EMI Reduction

In general, the design practices used to ensure good signal integrity and timing design will go a long way towards ensuring acceptable EMI and RFI limits are not exceeded. A few examples that Interconnect Engineering uses to reduce radiated emissions are:

  • Minimize routing on primary and secondary surface layers.

  • Stackup design incorporates ground planes on layers 2 and n-1.

  • Use of ferrite for power filtering where needed.

  • Reduce use of split planes so return current paths are not disrupted.

  • Minimize via usage and impedance discontinuities.

  • All traces longer than the rise time of the signal must be terminated.

  • No signals routed near PCB edge unless edge plated or stitching vias.

  • Use of chassis to digital ground capacitor connection (if applicable).

  • Use of general signal integrity principals such as termination of all transmission lines, etc.

  • Use of highly accurate EMI analysis can be provided using Ansoft HFSS. This tool has the ability to simulate radiated fields from any 3D model. Works very well with mechanical CAD tools such as Pro Engineer and AutoCAD. The use of the type of tool is absolutely necessary for high-speed backplane design to analyze the parasitic L’s, R’s and C’s of vias, packages, pads and connectors when the data-rate exceeds 5 Gbit/s.