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

Abstract

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. INDEX TERMS asymmetric fixture, de-embedding, mode generator, overmoded mode converter, offset waveguide, S-parameter, thru-reflect-line (TRL) calibration.

A High-Power Radar Rotary Joint

“…Conventional circular waveguides have a small power capacity, and if they are used in the HPW system, breakdown will occur inside the waveguide. The over-mode waveguide is a waveguide whose size is larger than the traditional waveguide size at the operating frequencies, which can withstand a higher power due to its increased sectional area [11][12][13][14]. The field distribution in the rotary joint must have the characteristics of axisymmetric distribution to ensure stable output in the continuous rotation process.…”