Analysis and simulation of collision avoidance TCAS antennas mounted on aircraft

Two different implementations of the TCAS (traffic-alert collision avoidance system) are discussed: one uses an eight-element circular antenna array and works on a monopulse principle: the other uses a four-element antenna array and an amplitude comparison scheme. The system models and results for the TCAS on a Boeing 737-200 aircraft are presented. Both the elevation angle and the distance of the antenna from the nose were varied. The performance of the systems was shown to get better in the forward quadrant as one gets closer to the nose of the aircraft. The performance of the four-element TCAS was was generally not as good as that of the eight-element monopulse system, except in the nose quadrant where they were comparable. However, the four-element amplitude system is much simpler in its implementation than the eight-element monopulse system.<>