Transmitter and receiver of an identification message

摘要

An identification system of the mode 4 IFF type. The preamble to the mode 4 IFF identification message is modified by carrying out a phase inversion modulation of some of the pulses in the preamble. This encoding is preferably carried out according to a four-element Barker code. The receiver of the responder then includes a correlation device 202 followed by a threshold detector 206. The correlator is preferably formed using a surface wave acoustic line. The invention increases the security of aircraft identification systems. <IMAGE>