Rochester MTT/APS - Phased Circular Arrays for Beam Steering in Automotive Radar Applications

#beam #steering #automotive #radar #phased #circular #array

Currently, many automotive radar systems employ linear arrays of series fed antennas whose beam
steering is limited to a single plane. Circular antenna arrays offer unique beam steering advantages over
linear arrays which make them desirable for adaptive beam steered radar applications. Due to their
inherent symmetry, circular arrays are capable of beam steering in the elevation plane as well as 360-
degrees in the azimuth plane. Two types of circular arrays are presented both with uniform magnitude
excitation and non-uniform phase excitation. The first one is an 8-element conformal circular array of
CPW-fed dual dipole radiating elements, designed at 2.45 GHz using HFSS, to scan a 360-degree azimuth
region. This array may be placed on top of a road vehicle and used in an autonomous or semi-autonomous
driving system to scan the surrounding environment for obstacles or to supplement other sensing systems
such as LiDAR and computer vision in inclement weather such as fog, low-light conditions, or snow
where the performance of other sensors suffer. The electronic steering of the array would eliminate the
mechanical rotation of conventional and commercially available nautical radar systems. The distortion of
the radiation pattern of a single dipole fed by a coplanar waveguide (CPW) is overcome with a dual dipole
configuration as the radiating element. The primary challenge is the design of the feed system that starts
as a corporate microstrip transmission line system and is aperture coupled with a transition to the CPW
feeding the dipoles. Both the feed system and antenna elements are etched on either side of a single thin
dielectric sheet which is then wrapped into a cylinder to form the circular array. The second one is a
circular microstrip patch array designed at 10 GHz using HFSS to scan a narrow beam in a conical
broadside region. The array may be placed on the front of a vehicle used in adaptive beam-steering
applications for obstacle detection with the beam steered for two degrees of freedom, to anticipate
curvature in the road to increase the effective range over a conventional radar array. Prototypes are
fabricated on duroid with passive phase excitations to demonstrate beam steering. Measured radiation
pattern and gain of both types of the prototypes show excellent agreement with simulated results.