Multiple Pulse and Phase Code Modulation in the Loran-C System

Transmission of a group of closely spaced pulses increases the duty cycle and consequently the range of the Loran-C (formerly called Cytac) 100-kc pulsed hyperbolic radio navigation system while retaining the advantages of time sharing. Phase coding by carrier phase reversal, coupled with synchronous detection, facilitates automatic master and slave identification and search, and prevents multihop skywave interference. Instrumentation for simple and complex pulse patterns is considered. The phase codes used are characterized by lack of spurious responses associated with other bipolar codes.