A method of processing offset carrier modulated ranging signals

A receiver for processing offset carrier modulated, OCM, ranging signals in a radionavigation system comprising a plurality of satellite-borne transmitters and at least one ground-based receiver, the receiver comprising:

• an antenna configured for receiving a first radionavigation signal from at least one of the plurality of satellite-borne transmitters and a second signal SB synchronously broadcast with the first radionavigation signal, the second signal SB having the same or substantially the same center frequency as the first radionavigation signal;
• and
• processing circuitry coupled to the antenna and configured for performing:
• receiving the first radionavigation signal from antenna and down-converting and digitizing the first radionavigation signal to derive therefrom a first offset carrier modulation (OCM) signal SA;
• receiving the second signal SB from the antenna, the second signal SB having the same or substantially the same center frequency as the first OCM signal SA;
• coherently combining the first OCM signal SA with the second signal SB at the receiver to generate a combined signal SC;
• generating a combined correlation value YC corresponding to a correlation of the combined signal SC with a local replica of the first OCM signal SA;
• and
• deriving ranging information based on the combined correlation value YC.

A system comprising:

• a processor;
• and
• a memory coupled to the processor, wherein the memory stores instructions that, when executed by the processor, cause the processor to:
• receive a first radionavigation signal and down-converting and digitizing a first radionavigation signal to derive therefrom a first offset carrier modulation (OCM) signal SA;
• receive a second signal SB synchronously broadcast with the first OCM signal SA, the second signal SB having the same or substantially the same center frequency as the first OCM signal SA;
• coherently combine the first OCM signal SA with the second signal SB at a receiver to generate a combined signal SC;
• generate a combined correlation value YC corresponding to a correlation of the combined signal SC with a local replica of the first OCM signal SA;
• and
• derive ranging information based on the combined correlation value YC.