UTP Cable Auto-Compensation System

Unshielded twisted pair (UTP), such as Cat 5e, is primarily designed for local area network (LAN) transmission. Because of its good performance and low cost, it has become economical solution for many other signal transmission applications.

RGB computer graphics and analog HDTV component video (YPbPr) comprise two important categories of analog broadband video signals. These signals suffer from two major impairments when transported over standard four-pair Unshielded Twisted Pair (UTP) cables, such as Cat-5e. One impairment is time dispersion caused by the nonlinear lowpass frequency response of the cable, due to the skin effect. The time dispersion increases the settling times of pixel-to-pixel transitions to the point where information from early pixels spreads into later pixels, causing visible interference. The other impairment is pair-to-pair time skew between the three pairs due to variances in lengths, and therefore propagation delays, between the pairs.

The Analog Devices UTP Cable Auto-Compensation System provides the user with a complete end-to-end UTP cable compensation solution that automatically corrects for cable loss characteristics and pair-to-pair skew. The solution produces an image that exhibits minimal streaking and skew effects with no user intervention required. Adjustments are automatically made whenever the cable is switched.

For more detailed information, please contact ADI customer interaction center. Send email to cic.asia@analog.com.


 
基于UTP视频传输的自动补偿系统
PCB
Technical documents and software download
Include
1. User Guide
2. MCU firmware HEX file
3. Schematics and PCB layout files
 
 
Hardware Design   Software Design
基于UTP 视频传输的自动补偿系统硬件设计   基于UTP 视频传输的自动补偿系统软件设计
• Key Parts in the UTP Cable Auto-Compensation System:
    • AD8147: Triple Differential Driver for Wideband Video.
    • AD8122: Triple Differential Receiver with Adjustable Cable Equalization.
    • AD8120: Triple Skew-Compensating Video Delay Line.
    • AD9280: 8-Bit, 32 MSPS A/D Converter(ADC).
•  The system consists of two parts: the driver board and the receiver board.
•  Video signal input from VGA interface.
•  Driver board: The single-ended RGB signal is conditioned into differential signal, Vsync and Hsync signals are encoded among the common mode voltages.
•  Long distance signal transmission by UTP cable
•  Receiver board: Recover the single-ended RGB signal, decode Vsync and Hsync signals.
•  EQ and pair-to-pair skew compensations are implemented on receiver board.
  • Driver Board Side:
    • Add Test Pulse (TP) into the VGA input signals (R,G,B,Vsync/Hsync).
• Receiver Board Side:
    • Capture the TP distortion in G signal by high speed ADC and do equalization accordingly.
    • Capture the TP delay among R,G,B signals and do skew correction accordingly.

未补偿与补偿后的图像对比
     
 
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* Disclaimer: This reference design is provided for reference only. This reference design is provided to ADI clients to assist in the design and development process. ADI reserves the right to modify the provided reference design at any time without prior notice. The client shall be responsible for their own designs based on or adapted from the reference design. Please carefully read through the ADI provided information before referencing or using this reference design. ADI shall not be responsible for the risks associated with referencing or using the reference design.
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