Doppler tracking for signals of opportunity using rate-line detection

A Doppler tracking receiver comprising:

• an antenna port for capturing an electromagnetic transmission carrying a bauded signal from a transmitter carried by a satellite that is in motion relative to the tracking receiver;
• and
• a signal processing system having digital circuits programed to execute the following process:
• perform a non-linear operation on the captured transmission to expose a cyclostationary feature of the captured transmission that defines a rate-line having a rate-line frequency that is related to the bauded signal and to the motion of the transmitter relative to the receiver;
• detect the rate-line frequency and generate Doppler shift data indicative of the Doppler shift associated with the satellite in motion;
• acquire the Doppler shift data and at least one of position and velocity information of the satellite supplied by a satellite propagator;
• and
• compute at least one of positioning, navigation and timing information for the satellite supplied as the output of the receiver.

A method for processing signals from a satellite transmitter that is in motion relative to a tracking receiver, the method comprising:

• capturing an electromagnetic transmission carrying a bauded signal from the satellite transmitter with the tracking receiver;
• performing a non-linear operation on the captured transmission to expose a cyclostationary feature of the captured transmission that defines a rate-line having a rate-line frequency that is related to the bauded signal and to the motion of the satellite transmitter relative to the tracking receiver;
• detecting the rate-line frequency and generating Doppler shift data indicative of the Doppler shift associated with the satellite transmitter in motion;
• acquiring at least one of position and velocity information of the satellite from a satellite propagator;
• and
• computing at least one of positioning, navigation and timing information for the satellite based on the Doppler shift data and the at least one of position and velocity information of the satellite.