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128 results on '"Yao, Yelei"'

4. An air gap correction method for permittivity extraction of high-loss materials.

Author

Wang, Weijie, Jiang, Wei, Yao, Yelei, Wang, Jianxun, and Liu, Guo

Subjects
ELECTRON tubes, PERMITTIVITY measurement, VACUUM tubes, CORRECTION factors, PERMITTIVITY, AIR gap (Engineering)
Abstract

This paper developed a method for more accurate permittivity extraction of high-loss materials using the waveguide method to reduce the effect of the air gap. This method improves the Baker-Jarvis algorithm. It makes the errors of S-parameters caused by the air gap compensated by a correction factor β of the form: (S21 + S12) + β(S11 + S22). In our study, the correction results of β for materials on different frequencies and air gap sizes are quantitatively investigated. Furthermore, we propose a method to obtain an optimal frequency-independent β for different materials. A typical high-loss BeO-SiC ceramic commonly used in vacuum electron tubes is analyzed and discussed in detail. It shows that compared to traditionally utilizing only S21 (β = 0), adopting an optimal β can reduce the average errors of the complex permittivity from 17.7% to 7.9% with a 0.10 mm air gap. The proposed method is verified by measurements of unshaved and shaved samples. [ABSTRACT FROM AUTHOR]

Published
2024
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7. Design of 1.1T/300 mm Bitter-type magnet for gyro-traveling-wave tube with power consumption optimization theory.

Author

Dai, Xinge, Yao, Yelei, Feng, Chengzhen, Liu, Guo, Jiang, Wei, Tang, Zeping, Wu, Xu, Wang, Jianxun, and Luo, Yong

Subjects
*MAGNETIC flux density, *FERROMAGNETIC materials, *ELECTROMAGNETIC theory, *MATHEMATICAL optimization, *MAGNETIC fields
Abstract

To improve the portability of magnets in gyrotron devices, we designed a compact Bitter-type magnet with power consumption optimization theory. This magnet operates at room temperature in a small volume. The theory revises existing electromagnetic theory for non-uniform structural Bitter-type magnets and achieves the lowest energy consumption through iterative optimization. To extend the magnetic field homogeneity region, the ferromagnetic material armature is applied to the Bitter-type system without additional power consumption. Unlike previous manual designs, the proposed Bitter-type magnets can obtain optimal parameters with a significant reduction in computing time. Through the introduction of correction factors, we improve accuracy through multiple verifications of simulations and experiments. On this basis, a room-temperature Bitter-type magnet system for Ka-band fundamental mode gyrotron amplifiers is designed. Its maximum magnetic field strength is 1.1 T, and the length of the homogeneity region is 300 mm. Through optimization, its energy consumption is only 27.5 kW. [ABSTRACT FROM AUTHOR]

Published
2024
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19. Design and Experimental Results of a W-Band Gyro-TWA With the Widest Bandwidth

Author

Yao, Yelei, Liu, Guo, Jiang, Wei, Cao, Yingjian, Wang, Yu, Dai, Xinge, Wang, Jianxun, and Luo, Yong

Abstract

This letter presents the design and experimental results of a 152-kW W-band gyrotron travelling-wave amplifier (gyro-TWA) that boasts an enhanced 3-dB instantaneous bandwidth ranging from 8.8 GHz to 12.5 GHz, and 1-dB bandwidth from 7.0 GHz to 11.5 GHz. This was achieved by powering the gyro-TWA with a 60 kV, 11 A electron beam. The amplifier demonstrates an output power exceeding 120 kW and an interaction efficiency above 19.1% within 89.8-101.3 GHz. This performance improvement was made possible by using a curved-profile circuit that matches with the gyrotron solenoid across a wide frequency band. The theoretical predictions, particle-in-cell simulations and experimental results are compared and found to be in good agreement.

Published
2024
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20. Experimental Investigation on Trapped Electrons Oscillation Suppression for W-Band Gyro-TWT

Author

Han, Binyang, Jiang, Wei, Wang, Jianxun, Lu, Chaoxuan, Dai, Boxin, Yao, Yelei, Liu, Guo, Xu, Jianhua, and Luo, Yong

Abstract

The fluctuation of current can destroy the performance of the gyrotron traveling-wave tube (Gyro-TWT). We found that the fluctuation of the current is related to the generation of trapped electrons in the interaction circuit. Through experimental and simulation verification, it has been found that the oscillation characteristics of the current are consistent with the motion characteristics of the trapped electrons in the interaction circuit. This indicates that trapped electrons have a significant impact on the current. To suppress the trapped electrons, a novel magnetron injection gun (MIG) with the rear electrode (MSRE) has been designed. The absorbed power of the interaction circuit has decreased by 50%. When a W-band Gyro-TWT with MSRE is operated at 60.5 kV/10.15 A, zero drive with a pulse duration of $200~\mu $ s, and a duty cycle of 15%, there is no current fluctuation. The tube achieves a peak power of 136 kW, a gain of 71 dB, and an average power of 20.54 kW at 94 GHz. The hot test shows that MSRE can suppress the generation of trapped electrons. This greatly enhances the stability of the tube.

