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Waveguide Transition Modelled in FEKO and FEST3D

A rectangular to circular waveguide transition is modelled in FEKO and FEST3D. The interface between FEKO and FEST3D allows the usage of FEST3D results (the modes calculated at one of the ports of the FEST3D model) as excitation for the FEKO model.

A rectangular to circular waveguide transition is designed, following the design guidelines described in [1].  The input waveguide is chosen as WR137 and the output waveguide has a diameter of 28.9mm, similar to the first structure proposed in [1].  The dimensions of the three sections of the transition are obtained by optimising the structure in FEST3D for a response coinciding with [1, Fig. 3].

The transition is modelled in FEKO to validate the design.





The FEKO model of the transition from WR137 rectangular waveguide to circular waveguide (28.9 mm in diameter). S11 response of the transition designed in FEST3D and verified in FEKO, compared to published results for a similar structure (dimensions unknown) presented in [1].

This transition may be used to connect a horn antenna to its receiver, e.g. through a standard, commercially available coaxial to waveguide adapter.  The impressed modes calculated by FEST3D may be used as the excitation for the antenna in FEKO.  As an example, a corrugated conical horn was designed with Antenna Magus.  The transition was added to the antenna model from Antenna Magus in CADFEKO and modelled in FEKO to provide the far field pattern shown below.


Far-field of horn (with transition) modelled in FEKO.  The horn model can be obtained with Antenna Magus.

[1] Rosenberg, U., Bornemann, J. and Rambabu, K., "Analysis and Design of Flange-Integrated Rectangular-To-Circular Waveguide Transformers for Splashplate Antenna Feeds", Microwave Conference, 2002. 32nd European , vol., no., pp.1-4, 23-26 Sept. 2002 doi: 10.1109/EUMA.2002.339356 URL: