Direct current injection as a method of simulating high intensity radiated fields (HIRF)

As the realisation of the true RF environment in which military aircraft must operate has developed over the years, there has been a corresponding increase in EMC clearance levels. The need to test aircraft systems to these high levels is posing great problems for the test community. Established test methods such as high intensity radiated field (HIRF) and bulk current injection (BCI) were sufficient in the past for clearance of in-service aircraft. For new systems bulk current injection has become less acceptable in it´s present form. Thus, British Aerospace (BAe) has researched alternative test techniques which will allow high level testing of complete aircraft systems at an affordable price. A possible candidate for a high level clearance tool was direct current injection (DCI). A form of DCI has been used for many years to test aircraft against lightning strike, covering the frequency band below 1 MHz. This technique was adopted and refined to extend it´s useful frequency range to above 100 MHz in several stages. Initial research into DCI conducted by BAe has concentrated on implementing DCI using a co-axial return conductor rig, with the aircraft fully enclosed by the rig and forming the centre conductor of the transmission line. The paper gives an overview of the research performed by BAe to develop a practical DCI test technique for use in high level EMC testing of a whole aircraft