Single-Layer Dual-Circularly Polarized Series-Fed Gap Waveguide-Based Slot Array for a 77 GHz Automotive Radar

A series-fed single-layer dual-circularly polarized slot array antenna fed by a stepped ridge gap waveguide (RGW) is proposed at the 77-GHz band. The antenna generates dual-circularly polarized waves, which shows potential to be used in next-generation polarimetric radar for automotive applications. The antenna contains eight columns of linear arrays and two feeding ports for exciting the columns of the slots. The design process and measured results are described in this article. The measured results show that the realized gain of the proposed antenna is above 27.3 dBi and the axial ratio is about 2 dB over the proposed 76-79 GHz with dual-CP patterns. The measured S-11 and S-22 for the proposed antenna is below -10 dB and the measured port isolation is above 17.5 dB.