Digital Video Transmisssion in industrial environment

[beetlejuice]

Digital Video Transmission in industrial environment

Hi Everyone

I have a project whereby I need to capture and transmit a single video image (768x576 pixels) over about 20metres in an industrial environment. The framegrabber part is done, but now I need to transmit the digital image data to another device.
The image data is about 885KByte in size (768x576x16bits) or about 7Mbits. I need to do a complete image transfer about 4 to 5 times per second, which means I will have to transmit data at about 40- 50MBits/sec.

I plan to use cat 5/6 cable.

I have done some research and come up with various SERDES devices using embedded clock, but I have two concerns.
1. The cable length seems to be borderline for the devices I have found
2. The frequency I am operating at seems to be low for most SERDES devices.

I could up the transmission rate to fall in line with some of the SERDES devices, but it seems silly to go faster than I need, and I'm concerned about how robust the interface would be at higher speeds.

I could gear down the transmission and use 3 of the twisted pairs in the cable for data and the forthe pair as a parallel clock. This would reduce my data rate to less than 20MBits per second. The concern here is clock skew, although with a 20MHz clock (50nsec perios), how much skew am I likely to get?

Oh, and I also need to galvanically isolate the transmitter from the receiver, although this could be done seperately after the serial transmission if necessary.

I'm looking for some advice and options on whats the best way to achieve this.

Thanks
Mike

 

[jiripolivka]

Please forget twisted wires! The only reasonable cable is a coaxial. Use suitable "balun" transformers on both ends for impedance matching, and use costly 50-Ohm high quality cables which have a thick sheath. The best coax cables have copper tube sheath, the best for a bad environment.

 

[p.0774023179]

Re: Digital Video Transmission in industrial environment

Hello,
What about using Optical Fiber? You can get some decent SFFs from Avago for instance...
This way you have no problem with interfecence, you naturally isolate the receiver from the transmiter, no limitation/borderline conditions with the cable length, and you can simply go with the SERDES as high as it is required ... maybe even use the spare BW for a higher resolution image.
Good luck!