EMC engineering of small communications systems using a CISPR absorbing clamp.

Abstract

This thesis describes how the Comite International Special des Perturbation Radioelectriques (CISPR) Absorbing Clamp can be used in design testing to optimize radiated emissions from small systems, whose physical size (up to approx. 1 m3) is small in comparison with a wavelength at the measured frequency, and the electromagnetic interference is radiated mostly by the cables. The Absorbing Clamp is a simple, repeatable test which requires less investment in time and cost than Open Field Site testing, which is the main alternative. Cost and time to market are main criteria used to design new electronic hardware. During an engineering phase of the product development stage, repeated testing is done to assess the impact of design modifications on system performance. Open Field Site testing remains the only legally accepted test method for conformance testing of radiated electromagnetic interference (EMI) today. Proper design practices to achieve optimal electromagnetic compatibility performance are first reviewed. The theory and operation of the Absorbing Clamp are discussed. Finally, successful use of the Absorbing Clamp during product development, to evaluate the impact of design modifications on system radiated electromagnetic emissions, is demonstrated. Test results confirm that the Absorbing Clamp is a repeatable and inexpensive test method for electromagnetic compatibility (EMC) engineering on small systems where cable radiation is a major contributing factor to the radiated EMI profile.