Compact E-Band Sheet Beam Folded Waveguide Traveling Wave Tube for High Data Rate Communication

The design of a compact E-band (71-76 GHz) sheet beam (SB) folded waveguide (FWG) traveling wave tube (TWT) for high data rate communications is presented in this article. The round beam tunnel for a pencil FWG slow wave structure (SWS) has been redesigned with a rectangular beam tunnel to be suitable for the SB with increased beam current. A novel periodic permanent magnet (PPM)-periodic quadrupolar magnet (PQM) focusing system has been developed to reduce the beam ripple and improve the transmission ratio. A multistep side-out coupler is designed to import and extract the RF power from the SWSs and be compatible with the planar periodic magnetic focusing system. Particle-in-cell (PIC) simulations are employed to evaluate the performance of the high-frequency circuit. Driven by a 1 W signal, the 30-period circuit is estimated to produce more than 100 W power and achieve a 21 dB gain with a less than 0.4 dB variation over 71-76 GHz. Moreover, phase and linearity analysis show a less than 6 degrees in-band phase distortion and similar to 30 dB third-order intermodulation distortion (C/3IM) at 30 W of output power, meeting the requirements of a communications-focused TWT. Over 5% circuit efficiency and 40% overall efficiency when equipped with a single-stage collector can be achieved by the compact TWT over the target band.

Automated summary

This article presents the design of a compact and efficient folded waveguide traveling wave tube (TWT) for high-speed data communications in the E-band frequency range. Various innovative techniques, including a rectangular beam tunnel, a novel focusing system, and a multi-stage coupler, have been employed to enhance the performance of the TWT. The simulations and experimental results show that the designed TWT can achieve a high power output, low variation, low distortion, and high efficiency over the target frequency band.