One of the difficulties in solving E:MI problems is the lack of diagnostic tools
available. In this thesis work, a tool, called Noise Separator, is developed, which can be
used to decipher the differential-mode (DM) noise and the common-mode (CM) noise
from the total noise. A noise separator hardware is built and tested. The results show that
at least 50 dB rejection to either DM or CM noise is achieved for frequency ranging from
10 KHz to 30 MHz. With the aid of the Noise Separator, EMI filter design is made easier.