Telegraphy – Systems – Alternating or pulsating current
Patent
1975-10-29
1977-09-20
Safourek, Benedict V.
Telegraphy
Systems
Alternating or pulsating current
325 45, 325145, H04L 2724
Patent
active
040499090
ABSTRACT:
A modulator for differentially encoded phase-shift keyed digital data is implemented entirely by digital means. Baseband serial binary data are illustratively transformed into dibit pairs which are assigned discrete quaternary carrier-wave phase shifts. A "staircasing" shift register whose weighted outputs are combined to form a quantized phase-modulated carrier wave is advanced by a relatively high-speed counter through a frequency divider network. The division rate of the divider is selectively accelerated in each baud interval in accordance with the assigned dibit coding. The resultant quantized carrier wave is then lowpass filtered prior to application to a telephone transmission line. By controlling the division rate of the divider rather than the advancement rate of the shift register, gradual transitions are imparted to the output carrier wave with minimal harmonic distortion.
REFERENCES:
patent: 3128342 (1964-04-01), Baker
patent: 3128343 (1964-04-01), Baker
patent: 3597599 (1971-08-01), Melvin
patent: 3611143 (1971-10-01), Van Gerwen
patent: 3747024 (1973-07-01), Choquet
patent: 3818135 (1974-06-01), Tannhauser
patent: 3935386 (1976-01-01), Glasson
Bell Telephone Laboratories Incorporated
Kearns Joseph P.
Masinick Michael A.
Safourek Benedict V.
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