Ka-Band Meander-Line Slow Wave Structure Design for Traveling Wave Tube for High Data Rate Wireless Links

Ka-band (26–40 GHz) is widely used for satellite links. In particular, the 26.5–29.5-GHz band is mostly used for uplink in low-Earth-orbit (LEO) constellations and is also part of the FR2 (24.25–52.6 GHz) for high-capacity terrestrial links. The addition of the 26.5–29.5-GHz band for downlink would increase the satellite throughput, but presently, solid-state power amplifier (SSPA) modules do not provide enough power and have too low efficiency. Ka-band traveling wave tubes (TWTs) are traditionally used in geostationary Earth orbit (GEO) satellites for their high transmission power and high efficiency. Compact and affordable Ka-band TWTs would be a promising solution to provide transmission power to enable downlink at the Ka-band. Meander lines (MLs) have been extensively investigated as slow wave structures (SWSs) for lightweight, small dimensions, and low voltage operation. In this article, an interaction circuit for compact and affordable Ka-band TWTs based on the ML (ML-TWT) is discussed. The first TWT with two ML sections interacting with an elliptical sheet beam with 4.56-kV beam voltage, in the 26.5–29.5-GHz frequency range, is proposed. More than 31-W output power with about 38-dB gain in the linear region is achieved. A single-section ML-SWS and a sever for the two-section ML-TWT are fabricated and measured. The compact dimensions and low voltage of the novel ML-TWT make it a competitive solution for medium transmission power in the future Ka-band high-capacity LEO satellite and terrestrial links for future 5G and 6G network integration.