SIW horn antenna built on thin substrate with improved impedance matching

Substrate-integrated-waveguide (SIW) horn antennas built on thin substrates (substrate thickness smaller than λ₀/10) are not widely used owing to their low front-to-back ratio and the impedance mismatch between the aperture and the free space. A SIW horn antenna with metalised via holes in front of the aperture is proposed to deal with the issue of impedance mismatch. The metalised via holes introduce shunt inductance between the top and bottom metal planes of the SIW, which increases the impedance of the SIW and improves the impedance matching. Two prototypes working at the Ku band with via holes positioned differently are designed, manufactured and measured. The simulated and measured S- parameters, antenna gain and radiation patterns are presented.