Demonstration of W-Band 30-W Continuous-Wave Folded Waveguide Traveling Wave Tube with Lowered Operation Voltage and Imp
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Demonstration of W-Band 30-W Continuous-Wave Folded Waveguide Traveling Wave Tube with Lowered Operation Voltage and Improved Gain Flatness Fei Li 1 & Liu Xiao 1 & Tianjun Ma 1 & Yuhui Sun 1 & Jiandong Zhao 1 & Jian Wang 1 & Cha Gao 1 & Linlin Cao 1 & Mingguang Huang 1 Received: 1 January 2020 / Accepted: 19 July 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
We have demonstrated and developed a W-band 30 W continuous-wave folded waveguide traveling wave tube (CW FWTWT) with 13.5-kV operation voltage and 4.8 dB gain flatness. In this paper, we quantitatively study the relationship between operating voltage and the key geometric dimensions of a folded waveguide, which is the key to the design of the low-voltage TWT. In addition, problems of improving beam transmission and suppressing oscillations are also studied, and the related design methodologies of the long-range electron gun, periodic permanent magnet (PPM) focusing system, low-voltage standing wave ratio (VSWR) coupling system, and horseshoe attenuator are discussed. On the basis of the above analysis, we have designed and fabricated two types of W-band CW TWTs. The test results show that beam transmissions are over 98.5% at DC and better than 96.5% at the highest peak RF power. Measured saturated output powers are greater than 33.6 W with saturated gain more than 42.2 dB within frequency range of 91– 99 GHz, and an improved gain flatness of 4.8 dB is achieved. Keywords W-band CW TWT . Folded waveguide . Operation voltage . Beam transmission . Oscillation suppression
1 Introduction W-band traveling wave tubes (TWTs) have a wide application prospect in satellite-ground communication, high-resolution radar, precise tracking, electronic countermeasures, and deep-space exploration [1–3]. At present, some countries in the world have developed W-
* Fei Li [email protected]
1
Aerospace Information Research Institute, Chinese Academy of Science, No.5, Yanqi East 2nd Road, Yanqi Economic Development Zone, HuairouDistrict, Beijing, China
Journal of Infrared, Millimeter, and Terahertz Waves
band TWTs [4–9]. Communications & Power Industries, Inc. (CPI) offers a type of Wband CW TWT-VTW6495A2, which adopts a ladder circuit providing output power of 50 W within 2 GHz bandwidth [8]. A W-band CW FWTWT with 16-kV operation voltage and gain flatness of about 10 dB was developed by Beijing Vacuum Electronics Research Institute [9]. With the wide application of W-band TWT, some studies have begun to focus on lowering operating voltage and improving gain fluctuation of devices working in high frequency [2, 10, 11]. In this paper, problems of lowering operation voltage, improving beam transmission, and suppressing oscillation are studied, and the related design methodologies of electron gun, periodic permanent magnet (PPM) focusing system, energy coupling system, and horseshoe attenuator are discussed. The optimized design is developed for an existing W-band CW TWT with its main operation parameters listed in Table 1. The structure
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