Technical Considerations for Establishing Narrow-Band EMI Requirements for Data-Processing Equipment and Office Machines

Technology studies of the electromagnetic emanation charactersitics of electronic data processing (EDP) and office machine (OM) equipment was initiated within IBM about a decade ago. Since then, experimental and theoretical studies have been made of both radiated and conducted modes of electromagnetic propagation, and, in particular, the relationship of this propagation to communication receiver interference has been explored. This paper focuses on: 1) development of a worst-case narrow band interference model for most classes of communication services in the United States, and 2) a general approach to narrow band radiated and conducted limit setting. The low incidence of narrow band EDP interference problems is examined, and a statistical estimate of EMI is made for TV services (radiated) and AM radio (conducted). The significance of various limit levels is then discussed.