Properly routing USB, DVI and Ethernet signals over long distances (30 to 40 cm) on a PCB seems to be relatively challenging (skew, characteristic impedance, cross-talk, etc.). Yet using the standard off-the-shelf cables appears to allow proper signal transmission over meters without putting too much thinking into the design. (see for example USB tech doc suggesting 18inch as max trace length on a PCB http://www.usb.org/developers/docs/hs_usb_pdg_r1_0.pdf but most USB cables easily going beyond this value).
Do our colleagues here with experience in high-speed signal routing agree? Are USB/DVI/Ethernet cables a trivially easier solution for tens of cm? Intuitively shielding of a cable against EMI and cross-talk seems easier than achieving the same performance with a 4-layer PCB. But then skew control seems easier with PCBs than with twisted pairs. Are we overdoing it by trying to route USB, DVI and Ethernet over 40cm instead of just using cables, even if somewhat untidy inside a production quality enclosure?
How would a top tier design team approach the PCB routing versus cable decision for 40cm signal paths inside an enclosure?
thanks in advance for your comments
Addtional info: To answer the question why I need to take USB/DVI/Ethernet signals as far as 40cm on a PCB, consider a medium size (40cm wide x30cm deep) lab instrument enclosure with a front-panel TFT and multiple back-panel USB/DVI/Ethernet connectors. The MCU/CPU on the main PCB needs to be within 5cm or so of the front-panel TFT (limited by the available flat cable) but the interface connectors need to be at the back of the instrument, >30cm away from the MCU/CPU providing the interface signals. Internal cables are clearly a possible solution. But given the dimensions of the enclosure and internal PCB, routing end-to-end is also possible. The question is, what would be best practise: cables or routing on a large PCB?