An SIW Horn Antenna Fed by a Coupled Mode Emulating Pyramidal Horn Antennas

A novel feeding method to dielectric loaded substrate-integrated waveguide (SIW) horn antennas is presented, resulting in equal half power beamwidths (HPBWs) and low sidelobe levels (SLLs) in both the E-plane and H-plane. The concept is to synthesize a unique electromagnetic field distribution using four vertically stacked SIWs. In particular, a uniquely adjusted excitation of magnitudes and phases of the four SIWs is employed as the feeding of the SIW horn, emulating the field distribution of pyramidal horn antennas. This approach realizes the phase correction of the electric field at the horn aperture and concentrates the radiation to the endfire direction to reduce the sidelobes. To prove the concept, a stacked dielectric loaded SIW horn antenna fed by four TE10 excitations was simulated at 35 GHz, yielding a gain of 15 dBi, an HPBW of 33° for both the E-plane and H-plane, and an SLL of approximately -24 dB for both the E-plane and H-plane. To achieve the desired excitation at each port, a narrowband SIW power splitter was designed to adapt a 3.5 mm coaxial connector to the four waveguide ports with the required phase shift. The entire feeding and antenna structure were fully substrate integrated and fabricated on Rogers 5880 panels. The measured radiation patterns show good agreement with the simulation with the best performance at 35.1 GHz.