A Method for Accurately Characterizing Single Overmoded Circular TM₀₁-TE₁₁ Mode Converter

• Main Authors: Junkai Yan, Jianguo Wang, Wenxi Hao, Xinhong Cui, Yingjun Liu, Xiaoxin Zhu, Zhiqiang Zhang
• Format: Article
• Language: English
• Published: IEEE 2020-01-01
• Series: IEEE Access
• Subjects: Asymmetric fixture; de-embedding; mode generator; overmoded mode converter; offset waveguide; S-parameter
• Online Access: https://ieeexplore.ieee.org/document/9123399/

In the case of characterizing waveguide mode converter, the widely applied back-to-back method can only extract two mode converters' joint S-parameters, the accuracy of the far-field radiation pattern method is limited. This paper experimentally demonstrates a method for accurately characterizing single circular TM₀₁-TE₁₁ mode converter, which consists of extracting the asymmetric two-port TM₀₁ and TE₁₁ mode generator test fixtures' S-parameters and de-embedding them from the “TM₀₁ mode generator + TM₀₁-TE₁₁ mode Converter + TE₁₁ mode generator” cascade measurement results. The peak problem occurring in measuring overmoded circular waveguide devices with VNA is analyzed and settled with an offset waveguide based peak-shifting tactic plus the Loess smoothing method. Fairly good agreement between the simulated and finally extracted complex S-parameter matrix of a TM₀₁-TE₁₁ mode converter throughout the device's working frequency span validates the proposed method's merits over traditional methods.