Satellite receiver system having doppler frequency shift tracking

DETAILED DESCRIPTION An aspect of the present invention is a satellite receiver system that provides acquisition and frequency tracking of a Doppler-shifted radio signal received from an orbiting satellite.
The satellite receiver system comprises a Costas phase-lock loop that receives the radio signal and provides an error signal at an error signal output for controlling a conversion frequency generated by a voltage controlled oscillator.
The satellite receiver system further comprises the voltage controlled oscillator, which is coupled to the Costas phase-lock loop-and generates the conversion frequency for down-converting the radio signal in the Costas phase-lock loop.
The voltage controlled oscillator comprises a programmable frequency synthesizer that can be programmed to generate a plurality of frequencies selectable in steps.
The satellite receiver system further comprises a Doppler frequency acquisition and tracking element coupled to the voltage controlled oscillator.
The Doppler frequency acquisition and tracking element adjusts the conversion frequency to compensate for a Doppler frequency shift occurring in the radio signal due to orbital motion of the orbiting satellite.
The Doppler frequency acquisition and tracking element comprises a coarse adjustment element coupled to the programmable frequency synthesizer for selecting a suitable one of the plurality of frequencies to provide a coarse adjustment of the conversion frequency to compensate for the Doppler frequency shift, and a fine adjustment element coupled to the error signal output for generating a fine adjustment signal at an adjusted error signal output for providing a fine adjustment of the conversion frequency to compensate for the Doppler frequency shift.
Another aspect of the present invention is a satellite receiver system that provides acquisition and frequency tracking of a Doppler-shifted radio signal received from an orbiting satellite.
The satellite receiver system comprises a Costas phase-lock loop that receives the radio signal and provides an error signal at an error signal output for controlling a conversion frequency generated by a voltage controlled oscillator