Near Field Propagation Method in Automotive Radar Simulations

Near Field Effects

Multiple near field propagation characteristics are accounted for in WaveFarer’s automotive radar simulation technique, increasing accuracy.  

First, transmitters emit spherical waves, modified by complex antenna radiation patterns, causing non-uniform wavefronts to be incident on target objects.  This is an enhancement over traditional far field RCS methods that use a plane wave excitation with a constant phase front to illuminate targets.  This leads to more accurate phase information at the receiving antennas.

Second, WaveFarer’s surface integration calculations have been formulated to allow receivers and secondary scatterers to be in the near field and Fresnel regions of the target.  This is required because the far field region of a vehicle at 24 and 79 GHz is several kilometers, extending well beyond the typical range for an application like automotive radar.  This is another enhancement over traditional far field RCS methods, because it removes the assumption that the receiver is in the far field region of the target.  

Ray-Tracing Interactions

Ray-tracing techniques accumulate reflections, diffractions, and transmissions along a ray’s path as it interacts with the ground, target, and secondary scatterers.  WaveFarer supports up to 30 reflections, 3 diffractions, and 7 transmissions along any single ray path.  For paths that interact with scattering objects, these are then incorporated into surface integrations on target surfaces based on physical optics (PO) and the method of equivalent currents (MEC), which incorporate scattering effects into the paths. In addition, paths may include diffuse scattering from rough surfaces, incorporating additional effects from clutter that are critical at millimeter waves and higher frequencies.