Oral Presentation

Improved TRL calibration for circular waveguide ports using a lossy dielectric slab

Author(s): Bangwon Lee (KASI), Ming-Jye Wang (ASIAA), Teddy Huang (ASIAA)

Presenter: Bangwon Lee (Korea Astronomy and Space Science Institute)

A wideband corrugated horn is essential for expanding the RF bandwidth of future radio receivers. We have developed a wideband corrugated horn operating in the W- and D-bands to investigate the origin of resonances that limit bandwidth extension.
The Thru-Reflect-Line (TRL) calibration method was employed to measure the return-loss performance of the corrugated horn. Since the horn has a circular output port, a circular-to-rectangular transition was used to connect the vector network analyzer (VNA) to the device under test (DUT). However, this transition is not used in actual operation because the horn is connected to an orthomode transducer (OMT) through a circular-to-square transition. To obtain the intrinsic performance of the horn, we applied the TRL calibration to remove the effects of the circular-to-rectangular transition using a quarter-wavelength circular straight waveguide. Nevertheless, the TRL method employing the custom-made calibration kit exhibits strong resonant features.
We present an effective technique to improve the TRL calibration quality for non-standard ports by inserting a thin lossy dielectric slab into the circular-to-rectangular transition. This approach effectively suppresses the resonances while minimizing insertion loss in the main signal path.