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Proceedings CEEM'2009/Xi'an
The EMC Research on Mobile multimedia broadcasting system equipment
Gong Bo1,2, Xie Jinghui'
1. Communication University of China, 2.Academy of Broadcasting Planning, China SARFT
Abstract: With the standards of system and
related equipment being promulgated and
implemented, China mobile multimedia broadcasts
(CMMB) has already begun to broadcast throughout
the country. The electromagnetic compatibility (EMC)
of CMMB is becoming the focus both inside and
outside the industry. In this paper, we preliminary
studied the EMC of CMMB system such as electro
magnetic disturbance, electromagnetic sensitivity,
electromagnetic radiation protection and so on. Then
we proposed the focus of the future research
directions, including limits and methods of measure
ment. At last, CMMB indoor coverage system
equipment standards in EMC testing and evaluation
issues were discussed.
I Standards and implementation overview of
CMMB system equipment
As an important components of the broadcasting
transmission system, mobile multimedia broadcasting
system, terrestrial digital television broadcasting
system, cable digital TV broadcasting system and
satellite digital TV broadcasting systems work
together to provide coverage for whole country. In
October 2006, China State Administration of Radio
Film and Television (SARFT) promulgated "frame
structure, channel coding and modulation standard of
Mobile Multimedia Broadcasting system (CMMB)",
then the application of CMMB system expanded
rapidly, and terrestrial CMMB network constructing,
frequency planning and equipment testing were also
carried out promptly. With CMMB receiving terminals,
the majority watched several sets of radio and
television programs and experienced an
unprecedented new feeling of game-watching during
the 2008 Beijing Olympic Games. It created a
precedent of watching the Olympic Games at all times
and all places and became a shining bright technical
spot of the Beijing Olympic Games.
In addition to the advanced transmission
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performance, the EMC of CMMB system has also
caused serious concern to the public and the relevant
departments. We noted that the published standards
for CMMB system were all about the transmission
performance, not involving the content of EMC. But
in CMMB, what are the concerned issues about EMC?
II The EMC issues needed to consider of
CMMB system equipment
1 The electromagnetic disturbance of equipments
The electromagnetic disturbance of equipments is
important, because on the one hand, people's health is
closely related to it, at the same time it directly affects
the system and equipment performance, On the other
hand, as the market globalization promoted and
popularized, international standards and national
standards for EMC requirements reached unanimity,
electromagnetic disturbance of equipments must be
the key parameter as transmission performance (to
some extent even more than the performance
parameters ofequipment in the importance).
At present, electromagnetic disturbance limits
of the Mobile Multimedia Broadcasting system
equipment are not proposed in whole world. In our
country, there are national standards for
electromagnetic disturbance of similar devices being
used currently including GB9254-1998: information
technology equipment- radio disturbance
characteristics- limits and methods of measurement,
GB/Z19871-2005: EMC requirements and
measurement of the digital television broadcast
receivers, GB13836-2000: television and sound signal
cable distribution systems 2: EMC of equipment,
GB13837-1997: radio disturbance characteristics
limits measurement of the sound and television
broadcast receivers and related equipment, etc.. The
disturbance limits are proposed in the above standards
for the similar equipment. The paper studied radiation
and conduction disturbance by referring to two related
national standard.
Proceedings CEEM'2009/Xi'an
1) characteristics of radiation disturbance environment and other major equipment. This "living
For the characteristics of radiated disturbance, environment" is referred to that it is likely to be the
"radio disturbance limits and measurement of the definition of environment using radio and television
information technology equipment" (the standard receivers within the 10m far from the related
currently being revised) was promulgated and equipment(in accordance with this definition, the UHF
implemented in 1998, which is valuable for our study band Mobile Multimedia Broadcasting repeater
of electromagnetic radiation disturbance amplifiers are probably installed m living
characteristics of CMMB system equipment (such as environment). Corresponding to the B-c1ass
repeater amplifier). equipment, A-class equipment must meet the A-limit
Information technology equipment was divided but does not meet B limits requirements of the type of
into A- and B-class types in the GB9254-l998, in equipment, such equipment is not limited for market
which B-class equipments must meet B-c1ass sale, but it should be contained in its using notes and
disturbance limits of the equipments including nameplate as following: This is the A-c1ass products.
