High Frequency Circuit for E-Band Sheet Beam TWT

A folded waveguide (FWG) slow-wave structure (SWS) circuit for a compact E-band sheet beam traveling wave tube amplifier (SB-TWTA) has been designed, fabricated, and cold tested by UC Davis and Elve Inc. The circuit is compatible with sheet electron beams and predicted to produce high output power with reduced beam current density, hence suitable for periodic permanent magnet (PPM) focusing and lower voltage operation. The optimized SWS can fulfill the 5 GHz (81 - 86 GHz) bandwidth requirement while avoiding backward wave oscillation. A multi-step, side-out coupler is designed to be compatible with the planar periodic magnetic focusing system. A cold test was performed to verify the circuit performance and effects arising from fabrication errors were analyzed with simulation tools.