ULg - EMC Lab Cost 286 Wroclaw1 Research activities in Liège Ir. V. Beauvois, Ir. S. Coets, Ir. M. Renard and Ir. Ph. Camus

ULg - EMC Lab Cost 286 Wroclaw2 1 st Research interest: conducted and radiated emissions measurements on large systems Ir. V. Beauvois, Ir. S. Coets and Ir. M. Renard (Sorrento 2002 and Zurich 2003) in coll. With Johan Catrysse (KHBO, Oostende, Belgium)

ULg - EMC Lab Cost 286 Wroclaw3 Conducted Emission – Introduction In the low frequency range [150kHz - 30MHz], conducted emission measurements are performed with:  a LISN (Line Impedance Stabilized Network) which  a passive voltage probe if LISN unavailable (i.e. if currents too large)  prevents the EUT from the noise coming from the mains  provides a defined impedance at the point of measurement

ULg - EMC Lab Cost 286 Wroclaw4 Conducted Emission - Measurement Setup

ULg - EMC Lab Cost 286 Wroclaw5 Conducted Emission - Problems encountered  With the LISN, the measurement is always performed at point 1b The point of measurement is ‘‘standardized’’ (fixed)   Oppositely, the voltage probe (point 2) can be placed anywhere between points 1b and 3, depending on the ‘‘accessibility’’ of the EUT Which signal voltage is measured (distributed impedance between 1b and 3 not negligible) ??   Solution: introduction of a new concept:the six-pole

ULg - EMC Lab Cost 286 Wroclaw6 Conducted Emission - Six-pole Concept  In this research, only single-phased situations are considered  concept of the six-pole  If three-phased situations with neutral (3P + N + PE)  ten-pole  If three-phased situations without neutral (3P + PE)  eight-pole

ULg - EMC Lab Cost 286 Wroclaw7 Cond. Emission - More accurate model  H 1 : six-pole between mains and point of measurement (1b or 2) EUT emission signal voltage  H 2 : six-pole between point of measurement and EUT

ULg - EMC Lab Cost 286 Wroclaw8 Cond. Emission - Actual and Future Works As the tests performed without LISN may not be compared with those performed with LISN, the next steps of the study are:  create a ‘‘virtual’’ power mains network similar to the LISN ’s one and perform measurements with the help of this ‘‘LISN-equivalent network’’  for instance by the use of an EMI filter instead of the LISN  an alternating method to the LISN could then be reached

ULg - EMC Lab Cost 286 Wroclaw9 Cond. Emission - Actual and Future Works (contd) time domain and frequency domain measurements are done. alternate measurement methods : - classical passive voltage probe (one or two with differential method) - alternate probes and clamps (capacitive clamp, EM clamp, current probe)  improve the sensitivity of the measurements and the signal -processing to get more accurate results

ULg - EMC Lab Cost 286 Wroclaw10 Radiated emission - Introduction Theoretical test configuration:

ULg - EMC Lab Cost 286 Wroclaw11 Radiated emission - Problems encountered  Noise coming from the environment.  Multiple reflexions « against » the environment which leads to an over-estimation or an under-estimation of the emission of the EUT.  The measurement cannot necessarily be performed at a 10 meters distance from the EUT.  How many measurements are to be done? And where?

ULg - EMC Lab Cost 286 Wroclaw12 Radiated emission - Solutions to consider  Retrieve the right signal from noise by using a differential method.  As the measurements cannot be performed at a 10 meters (or 3 meters) distance, perform near-field measurements in addition with a near-field  far-field transformation.  Take into account the reflecting characteristics of the global environment

ULg - EMC Lab Cost 286 Wroclaw13 2 nd Research interest: Characterization and modelling of embedded systems emissions Ir. V. Beauvois, Ir. Ph. Camus

ULg - EMC Lab Cost 286 Wroclaw14 Architecture of embedded systems µcontroller Main clock Memory I/O Controller Analog and Power Section Sensors and Actuators Level shifters Power Supply Data Transmission Lines

ULg - EMC Lab Cost 286 Wroclaw15  Fast switching occurs on the bus and transmission lines which leads to current pulses.  Current pulses produce electromagnetic emissions radiated through the P.C.B. traces, integrated circuits pads and connected cables.  For a given architecture and software, the current waveforms on the board connections can be evaluated - they are related to electromagnetic emission.  By mean of Fourier transform the spectrum can be computed and compared with EMC limits.

ULg - EMC Lab Cost 286 Wroclaw16 Typical waveforms – Data bus Data bus, address bus and control signal are combined (summation) in time domain. As signals are synchronous (one main clock) phase is the same for each signal at a given frequency -> spectrum can be easily computed. One simple loop on 80C320 Dallas

ULg - EMC Lab Cost 286 Wroclaw17 Typical waveforms – Power supply White filtered noise for analog parts Simple pulse noise for switched circuits 7805 linear regulator (white noise with cut off frequency near 1 MHz) and MAX232 level shifter (245 kHz and harmonics)

ULg - EMC Lab Cost 286 Wroclaw18 Typical waveforms – Analog and Power section Classification into families of circuits with same noise signatures White filtered noise and switching noise.

ULg - EMC Lab Cost 286 Wroclaw19 First results and actual works Conducted and radiated emission of a 80C320 board were measured for different codes and compared with computed spectrum : computed spectrum components occur at the same frequency as in the measurement on a real circuit ; variation of amplitude follows a similar envelope.

ULg - EMC Lab Cost 286 Wroclaw20 Actual and Future Works Characterization of a great number of boards : same CPU with different clocks and different peripherals, … Better modelling of switching process and relationship with conducted and radiated noise. VHDL modelling of CPU to gain a better comprehension of processor noise sources, synthesis into an FPGA and measurements in anechoic chamber. Development of software tools to predict noise behaviour of embedded systems.