The Role of Supply Conditions on the Measurement of High-Frequency Emissions

A standardized measurement procedure and source specification for laboratory high-frequency (HF, 2-150 kHz) emissions tests of low-voltage (LV) electronic equipment are still in development. To date, emissions have been measured by direct supply from the mains network or a controllable power source (PS), but both methods are known to interfere with the assessment process. A line impedance stabilization network (LISN) limits supply-load interactions but has been underevaluated until now in the HF analysis, despite being named a potential approach in IEC Standards. This article quantifies the effect of supply conditions on HF emission assessment and the role of the LISN. The effect of the supply voltage fundamental amplitude and low-frequency background distortion on the magnitude and frequency of the characteristic HF emissions is presented, and a new supply configuration combining a programmable PS with LISN is proposed. Experimental results from a case study of two LED lamps with distinct HF emissions, representative of a number of typical LV electronic devices, indicate that only the proposed programmable PS+LISN supply can guarantee the accurate and repeatable measurements under controllable voltage supply conditions and impedance separation that are needed by ongoing HF standardization and modeling activities.