A satellite receiver system provides acquisition and frequency tracking of a Doppler-shifted radio signal received from an orbiting satellite. The satellite receiver system includes a Costas phase-lock loop that receives the radio signal and provides an error signal at an error signal output for controlling...http://www.google.co.uk/patents/US5432521?utm_source=gb-gplus-sharePatent US5432521 - Satellite receiver system having doppler frequency shift tracking
