Measurement of Microcontroller Radiated Emissions at Different Operation Modes

The paper presents the results of the investigation of the radiated emissions from microcontroller (MC) 1986BE91T with its different software configurations in a TEM cell. Radiated emissions were measured multiplying the clock frequency of the microcontroller using the high speed internal and external oscillator clocks, as well as when the arithmetic-logic unit, analog-to-digital and digital-to-analog converters units are functioning. It was revealed that emissions from the considered MC units are concentrated at frequencies up to 20 MHz and do not exceed
$\mathrm{25}\ \text{dB}\mu\mathrm{V}$
, and an increase in the clock frequency from 8 to 80 MHz leads to an increase in the maximum emission value from 11 to
$\mathrm{29}\ \text{dB}\mu\mathrm{V}$
at the fundamental and higher harmonics of the clock frequency.