A novel H-plane loaded on a double-staggered grating waveguide slow-wave structure for W-band traveling-wave tubes
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A novel H‑plane loaded on a double‑staggered grating waveguide slow‑wave structure for W‑band traveling‑wave tubes Akbar Babaeihaselghobi1 · Habib Badri Ghavifekr1 Received: 28 April 2020 / Accepted: 28 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A novel H-plane loaded on a double-staggered grating waveguide (DSGW) slow-wave structure (SWS) is proposed. The main advantage of this SWS is its high interaction impedance and low phase velocity, based on which higher output power can be expected. Electromagnetic characteristics and particle-in-cell simulations were performed using CST Microwave Studio software. The dispersion diagram of the SWS was optimized for a central frequency of 94 GHz which corresponds to a beam voltage of 13.2 kV in the second spatial harmonic (2𝜋–3𝜋 ). A sheet electron beam with a current of 200 mA is used to interact with the longitudinal electric field. The reflection signal at the input port is below −15 dB for frequencies of 89–98 GHz and a small-signal gain of 35 dB is achieved at the output port for a tube length of 80 mm. Keywords Double-staggered grating waveguide · Slow-wave structure · W-band · Traveling-wave tube
1 Introduction Traveling-wave tubes (TWTs) are some of the most common vacuum electron devices (VEDs), being used to amplify W-band power levels for high-date-rate communications, radar, imaging, and security applications [1, 2]. The enhancement of the output power level in W-band frequencies (75–110 GHz) due to the presence of various kinds of slow-wave structures (SWSs) lies as the heart of TWTs. Folded-waveguide (FW) SWSs (FW-SWSs) can potentially provide a wide bandwidth of operating frequencies and can be fabricated using conventional microfabrication technologies [3]. Most applications of FW-SWSs use W-band frequencies, for which many studies have manipulated the shape of the FW and added taper structures to achieve higher gain and power levels over this frequency range [4–6]. Recently, for an FW-SWS with a voltage of 20 kV and a current of 100 mA, a normal gain of 36.1 dB was achieved for a tube length of 80 mm, while use of a phase velocity taper increased the gain to 39.4 dB [7]. The FW-SWS has * Habib Badri Ghavifekr [email protected] Akbar Babaeihaselghobi [email protected] 1
Department of Electrical Engineering, Sahand University of Technology, Tabriz, Iran
a wide bandwidth of operating frequencies but suffers from low interaction impedance, requiring the use of a high beam voltage to achieve high output power. Some meander line or planar SWSs have also been proposed for use in W-band applications [8–10]. Another structure used in W-band TWTs relies on a grating inside the waveguides [11–13], using which, for a sine-waveguide SWS with a voltage of 19 kV and current of 200 mA, a maximum gain of 33.5 dB was achieved for a tube length of 100 mm [14]. However, these structures also exhibit a low interaction impedance, thus a high-voltage electron beam is required to achieve high gain and power levels. A novel
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