Abstract
High power vacuum electronic devices of the millimeter wave to terahertz regime are attracting extensive interest due to their potential applications in science and technologies. In this paper, a novel sheet beam (SB) folded waveguide (FWG) slow-wave structure (SWS) is applied and studied for enhanced output power of oscillators. Through the analysis of high-frequency characteristics of the SB FWG-SWS, the selection of an appropriate beam–wave interaction point on the dispersion curve and beam position is determined for an SB folded waveguide oscillator (FWO) operating near the 2π stopband point. The fundamental mode operation of the SB FWO was verified by the particle-in-cell simulation results, which also indicate that the SB FWO exhibits a better outstanding performance (84.6 W with a beam voltage and current of 25.1 kV and 200 mA, respectively) than the conventional circular beam FWO. The transmission stability of the SB was analyzed by observing the interception beam current in the FWO. The voltage and frequency tuning performance of the SB FWO were discussed in combination with clutter suppression. A preliminary experiment was conducted by fabricating a 220 GHz SB FWG-SWS and measuring the S parameter.
Highlights
The critical barrier to full exploitation of the terahertz (THz) band is the lack of compact, powerful, coherent radiation sources that are efficient, frequency agile, reliable, and comparatively inexpensive.1,2 Vacuum electron devices based on slow-wave structures (SWSs) are the most promising solution for the generation of watt-level power at millimeter wave and terahertz (THz) frequencies in a compact and affordable way.3Among them, the oscillator based on the SWS is a promising candidate that can produce continuous terahertz waves at low cost at room temperature and finds a wide range of applications in high-resolution imaging, material research, deep space research, and communications
An folded waveguide oscillator (FWO) operating near the stop-band based on the sheet beam (SB) folded waveguide (FWG) circuit is proposed for enhanced output power in this paper
The interception current in the SB FWO was observed to give an intuitive understanding of transmission stability of the sheet beam
Summary
The critical barrier to full exploitation of the terahertz (THz) band is the lack of compact, powerful, coherent radiation sources that are efficient, frequency agile (instantaneous bandwidth >1%), reliable, and comparatively inexpensive. Vacuum electron devices based on slow-wave structures (SWSs) are the most promising solution for the generation of watt-level power at millimeter wave and terahertz (THz) frequencies in a compact and affordable way.. Vacuum electron devices based on slow-wave structures (SWSs) are the most promising solution for the generation of watt-level power at millimeter wave and terahertz (THz) frequencies in a compact and affordable way.. This paper focuses on the oscillation characteristics in FWOs near the 2π point This is motivated by the following reasons: (a) For wideband applications of TWTs based on the same SWSs, the beam line is normally set to intersect the first spatial harmonic near the 2π point by necessity, usually causing a band-edge oscillation. Researchers in Ref. 20 studied the stopband and pass-band properties of SB FWG-SWSs. Differently, this paper will present a further study on the oscillation performance with respect to starting current and power capacity, followed by an analysis on mode competition, taking the associative influence of dispersion characteristics and coupling impedance into account.
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