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

• Published in: IEEE access Vol. 8; pp. 113383 - 113391
• Main Authors: Yan, Junkai, Wang, Jianguo, Hao, Wenxi, Cui, Xinhong, Liu, Yingjun, Zhu, Xiaoxin, Zhang, Zhiqiang
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Asymmetric fixture; Calibration; Circular waveguides; Converters; de-embedding; Far fields; Fixtures; Generators; Measuring instruments; mode generator; offset waveguide; overmoded mode converter; Parameters; Pattern method (forecasting); S-parameter; Scattering parameters; thru-reflect-line (TRL) calibration; Transmission line matrix methods; Transmission line measurements
• ISSN: 2169-3536
• DOI: 10.1109/ACCESS.2020.3002501

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 TM 01 -TE 11 mode converter, which consists of extracting the asymmetric two-port TM 01 and TE 11 mode generator test fixtures' S-parameters and de-embedding them from the "TM 01 mode generator + TM 01 -TE 11 mode Converter + TE 11 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 TM 01 -TE 11 mode converter throughout the device's working frequency span validates the proposed method's merits over traditional methods.