DUPLEX CABLE COMMUNICATIONS NETWORK EMPLOYING AUTOMATIC GAIN CONTROL UTILIZING A BAND LIMITED NOISE AGC PILOT

• US 3,835,393 A
• Filed: 04/17/1972
• Issued: 09/10/1974
• Est. Priority Date: 04/17/1972
• Status: Expired due to Term

• Current Assignee: Henry B. Marron
• Original Assignee: Henry B. Marron
• Inventors: Marron, Henry B.
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Psitos, Aristotelis M.
• Application Number:
  US05/244,470
• Time in Patent Office: 876 Days
• Field of Search: 325/1,3,308,309 179/17R,17A,17B,170.8,170.4,170.6,175.31R 178/71,73,DIG.13,15BP 333/16,17 328/104
• US Class Current: 725/124
• CPC Class Codes: H03G 3/20 Automatic control H03G3/005 takes precedence; combined with volume compression or expansion H03G7/00
• CPC Class Codes: H04B 3/04 Control of transmission; Equalising
• CPC Class Codes: H04N 7/173 with two-way working, e.g. subscriber sending a programme selection signal

Abstract

A full duplex private communications network provides independent automatic gain control circuitry for the oppositelypropagating signals. Band limited white noise is used to effect automatic gain control for information converging in the distribution network towards common head end equipment. Automatic gain control for this reverse direction propagation is thereby made insensitive to frequency and phase perturbations of any AGC pilot, and also performs well notwithstanding malfunctions in system communications links.

Claims

1. In combination in a cable television bidirectional signal propagating system wherein plural first system signal propagating channels converge into a second system signal propagating channel at a convergence point for conveying signals in a cable network in a reverse direction toward a cable system head end, at least one variable gain repeater amplifier included in each of said first and second system signal propagating channels, means for supplying a prescribed frequency band of noncoherent noise signals to the input of said repeater amplifier in each of said first signal propagating channels, and automatic gain control circuit means included in each of said repeater amplifiers for adjusting the gain of the associated repeater amplifier responsive to the amplitude of the noise signal at said amplifier.

2. A combination as in claim 1 wherein said noncoherent noise signal supplying means includes means for supplying white noise.

3. A combination as in claim 1 wherein said automatic gain control circuit means includes feedback means comprising band pass filter means for passing a part of the noise band supplied by said noncoherent noise signal supplying means, a noise detector, and additional amplifier means.

4. A combination as in claim 1 further comprising head end video signal supplying means connected to said second system signal propagating channel, wherein said signal propagating channels further comprise means for amplifying said video signals.

5. A combination as in claim 1 further comprising band attenuating means associated with and coupled to one amplifier in each of said first signal propagating channels, said attenuating means attenuating signals of the same frequency range as that of the noise signal supplying means.