Progress In Electromagnetics Research Symposium Proceedings, KL, MALAYSIA, March 27–30, 2012
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The Conducted and Radiated Emission Levels from IT Devices
Rafal Przesmycki, Marian Wnuk, Leszek Nowosielski,
Kazimierz Piwowarczyk, and Marek Bugaj
Faculty of Electronics, Military University of Technology
Gen. S. Kaliskiego 2 Str., Warsaw 00-908, Poland
Abstract— The article concerns problems of electromagnetic compatibility of contemporary IT
devices. Particular attention was paid to undesirable emissions, which are by-products generated
unintentionally during realization of basic functions of device. In the article the methodology of
measuring conducted emission on supply terminals of IT devices according to the EN 55022:2006
standard in the frequency range from 0.15 MHz to 30 MHz has been presented as well as the
methodology of measuring radiated emissivity of IT devices in accordance with the EN 5022:2006
standard in the frequency range from 30 MHz to 6000 MHz. Also the results of measurements
conducted on particular number of central processing units have been demonstrated along with
keyboards and mice produced in the years 2007–2011 and next their analysis has been made.
1. INTRODUCTION
Telecommunications and data communications devices are integral part of complex systems, which
determine the correct functioning of economy. Efficiency and reliability of the functioning of electric
and electronic devices decide about the functioning and development of national economy. To a
large extent it depends on hazards and the level of disturbances occurring in the environment
surrounding us. Thus it is necessary not only to study sensitivity of electric and electronic devices
to electromagnetic fields but also to control the level of electromagnetic disturbances emitted to
the surrounding environment through different ways.
The problem is important not only because of electromagnetic compatibility but also due to
necessity of providing security of sent or processed information. Currently there are available devices
which allow to reconstruct processed or sent information by using dispersed electromagnetic fields
(unintentionally radiated). Therefore issues connected with the control of disturbance emissions
become particularly significant.
In the article the measuring results of levels of radiated or conducted emission on supply terminals of contemporary IT devices including the measurement methodology have been presented.
2. ASSESSMENT OF THE DEVICE EMISSION
Each device is characterized by parameter ε determining emission ability. It is the function of
emission direction ϕ, pulsation ω and time t,
ε = f (ϕ, ω, t) .
(1)
Electromagnetic emissions to the environment can be divided into two large groups — namely:
desirable and undesirable emissions. Desirable emissions are associated with the sending of signals
carrying useful information. Disturbances in the device operation which are caused by desirable
radiation are eliminated by appropriate assignment of frequency band or operating frequency.
In this study a particular attention was paid to undesirable emissions. They are by-products
generated unintentionally during realization of basic function of the device. They are formed
in electric circuits containing inductances and capacities in which there occur sudden changes of
current or voltage, relatively fluctuating changes of density of electric charge carriers or in which
there occurs positive back coupling.
Distribution of energy of electromagnetic disturbances in the frequency spectrum and their
transient performances depend on the structure and electric parameters of the device generating
them in the RF range, its transient response and impedance of loading circuits. Taking into account
transient performances of desirable and undesirable emissions, we can divide generated disturbances
into constant and impulse ones or due to frequency characteristic into: narrow and broad-band.
Because of different ways of energy emission of disturbances to the environment various parameters define the level of disturbances generated by one source or some set of sources. Usually the level
of generated disturbances is determined by providing the value of power of emitted electromagnetic
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PIERS Proceedings, Kuala Lumpur, MALAYSIA, March 27–30, 2012
Figure 1: Block diagram of the measuring position
for measuring conducted emissions.
Figure 2: Block diagram of the measuring position
for measuring radiated emissions.
field (Pz ) or the value of electromagnetic field strength (electric component Ez or magnetic component Hz ) within the determined distance from the source or the voltage value (Uz ), or current
(Iz ) measured in an added to the source circuit loaded with known impedance. The values of
these parameters are given in the frequency function i.e., in the form of spectral characteristics.
Determined values of disturbances emitted to the environment are compared to admissible levels
determined for a particular class of device during the process of supervising devices admitted to
trade turnover.
