Itt Manufacturing Enterprises, Inc.

David W Lagrow

Michael Mayor

An EMI testing scheme involves analyzing an analog input signal in frequency band segments. The input signal is passband filtered and digitally sampled before being converted to a complex analytic signal via a Hilbert transform filter and then transformed into a frequency domain signal via a Discrete Fourier Transform (DFT). Pre-stored frequency window filters are then applied to the frequency domain signal. The set of discrete filter sample points which form the window filters are designed such that particular frequency sub-bands of a desired bandwidth within the frequency segment are selected for EMI analysis. By applying different frequency window filters to the frequency domain signal, different frequency sub-bands are sequentially selected for analysis. An inverse DFT transforms the filtered signal back to the time domain, and the peak voltage of the time domain signal is compared with a threshold to determine whether EMI levels within the selected sub-band are acceptable.

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Fort Wayne, IN, United States of America

David W Lagrow