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Circular Corrugated Miter Bend and Gap Losses for Broadband Frequency Applications
摘要： Circular corrugated waveguides are often used in fusion applications at single, multiple, or broadband millimeter frequencies due to their low ohmic loss, expected large frequency bandwidth, and direct coupling to free-space Gaussian modes. For single-frequency corrugated waveguide systems, transmission line components can be optimized to the desired frequency. For broadband or multiple-frequency applications, this is not possible. The goal of this paper is to demonstrate that the frequency bandwidth of circular corrugated waveguides can be compromised by diffraction losses to miter bends and gaps. It is shown that if the corrugation depth differs significantly from λ/4, a theory can substantially underpredict the gap and miter bend losses. The simulations are also shown to compare favorably to experimental measurements. To improve the transmission line performance in large frequency bandwidth systems, such as 33–165 GHz reflectometry, reducing the number of miter bends may, therefore, be necessary. For the improvement of performance in narrower frequency bandwidth or multiple-frequency systems, especially high-powered systems, wavelength-dependent techniques may be applicable. One such application is shown for a Bragg reflection technique to reduce the thermal load to insulating ceramic rings in a dc break component for multiple-frequency ITER electron cyclotron heating transmission lines.
关键词： gap,miter bend,full-wave simulation,waveguide theory,Corrugated waveguide
更新于2025-09-23 15:22:29
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[IEEE 2018 11th UK-Europe-China Workshop on Millimeter Waves and Terahertz Technologies (UCMMT) - HangZhou, China (2018.9.5-2018.9.7)] 2018 11th UK-Europe-China Workshop on Millimeter Waves and Terahertz Technologies (UCMMT) - Measurement of W-band gyro-TWA with wide bandwidth input signal
摘要： A W-band gyro-TWA has been developed to provide high output power and wide bandwidth. This letter presents the upgrade of the input signal generation of the W-band gyro-TWA, and the experiment results with frequency-swept input signals. The results show a 30 dB gain was achieved at a 1 GHz bandwidth input signal when the gyro-TWA was driven by a 40kV, 1.5 A electron beam.
关键词： gyrotron,frequency-swept,helically corrugated waveguide,traveling wave amplifier
更新于2025-09-23 15:21:01
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[IEEE 2019 International Vacuum Electronics Conference (IVEC) - Busan, Korea (South) (2019.4.28-2019.5.1)] 2019 International Vacuum Electronics Conference (IVEC) - Design of D-band Double Corrugated Waveguide TWT for Wireless Communications
摘要： The European Commission Horizon 2020 ULTRAWAVE, “Ultra capacity wireless layer beyond 100 GHz based on millimeter wave Traveling Wave Tubes”, aims to exploit portions of two frequency bands in the millimetre wave spectrum, the D-band (141 – 148.5 GHz) and the G-band (275 – 305 GHz) for creating a very high capacity layer. Due to the high atmosphere and rain attenuation, high transmission power is needed to provide a useful transmission range. Traveling Wave Tubes are the only devices that can provide the multi-Watt transmission power above 100 GHz. In this paper, the design of the Double Corrugated Waveguide (DCW), as slow wave structure, for a novel D-band TWT, for wireless communications, will be described.
关键词： Double corrugated waveguide,traveling wave tube,5G,Millimeter wave networks
更新于2025-09-19 17:13:59
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Characterization of Optical Fibers Directly Embedded on Metal using a Particle Spray based Method
摘要： The double corrugated waveguide (DCW), incorporating a row of metallic pillars on each side of the electron beam, is demonstrated as a promising slow-wave structure for millimeter wave, Ka-band, traveling wave tubes (TWTs). Different configurations, including novel bent couplers with tapered pillars, have been designed, realized, and validated by S-parameter measurements. The design and simulation of a DCW TWT demonstrated very good performance in the frequency band 32–37 GHz. The ease of fabrication and assembly make the DCW a suitable basis for a new generation of millimeter wave TWTs.
关键词： microfabrication,millimeter waves,slow-wave structures (SWSs),Double corrugated waveguide (DCW),traveling wave tubes (TWTs),satellite communications
更新于2025-09-19 17:13:59
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Studies of a Gyrotron Traveling-Wave Tube with Helically Corrugated Waveguides at IAP Ras: Results and Prospects
摘要： The gyrotron traveling-wave tube (gyro-TWT) is a wideband version of gyrotron amplifiers, which produce pulsed or continuous-wave radiation in the millimeter-wavelength band at a power level that exceeds the powers produced by conventional TWTs with slow-wave structures and rectilinear beams by 1–2 orders of magnitude. Since 1996, researchers at the Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS) have been developing the concept of the gyro-TWT based on the use of a waveguide with a helically corrugated surface, which changes the dispersion of one of the eigenmodes in a circular waveguide radically. In this paper, we discuss several problems that arise in implementation of such devices, which many years of experimental studies have revealed, present the parameters of gyro-TWTs developed with allowance for specific applications of their end users, and discuss lines of further perfection of such amplifiers.
