Investigation on 220 GHz Taper Cascaded Over-Mode Circular Waveguide TE0n Mode Converter

Tongbin Yang,Xuesong Yuan,Yang Yan,Wenjie Fu,Xiaotong Guan,Dun Lu

doi:10.3390/electronics10020103

Tongbin Yang, Xuesong Yuan + Show 4 more

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https://doi.org/10.3390/electronics10020103

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Abstract

This paper proposes a taper cascaded over-mode circular waveguide TE0n mode converter for the millimeter and terahertz wave gyrotron. The mode converter of this structure can effectively reduce the difficulty of high frequency mode converter in fabrication. This paper verifies the feasibility of this new structure from theory, simulation, and experiment. Based on coupled wave theory calculations, three TE02-TE01 mode converters with lengths of 65.43 mm (4 segments), 119.3 mm (6 segments) and 136 mm (8 segments) and a TE03-TE02 mode converter with a length of 92 mm (8 segments) are optimized. The conversion efficiency in the frequency band 215–225 GHz is 91.8–94%, 93–95%, 95–98.78% and 95–98.44%. Because the length of the mode converter is clearly limited, this paper selects the TE02-TE01 mode converter with a length of 65.43 mm (4 segments) and the TE03-TE02 mode converter with 92 mm (8 segments) for simulation and experimental verification. In the simulation software Computer simulation technology (CST), the TE02-TE01 and TE03-TE02 mode converters and their composed TE03-TE01 mode converters are selected for modeling and analyzing. The simulation results and theoretical calculation results of the three mode converters only have different degrees of frequency deviation, and the frequency deviation of the 4-stage TE02-TE01 mode converter can be ignored; the frequency deviations of TE03-TE02 mode converter and TE03-TE01 mode converter are 2 GHz and 3 GHz, respectively. The experimental system is a field scanning system based on a vector network analyzer (VNA), which scans the input and output of the mode converter respectively. The experimental result is that when the input mode purity is 92% in TE01 mode, the output mode TE03 mode has a mode purity of 82%, and it has lower transmission loss. In this paper, the results from theory, simulation and experiment are in good agreement. This type of mode converter is easy to prepare, which makes it an effective alternative for high frequency curvilinear waveguide mode converter.

Highlights

Vacuum electronic devices (VEDs) (e.g., Traveling-Wave Tube (TWT), Backward-WaveOscillator (BWO), Magnetron, Klystron, Gyrotron) are important high-power microwave radiation sources for scientific, industrial and military applications [1]
It can be seen from the results that the parasitic modes of the converter are TE01 and TE04, which are effectively suppressed during the mode conversion process
The conversion efficiency in the 215–224.2 GHz frequency ba6nodf 1i2s higher than 95%

Summary

Introduction

Vacuum electronic devices (VEDs) (e.g., Traveling-Wave Tube (TWT), Backward-Wave. Oscillator (BWO), Magnetron, Klystron, Gyrotron) are important high-power microwave radiation sources for scientific, industrial and military applications [1]. As the VEDs operating frequency extends to the millimeter wave and terahertz wave bands, the size of the interaction circuit shrinks, and the power capability is reduced. Operating at high-order mode is proposed and attempted. As a fast wave VED, is successfully operated at high-order modes. Thumm et al reported that the gyrotron operated at the highest TE32,19 (Transverse Electric) mode [2]. Modes (TEmn, m > 1, n = 1, 2) [4] and its adFovranatawgaesveagreuihdieghmpoodweecrocnavpearctietry,, ltohwe mtroandsemcoisnsvioenrslioosns,sacnhdemhiegihs onuotrpmuatlmlyoadsefpoul-rity.

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Results

Conclusion