System Design of a FMCW Radar-Based Detect-and-Track Subsystem for an Airborne Detect-and-Avoid System On-Board of Small Unmanned Aircraft Systems

摘要

This paper describes and evaluates an all-weather capable detect-and-track subsystem based on a miniaturized frequency-modulated continuous-wave radar sensor operating between 23.55 and 24.4 GHz. This radar sensor was designed to detect obstacles like other airspace participants on board of a small unmanned aircraft system (sUAS) during automated flights. The radar consists of one transmit and four receiver patch-antennae arrays, which are placed in a square formation close to the transmitting antenna array. By evaluating the time-of-arrival parameter from a pair of two vertically displaced antenna arrays the calculation of the elevation angle becomes possible. In addition, the azimuth angle is calculated the same way using the alternative horizontally displaced patch-antenna array couple. Thus, the received radar signals can be used for detection and tracking of targets in three-dimensional space. A specific constant false alarm rate (CFAR) has been implemented, which applies an appropriate threshold that maximizes the probability of detections and keeps the probability of false alarm below a preset level. First flight tests were carried out to validate this radar prototype and its target detection and tracking capabilities as a subsystem of a radar-based detect-and-avoid system (DAA), suitable to be installed on board of small unmanned aircraft systems.