Design considerations for improved efficiency characteristics of M-type backward-wave oscillators

It has been observed that under certain conditions the electronic efficiency of M-type backward-wave oscillations (M-BWO´s) can deteriorate appreciably. The deterioration in the efficiency of M-BWO´s has been investigated from the viewpoint of cyclotron-wave interactions. It has been found that although the main cause of the deterioration is the interaction of the slow cyclotron wave with one of the forward circuit harmonic waves, other cyclotron-wave interactions can also result in reduction of efficiency. Design considerations of M-BWO´s have been discussed that will avoid the simultaneous occurrence of any of the cyclotron-wave interactions within the useful frequency range of the oscillator. In this manner the useful bandwidth can also be maximized.