Carrier recovery system and digital phase demodulator

Details Carrier recovery system and digital phase demodulator Carrier recovery system and digital phase demodulator

1990-09-13

1991-09-17

Grimm, Siegfried H.

Demodulators

Phase shift keying or quadrature amplitude demodulator

Input signal combined with local oscillator or carrier...

329346, 375 83, 375 96, 375118, H04L 2722

Patent

active

050498304

ABSTRACT:
A carrier recovery system combining a narrow band carrier phase estimator and a wide band carrier phase estimator, and a digital phase demodulator using this carrier recovery system. The narrow band carrier phase estimator extracts a carrier phase having a low pulse slip rate from received signal. This carrier phase, however, cannot track fast phase fluctuation due to fading. On the other hand, the wide band carrier phase estimator tracks fast phase fluctuation due to fading, and extracts a carrier phase from the received signal. From this carrier phase is subtracted the other carrier phase obtained by the narrow band carrier phase estimator, and the balance, after its fluctuating range is limited, is added to the carrier phase obtained by the narrow band carrier phase estimator, thereby making it possible to obtain a carrier phase which can track fast phase fluctuations due to fading without sacrificing the phase slip rate. By using the carrier phase obtained in this manner, there can be structured a digital phase demodulator suitable for mobile communication systems based on coherent detection. If carrier component is extracted by reversely modulating the received signal with reference signal obtained by subjecting to decision the signal demodulated by this digital phase demodulator, a carrier phase is recovered by filtering the extracted carrier component in a wide band, and the received signal is synchronously detected with this carrier phase, the error rate can be further reduced.

REFERENCES:
patent: 4328587 (1982-05-01), Mizuno et al.
patent: 4581586 (1986-04-01), Rubin
Gardner, Floyd M., Ph.D, Phaselock Techniques, 2nd Edit., John Wiley & Sons, Inc., 1979, pp. 217-225.
Schwartz, Mischa et al., Communication Systems and Techniques, McGraw-Hill, Inc., 1966, pp. 372-374.
Viterbi, Andrew J. et al., IEEE Transactions on Information Theory, vol. IT-29, No. 4, Jul. 1983, pp. 543-551.

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