Signal distribution system
First Claim
1. A head-end signal distribution system comprising:
- means for encoding a plurality of wideband input signals into a plurality of mutually asynchronous digital signal streams;
a space switching network for selectively switching said plurality of mutually asynchronous digital signal streams to a plurality of at least three output terminals;
multiplexing means for combining signals from said at least three output terminals into a composite signal comprising;
modulating means for amplitude modulating two of said terminal output signals on first and second carrier signals of the same frequency and differing in phase by 90°
; and
summing means for combining a remaining output terminal signal from said space switching network with said first and second modulated carrier signals to form a single composite signal for distribution.
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Accused Products
Abstract
A head-end for a signal distribution system with selection facility, includes a matrix (8) and a multiplexer (12) connected thereto for forming a multiplex signal. The head-end further comprises A/D converters (4-1 to Δ-N) for converting the wide-band input signals into digital signals prior to supply to the matrix. The multiplexer comprises two amplitude modulators (13, 14) for the mutual quadrature amplitude modulation of a carrier (17) by two digital signals, and a summing means (18) for adding a digital signal in the base band to the modulated signal. A signal receiver for one of the modulated signals comprises a synchronous amplitude demodulator (21) connected to a synchronized carrier source (20) and also comprises means for digital-to-analog conversion (24).
227 Citations
4 Claims
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1. A head-end signal distribution system comprising:
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means for encoding a plurality of wideband input signals into a plurality of mutually asynchronous digital signal streams; a space switching network for selectively switching said plurality of mutually asynchronous digital signal streams to a plurality of at least three output terminals; multiplexing means for combining signals from said at least three output terminals into a composite signal comprising; modulating means for amplitude modulating two of said terminal output signals on first and second carrier signals of the same frequency and differing in phase by 90°
; andsumming means for combining a remaining output terminal signal from said space switching network with said first and second modulated carrier signals to form a single composite signal for distribution. - View Dependent Claims (3)
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2. The head-end signal distribution of claim 6 further comprising:
means for supplying a reference signal for demodulating said modulated carrier signals to said summing means.
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4. A receiver for processing a composite signal, said composite signal including first and second quadrature carrier signals modulated with space-switched asynchronous digital data streams, and including a baseband asynchronous digital signal stream, as well as a reference signal for demodulating said carrier signals, each of said quadrature carrier signals and baseband asynchronous digital signals including a digital video signal, and an associated digital audio signal FSK modulated on a subcarrier signal, comprising:
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a synchronous amplitude demodulator connected to receive said composite signal and to receive a local carrier signal synchronized with said reference signal, said demodulator providing one of said digital asynchronous data streams from one of said carrier signals; a clock extraction circuit connected to said synchronous amplitude demodulator to generate a video clock signal for generating a video signal from said digital asynchronous data stream; a regenerator connected to receive said video clock signal and a signal from said synchronous amplitude demodulator for producing a demodulated digital video signal; digital to analog converter connected to receive said digital video signal from said regenerator whereby an analog video signal is produced; an FSK demodulator connected to said synchronous amplitude demodulator for removing a digital audio signal from a subcarrier signal contained in said composite signal; an audio clock signal regenerator for generating an audio clock signal from said digital audio signal; and audio regeneration means receiving said audio clock signal and a signal from said FSK demodulator for generating said digital audio signal, and a second digital to analog converter means for converting said digital audio signal from said audio regeneration means into an analog audio signal.
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Specification