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I am using a D-coded M12 Ethernet connector in my device for a Fast Ethernet (100 Mbps) connection. Due to physical limitations, the connector can't be PCB-mounted, so I selected a panel-mount version with flying leads connected to the PCB. The LAN transformer is located on the PCB side, and I don't have the space for an RJ45

What is the typical method for terminating these wires onto the PCB in industrial products to ensure signal integrity and EMI/EMC compliance?

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  • \$\begingroup\$ What Ethernet? 100BASE-T? \$\endgroup\$
    – Tim Williams
    Commented Oct 18 at 15:24
  • \$\begingroup\$ @TimWilliams yes, Fast Ethernet (100 Mbps) \$\endgroup\$
    – HV16
    Commented Oct 18 at 15:41
  • \$\begingroup\$ Post a link to the datasheet of the panel mount connector (with leads). What's your final cable length from the connector to the PCB? In general, keep the pairs twisted, and all's good. \$\endgroup\$
    – Chris Knudsen
    Commented Oct 18 at 15:53
  • \$\begingroup\$ @ChrisKnudsen about 3-4 inches. Are there connectors for high-speed applications or any connector will suffice? \$\endgroup\$
    – HV16
    Commented Oct 18 at 16:22
  • \$\begingroup\$ If any two-wire line of finite length does not have a load at one end, it is easy for multiple reflections of the energy carrying the information to occur along it, causing the information to become unreadable. In order for there to be no reflections, a resistive termination equal to the characteristic impedance of the line must be applied. Therefore, for example, a cable made up of eight lines must be adapted so that each end of the lines is connected to a resistance of a value equal to that of the single line. \$\endgroup\$
    – Francesco M.
    Commented Oct 18 at 16:29

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What is the typical method for terminating these wires onto the PCB in industrial products to ensure signal integrity and EMI/EMC compliance?

In the past for special connectors I'd use an extender, it makes it easier to install for assembly and rework. I'd see if you could make space for an RJ45 and then use one of these: enter image description here Source: Binder

That being said, if you really don't have room, you could just solder the wires to the board, making sure that you keep the pairs twisted to preserve signal integrity.

Another option is to try a connector like this which is easy to terminate wires to a board, I'm not sure from a signal integrity standpoint, but it shouldn't be worse than the separation that you might find in a keystone jack: enter image description here
https://www.digikey.com/en/products/detail/phoenix-contact/1706196/267608

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