equipments used under unfixed location (such as In the living environment. the product may cause
portable devices built-in battery-powered), radio interference. In such cases. users may need to
telecorm'nunications terminal equipment powered by take practical measurements.
the telecommunications network, personal computers A- and B-class equipment radiated disturbance
and related auxiliary equipment for the living limits are as follows:
Table I the A-and B-class disturbance radiation limit of equipment (10m measuring distance) defined in GB9254
frequencyA-class equipment B-class equipment
Remarkslimit (quasi-peak) limit (quasi-peak)
30MHz----230MHz 40dBJ.1V/m 30dBJ.1V/mAssume lower limit in the
230MHz----l GHz 47 dBJ.1V/m 37 dBJ.1V/m transition frequency
Disturbance emission of equipment is varied in
different working conditions and frequency. During
the authentication of equipment, it is necessary to
predict the biggest disturbance of equipment, so in the
specific test or measurement, the frequency of the
largest disturbance must be found and determined. A
typical test layout of desktop equipment as shown in
Figure 1. The testing engineers should comply with
Figure 1 and set EDT in typical working conditions
including layout of accessories, cables and so on.
Then the highest frequency of disturbance should be
determined by measuring in typical work frequencies,
at the same time the maximum emission also should
be determined in this state such as device
configuration, the working state and arrangements of
accessories. The test arrangement of Figure 1
generally is a typical test scenarios, including:
non-metallic test table with the size of 150cm x
100cm x 80cm (unless the special requirements of test
equipment), equipment and accessories being placed
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under the normal using requirements, the distance of
all measured device units is 10cm, the back of units
should be consistent with the back of the table, the
cables falling from the back of table (the distance to
the grounded floor should not be less than 40cm) and
so on.
Figure 1 a typical layout of testing disturbance emission of
desktop device
Another important standard referred IS
GB/Z19871-2005. It ordains some general EMC
characteristics of digital television receiver, including
Proceedings CEEM'2009/Xi'an
the following limits of radiated emission:
Table 2limit requirement of radiated emission in GB/Zl987 I
EMD source on test frequency The limit of radiated emission(quasi peak value)
:::IOHz Fundamental wave 57 dBllV/m
Local Oscillator 30 MHz.......... 300MHz Harmonic wave 52 dBllV/m
300MHz.......... lOHz Harmonic wave 56 dBllV/m
30 MHz..........230MHz 40 dBllV/mothers
230 MHz""""" IOHz 47 dBj.lV/m ..I---"!
Figure 2 the radiated emission testing layout (3 meter)
The limits and measurement methods defined by
OB9254 and OB/Z19871 can be referred in the
research on the terminal receiver's radiation limits of
CMMB. In the research, what we are going on
includes finding reference limits by testing and
statistical analysis, indicating the sense of the limits
(that is, in which way we use the equipments and limit
values can make the equipment up to grade) and
taking the sampling method into account. Besides,
what is also left to research is whether the channel
coding, modulation and circuit design would, effects
the form and limits of radiated emission badly.
2) Characteristics of conducted disturbance
OB9254 and OB13837 are also the key
references to the research on characteristics of
conducted disturbance. And the limits defined by them
become the researching focus when we constitute the
performance requirements of conducted disturbance.
OB9254 and OB13837 defined some limit values as
followed:
The requirement on test site, test equipment and
test disposal in OB/Z19871-2005 is basically the same
as OB13837-1997 (see Figure 2). Standard digital
television image signal, still or motion, and 1 kHz
audio signal which are generated by signal generator,
and passed through the transmission path are finally
accessed by the digital television receiver under test.
