HIDDEN PREAMBLE FOR FREQUENCY HOPPED SYNCHRONIZATION

A method is provided for achieving initial synchronization of the transmission and reception of a frequency hopped communication signal, which comprises the steps of transmitting a preamble defined by a sequence of synchronizing pulses on a single channel and transmitting random dummy pulses over the remaining channels to hide the preamble. The received signal is filtered to obtain the preamble which is then convolved with a stored replica of the preamble to produce a synchronizing signal that is used to synchronize frequency hopping of the receiver and transmitter in preparation for the transmission of information. The received, constituent pulses of the preamble are delayed and accumulated by a baseband correlator (18) to form a composite pulse whose magnitude is detected by a threshold detector (20). The threshold detector produces the synchronizing signal (22) when the accumulated pulse reaches a prescribed value indicating that all of the bits of the preamble have been received.