Design and Measurement of an H-Band Rectangular TE10 to TE20 Mode Converter

Guoxiang Shu,Wenlong He,Zhengfang Qian

doi:10.1109/access.2020.2974819

Guoxiang Shu, Wenlong He + Show 1 more

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https://doi.org/10.1109/access.2020.2974819

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Abstract

A novel methodology of the mode conversion between rectangular TE 10 and TE 20 mode based on the H-plane T-junction power dividing network is proposed in this paper. A mode converter operating in the H-band (220-325 GHz) was analyzed and designed. To decrease the port reflection caused by the T-junction discontinuity, a septum and two symmetric irises were introduced in the converter. Two identical rectangular TE 20 mode converters joined back-to-back were manufactured by Nano-CNC machining and the electromagnetic properties were measured by using a vector network analyzer. A bandwidth of 228.8-293.1 GHz (64.3 GHz) for transmission coefficient S 21 around -1.0 dB and port reflection S 11 around -15.0 dB was measured. The measured results were in good agreement with the simulated ones and manifested high mode conversion efficiency.

Highlights

Vacuum electron devices based on high-order overmoded (HOOM) planar slow wave structures (SWSs) are promising terahertz radiation sources due to the large structural dimension, high electron beam current, and high power capacity [1]–[4]
A TE20 mode converter based on an H -plane T-junction power dividing network was designed and measured in this paper
The measured transmission coefficient was higher than −1.0 dB and the port reflection was around −15.0 dB over the frequency range of 228.8-293.1 GHz, indicating a high mode conversion efficiency

Summary

Introduction

Vacuum electron devices based on high-order overmoded (HOOM) planar slow wave structures (SWSs) are promising terahertz radiation sources due to the large structural dimension, high electron beam current, and high power capacity [1]–[4]. Several kinds of TE20 mode (here the symbol represents the rectangular waveguide) planar SWSs, including a ridge-loaded double staggered grating waveguide [3] and a photonic crystal-loaded folded waveguide [4], have been explored. A TE20 mode converter, which is used to convert the fundamental TE10 mode to the desired TE20 mode, is necessary for the cold test of a TE20 mode SWS. To accurately measure the electromagnetic properties of the TE20 mode planar SWS, the TE20 mode converter should have high mode conversion efficiency, low port reflection, broad frequency bandwidth and flat transmission response. In additional to the aforementioned application in the TE20 mode planar SWSs, the TE20 mode converter could be

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