CPW Center-Fed Single-Layer SIW Slot Antenna Array for Automotive Radars

A compact co-planar waveguide (CPW) center-fed substrate-integrated-waveguide (SIW) slot antenna array is proposed to achieve narrow H-plane beamwidth and low sidelobe levels for automotive radars such as across-the-road (ATR) radar. The antenna consists of an array of SIW slot elements, a CPW-SIW transition, and a CPW power divider. A new type of CPW-SIW transition is proposed to minimize the blockage aperture of the slot antenna array for suppressing the sidelobe levels of the array. A parallel center feeding configuration is applied to avoid beam squinting. The antenna prototype printed onto a single-layer Rogers 5880 is with 32 ×4 slot elements and an overall size of 195 mm×40 mm×0.79 mm. Measured results show that the proposed antenna exhibits a gain of > 22.8 dBi, an efficiency of > 67%, a return loss of > 10 dB, a sidelobe level of <;-21 dB, and a fixed boresight beam of <;4.6° in H-planes over 24.05-24.25 GHz, suitable for ATR radar.