In further part of the article the disturbances are defined, the methodology of measuring conducted and radiated emissivity of IT devices in accordance with the EN 55022:2006 standard is
presented and the results of measurements carried out on particular number of samples consisting
of central processing units produced in the years 2007–2011 are demonstrated. The measurements
of conducted and radiated emissivity have been performed in the Electromagnetic Compatibility
Laboratory at the Faculty of Electronics of the Military University of Technology in Poland.
3. MEASUREMENT OF CONDUCTED DISTURBANCES OF IT DEVICES IN THE
RANGE FROM 150 KHz TO 30 MHz
The measurements of conducted disturbances emitted by IT devices have been performed in accordance with the EN 55022:2006 standard. They consist in measuring the level of electromagnetic field
on supply terminals of device with the use of artificial mains network (AMN) line and measuring
receiver in the frequency range from 0.15 MHz to 30 MHz.
Conducted disturbances are measured between phase circuit and reference ground and between
neutral circuit and reference ground. Steering the measuring process (change of setting of measuring receiver and artificial network) is carried out by the software EMC32 of the Rohde&Schwarz
company, installed on a computer which steers the measuring process.
To measure conducted disturbances it is necessary to set up a measuring position in the configuration as it is shown in Figure 1.
The measurements are performed in the frequency range from 0.15 MHz to 30 MHz, using the
measuring receiver equipped with detectors of quasi-peak and average values and RBW filter of the
frequency band equal to 9 kHz. Both detectors can be situated in one receiver and the measurements
are carried out by turns for particular detectors. Due to the measurement automation, in the above
mentioned measuring method the artificial means network ENV216 is used.
4. MEASUREMENT OF RADIATED DISTURBANCES OF IT DEVICES IN THE
RANGE FROM 30 MHz TO 6000 MHz
Measurements of radiated disturbances emitted by IT devices have been performed in accordance
with the EN 55022:2006 standard. They consist in measuring electromagnetic field strength within
the distance of 3 m from the device with the use of measuring antennas and measuring receiver in
the frequency range from 30 MHz to 6000 MHz. The measurements are conducted for vertical and
horizontal polarization of measuring antennas and for particular combinations of location of the
EUT. The EUT location towards measuring antenna is changed with the use of turntable and aerial
mast automatically. It can be obtained due to using a suitable controller which steers the turntable
Progress In Electromagnetics Research Symposium Proceedings, KL, MALAYSIA, March 27–30, 2012
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and height of the aerial mast as well as computer steering the whole measuring process. To measure
radiated disturbances it is necessary to set up the measuring position in the configuration as shown
in Figure 2.
The measurements are made in the frequency range from 30 MHz to 6000 MHz, using measurement receiver with peak detector and RBW filter with frequency band equal to 120 kHz for the
range 30 MHz–1000 MHz and 1 MHz for the range 1 GHz–6 GHz. Due to the measurement automation, in the above mentioned measuring method broad-band antennas have been used, which do not
require adjustment of antenna’s length to resonant length for particular measuring frequency. The
biconical antenna SAS544 is used for measuring radiated disturbances in the frequency range from
30 MHz to 230 MHz, the log-periodic antenna 3147 is used in the frequency range from 230 MHz to
1000 MHz, whereas the horn antenna DRG-118/A — in the frequency range from 1 GHz to 6 GHz.
5. MEASURING RESULTS-LEVELS OF CONDUCTED EMISSION ON SUPPLY
TERMINALS OF IT DEVICES IN THE RANGE FROM 0.15 MHz TO 30 MHz
The measurements of the disturbance levels of conducted emissions on supply terminals emitted by
IT devices have been carried out on particular number of device items. On the basis of the obtained
measuring results an analysis of levels of conducted emissivity of contemporary IT devices has been
made. The measurements have been completed in the frequency range from 0.15 MHz to 30 MHz.
Twenty items of PCs have been examined. In Figure 3 maximal and averaging levels of conducted
emissions on supply terminals of contemporary IT devices are shown, taking into account all the
tested devices.
6. MEASURING RESULTS-LEVELS OF RADIATED EMISSION OF IT DEVICES IN
THE RANGE FROM 30 MHz TO 6000 MHz
The measurements of the disturbance levels of radiated emission emitted by IT devices have been
carried out on particular number of device items within the distance of 3 m from the tested device.
