Noise-Reduction Effects of Oven Magnetron With Cathode Shield on High-Voltage Input Side

Mitani, Tomohiko; Shinohara, Naoki; Matsumoto, Hiroshi; Aiga, M.; Kuwahara, N.; Ishii, Takeshi

doi:10.1109/ted.2006.878238

Cited by 16 publications

(11 citation statements)

References 12 publications

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“…[14]. This magnetic flux distribution was also reported in Mitani et al [15], where it was concluded that the noise reduction effect in a CW oven magnetron is attributed to the disappearance of the azimuthal E ×B drift and filament temperature distribution due to the cathode shield. In the pulsed magnetron, the unwanted emission at the LHS is affected more strongly by distribution of the magnetic flux density in the cathode-anode gap because the pulse voltage starts up the oscillation from a lower voltage than the rating voltage at each pulse.…”

Section: Design Methodologysupporting

confidence: 77%

Frequency bandwidth narrowing technology for cavity magnetrons installing cavity magnetrons into commercial marine radar

Obata

Furumoto

Tsuji

et al. 2010

2010 International Conference on the Origins and Evolution of the Cavity Magnetron

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The unmodulated pulse magnetrons design and technology has advanced over the last seven years at New Japan Radio Co., Ltd. (New JRC). These developments have resulted in a dramatic reduction in the unwanted emission levels produced by magnetron devices. This was necessary to meet the increasing global demand for a more efficient use of the radio frequency spectrum, which is seen as a limited and scarce resource. These magnetrons utilise new techniques to reduce the unwanted emissions, while also improving the spectrum in the utilised frequency bandwidth. This paper explains in detail the processes and methodology used to reduce the unwanted emission levels for unmodulated pulse magnetron devices. In addition, this paper will describe Japan Radio's (JRC) commercial marine radar systems, operating in the S and X bands.

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Section: Design Methodologysupporting

confidence: 77%

Frequency bandwidth narrowing technology for cavity magnetrons installing cavity magnetrons into commercial marine radar

Obata

Furumoto

Tsuji

et al. 2010

2010 International Conference on the Origins and Evolution of the Cavity Magnetron

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“…The pilot-plant scale microwave irradiation reactor has 8 magnetrons. In general, magnetron has a broad frequency spectrum [16], [17]. We measured the magnetron spectrum with a spectrum analyzer.…”

Section: Experiments and Discussionmentioning

confidence: 99%

Pilot-Plant Scale 12 kW Microwave Irradiation Reactor for Woody Biomass Pretreatment

Hasegawa

Mitani

Shinohara

et al. 2014

IEICE Trans. Electron.

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A simple, low reflection, and highly-efficient pilot-plant scale microwave irradiation reactor for woody biomass pretreatment was fabricated. Pretreatment is an essential process for effective bioethanol production. The fabricated reactor consists of 8 microwave irradiators which are attached to a metal pipe. The woody biomass mixture which contains water and organic acid flows through the metal pipe and is heated by microwaves at a total power of 12 kW. To design the microwave irradiators, we used a 3D Finite Element Method (FEM) simulator, which was based on the measured complex permittivity data of the woody biomass mixture. The simulation results showed that the reflection coefficient |S 11 | from the reactor was less than −30 dB when the woody biomass mixture temperature was between 30 • C and 90 • C. Finally, we experimentally confirmed that the fabricated irradiation reactor yielded a microwave absorption efficiency of 79%. key words: Microwave heating, permittivity measurement, finite element method, magnetron neers (IEICE) and the Institute of Electrical Engineers of Japan (IEEJ) Masakazu Daidaireceived the B.E., M.E., and Ph.D. degree in chemical engineering from

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“…Cathode magnetron are widely used in both military applications 1,2 as well as household microwaves 3,4 . The core of a cathode magnetron is the cathode filament, which is typically made of thorium tungsten or barium-tungsten alloy.…”

Section: Introductionmentioning

confidence: 99%

“…Though the chemical composition of the cathode filament determines the escape power, emission stability, and lifespan of a microwave oven. However, when the chemical composition is optimized and fixed, the manufacturing quality of the cathode filament determines the level of noise, stability, efficiency, and lifetime of a microwave oven 3 . Thanks to its rich resources in rare earth raw materials of tungsten and thorium, over three quarters of worldwide microwave oven used filament cathodes are made in China.…”

Section: Introductionmentioning

confidence: 99%

Defect Detection and Full Surface Characterization of High Curvature Cathode Filaments

Yi¹,

Huang²,

Xie³

et al. 2019

Proceedings of the 2019 International Conference on Modeling, Analysis, Simulation Technologies and Applications (MASTA 2019)

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Surface defects of cathode filaments of microwave magnetron would cause magnetron failure and scrapped microwave systems. Therefore, surface defects on cathode filaments must be carefully inspected. Conventionally, filaments are manually and visually inspected using their amplified images under an optical microscope. This is because automatic defect detection of cathode filaments is a challenging problem. The difficulty comings from its complex surface shape with multiple turns of high curvature spiral circles, which occlude each other. Such complex shape prevents capturing of sharp focusing images, which are essential for a computerized automatic detection algorithm. Further, the variable nature of production defects complicated the process of automatic defect detection task. To solve these problems, this paper proposes an automatic defect detection method to deal with issues related to complex shapes containing occlusions as well as high curvatures, particularly for the quality inspection of spiral shaped cathode filaments. The method includes a novel digital scanner, which sequentially brings all sections of the filament sides into sharp focusing of the optical imaging system. The method also employs multiple optical systems to imaging multi-sides of the spiral filament. The computational algorithm primarily uses line-detectors. In an evaluation experiment, the proposed method was used to automatically inspect over 14 million cathode filaments. Experimental results indicate that its false negative rate was 0.0065%, and its false positive rate was 6.83%. This indicates that the proposed method could successfully detect all kinds of surface defects at over 99.99% accuracy. It reduces the workload for manual inspection from 100% down to 93.17%, over an order of magnitude reduction. Further, the efficiency of the proposed method is 70 spiral filaments per minute, satisfying the requirements of online quality detection of existing manufacturing lines of filament cathodes.

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Noise-Reduction Effects of Oven Magnetron With Cathode Shield on High-Voltage Input Side

Cited by 16 publications

References 12 publications

Frequency bandwidth narrowing technology for cavity magnetrons installing cavity magnetrons into commercial marine radar

Frequency bandwidth narrowing technology for cavity magnetrons installing cavity magnetrons into commercial marine radar

Pilot-Plant Scale 12 kW Microwave Irradiation Reactor for Woody Biomass Pretreatment

Defect Detection and Full Surface Characterization of High Curvature Cathode Filaments

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