Advanced Antenna Systems for Fully Polarimetric Radar in Automotive Scenario

Doktorsavhandling, 2024

The increasing dependence on Advanced Driver Assistance Systems (ADAS)
highlights the critical need for fast target recognition, effective collision avoidance, cruise control, lane assistance, etc. This necessitates a significant advancement in sensor technology, particularly for accurate target classification
and road surface sensing. In this context, automotive radar systems, especially
fully polarimetric radars, play a crucial role due to their superior capability
in detecting low radar cross-section in all weather conditions.
This thesis focuses on developing an advanced antenna system optimized for
fully polarimetric automotive radar applications. The design criteria for these
antennas include high polarimetric performance, compact size, high efficiency,
seamless integration in the system, and cost-effectiveness suitable for mass
production. In response to these requirements, we present several 77 GHz
advanced antenna designs for various automotive polarimetric radar systems.
Employing gap waveguide technology, we have developed two single-layer
dual circularly polarized antenna arrays and one single-layer circularly polarized antenna array, each designed specifically for automotive radar applications. The first model is an 8x1 array with dual circular polarization, featuring
a wide impedance bandwidth, 11% axial ratio bandwidth, high port isolation
(18.6 dB), and moderate gain (14.8 dBi). The second model, an 18x8 seriesfed planar array, utilizes the leaky-wave principle to achieve a bandwidth of
approximately 3.9%, a gain of 27.3 dBi, and port isolation exceeding 17.5 dB.
The third model is a single circularly polarized antenna, designed for easy
integration with radar systems. It achieves high port isolation (≥ 35 dB)
for adjacent receiver channels, reducing mutual couplings through thin decoupling walls and dummy elements. This antenna offers an impressive field of
view, with an embedded axial ratio (E-AR) below 3 dB within the azimuth
plane, covering approximately ±60◦ at the receiver and ±50◦ at the transmitter. Additionally, this antenna system has been integrated into a radar
front-end, with measurement results indicating enhanced detection from low
radar cross-section targets.
This thesis provides a comprehensive exploration of the design concepts,
including comparative analyses and interpretation of results. The simplicity,
low loss, and cost-effectiveness of these antenna designs make them viable for
widespread applications in both academic research and industrial settings.