Compact Wideband SIW Horn Antenna Fed by Elevated-CPW Structure

This communication presents a compact substrate-integrated waveguide (SIW) H-plane horn antenna fed by a novel elevated coplanar waveguide (ECPW) structure. First, the wideband characteristic of the SIW horn antenna is achieved through loading a dielectric slab with gradually decreasing dielectric constants, which can be realized through simply perforating different air vias on the extended slab. Second, in order to sustain an efficient feeding for the relatively thick substrate (0.27λ
₀
), an additional metal ground is inserted in the middle of the grounded coplanar waveguide (GCPW). Moreover, a triangular-shaped transition structure is placed at the end of the ECPW to smoothly transmit the energy from the thin ECPW to the thick SIW horn antenna. Finally, a prototype is fabricated to validate the proposed concept. Measured results indicate that the proposed horn antenna operates from 17.4 to 24 GHz. Stable radiation patterns can be observed in the whole operating band. The measured results show good accordance with the simulated ones. Above all, the proposed antenna occupies an area of 22 × 56.5 × 4 mm
³
(1.47λ
₀
× 3.77λ
₀
× 0.27λ
₀
), which is much more compact than the previous rectangular waveguide-fed horn antenna (2.33λ
₀
× 9.21λ
₀
× 0.31λ
₀
) (where λ0 is the wavelength at 20 GHz in the free space).