This article presents a circularly polarized (CP) dual lens (DL) antenna with high gain and wide axial ratio (AR) bandwidth for automotive radar applications. Proposed antenna system provides low AR and scan loss over a wide angular range. It consists of a linearly polarized (LP), wide band, aperture coupled planar feed antenna, an extended hemispherical lens and a planoconvex lens with thin parallel plates and air slabs. In-lens polarizer mounted to the flat surface of the planoconvex lens converts LP wave to CP state. Fundamental design rules to obtain CP is defined. A CP DL design in low dielectric permittivity material (εr=3) is introduced. It achieves simulated efficiency that varies between 75 and 82% within the 77-81 GHz automotive radar band. AR is below 2.2 dB for all scan angles up to 25˚. Realized gain at boresight radiation is 25.6 dBic at the center frequency. 0.85 dB scan loss is observed at ±30˚ scan angle. A frequency-scaled prototype has been fabricated by additive manufacturing process with fused deposition modeling, and the concept is proved by the experimental results in 22-28 GHz band.
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