Published
2024
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34. Theory and measurement of the single and hybrid-mode excitation and evolution in a lossy-dielectric-loaded waveguide.

Author

Wang, Weijie, Liu, Guo, Cao, Yingjian, Chen, Bailiang, Yao, Yelei, Wang, Yu, Gong, Xiaoqing, Jiang, Wei, Wang, Jianxun, and Luo, Yong

Subjects
TRAVELING-wave tubes, NUMERICAL calculations, PARTICLE beam bunching, ELECTROMAGNETIC fields
Abstract

This paper investigates the mode excited, evolved, and propagating properties of the lossy dielectric-loaded waveguide (DLW) used in a Ku-band TE11-mode gyrotron traveling wave tube (gyro-TWT). Theoretical calculation and numerical simulation show that different DLW eigenmodes can be excited by the hollow circular waveguide as a single or hybrid-mode. This study clearly reveals the transformation conditions of the single and hybrid-mode, and the mechanism of the resulting specific dispersion, loss, and electromagnetic field distribution. According to the mode excitation principle and its evolution laws, the propagating properties can be accurately controlled by adjusting the dielectric thickness, which can effectively suppress the potential oscillations and improve the electron bunching phase in the gyro-TWT. As a result, the dielectric loading scheme can be optimized by properly arranging the DLWs, thus enhancing the stability and gain of the gyro-TWT. The theory and simulation are verified by the vector network analyzer measurement at Ku-band, and the results show a good agreement. [ABSTRACT FROM AUTHOR]

Published
2023
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38. A Cascaded W-Band Gyro-TWT With the Configuration of Coaxial and Circular Waveguides

Author

Cao, Yingjian, Liu, Guo, Wang, Yu, Jiang, Wei, Yao, Yelei, Wang, Jianxun, and Luo, Yong

Abstract

To realize a high-gain wideband millimeter-wave amplification, we present and simulate a ${W}$ -band gyrotron traveling wave tube (gyro-TWT) with cascaded coaxial- and circular-waveguide amplifiers. The amplifiers are operated in a coaxial and circular TE01 mode, respectively, and driven by two 60-kV gyrating electron beams with a pitch factor of 1.2 but different beam currents of 1 and 10 A. They are designed to possess relatively low individual gains below all oscillation thresholds to maintain high stability and achieve a high total cascaded gain for the whole gyro-TWT. A coupling circuit is adopted to cascade these two sections, converting the coaxial TE01 mode to the circular one with a −3-dB bandwidth of 6.8 GHz (94.1–100.9 GHz). particle-in-cell (PIC) simulation shows that the designed gyro-TWT can achieve a maximum saturated output power of 239.8 kW at 100 GHz, with a gain greater than 60 dB over a −3-dB bandwidth of 8.0 GHz (94.5–102.5 GHz).

Published
2023
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48. Microwave Measurement of a Compact Circular TE11 Mode Coupler Loaded With Ridges.

Author

Weijie, Wang, Guo, Liu, Jiang, Wei, Wu, Zewe, Yao, Yelei, Pu, Youlei, Wang, Jianxun, and Luo, Yong

Subjects
MICROWAVE measurements, TRAVELING-wave tubes, POWER transmission, CIRCULAR waveguides
Abstract

Design and microwave measurement of a linearly polarized circular TE11 mode coupler are reported in this article. Based on our earlier designed input coupler with smooth wall, we proposed an improved structure with ridges loading resulting in a bandwidth up to 29.2%. Simulation results show the port reflection S11 less than −10 dB is in 7.9–10.6 GHz. And the split transmission S21 and S31are over −3.4 dB in this frequency range. According to the simulation results, the designed input coupler is fabricated and measured with the vector network analyzer. The measurement results show excellent performance, which is in good agreement with the simulation when the conductor loss is taken into consideration. In addition, an input coupler with a cutoff waveguide is designed to improve the efficiency of single-port transmission and the power utilization. Simulation results show the transmission efficiency of the single port achieves 91%. [ABSTRACT FROM AUTHOR]

Published
2021
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