Method and apparatus for equalizing video transmitted over twisted pair cable

Abstract

A apparatus and apparatus for compensating for video insertion loss due to transmission over long twisted pair cable lines is presented. Transmission of video over twisted pair cable is advantageous because of its superior cost advantage over coaxial cable. However, twisted pair cables have significant loss characteristics at the higher frequencies (i.e., broadband) compared to coaxial cables. At a transmitter station, the video signal is amplified in the high frequency region for possible skin effect losses thereby brute forcing the high frequency components to the receiving station. At the receiver station, the video signal is further compensated for diffusion line and skin effect losses. The total skin effect compensation applied in both the transmitter and receiver stations is such that the square root of frequency characteristics of skin effect losses is compensated for. Thus, at the receiving station, the high frequency compensation added at the transmitter to brute force the high frequency components to the receiving station may be removed if found excessive. Additionally, compensation is included to adjust for skew that may occur because of irregularities between the various twisted pairs used to transmit the individual video components. Non-minimum phase type filters are used to inject delay into the faster arriving signals so that they may coincide in phase with later arriving signals resulting in a true reproduction of the video.

1 .- 24 . (canceled)  
   
   
       25 . A method for equalizing video transmitted over twisted pair cable comprising: 
 receiving an input signal having a plurality of video components;    compensating one or more of said plurality of video components for transmission;    transmitting each of said plurality of video components over a twisted pair cable to a receiving station;    applying compensation to each of said plurality of video components for accumulated amplitude losses due to said transmission over said twisted pair cable; and    generating a plurality of output video components by applying desired phase compensation using adjustable non-minimum phase filters on one or more of said plurality of video components, said non-minimum phase filters having poles and zeros configured to provide said desired phase compensation.    
   
   
       26 . The method of  claim 25 , wherein said plurality of video components comprises a color system's color components.  
   
   
       27 . The method of  claim 25 , wherein each of said plurality of video components comprises a high frequency portion and a low frequency portion.  
   
   
       28 . The method of  claim 27 , wherein said compensating said plurality of video components for transmission comprises application of high frequency boosting on each of said plurality of video components.  
   
   
       29 . The method of  claim 25 , wherein said applying compensation for accumulated amplitude losses comprises: 
 applying low frequency shaping to account for diffusion effect losses occurring during transmission over said twisted pair cable; and    applying high frequency shaping to account for skin effect losses occurring during transmission over said twisted pair cable.    
   
   
       30 . The method of  claim 29 , wherein said high frequency shaping comprises a compensation network that effectively compensates for said skin effect losses.  
   
   
       31 . The method of  claim 25 , wherein said twisted pair cable is unshielded twisted pair.  
   
   
       32 . The method of  claim 25 , wherein said compensation for accumulated amplitude losses is adjustable.  
   
   
       33 . The method of  claim 25 , wherein said compensating said plurality of video components for transmission is performed in a transmitting station.  
   
   
       34 . The method of  claim 25 , wherein said compensation for accumulated amplitude losses is performed in said receiving station.  
   
   
       35 . An apparatus for equalizing video transmitted over twisted pair cable comprising: 
 an input signal with a plurality of video components;    a first compensation circuit coupled to said plurality of video components;    a plurality of twisted pair cables coupled to said compensation circuit for transmitting said plurality of video components to a receiving station;    a second compensation circuit in said receiving station coupled to said twisted pair cables for compensation of said plurality of video components for accumulated amplitude losses due to transmission over said twisted pair cables; and    a phase delay circuit coupled to said second compensation circuit for application of desired phase delay to one or more of said plurality of video components.    
   
   
       36 . The apparatus of  claim 35 , wherein said plurality of video components comprises a color system's color components.  
   
   
       37 . The apparatus of  claim 35 , wherein each of said plurality of video components comprises a high frequency region and a low frequency region.  
   
   
       38 . The apparatus of  claim 37 , wherein said first compensation circuit comprises amplifier circuits to boost said high frequency region of said plurality of video components.  
   
   
       39 . The apparatus of  claim 35 , wherein said second compensation circuit comprises: 
 low frequency shaping filters to account for diffusion effect losses occurring during transmission over said twisted pair cable; and    high frequency shaping filters to account for skin effect losses occurring during transmission over said twisted pair cable.    
   
   
       40 . The apparatus of  claim 39 , wherein said high frequency shaping filter comprises a compensation network that effectively compensates for said skin effect losses.  
   
   
       41 . The apparatus of  claim 35 , wherein said twisted pair cable is unshielded twisted pair.  
   
   
       42 . The apparatus of  claim 35 , wherein said phase delay circuit comprises a non-minimum phase zero filter having adjustable poles and zeros.  
   
   
       43 . The apparatus of  claim 35 , wherein said second compensation circuit is adjustable.  
   
   
       44 . The apparatus of  claim 36 , wherein said color system is RGB.