Design and Simulation of a 0.23-THz Extended Interaction Amplifier With Trapezoid-Neck Cavities

We address extended interaction amplifier (EIA) and put forward a novel resonant cavity design based on a traditional ladder-type resonant cavitycombined with symmetrically trapezoidal neck cavities. The resonant cavity exploits a three-gap structure with characteristic impedance higher than the corresponding single-gap structure. The effects of the trapezoidal necks are analyzed for the TM31- $2\pi $ mode in the terahertz range. To broaden the gain bandwidth of the EIA, a stagger-tuning method is employed, and a six-cavity structure is proposed. After the stagger-tuning state, the designed multicavity EIA produces stable output power from a 20-mW input driving signal, with a gain of about 35.05 dB and efficiency 1.51% at 0.23 THz, with more than 1.1 GHz–3 dB bandwidth when a sheet beam with a dimension of 0.7 mm $\times $ 0.1 mm, 14.7-kV voltage and 0.29-A current passes through the beam tunnel.