Interface and wiring design to alleviate the impact of high-energy RF fields upon signal transmission

It is pointed out that the effects of high-energy RF (HERF) upon avionic system operation can be reduced to a benign level if the external interface circuits and cabling possess sufficient design margin to allow continuous and accurate operation while this radiated threat is present. Digital interfaces constructed of balanced and differential transceivers can obtain in excess of 15 dB rejection of the coupled common-mode threat when compared to single-ended circuits. It is noted that transformer coupling of balanced, differential interface circuits to the cable will further reduce the amount of coupled common-mode noise detected by the receiving circuit. The effectiveness of cable shielding with overbraid is strongly dependent on the shield termination at each cable end; peripheral terminations into EMI backshells can offer up to 30 dB greater shielding effectiveness than wire (pigtail) terminated shields