Development of a Multiresolution Time Domain EMI Measurement System that Fulfills CISPR 16-1 Stephan Braun ∗ , Martin Aidam † , Peter Russer ∗ ∗ Institute for High-Frequency Engineering, Technische Universit¨ at M¨ unchen, Arcisstrasse 21, 80333 M¨ unchen, Germany stephan.braun@tum.de, russer@tum.de † DaimlerChrysler AG, Hedelfinger Strasse 10 - 14, 73734 Esslingen-Pliensauvorstadt martin.aidam@daimlerchrysler.com Abstract— Measurement systems, that allow to measure within short measurement time Electromagnetic Interference (EMI), will reduce the costs for compliance tests. A time-domain EMI (TDEMI) measurement system can reduce the measurement time by several orders of magnitude. In order to have the permission to use a time-domain EMI measurement system for compliance measurements it has to fulfill the CISPR 16-1 [2] completely. In the following the requirements given by CISPR 16-1 are applied to the TDEMI measurement system. The characteristics of the TDEMI measurement system are compared with the rules of CISPR 16-1. A multiresolution TDEMI (MRTDEMI) measure- ment system that uses several analog-to-digital converters (ADCs) is presented. With such a system the signal-to-noise ratio (SNR) is enhanced. Measurements have been carried out in the frequency range 30 MHz - 1 GHz. It is shown, that almost all requirements are fulfillled by the MRTDEMI measurement system. I. I NTRODUCTION Traditionally EMI measurements are performed with EMI- Receivers operating in frequency domain. Measurements in frequency domain take long measurement times, up to several hours, for a single frequency scan. Full compliance EMI- Receivers have to fulfill the CISPR 16-1 [2] completely. CISPR 16-1 describes the fundamental characteristics e.g. the masks of the IF-Filter and the response curve of the quasi- peak detector. Requirements concerning the dynamic range for transient broadband and stationary narrowband signals are described. For each requirement a measurement procedure is specified. By these measurement procedures the conformity of the system can be validated. By a time-domain EMI (TDEMI) measurement system the measurement time can be reduced by several orders of magnitude. In the following the TDEMI measurement system is shown. The minimum requirements that apply to the system given by the CISPR 16-1 are discussed. A multiresolution time-domain EMI (MRTDEMI) measurement system is pre- sented, which shows an enhanced signal-to-noise ratio (SNR). By this way the dynamic range is enhanced by at least 50 dB. The performance of both systems is investigated and compared using the measurement procedures described in CISPR 16-1. II. TIME- DOMAIN EMI MEASUREMENT SYSTEM The time-domain EMI Measurement System consists of a low noise amplifier, an anti-aliasing low-pass filter, an analog-to-digital converter (ADC) for data acquisition and a PC for digital signal processing [1]. For measurements LISN Multiresolution TDEMI Measurement System LP Floating Point ADC Digital Signal Processing Amplitude Spectrum Fig. 1. Measurement Setup of the conducted emissions a line impedance stabilization network (LISN) is used. Radiated emission measurements are performed with a logarithmic periodic antenna with biconical antenna that works in the frequency range 30 MHz - 3 GHz [3]. An algorithm for measurements in time-domain and evaluation of EMI spectra in the Peak, Average and RMS detector modes has been presented in [4]. A operation of the TDEMI measurement system with implemented quasi- peak detector mode has been shown in [1]. The setup for the MRTDEMI measurement system is presented in Fig. 1. The MRTDEMI Measurement System is connected via a switch to a Line Impedance Stabilization Network for conducted emission measurements or to an Antenna for radiated emission measurements. III. ANTENNA For radiated emission measurements in time- and frequency- domain the HL562 ULTRALOG [3] is used. This antenna combines a logarithmic periodic antenna with a biconical antenna. The antenna is characterized with the given antenna factor for full compliance measurements. Because an EMI- Receiver is a non coherent system the phase response of the antenna is omitted during the calculation of the field strength after a measurement. Logarithmic periodic antennas exhibit phase distortion. The maximum dispersion caused by the antenna can be estimated by length of the antenna. The used antenna has a length of 1.5 m for the frequency range up to 3 GHz. When we consider that the signals with higher frequencies are received at the top of the antenna and the signals with lower frequencies at the end of the antenna and assuming velocity of c 0 we get a maximum dispersion of 1.7 ns for the frequency range up to 1 GHz. For accurate measurements by the time-domain EMI measurement system 0-7803-9380-5/05/$20.00 ©2005 IEEE. 388