关键词： gyrotron traveling-wave tube,helically corrugated waveguide,high-power amplifiers,gyro-TWT,millimeter-wavelength band
更新于2025-09-19 17:13:59
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Theoretical Research on Properties of Spatial Harmonics in Corrugated Waveguide
摘要： This paper investigates the dependence of the properties of the spatial harmonics on the overmoded ratio of the corrugated waveguide operating in TM01 at 30 GHz with the consideration of the effects of the ripple shape. It is found that as the overmoded ratio grows, the electric ?elds concentrate towards the ripple surface, which weakens the enhancement of the power handling capacity caused by augmentation of the overmoded ratio. As the overmoded ratio grows, the ratio between the ?eld amplitudes of the ?1st spatial harmonic and the fundamental harmonic increases monotonically. Therefore, the total electric ?elds composed of the spatial harmonics become the spatial beating-wave with the single frequency, whose amplitudes vary along z-axis with the spatial period determined mainly by the ?1st spatial harmonic and the fundamental harmonic. Researches on coupling impedances show that with the same overmoded ratio, the corrugated waveguide consisting of the improved rectangular ripples provides better synchronous coupling for the wave-beam interaction than that of the sinusoidal ripples does. Moreover, it is better to choose the fundamental harmonic close to the light line as the synchronous wave for the wave-beam interaction in the low magnetic ?eld. In that case, even if the electron beam keeps far away from the ripple surface, the synchronous wave still provides strong enough coupling for the electron beam.
关键词： ?eld distribution,coupling impedance,high power microwave generation,Corrugated waveguide,overmoded ratio
更新于2025-09-16 10:30:52
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Selectivity Properties of Cylindrical Waveguides with Longitudinal Wall Corrugations for Second-Harmonic Gyrotrons
摘要： Spatial harmonic method is applied to investigate selectivity properties of longitudinally corrugated waveguides for potential application in second-harmonic gyrotrons. The effect of corrugations on frequencies, ohmic losses, and mode conversion of guiding TE modes is studied in details. Numerical results are presented for operating second-harmonic and competing first-harmonic modes of a 0.4-THz gyrotron with corrugated RF structure. It is shown that longitudinal wall corrugations of proper dimensions can ensure increase in ohmic losses and decrease in beam-wave coupling strength for the first-harmonic modes, while their effect on the operating mode is only slight. This demonstrates improved selectivity properties of corrugated waveguides for second-harmonic gyrotrons.
关键词： Ohmic losses,Gyrotron,Mode conversion,Cyclotron harmonic,Corrugated waveguide,Eigenvalue
更新于2025-09-11 14:15:04
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Design and development of the W‐band corrugated waveguide mode converter for fusion plasma experiments
摘要： In this paper, a W-band mode converter is designed using a circular corrugated horn and its detailed numerical study is presented. The proposed mode converter was fabricated, and the measured results are validated. The device converts fundamental mode (TE11) into a Hybrid mode (HE11) mode in a frequency range of 75 GHz to 105 GHz. The reflection coefficient is less than ?15 dB and a peak directivity of 24.5 dB is achieved. The corrugated horn also shows good mode purity. The measured gain of the device was found to be 18.05 dB. The designed mode converter will be useful in Electron Cyclotron Resonance Heating system for fusion plasma experiments.
关键词： W-band,mode converter,circular corrugated waveguide,hybrid mode
更新于2025-09-11 14:15:04
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Developments of Equipment for sub- THz Collective Thomson Scattering in LHD
摘要： Equipment for collective Thomson scattering diagnostics in the Large Helical Device has been developed. The probe beam source is a 303 GHz Gyrotron. It operates in a pulse mode. No parasitic mode is excited during the whole pulse width including the turn-on and turn-off phases. Single mode oscillation at several frequencies has been confirmed. For power transmission, a 3.5 inch corrugated waveguide line installed for electron heating with lower frequency gyrotrons will be used. The test with the 303 GHz gyrotron has shown a sufficiently low transmission loss.
关键词： Gyrotron,collective Thomson scattering,corrugated waveguide,sub-THz,Large Helical Device
更新于2025-09-10 09:29:36