A far-field calibration method based on broadside measurements with a co-polarized and a cross-polarized reference dihedral target is demonstrated for the first time for an asymmetric ±45o linearly polarized 77 GHz frequency modulated continuous wave (FMCW) multiple-input multiple-output (MIMO) automotive radar. A novel extension of the calibration technique for off-broadside targets' phase response is proposed by using an optimized progressive phase compensation. Rotated dihedral and trihedral targets are used for validation. On broadside, the standard deviation of the channels' phase difference is nearly zero degrees for reference targets and under 5o for validation targets. The calibration for off-broadside targets shows that the phase relation in the target's scattering matrix can be retrieved, the accuracy of which is dependent on the target's type and angular position.

The frequency-dependent distortions in the beam peak direction and cosecant-squared shape are jointly analyzed for the first time in travelling-wave antennas. A novel center-fed proximity-coupled patch array at 26 GHz is proposed and compared with the edge-fed counterpart. The proposed center-fed array provides less than 1 degree beam squint, less than 1.5 dB variation in the realized gain and less than 20% root-mean-square error in the beam shape within a 700-MHz bandwidth.