SIW multilayer Rotman lens antenna in the 24-GHz band

A multi-beam antenna system fed by a dual-layer Rotman lens is presented in multi-layer SIW (substrate integrated waveguide) technology. The lens is folded in two layers using a new transition based on several star-shaped coupling slots and a SIW integrated reflector along the array port contour. This original transition is broadband and maximizes power transfer between the two layers of the lens regardless the position of the primary source along the beam port contour of the Rotman lens. A Geometrical Optics (GO) approach is used to verify the lens design and the resulting phase aberrations. The radiating part is an array of fifteen slotted waveguides. The proposed concepts are validated numerically at 24.15 GHz The final antenna footprint corresponds to the radiating part of the structure reducing the space occupation of the Rotman lens. The proposed structure has very good scanning performance over an angular range of ±32° with side lobe levels lower than -15 over the entire field of view.