1. Total conducted interference of the power supply without EMI filters

Figure 1 Total conducted interference( exceeded at 98kHz)

2. Differential mode interference of the power supply without EMI filters

Figure2 Differential mode interference( exceeded at 98kHz)

3. Common mode interference of the power supply without EMI filters

Figure3 Common mode interference

The figures above indicates that the conducted interference of power supply of military desktop computer is out of limits, especially differential mode interference.

4. Consider the frequency 98kHz at which point it is exceeded and the amplitude 10dB, according to engineering calculation method of EMI filters, we can get the following filter circuit and parameters:

Figure4 Differential mode circuit and parameters

5. Result after applying EMI filters