Demodulators – Amplitude modulation demodulator – Having specific distortion – noise or other interference...
Patent
1977-10-12
1978-07-11
Grimm, Siegfried H.
Demodulators
Amplitude modulation demodulator
Having specific distortion, noise or other interference...
325320, 325346, 329124, H04L 2722
Patent
active
041004990
ABSTRACT:
This invention concerns a carrier synchronization system for a four-phase coherent PSK demodulator. The four-phase PSK signal is demodulated by an in-phase reference carrier and a quadrature reference carrier both of which are locally generated by a reference carrier source. The in-phase and quadrature components of the four-phase PSK signal that result from these demodulation operations are delayed a time interval substantially equal to T/2 seconds, T being the signaling period. The product of the delayed in-phase component and the sign of the quadrature component is compared with the product of the delayed quadrature component and the sign of the in-phase component, to produce a phase error signal. This error signal is used to control the adjustment of the reference carrier source.
REFERENCES:
patent: 3806815 (1974-04-01), Fletcher et al.
patent: 3878468 (1975-04-01), Falconer et al.
Baker et al., Satellite Communication Systems Technology, London, Apr. 7-10, 1975, pp. 201-206.
Proceedings of the Second International Conference on Digital Satellite Communications, Paris, Nov. 1972, papers D2 to D6.
Frisone John B.
Grimm Siegfried H.
International Business Machines - Corporation
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