Radiated noise due to individual spark events in an internal combustion engine

TLDR: In this article, a correlation between the time at which a particular event in the ignition sequence occurs and the RFI produced at that time is made by obtaining synchronization signals from the engine's ignition system, which are used to view the video output of an RFI receiver or spectrum analyzer as a function of time on an oscilloscope.

Abstract: Due to increasing concern about emissions from internal combustion engines that cause radio frequency interference (RFI), investigations are being made to identify sources of the interference and into possible methods of remedying them. In the investigations, it is useful to have a system by which a correlation can be made between the time at which a particular event in the ignition sequence occurs and the RFI produced at that time. See. Fig. 1 for a definition of the ignition events. A system is described in the paper which permits this correlation by obtaining synchronization signals from the engine's ignition system. The synchronization signals are used to view the video output of an RFI receiver or spectrum analyzer as a function of time on an oscilloscope. This allows for discrimination of the ignition related RFI to a time resolution determined by the bandwidth of the receiver being used. A particular advantage of this technique is that it permits a more accurate assessment of the effect of individual component modification in a complex system and, in addition, it permits discrimination against RFI sources unrelated to the automobile being tested.