New Demo Kit From Solid State Supplies Drives VGA Over 300M Of CAT5 Cable

A new demo and development kit from Solid State Supplies includes a transmission and a receiver circuit which enables the successful transmission of video signals over long distances of CAT5 cable.

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Although standard un-shielded CAT5 twisted-pair interconnect is a good choice for long distance transmission of electrical information due to its low cost, wide availability and predictable electrical characteristics, it has never been the carrier of choice for video. The new demo kit however, which includes a CADEKA driver and receiver, offers a solution that will handle VGA (640x480), SVGA (800x600), and XVGA (1024x768) formats while using up to 300 meters of CAT5 cable.

Typical CAT5 cable consists of 4 separate twisted-pair channels, usually from 24 AWG wire. For a remote video system, this allows 3 channels to carry video information while allowing an additional channel to carry audio and/or control information.

Twisted-pair transmission allows for differential signaling and provides better quality video by allowing a larger signal swing and the suppression of even ordered harmonic distortion. Single ended RGB video information is first converted to a differential signal before transmission, then the signal is converted back to single ended at the receiver in order to drive a standard video monitor.

For long distance transmission, the electrical characteristics of the cable will attenuate the higher frequency components of the signal. For good quality video, this must be corrected at the receiver by incorporating a frequency response equaliza­tion function to boost the higher frequency components back to their original values.

To run the 5 separate video information signals, three video and two timing, over three channels, CADEKA’s driver/receiver solution encodes the Hsync and Vsync information onto the common-mode level of the three video channels. This is done in a manner in which the encoded levels cancel EMI radiation which may corrupt the video signal. Common-mode levels are then de­tected at the receiver and de-coded into the original Hsync and Vsync information.