phase Shift Curve Distortion in Millimeter-Wave Helix Traveling Wave Tubes for Satellite Communications

This article explores the phenomenon of anomalous variations in phase shift curves along with their underlying mechanisms. It provides an analysis of the observed irregularities in phase shift curves and investigates the characteristics of the associated spurious spectrum. The study further examines the frequency relationships within the spurious spectrum and identifies trends in amplitude variations, such as operating voltage and current change. Through simulation, the slow wave properties of helix high-frequency structures and the beam–wave interaction dynamics are analyzed. The results reveal that the existence of backward wave operating frequency points within the traveling wave tube’s (TWT) high-frequency structure leads to the generation of spurious frequencies during output regression, which in turn causes anomalies in the phase shift curve and distortion in the amplitude modulation to phase modulation (AM/PM) characteristics.