Differential ranging for a frequency-hopped remote position determination system

A differential ranging mobile transmitter location system, comprising:

• a mobile transmitter having a unique identifier, and having a transmitter for simultaneously sending a first frequency-hopped spread spectrum carrier signal and a second frequency-hopped spread spectrum carrier signal, at least one of which containing the unique identifier, the first frequency-hopped spread spectrum carrier having a different frequency than the second frequency-hopped spread spectrum carrier signal;
• a first base station having an antenna operable for receiving the first and second frequency-hopped spread spectrum carrier signals and capable of determining a first time of arrival of the frequency-hopped spread spectrum carrier signals;
• a second base station also having an antenna operable for receiving the first and second frequency-hopped spread spectrum carrier signals and capable of determining a second time of arrival of the frequency-hopped spread spectrum carrier signals;
• and
• a central station connected to the first base station and the second base station, and operable for:
• 1.) receiving the first time of arrival of the first and second frequency-hopped spread spectrum carrier signals from the first base station;
• 2.) receiving the second time of arrival of the first and second frequency-hopped spread spectrum carrier signals from the second base station;
• 3.) generating a first hyperbolic plot based on the differential time of arrival of the first and second frequency-hopped spread spectrum carrier signals at the first and second base stations;
• and
• 4.) using a third information source to determine the location of the transmitter along the first hyperboplic plot.