Design and development of 77-GHz pair-slot array antenna with single-mode post-wall waveguide for automotive radar

A 77-GHz slot array antenna with a single-mode post-wall waveguide is presented for automotive radars. First, transmission losses and fabrication costs of various transmission lines in millimeter-wave band are compared. The measured transmission loss in the 77-GHz post-wall waveguide integrated in a PTFE substrate at 77 GHz is shown 0.20 dB/cm, which is less than that of the microstrip line. Then, the design method of one-dimensional slot subarray with the single-mode post-wall waveguide is discussed. Finally, an antenna system composed of four subarrays has been fabricated. The measured gain of the antenna system is 24.4 dBi gain at the designed frequency of 76.5 GHz, and the efficiency for aperture size of 55 mm by 9.2 mm is 67%.