On the basis of the obtained measuring results an analysis of levels of radiated emission of contemporary IT devices has been made. The measurements have been performed in the frequency range
from 30 MHz to 6000 MHz, using a peak detector, however because of measuring abilities of the
laboratory and used measuring equipment (mainly antennas) the measurements have been divided
into two sub-bands. The first frequency range spreads out from 30 MHz to 1000 MHz, the second
frequency range is contained in the range between 1000 MHz and 6000 MHz. In the first frequency
range 139 PCs have been examined while in the second frequency range 104 computers. In Figure 4
and Figure 5 maximal and averaging levels of measured values of electromagnetic field strength
radiated by contemporary IT devices are showed, taking into account all the tested devices.
7. MEASURING RESULTS-ANALYSIS OF THE MEASURING RESULTS OF
CONDUCTED AND RADIATED EMISSION OF IT DEVICES
Analyzing averaging values of conducted and radiated disturbances we can notice that for a few frequencies there occur much larger levels of emission when compared to others. For these frequencies
an identification of components by the elimination method has been made. This method consists
in consecutive disconnections of loads of interfaces in central processing units during the research
Figure 3: Maximal and averaging levels of conducted emissions of all EUT in the frequency range from
0.15 MHz to 30 MHz.
PIERS Proceedings, Kuala Lumpur, MALAYSIA, March 27–30, 2012
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Figure 4: Maximal and averaging levels of radiated
disturbances within the distance of 3 m from all EUT
in the frequency range from 30 MHz to 1 GHz.
Figure 5: Maximal and averaging levels of radiated
disturbances within the distance of 3 m from all EUT
in the frequency range from 1 GHz to 6 GHz.
Table 1: Levels of electromagnetic field strength of the examined device deriving from components located
in central processing unit.
Device/ type of interface
Frequency [MHz]
USB
USB
Mouse / PS2
Printer / LPT
Mouse / PS2
USB
Keyboard / USB
USB
USB
Graphic card / DVI
USB
119.00
120.00
126.00
144.00
166.00
180.00
200.00
240.00
480.00
720.00
960.00
Emission level within the
distance of 3 m from EUT [dBµV/m]
MAX
AVERAGE
46.48
29.86
65.26
35.11
49.66
30.04
48.33
33.42
39.58
30.54
57.50
35.96
48.31
35.37
69.17
42.21
55.56
42.34
68.89
44.96
58.89
43.18
described in the above mentioned chapters. In Table 1 frequencies of occurrence of radiated emissions coming from particular components located in the CPU are presented as well as their levels
measured in accordance with the methodology described in the EN 55022:2006 standard.
8. CONCLUSIONS
Every IT device from the European Union market should comply with particular standards concerning valid directives of new approach. Due to the necessity of conformity with the directive
of electromagnetic compatibility of IT equipment, in the article the methodology of measuring
conducted emissivity on supply terminals of IT devices in the frequency range from 0.15 MHz to
30 MHz has been presented as well as the methodology of measuring radiated emissivity of IT
devices in the frequency range from 30 MHz to 6000 MHz in accordance with the EN 55022:2006
standard. Also the measuring results deriving from modern IT devices have been demonstrated.
The maximal levels of conducted and radiated undesirable emissions coming from contemporary
IT equipment present in the EU market have been determined and estimated. Those emissions are
by-products generated unintentionally during realization of basic function of the device, therefore it
is necessary to strive to make their level as low as possible. Moreover the identification of particular
components which are part of central processing unit has been made, based on spectra of radiated
emissions of PC units. The determined levels can be fundamental at initial stages of designing
electromagnetic securities of contemporary IT devices with striving to provide conformity with
appropriate EMC standards valid in the European Union.
Progress In Electromagnetics Research Symposium Proceedings, KL, MALAYSIA, March 27–30, 2012
81
ACKNOWLEDGMENT
The research work financed from the financial funds assigned to the science in the years 2010/2012
as the development work. The research work is realized in Poland.
REFERENCES
1. EN 55022:2006 +A1:2007 standard, Information technology equipment, Radio disturbance
characteristics, Limits and methods of measurement.