EMI structure for electronic circuit box

An EMI filter arrangement comprising:

• a noise source;
• an input filter connected to the input of the noise source;
• an output filter connected to the output of the noise source;
• an electrically conductive electronics box, wherein the noise source, input filter and output filter are in the electrically conductive electronics box;
• and
• an input filter capacitor electrically connecting the input filter to the electrically conductive electronics box;
• an output filter capacitor electrically connecting the output filter to the electrically conductive electronics box;
• an intermediate reference plane provided in the electrically conductive electronics box;
• and
• an intermediate capacitor provided in the electrically conductive electronics box electrically connected between the intermediate reference plane and the electrically conductive electronics box;
• wherein the input filter capacitor and the output filter capacitor are electrically connected to the electrically conductive electronics box via the intermediate reference plane and the intermediate capacitor such that each of the input and output filter capacitors are connected in series with the intermediate capacitor between their respective one of the input filter and output filter and the electrically conductive electronics box;
• wherein the electrically conductive electronics box has an input interface and an output interface, wherein an input capacitance seen from the input interface is the total capacitance resulting from the series connected input capacitor and intermediate capacitor and an output capacitance is the total capacitance resulting from the series connected output capacitor and intermediate capacitor.