Analysis of bandpass characteristics of high-power traveling-wave tubes based on a coupled-resonator chain with interaction beyond the passband of the slow-wave system

The characteristics of a traveling-wave tube (TWT) with a slow-wave system (SWS) based on a coupled-resonator chain (CRC) with interaction beyond the SWS transparency band are numerically and experimentally analyzed. The effect of gain zeros, which does not allow obtaining considerable amplification bands in the case of a constant input signal is theoretically predicted and revealed by the numerical simulation of the interaction space of a multisection CRC TWT. The discovered effect is experimentally confirmed by the example of a high-power four-section TWT. The effect of a dip in the amplitude-frequency characteristic is explained within the theory of the interaction between an electron flow and the field of a distributed resonator and the way of elimination of this effect is proposed. Experimental characteristics of a UVI-155 four-section TWT are presented, in which a 8% gain bandwidth in the case of a constant input signal and a drop of the output power drop of no more than 1.5 dB are attained by shifting the gain zeros beyond the operating band.