A 100 W, V-Band Elliptical Beam Traveling Wave Tube Amplifier

ABSTRACT: We propose to develop a 100 W TWT for operation in the 71-76 GHz band. The design will be compatible with space qualification for operation in a geostationary earth orbit (GEO) satellite platform. The performance of the TWT will be optimized to support 12/4 quadrature amplitude modulation (QAM) with 30 dB suppression and no more than 3 dB backoff. We propose to use a rectangular circuit with an elliptical beam to reduce the operating voltage and cathode current density while providing high efficiency and linearity and long lifetime necessary for an amplifier in a communication system on a space platform. During this proposed Phase I program we will develop the complete electrical and mechanical design of the major subsystems of the TWT including the electron gun, interaction circuit, vacuum windows, input and output couplers and a multistage depressed collector. The gain and bandwidth characteristics of the TWT will be rigorously modeled using state-of-the-art commercial particle-in-cell codes and the electron gun and collector will be designed using MICHELLE gun and collector code. We will simulate the linearity characteristics of the TWT, spurious power generation in the adjacent bands to estimate the self-interference and adjacent channel interference. BENEFIT: The proposed TWT amplifier technology can also be scaled to 81-86 GHz frequency range for satellite uplink on a mobile or a ground platform. Further applications of the proposed technology would be in communication and imaging at 220 GHz (G-band) and for Video Synthetic Aperture Radar (ViSAR) in the 231.5-235 GHz range with an output power in the range of 50 W. Higher frequency devices at 263 GHz, 395 GHz and 527 GHz with output power in the 1-5 W range will find application in Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance (DNP-NMR) spectroscopy.