System for tracking and correcting drift and dispersion in satellite transmission signals

• Main Authors: MCMULLEN; JOHN W. G, MAGIN; GREGORY A
• Format: Patent
• Language: English
• Published: 14.02.1995
• Edition: 6
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; TRANSMISSION

A system for tracking and correcting drift and dispersion of carrier frequencies in a transmitted signal which includes one or more carrier frequencies and a pilot frequency. The system includes one or more carrier tuners, each for receiving the transmitted signal and for deriving from the received signal and IF carrier signal representing a respective carrier frequency, a mixer for mixing the IF carrier signal and a local oscillator signal to produce a resultant IF information signal, and a demodulator for demodulating the resultant IF information signal to recover the transmitted information. The system also includes a pilot tuner for receiving a transmitted signal, the pilot tuner deriving from the received signal an IF pilot signal representing the pilot frequency, a pilot mixer for mixing the IF pilot signal and the local oscillator signal to produce a resultant pilot signal, a local oscillator responsive to a control signal level for developing a local oscillator signal having a frequency corresponding to the control signal level and for supplying the local oscillator signal to the carrier mixers and pilot mixer to compensate for any drift or dispersion of frequency of the IF carrier signals and IF pilot signal, and a frequency discriminator for detecting frequency drift and dispersion of the IF pilot signal from a predetermined center frequency and for supplying to the local oscillator a control signal whose level identifies the drift and/or dispersion.