Injecting Noise In Power Supplies Improves Security For Communications Devices

by Gregory Mirsky, Vitesco Technologies, A Spinoff Of Continental Automotive Systems, Deer Park, Ill., How2Power Today, Jan 17 2020

Focus:
In communication devices such as cell phones, voice-generated audio signals that pass through audio amplifiers modulate the dc supply voltage and thus also modulate the power supply’s switching waveforms. As any switching power supply has some electromagnetic emissions, the modulating voice-generated information is emitted as well. This short article describes a very simple way of safeguarding this audio information to prevent eavesdropping of any emitted signals. The proposed method uses noise to modulate the power supply switching signal. A simple circuit used to implement this technique on a dc-dc converter is described and the simulated spectral results are shown.

What you’ll learn:

• How to mask audio information emitted by switched-mode power supplies in communications devices
• How to apply noise modulation to a switched-mode power supply to mask unintentionally emitted audio signals

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