Compact Rotman lens‐fed slot array antenna with low sidelobes

Abstract

A slot array in substrate‐integrated waveguide (SIW) technology fed by a microstrip Rotman lens is proposed. This compact multibeam antenna is designed in two layers using a novel transition based on double‐stepped coupling slots on the broad wall of SIWs. Compared with a rectangular transverse coupling slot, this transition is broadband and its coupling power can be controlled for low‐sidelobe applications. The radiating part is a 10 × 10 slot array and the beam‐forming network can generate seven beams with good coverage from −30° to 30° in the azimuthal plane. To validate the proposed concept, an antenna prototype is implemented at 10 GHz. The frequency response and measured radiation patterns are in good agreement with simulated results provided by full wave simulation software. Experimental results show that the sidelobe level is lower than −21 dB for the central beam in both H and E planes and better than −18 dB for the edge beams.