Amplitude Modulation in Traveling Wave Tube Phase Modulator

Abstract

Several problems of the amplitude modulation caused by the traveling wave tube used as a microwave phase modulator are discussed. Using Pierce's linear theory, some expressions for phase modulation and the amplitude modulation which occurs simultaneously are derived. From the derived composite modulation formula, various effects of the amplitude modulation on amplitude of carrier and each side band are calculated. To decrease amplitude modulation, experimental studies are performed by using the 1st anode to compensate it and a satisfactory improvement has been obtained.