RF Design, Thermal Analysis, and Cold Test of a Ku-Band Continuous Wave Sheet Beam Traveling Wave Tube

RF circuit design, thermal analysis, fabrication, and measurement of a continuous wave (CW) high-power sheet beam traveling wave tube (SB-TWT) operating in the Ku-band were demonstrated in this paper. The slow wave structure circuit was constructed by double staggered grating waveguides (DSGWs), and the lossy dielectrics attached in the H-plane were applied to suppress parasitic oscillations. The Particle-in-cell simulation predicted that the CW SB-TWT can provide 20-kW output power in the band range of 16.2-18.5 GHz, with a maximum small signal gain of 38 dB. Microchannel cooling, which has been proved to be an efficient cooling method for microelectronic chip, very large scale integration, and power electronic modules with very high heat flux were introduced to improve the thermal capacity and heat dissipation ability. A thermal analysis of the RF circuit considering attenuated losses and electrons interception was studied in detail. Investigation shows that the RF circuit can operate with maximum ~1-kW dielectric loss power (1.5 times of the loss power generated from the saturated output power at center frequency) and a maximum of 7% interception of electrons. Furthermore, an interaction circuit, including 23 DSGWs implanted with BeO-SiC to provide necessary attenuation, was fabricated and cold tested. Vector network analyzer RF measurement shows excellent performance and agrees very well with our prediction.