On the Relation Between Radiated and Conducted RF Emission Tests

This paper deals with the RF emission from small electronic products with a single (mains) cable in the frequency range from 30 to 230 MHz. Because it is important to have EMC assessments in an early stage of the product development, there is a need for simple, low-cost test methods that can be applied in the design lab. A workbench set-up, as described in IEC 61000-46, which is primarily intended for RF immunity testing, is also suitable for conducted RF emission testing. The relation between conducted and radiated test results is discussed and special attention is paid to systematic measurement uncertainties that may occur in both setups. A simple theoretical relation is derived, which corresponds well to the relation obtained from measurements, provided that the resonance effects in the radiated set-up are suppressed, e.g. by applying a common mode termination impedance to the cable.