Carrier recovery circuitry immune to interburst frequency variat

Details Carrier recovery circuitry immune to interburst frequency variat Carrier recovery circuitry immune to interburst frequency variat

1987-08-20

1988-10-25

Griffin, Robert L.

Pulse or digital communications

Repeaters

Testing

375 82, 375120, 329 50, H04L 2714

Patent

active

047808870

ABSTRACT:
A carrier recovery circuit comprises first and second mixers for mixing a received PSK signal with first and second reference frequency signals. A remodulator extracts a preamble from each burst of the PSK signal and supplies the extracted carrier to a carrier recovery means to cause it to derive a reference carrier from the extracted preamble. A phase detector is connected to the outputs of the first and second mixers for detecting a phase difference between the PSK signal and the reference carrier, the detected phase difference being applied to a resettable noise reduction circuit for reducing amplitude fluctuations contained in the phase difference, the noise reduction circuit being arranged to be reset in response to each of the bursts to discharge energy stored as a result of the noise reduction and eliminate interburst phase errors which occur as a result of interburst frequency variations. A variable phase shifter controls the phase of the reference carrier in accordance with the output of the noise eliminator and supplies quadrature versions of the phase controlled carrier to the first and second mixers as the first and second reference frequency signals.

REFERENCES:
patent: 3746994 (1973-07-01), Kramer
patent: 4246653 (1981-01-01), Malm
patent: 4458356 (1984-07-01), Toy
patent: 4516079 (1985-05-01), York
patent: 4591795 (1986-05-01), Tanimoto et al.
patent: 4642573 (1987-02-01), Noda et al.
patent: 4704582 (1987-11-01), Dixon et al.

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