Secondary Radar

Abstract

SSR, also known in the USA as beacon radar, has a number of similarities with primary surveillance radar. Both use a ground-based rotating antenna, with a pulse transmitter and receiver. Like its primary counterpart, the signals from an SSR normally undergo plot extraction at the radar site, followed by transmission by landline to an ATC or operations centre. Secondary radar antennas are often mounted above primary antennas (see figure 1.2), saving the cost of separate drive motors and gearboxes, and ensuring azimuthal alignment. Plot extraction may include correlation of primary and secondary radar signals, giving increased confidence about the position and identity of wanted targets.