Improvements in or relating to parametric amplification of space charge waves

摘要

832,172. Space-charge-wave tubes. WESTERN ELECTRIC CO. Inc. Nov. 3, 1958 [Nov. 25, 1957], No. 35156/58. Class 39(1). Parametric amplification of space charge waves is achieved by modulating an electron beam in the fast space-charge mode and introducing the signal to be amplified into fast mode coupling relationship with the beam. Noise in the fast mode is abstracted from the beam before the introduction of the signal. The introduction of the signal may be before or after the modulation of the beam in the fast mode. In Fig. 1 the tube comprises four twogap cavity resonators 16, 27, 39 and 52 separated by drift spaces. Noise abstracting cavity 16 is tuned to the midband frequency of the signal and fast wave modulating cavity 27 is preferably tuned to twice the frequency of the signal. Cavity 39 impresses the signal on the beam and the amplified signal is abstracted by the cavity 52. Grids may be provided on either side of the gaps in the cavities and the cavity resonator may be incorporated into the envelope of the tube or mounted externally. The cavity resonators may be replaced by helices with reflectionless terminations. Fast mode coupling is achieved by using the Kompfuer Dip condition with a suitable voltage on the helix dependent on the length of the helix. In Fig. 4 the signal is applied to and taken off from the helix 202. The beam velocity is slower than that of the wave propagating on the helix to secure the fast mode interaction. The theory of operation is given.