Pulse or digital communications – Repeaters – Testing
Patent
1979-07-05
1981-07-28
Safourek, Benedict V.
Pulse or digital communications
Repeaters
Testing
375120, 329112, H03D 322, H04L 2722
Patent
active
042814120
ABSTRACT:
Bit timing references are derived at a receiver for a carrier modulated by OQPSK. A carrier is transmitted with a constant reference phase modulation during a first interval. During a subsequent, second interval the carrier is transmitted with rotational phase modulation representing binary bit values so that orthogonal components phase modulate the carrier with a predetermined bit sequence. A receiver responds to the constant phase modulated carrier to lock the frequency and phase of a phase lock loop oscillator of a carrier recovery loop. Synchronization at the receiver is achieved in response to a reception of the rotational phase modulation, while maintaining the frequency and phase lock. A carrier recovery loop of the receiver is activated to a decision directed operation after bit synchronization has been achieved. Decision directed operation is achieved by sampling and comparing components derived in orthogonal channels of the carrier recovery loop while the receiver is responsive to the rotational phase modulation. The bandwidth of a filter used in achieving bit synchronization is reduced after there has been a decay of transients in the carrier tracking loop resulting from a transition between locking of the loop and initiation of the decision directed operation. Then the bandwidth of a filter in the carrier tracking loop is adjusted as a function of the quality of the received rotational modulated suppressed carrier.
REFERENCES:
patent: 3401339 (1968-09-01), Kluever et al.
patent: 3562710 (1971-02-01), Halleck
patent: 3626298 (1971-12-01), Paine
patent: 3815034 (1974-06-01), Kato
patent: 4023103 (1977-05-01), Malm
patent: 4076956 (1978-02-01), Dogliotti et al.
patent: 4092606 (1978-05-01), Lovelace
Dapper Mark J.
Kiliman Douglas A.
Martinet Robert L.
Smith Donald E.
Wissel Frank A.
Cincinnati Electronics Corporation
Safourek Benedict V.
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