A Terahertz-Band Rectangular TE<sub>10</sub> to Circular TE<sub>01</sub> Mode Converter
Guoxiang Shu, Xinlun Xie, Junchen Ren, Guangxin Lin, Qi Li, Jujian Lin, Jiacai Liao, Jingcong He, Biaogang Xu, Zhiwei Chang, H. Yin, Guo Liu, Cunjun Ruan, Wenlong He
Abstract
The design, fabrication, and experimental measurement of a broadband and compact TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\Box }_{{10}}$ </tex-math></inline-formula> –TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ }_{{01}}$ </tex-math></inline-formula> (symbols <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Box ^{^{^{}}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\circ $ </tex-math></inline-formula> represent the rectangular and circular waveguides, respectively) mode converter is presented in this article. The proposed mode converter consists of three components, including a TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\Box }_{{10}}$ </tex-math></inline-formula> –TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\Box }_{{20}}$ </tex-math></inline-formula> mode converter based on a two-way H-T junction power divider, a TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\Box }_{{20}}$ </tex-math></inline-formula> –TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{+}_{{22}}$ </tex-math></inline-formula> mode converter with variable cross-shaped waveguide, and a TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{+}_{{22}}$ </tex-math></inline-formula> –TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ }_{{01}}$ </tex-math></inline-formula> mode converter. Two distinct design schemes have been employed for the first part of the TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\Box }_{{10}}$ </tex-math></inline-formula> –TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ }_{{01}}$ </tex-math></inline-formula> mode converter, which are based on two-way H-T junction power dividers with a path difference of odd times half-waveguide wavelength (Scheme 1) and a 180° phase shifter (Scheme 2), respectively. This mode converter is highlighted by the significant advantage of high conversion efficiency over a wide bandwidth with a relatively easy-to-fabricate structure, which is evidenced by the measurement of two identical back-to-back joined mode converters based on Scheme 1. Measurement results matched with simulation ones within reasonable accuracy, which predicted that a 1-dB transmission bandwidth of ~56.7 GHz was obtained. Meanwhile, the reflection coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S} _{{11}}$ </tex-math></inline-formula> was below −13.2 dB over that bandwidth.