Analysis of coupled-structure traveling-wave tubes

Until now there has been no general method available for taking into account the effect of the electron beam on coupled-structure couplers and attenuators for traveling-wave tubes. This paper presents an analytical procedure for this purpose based on the coupled mode approach of S. E. Miller and J. R. Pierce. It is valid for loosely coupled structures with small loss, only one of which is coupled directly to the beam. In addition to other relations, a general root equation is developed which takes into account loss in either or both of the coupled structures, space charge in the beam, and the possibility of different phase velocities in each structure. Typical plots of the incremental wave parameters are shown. An experimental verification of the theory is presented that shows that predictions made by means of it will be fair to good.