I have a system where two boards need to communicate through a serial bus with several lines --- rates are in the order of up to 3MHz. The boards will be several meters away (say, 3 to 5 meters / 10 to 15 feet away). I'm planning to use a differential pair for each signal that needs to be transmitted. In particular, I'm planning to use LVDS, using TI's SN65LVDS1 driver and SN65LVDT2 receiver.
My current plan is to use ethernet cables, as they should comfortably and reliably carry those signals. However, two inconveniences are: (1) the connectors are bulky (compared to the size of my board's components); and (2) I don't want anyone to go and connect these boards to an ethernet switch, or in any case expect that they are intended to be connected to a LAN or the Internet.
Another inconvenience --- or rather, peeve --- is that I actually need to transmit five signals + GND. That exceeds the 8 pins of the ethernet cable, so that aggravates issue (1) above --- the connectos are already bulky, and it turns out I need two of them; or one RJ45 and another of some different type, which is also a peeve.
Are there any alternatives that you could suggest? I could perhaps attempt to use flat ribbon cable with header connectors --- I could leave GND wires in between differential pairs to avoid cross-talk; but I fear that the capacitance between the two wires of each differential pair may be too high, and transmission up to 3MHz may be challenging. Any thoughts?