However, higher frequency propagation comes with greater path loss, as isotropic free-space attenuation is inversely proportional to wavelength. In addition, along with this additional path loss, as wavelengths get smaller, physical processes such as diffraction, scattering, and material penetration loss make the channel properties of mmWave bands significantly more challenging.
Phased-array beamforming produces a directive beam that can be repositioned (scanned) electronically in order to overcome these greater channel losses. Beam-steering techniques such as minimum variance distortion-less response (MVDR) also improve target (road obstacle) identification.
Radar designers view the array antenna as a component with measurable input and output, and a set of specifications. Array designers see the details of the array and the physical and electrical limitations imposed by the radar system. Both must work together to achieve the goals of these very complex systems.
In addition, like their aerospace and defense-related counterparts, ADAS must perform over a range of operating conditions and object detection challenges in order to provide reliable coverage over the range (distance) and field of view (angle) as dictated by the particular driver assist function. Unlike the antenna systems developed for aerospace and defense applications, they must be designed for cost-effective, high-volume deployment.
This white paper examines several challenges behind developing mmWave radar systems for the next generation of smart cars and trucks and looks at new capabilities recently added to electronic design automation (EDA) software that supports a design flow for developing high-performance arrays that are also cost and space conscious. The radio-frequency (RF) front-end hardware supporting these new antenna systems must be optimized for performance, reliability, compactness, and cost.
The individual components must be specified and developed through a design flow that manages and combines this performance data in order to achieve accurate simulation of the overall array and feed structure across scan region, frequency range, and other operational requirements. This flow should also provide a pathway to physical realization of the individual components, including the antenna array itself.