Analysis of EMI dependence on signal duty and supplied voltage

In this paper, we analyzed EMI dependence on signal duty ratio and power supplied voltage. The EMI levels of the chip-mounted modules were tested and the near-field and far-field emission levels were measured at 800 MHz frequency (the 2
^nd
harmonic of the clock). The relation between EMI levels and line spectra of signals was analyzed for chip design quality, especially including clock generation circuitry and data paths. In addition, voltage-scaling operation and slew rate control operation which affect radiated emission levels, were tested to investigate the effect of duty ratio and slew asymmetry on EMI generation.