Common-Aperture Dual-Polarized Transceiver Antenna Systems for Millimeter-Wave Polarimetric Radar

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Millimeter-wave radar is a key sensor technology utilized in the automotive industry for advanced driver assistance systems and autonomous vehicles. Leveraging the Doppler effect and electromagnetic wave polarization, it is capable of detecting position and velocity of roadway obstacles, as well as distinguishing between obstacle types (pedestrians, vehicles, etc.). However, radar isn’t an all-encompassing sensing solution; a significant drawback is imaging resolution inferior to that of optical sensors like cameras and lidar.

A radar’s resolution is closely linked to its antenna system. Fine angular resolution demands a narrow antenna beam, which translates to a large effective aperture. Similarly, fine range resolution is achieved using the frequency-modulated continuous-wave technique, which requires high transmit-to-receive antenna isolation. Limited space on most vehicles prohibits the large radar size mandated by these requirements. The focus of this dissertation is the development of an antenna system architecture providing a narrow beam and high isolation, while supporting dual-polarized transmit/receive for polarimetry applications. The common transmit/receive aperture makes the antenna system relatively compact while eliminating parallax.

While modern automotive radars operate at 76-81 GHz, there is interest in the 230 GHz band for future systems. The shift to a shorter wavelength will result in improved angular and range resolution while reducing antenna size. Versions of the antenna system of this dissertation have been designed for use at both bands. Additionally, there is currently a lack of data on the backscattering properties of many target classes at 230 GHz. As a demonstration of the utility of 230 GHz automotive radar, a set of polarimetric backscattering measurements of various road surfaces is presented. The common-aperture antenna was used in the radar’s front end.

Professor Kamal Sarabandi