The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 30, 1978
Filed:
Apr. 13, 1976
Robert V Dickinson, Berkeley Heights, NJ (US);
Alan W Entenman, Hicksville, NY (US);
Jans Kliphuis, Huntington, NY (US);
Other;
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.