Research On EMI Radiation Source Noise Diagnosis Method Based On NLPCA And JADE Algorithm

With large scale integrated circuits, high frequency switch elements and radio communication modules widely used in electronic devices, a lot of radiated noise arises and transmits toward the outside in the form of space electromagnetic field, which not only affects the normal function of the device of itself, but also interferes with the operation of external devices by means of electromagnetic radiation. Current analysis methods of EMI issue are mostly about analysis of radiation problems based on theory and model, which cannot judge and diagnosis noise source characteristics, and lead to some errors between results and the facts due to an idealized model. As a result, the recognition and diagnosis of the electromagnetic radiation noise source in complicated electronic devices have become a huge challenge in EMI radiation analysisFor the above issues,this thesis studied "research on noise diagnosis method of EMI radiation source based on NLPCA and JADE algorithm”,which contains the followings:(1) Started with antenna radiation theory, radiation mechanism of complicated electronic devices was analyzed and model of convolutive mixed radiation noise was created especially for the two situations, one is signal transmission delay when the length of cable that emits radiation is electrically large dimension, the other is backward traveling wave is detected on the circuit when line impedance mismatches.(2) Location method of multi radiation sources was studied in this article. By using NLPCA and JADE algorithm to analyze the radiated noise from the time domain and frequency domain respectively, several separated radiation noise signals were obtained as alternative signals for overproof sources of radiation noise. Separated signals of EMI noise were analyzed based on power spectrum analysis, and the frequency features of individual signal was extracted. Compared with possible radiation sources of PCB, the main reason of excessive radiation was determined.(3) Three groups of validation experiment were made. The reason was found out and the feasibility of the filter and location method was validated by blind separation of noise signal using double common-mode model, double differential-mode model and common-mode & differential-mode hybrid model, and energy spectrum analysis being performed for separated signal. Case studies were done by two pieces of real and complicated electronics, the validity of this applied method was proved, and the reason of excessive radiation was figured out. In addition, corresponding modification was made according to the causes of exceeding standard, which allowing electronic devices pass national standard test.By the research of theory and the confirmation of experimentation , the location methods proposed in the thesis not only have important reference value to the signal separation research of EMI multi-radiation sources in the complex electronic equipment,but also have positive guiding significance to the corrections in EMI.