A <i>G</i>-Band Dual-Band Extended Interaction Klystron Based on the Modes of TM₁₁ and TM₂₁

A novel dual-band extended interaction klystron (DB-EIK) is proposed, which is combined with the interleaved tuning and mode overlap as a suitable solution for broadband terahertz (THz) power amplifiers. The DB-EIK operates in the modes of TM11 and TM21, differing from typical multimode circuits. The DB-EIK provides dual operating frequency ranges. The dispersion devices, the frequency intervals between modes, and the transmission performance of DB-EIK are investigated. Concurrently, a six-cavity DB-EIK for the two operating frequencies of 215.5 and 219.8 GHz is designed based on interleaved tuning. The particle-in-cell (PIC) simulation reveals that the DB-EIK has a power output of 210 W at 215.5 GHz and 270 W at 219.8 GHz, operating within two distinct bands, utilizing an operating voltage of 23 kV and an operating current of 0.15 A. Meanwhile, the novel DB-EIK was designed to operate in four modes by using mode overlap. The structural attributes of the DB-EIK have been confirmed by computer numerical control (CNC) milling. The DB-EIK shows great potential in extending the bandwidth of THz EIK circuits.