An Automotive Polarimetric Radar Sensor With Circular Polarization Based on Gapwaveguide Technology

This article presents a novel design of an automotive polarimetric radar sensor with circular polarization (CP) at 77 GHz band based on gap waveguide technology. The proposed design employs a multiple-input multiple-output (MIMO) configuration with single-CP TX antennas and dual-CP RX antennas, enabling the acquisition of sufficient polarimetric information while reducing the number of transmitters (TXs) by half. Gapwaveguide technology is utilized for the implementation of the multilayer waveguide front-end. Series-fed septum polarizers are employed for the antenna design with low-profile characteristics. Measurement results indicate that the antenna elements enable a high level of cross-polarization across the field of view (FoV). Integration of the waveguide front-end with RF boards is achieved using gap waveguide packaging techniques. Static measurements were conducted on common scattering objects to evaluate the sensor's performance. Polarimetric rotation signatures of the objects were acquired from the measurements, demonstrating the sensor's potential for use in object identification tasks. Dynamic measurements were performed to evaluate the sensor's Doppler response. The assessments indicate a high level of accuracy, confirming the effectiveness of the proposed sensor in analyzing dynamic movements. Overall, the proposed polarimetric radar sensor provides persuasive evidence that gap waveguide technology is a highly promising candidate for the realization of advanced automotive radar front-ends.