L-band multipath propagation in an airborne pulsed system

The results of a study and flight test program to investigate L-band multipath propagation in airborne pulsed systems under direction of the U. S. Navy Bureau of Aeronautics and carried out through the cooperative efforts of the U. S. Naval Research Laboratory and Hazeltine Corporation using facilities provided by U. S. Naval Air Development Unit, South Weymouth, Mass., are reported. Exact time delays for a smooth curved earth reflecting surface with a standard atmospheric line of sight propagation are charted. Pulse to pulse direct and multipath amplitude variations are recorded for various transmitter-receiver flight altitude combinations from 5,000 feet to 50,000 feet. Measured amplitudes are compared with calculated amplitudes using theoretical sea reflection coefficients and assumed antenna patterns. A wide range of grazing angles is covered and some correlation with angle of incidence and roughness criteria are examined, together with time variations of the sea reflection coefficient.