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:
Aug. 21, 1990
Filed:
Dec. 07, 1989
Hermann Gysel, San Jose, CA (US);
Synchronous Communications, Inc., San Jose, CA (US);
Abstract
A scrambled frequency modulated video signal transmission system is provided with a headend station having a DC coupled amplitude demodulator for removing the amplitude modulation of a scrambled amplitude modulated baseband video signal. The low frequency components, e.g. 0-50 Hz, of the resulting scrambled baseband video signal are separated from the remaining high frequency components thereof for modulating a sub-carrier. The sub-carrier and the high frequency components are then combined and frequency modulated in a frequency modulator. The resulting scrambled frequency modulated video signal is then transmitted via fiber optic, coaxial and/or microwave transmission lines to a frequency demodulator in a hub station. In the hub station the output of a frequency demodulator is provided to a sub-carrier demodulator for producing the low frequency components, e.g. 0-50 Hz, which contain the scrambled sync pulse information. The resulting signals are then combined with the high frequency components thereof and provided to a DC coupled amplitude modulator before being transmitted to a TV set. In the TV set the output of the amplitude modulator is then provided to a descrambler. The descrambler restores the sync pulse information to the amplitude modulated video signal. The amplitude modulated video signal is then provided to an amplitude demodulator for restoring the original baseband video signal.