1. Accuracy of the Finite Element Method for Directivity of Horn Antennas
Martin Vogel
Ansoft Corporation

2. Absorbing Boundary Condition reflects for non-normal incidence

3. SA 12-0.5 Standard Gain Horn test case for directivity in beam center

4. Quarter model of horn with partly spherical air object, terminated by absorbing boundary condition

5. Model of horn with box-shaped air object, terminated by Perfectly Matched Layers

8. Corrugated Horn - test case for angles off boresight

9. Horn model with partly-spherical air object with ABC

10. Corrugated horn model with Perfectly Matched Layers

11. Directivities corrugated horn, E and H Plane

18. Conclusions
Required mesh density on outer faces of air object: lambda/6
Required mesh density in rest of model: 0.4 lambda
Use either partly spherical ABC or use default PMLs
Accuracy maximum directivity in main beam: 0.1 dB
Accuracy directivity at -21 dB level: 0.5 dB
Accuracy directivity at -34 dB level: 1 dB
Directivity noise floor between -50 dB and -60 dB
Return Loss noise floor -70 dB