A Wideband Horn Array Ridge Waveguide Antenna for Millimeter Automotive Radar Applications

ABSTRACT A wideband horn array ridge waveguide antenna is presented for millimeter automotive radar applications. This antenna is a slotted waveguide antenna loaded with a horn layer. After introducing a pair of ridges to the waveguide cavity, the antenna operates in modes quasi TEM 180 , quasi TEM 190 , and quasi TEM 1−10−0 . By combing the three modes together, the ridge waveguide antenna obtains a wide band. A horn layer has been employed to narrow the half‐power beamwidth of the slotted waveguide antenna, thereby enabling a 3.5‐dB gain enhancement. The horn elements of the horn layer are not uniformly arranged and are interconnected in order to reduce sidelobe levels. The impedance matching is also obviously improved by the horn layer. The proposed antenna has been fabricated and measured. The results confirm that the ridge waveguide antenna has a wide bandwidth of 68.7–87.6 GHz with a gain of 17.5 dBi. A Stable fan‐beam radiation pattern is realized and the SLLs are around−20 dB.