Modifying Noise Source Amplitude Modulation Technique to Estimate Magnitude and Phase of Emissions from Individual Integrated Circuits

A method to separately estimate the magnitude of far-field emission caused by multiple noise sources each has been developed. The method is modified to improve the magnitude estimation in the higher frequency range where the wavelength of the emission becomes comparable to the size of printed circuit boards or systems. The modification also enables the evaluation of phase differences among multiple far-fields induced by multiple noise sources each. The method uses the noise source amplitude modulation and correlation analysis (NSM-CA) technique for determining significant noise sources generating intense emission that affects overall emission dominantly. The modified method was applied to a printed circuit board implementing three line-driver ICs. The intensities of far-field emission induced by the three ICs each were estimated separately and compared with measured intensities, indicating excellent agreement even in the higher frequency range. Phase differences among the three far-field emissions due to the three ICs were also estimated by the method. The results matched the general knowledge that the phase shifts as the frequency becomes higher, suggesting that the proposed method can also evaluate the phase relationship of multiple far-field emissions.