Automatic cable attenuation compensation system

• US 5,343,236 A
• Filed: 06/01/1993
• Issued: 08/30/1994
• Est. Priority Date: 06/03/1992
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Koppe, Rudolf P., Eck, Nicolaas J. H.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Hsia, Sherrie
• Application Number:
  US08/069,883
• Time in Patent Office: 455 Days
• Field of Search: 358/86, 358/36, 358/37, 358/38, 358/166, 358/167, 358/177, 358/174, 358/184, 358/195.1, 358/35, 358/188, 358/10, 358/139, 358/160, 455/234.1, 333/28 R, 333/18, 348/6, 348/181, 348/183, 348/192
• US Class Current: 725/149
• CPC Class Codes: H04B 3/04 Control of transmission; Equalising

Abstract

In an automatic cable attenuation compensation system comprising a fixed compensation part (FC-R/G/B) providing a stepwise adjustable attenuation compensation for substantially compensating cable attenuation, the stepwise adjustable attenuation compensation of the fixed compensation part being set after power-up, an adaptive compensation part (VC-R/G/B) is provided for a continuously active compensation for a further accurate compensation of the cable attenuation.

Claims

1. An automatic cable attenuation compensation system for use in compensating for cable attenuation losses in a signal transmitted in a cable, comprising:

means for generating and adding at least one test signal to the signal being transmitted in the cable at one end of the cable;

a fixed compensation part (FC-R/G/B) coupled to another end of the cable, said fixed compensation part having a plurality of fixed compensation sections thereby providing a stepwise adjustable attenuation compensation for substantially compensating cable attenuation over an entire predetermined range of compensation, said fixed compensation part further including a measuring and setting circuit for measuring the test signal and for activating selective ones of the plurality of fixed compensation sections until a level of said at least one test signal reaches a predetermined reference level, the stepwise adjustable attenuation compensation of the fixed compensation part being set after power-up; and

an adaptive compensation part (VC-R/G/B) coupled to an output of said fixed compensation part, said adaptive compensation part including a means for measuring said test signal and for generating a control signal based on the level of said at least one test signal, and automatic gain control means coupled to said measuring means for providing a continuously active compensation, equivalent to one of said stepwise adjustable attenuation compensation of said fixed compensation part, for a further compensation of the cable attenuation based on said control signal.

2. An automatic cable attenuation compensation system as claimed in claim 1, wherein said cable is a multi-core cable having a plurality of channels (R, G, B) and said adaptive compensation part (VC-R/G/B) includes a separate, independent adaptive compensator (VC-R, VC-G, VC-B) for each channel (R, G, B).

3. An automatic cable compensation system as claimed in claim 1, wherein said generating and adding means generates a low-frequency test signal and a high-frequency test signal, and wherein said automatic gain control means in said adaptive compensation part (VC-R/G/B) includes first automatic gain control means (WB-AGC) for compensating for an attenuation of said low-frequency test signal included in said signal transmitted through said cable, and second automatic gain control means (HF-AGC) for compensating for an attenuation of said high-frequency test signal included in said signal transmitted through said cable.

4. An automatic cable attenuation compensation system as claimed in claim 3, wherein said low-frequency test signal has a continuous high amplitude and said high-frequency test signal is a high-frequency sine wave signal with a high amplitude.