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EMC Experiments

RADIATED EMISSIONS OF CABLES THROUGH SHIELDED ENCLOSURE SEAMS AND EFFECT OF TIME RISE/FALL ON CLOCK SIGNALS

This experiment shows a means of measuring leakage of electromagnetic energy through seams of a shielded enclosure to analyse the effects in some test positions around the cover. This cover will be removable and will have 18 threaded fasteners distributed around its periphery.

An oscillator circuit capable of producing a typical periodic clock signal will be put inside the shielded enclosure. The output of the oscillator will be connected to a long twin lead to generate common-mode currents and to investigate their associated radiated emissions.

Next, to study the emissions, a probe will be placed in each defined test positions to measure the potential difference between the cover and the enclosure. Then, it will be used a ferrite common-mode chokes to suppress the common-mode current. Another solution to reduce the common-mode effects is to connect a filter adapter to the long twin lead. Nevertheless, this two methods will increase the rise/fall time of the signal.

Therefore, the final solution could be to use a gasket to shield the seams of the cover and to achieve emissions reduction as using a ferrite common-mode chokes or a filter adapter, but this method does not increase rise/fall times of the generated clock signal.

WIRELESS POWER WITH MAGNETIC SHIELDING

The integration of magnetically coupled technologies into integrated electronic circuitry can involve a number of undesired effects, caused by hysteresis and eddy currents internal to the magnetic material, which would reduce effectiveness and greater losses. These losses will transfer from magnetic field energy to heat, generating a self-heating of the product.

This experiment shows how to measure this effect and a means of reducing these losses while improving the efficiency of power transfers. A development kit based on Wireless Power transmitter and receiver boards will be used to measure signal quality of power transfers.

First, to study heating effect, a metal sheet will be put behind the transmitter board while it is communicating with the receiver board. Thereby, an IR thermometer will be used to measure metal sheet temperature and the quality of the communication can be analysed with the demo boards.

In order to reduce the transferred temperature to the metal sheet, a solution could be to place ferrite sheets behind the transmitter and receiver coils. This method will concentrate magnetic flux in the area between them. So, the metal sheet placed outside will be protected, the metal sheet temperature will be decreased and the signal quality will improve.

ExperimentoWP1

Wireless Power magnetic flux without shielding

ExperimentoWP2

Wireless Power with shielding