Transcript COST 286 Wroclaw - Applied Electromagnetics Lab

Research activities in Liège
Ir. V. Beauvois, Ir. S. Coets, Ir. M. Renard
and Ir. Ph. Camus
[email protected]
ULg - EMC Lab
Cost 286 Wroclaw
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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)
[email protected]
ULg - EMC Lab
Cost 286 Wroclaw
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Conducted Emission – Introduction
In the low frequency range [150kHz - 30MHz] ,
conducted emission measurements are performed
with:
 a LISN (Line Impedance Stabilized Network) which
 prevents the EUT from the noise coming from the mains
 provides a defined impedance at the point of measurement
 a passive voltage probe if LISN unavailable (i.e.
if currents too large)
ULg - EMC Lab
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3
Conducted Emission - Measurement
Setup
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4
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
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5
Conducted Emission - Six-pole Concept
 In this research, only single-phased situations are considered
 concept of the six-pole
 If three-phased situations without neutral (3P + PE)
 eight-pole
 If three-phased situations with neutral (3P + N + PE)
 ten-pole
ULg - EMC Lab
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6
Cond. Emission - More accurate model
EUT emission signal voltage
 H1 : six-pole between mains and point of measurement (1b or 2)
 H2 : six-pole between point of measurement and EUT
ULg - EMC Lab
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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 Wroclaw
8
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 Wroclaw
9
Radiated emission - Introduction
Theoretical test configuration:
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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
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11
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
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Research interest:
Characterization and modelling of
embedded systems emissions
Ir. V. Beauvois, Ir. Ph. Camus
[email protected]
ULg - EMC Lab
Cost 286 Wroclaw
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Architecture of embedded systems
Main clock
Data
Transmission
Lines
µcontroller
I/O
Controller
Level shifters
Analog and
Power Section
Sensors and
Actuators
Memory
Power Supply
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 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
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15
Typical waveforms – Data bus
Boucle while(1); durée =100 µs
7
6
5
4
3
2
1
0
0
50
100
150
200
t (µs)
250
300
350
400
Data bus,
address bus
and control signal
are combined
(summation) in time domain.
5000
4000
3000
2000
1000
0
0
20
40
60
80
f (kHz)
100
120
140
160
One simple loop on
80C320 Dallas
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As signals are synchronous
(one main clock) phase is
the same for each signal
at a given frequency
-> spectrum can be easily
computed.
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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 Wroclaw
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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 Wroclaw
18
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 Wroclaw
19
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.
ULg - EMC Lab
Cost 286 Wroclaw
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