I am creating a breakout board with two D-sub-15 connectors at the ends of the PCB. This board will handle RS485 and SpaceWire (differential signal) connections, with signals entering from one end of the connector and leaving from the other end. The breakout board will include test points to measure the signals. I need to understand the PCB design rules to consider while routing the PCB.

Since RS485 has two differential pairs (full duplex) and SpaceWire also has two differential pairs, I have already considered a 100-ohm track impedance. However, I need to understand the appropriate distance between two differential signals pairs. Additionally, while connecting to the D-sub-15 connector, is it necessary to select the pins for the differential signals in a specific manner to avoid interference? Do I need to place guard vias for all differential signals to prevent interference, given that SpaceWire will communicate at speeds up to 200 Mbps and RS485 at 10 Mbps?

Please provide any other guidance on this that need to be considered.

 

I think you should take the phase velocity in consideration and then calculate the track impedance over a length based on matching load. With 2.0 and 3.0 USBs it is not much considered I usually route with 90ohm if ranged within 10cm.

 

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Saturn PCB Toolkit – Saturn PCB

It is very helpful in designing pcb traces, etc.