Electromagnetic Compatibility Management in the 1980s

T he present administration in W ashington has a monumental task in maintaining a super power military status within tight budget constraints. T he President has asked for cooperation from all areas, and each individ­ ual, each discipline, must consider what contribution can be made to this endeavor. M uch can be done in the electromagnetic compatiblity (E M C ) community to minimize costs o f prime weapon systems without compro­ mising electromagnetic compatibility (E M C ) concerns. A plan is presented in this paper to place proper emphasis, and associated monies, in the critical areas of a total E M C program. T h e entire relationship of electromagnetic interference (E M I) design and test, fol­ lowed by E M C design and test, w ill be evaluated from a fresh viewpoint. T his report presents a critical look at E M I test methods and specification limits in relation to the attainment of E M C . Introduction T he ultimate goal of this paper is a new management approach to the work pertinent to attaining E M C . T he misuse o f funds chasing unrealistic E M I specification requirements must be modified. T his author has witnessed E M I test results from several manufactur­ ers’ products wherein emission levels tens o f dB above specification limits have typically not presented an E M C problem in field use. T oo often a manufacturer is pressured by the customer to redesign a system into specification compliance, or at least partial compliance, when the system in its original configuration may have been electromagnetically compatible with its operational environment. T h e E M I results should, to a large degree, be viewed as system characteristics to be used as data for an E M C analysis. Critically low thresholds in susceptibility testing certainly de­ mand immediate corrective action, but this area o f test performance re­ quires further study and evaluation. T he above argument is illustrated in Figure 1, which plots the narrowband (N B ) radiated emission limits of M IL -S T D -4 6 1 A, Notice 4. T h e two radiated susceptibility field levels stipulated in the same specification are also plotted. An 85 dB minimum safety margin exists between the emission and susceptibility test limits; nevertheless, only a 6 dB safety margin is required in the E M C specifica­ tion, M IL -E -6 0 5 1 D .