Automotive RADAR Planar Antenna Optimization Based on Conformal Transformation Optics

Abstract

A novel approach to mitigate diffraction effects from finite ground planes in antenna design is presented. The method is based on the conformal transformation optics. A computational framework has been developed to optimize the shape of the ground plane since it has a great impact on the beam ripple and width of the radiation pattern of an antenna. Due to the limited thickness of the outer wall of slotted waveguide antennas, it is not possible to shape this outer wall, which acts as the ground plane of the antenna. Conformal transformation optics presents a solution to virtually add a deformation without needing to change the physical shape of the ground plane. Although conformal transformation optics can also be applied to transverse-magnetic waves, large fluctuations in the dielectric constant with respect to the wavelength cannot be supported in practice. In order to mitigate this problem, we have proposed a rescaling of the dielectric constant. Furthermore, we derive the connection between conformal transformation optics and transverse electromagnetic modes, which serve as a tool for joint optimization of the radiation pattern together with the conformal transformation. This method is then used to optimize the radiation pattern of a slot antenna and evaluated for increasing curvature within the conformal transformation.Numerical computations have shown promising results, i.e. a reduction of the farfield ripple from 1.92 dB to 0.64 dB at a half-power beam-width of 112° at 77 GHz. This is a promising result for designing automotive radars with a wide field of view, especially, for advanced driver-assistance systems used in the corner radars. This will contribute to further improving safety on the roads.