1976-04-13
1978-05-30
Griffin, Robert L.
179 15BP, 325329, H04B 168
Patent
active
040925960
ABSTRACT:
A system including a data modem having transmitter and receiver sections. The modem transmitter includes a multi-level data encoding system, a stable carrier generator and a selected transmission frequency, and a double sideband suppressed carrier modulator to modulate the multi-level signals on the carrier. All filtering to shape the signals in the transmitter section is done prior to modulation and, in the receiver section, after demodulation. Signals from several modem transmitters, each occupying its own assigned band, are multiplexed with two pilot carriers spaced by a predetermined frequency difference. The modem receiver includes a circuit to separate one of the carriers from the received band and mix that carrier with signals in a limited part of the band to shift the frequency of signals in the limited part of the band to an intermediate frequency (IF) band. A desired signal can be selected by frequency-shifting the IF signals so that the carrier frequency of the desired signal is at zero. The frequency-shifting signal must be controlled to have the proper frequency and phase. Signals can be modulated on more than one axis of the transmitter carrier provided there is an exact reproduction of the carrier's phase for demodulation.
REFERENCES:
patent: 2778877 (1957-01-01), Caruthers
patent: 3443229 (1969-05-01), Becker
patent: 3649914 (1972-03-01), De Jager
Dickinson Robert V. C.
Entenman Alan W.
Kliphuis Jans
Bookbinder Marc E.
Gillette Donald P.
Griffin Robert L.
LandOfFree
Data transmission and reception system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data transmission and reception system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data transmission and reception system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-471665