Breakout box and circuits for direct injection experiments of electromagnetic susceptibility of aircraft electronics

Abstract

Often the determination of the electromagnetic susceptibility of an aircraft's electronics includes direct injection experiments. In that case, an interfering signal, possibly CW and/or transient in nature, is applied directly to the data bus and signal lines of the aircraft system under test. In the past, the frequency or spectrum of the injected signal was typically in the VHF regime and lower (<150 MHz). Recently, susceptibility of aircraft components to signals with spectrums to 1 GHz and higher have been of interest. Application and measurement of signals in these frequency regimes must he made with greater care since cable and component physical and electrical lengths can become significant fractions of a wavelength at the highest frequencies of interest. This paper describes a breakout box designed for narrow and wideband high-voltage direct injection experiments of aircraft 1553 bus systems to 1 GHz and higher. A description is given of the breakout box. Also presented is the design and analysis of the direct injection circuit, the voltage and current sensors, and the high-voltage wideband divider board. Frequency domain characterizations of the circuits are presented, and an example of wideband transient pulse injection, measurement, and compensation using the breakout box is given.