Investigation of W-Band Traveling-Wave Tube Amplifiers with Folded Waveguide Slow Wave Structures
I.S. Dmitriev1, A.A. Rostuntsova1,2
1Saratov State University, Saratov, Russia
2Saratov Branch, Kotelnikov Institute of Radioengineering and Electronics RAS, Saratov, Russia
Abstract
Theoretical analysis of a folded waveguide slow wave structure (FW SWS) was performed using analytical formulas [DOI: 10.1002/mop.11003]. The geometric parameters of the structure were optimized to ensure the passband of the fundamental mode within the W-band. The dispersion characteristics were calculated, showing that the lower cutoff frequency is 80 GHz, and synchronism with the electron beam is achieved at the +1st spatial harmonic at operating voltages up to 10 kV. Simulation of electromagnetic parameters of a single SWS period with Floquet periodic boundary conditions was carried out using COMSOL Multiphysics. The numerical results demonstrate good agreement with the theoretical predictions.
The influence of a rectangular tunnel for a sheet electron beam on the FW SWS dispersion was studied. It was found that the presence of the tunnel causes mode splitting at the 2π phase shift, resulting in the formation of a stopband whose width increases with the tunnel width.
To overcome this limitation, a modified SWS is proposed, consisting of two FWs positioned symmetrically above and below a wide central beam tunnel. The mode structure of the modified SWS was analyzed. The output characteristics of a traveling-wave tube (TWT) amplifier based on the developed SWS were simulated using the equations of nonlinear non-stationary theory [DOI: 10.1109/PLASMA.2004.1339729]. The results demonstrate that the TWT amplifier provides a gain exceeding 30 dB in the 100–115 GHz range at a beam voltage of 10.55 kV. In the saturation regime, an output power of approximately 30 W is achieved.
Speaker
Ivan S. Dmitriev
Saratov State University
Russia
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