Patent ID: 6452547
Filing Date: 2002-09-17
Classification: G01S,H04B

Abstract:
A method of expanding the digital bit rate potential for communication to be added to Loran-C and similar radio-frequency navigation system transmitter pulse trains and without affecting the navigation capability and integrity of the system, that comprises, generating such radio-frequency pulses centered on a predetermined carrier frequency, coupling the pulses to an antenna, and transmitting the same from the antenna to enable users to receive and use the initial part of each transmitted pulse for navigation timing and location; during the remaining parts of each transmitted pulse, switching impedance elements into and out of the coupling for effecting sweeping the generated carrier frequency thereof in opposite directions, first below or above, and then above or below the carrier frequency during successive further parts of each pulse, but within a predetermine band between predetermined lower and upper frequency limits on opposite sides of said carrier frequency; further, during said sweeping maintaining the pulse energies below the lower frequency limit and above the upper frequency limit substantially equal for each pulse while maintaining the center of the frequency spectrum for each pulse close to said carrier frequency; and using the frequency modulation effected by said sweeping to provide communication bits.