Radiated emission is measured by standard antenna
and testing equipments. Those testing equipments may
be testing receivers or spectrum analyzers with the
quasi-peak detector and the function of band power
measurement. It is a rather complex process to
measure radiated emission. Step 1, the maximum
reading should be searched during the adjustment of
testing antenna's height from I meter to 4 meter. The
antenna should be horizontally polarized. Step 2,
search the maximum reading when the tested
equipments are rotating horizontally on the turntable
of anechoic chamber, and then search the maximum
reading during the adjustment of testing antenna's
height from I meter to 4 meter again. Step 3, redo step
I and 2, but turn the antenna into vertically polarized
and adjust the height of antenna from 2 meter to 4
meter. Step 4, measure the radiated emission of all
frequency point in testing frequency band by redoing
the step from 1 to 3 and then get the fmal result use
the formula below:
radiated emission= reading of testing equipment
+antenna factor+cable losses
Table 3 conducted disturbance limits ofpower terminal ofA- and B-class equipments defined in GB9254. . . ---
Class A limit value Class B limit value
frequency quasi peak average quasi peak note
value value valueaverage value
150kHz..........500kHz 79dBIlV 66dBIlV 66"""""56dBIlV 56"""""46dBIlV Use low limit
500kHz..........5MHz 73dBIlV 60dBIlV 56dBIlV 46dBIlV value at
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Proceedings CEEM'2009/Xi'an
transition5MHz-----30MHz 60dBJlV 50dBJlV
frequency
Table 4 conducted common mode disturbance limits of telecommunication terminal ofA- and B-class equipments defined in OB9254
Class A limit value Class B limit value
Voltage limit value Current limit value Voltage limit value Current limit value
frequency quasi quasi quasi quasi
peakaverage
peakaverage
peakaverage
peakaverage
value value value valuevalue value value value
150kHz----- 97-----87 84-----74 53-----43 40-----30 84-----74 74-----64 40-----30 30-----20
500kHz dBJlV dBJlV dBllA dBllA dBJlV dBJlV dBllA dBllA
500kHz-----30dBIlA 74dBJlV 64dBJlV 30dBIlA 20dBIlA
30MHz87dBJlV 74dBJlV 43dBIlA
Table 5 conducted disturbance limit value ofPower terminal ofA- and B-class equipments defined in OB13837
Power terminal disturbance voltage limit value oftelevision and
frequency audio receivers and equipment related
quasi peak value average value
150kHz-----500kHz 66-----56 dBJlV 56-----46 dBJlV
500kHz-----5MHz 56 dBJlV 46 dBJlV
5MHz-----30MHz 60 dBJlV 50 dBJlV
Figure 3 the typical layout of the desktop device conduction
disturbance test
When we research in the radiated disturbance of
Mobile Multimedia Broadcasting system equipment,
we should pay attention to several problems. First of
all, radiated disturbance test is strict with the test site.
In addition to some necessary equipment, the
measurement must be carried out in OATS (open area
test site) or anechoic chamber and need some ancillary
facilities such as electric turntable, power filters and
take-off and landing antenna. Secondly, although
there are many standards which make provisions of
limit on the equipments with similar function, to the
specific CMMB system equipments, we still need
make a strict test on the radiated disturbance
performance of every working frequency and related
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frequency and present scientific and reasonable limits
of the specific equipment. In addition, since many
devices (such as the UHF band repeater amplifier in
Mobile Multimedia Broadcasting system, encoders,
etc.) are likely to work in the living environment, it
will have a direct impact on the user's health and other
electrical and electronic products' performance. Hence
study on these devices' electromagnetic disturbance
performance is extremely urgent.
III Research directions and priorities of
mobile multimedia broadcasting system's EMC
I. The study of limits of Mobile Multimedia
Broadcasting system headend and supplement
coverage transmission equipments' EMC
performance.
Firstly, the study of Mobile MultimediaBroadcasting system headend and supplementcoverage transmission equipments' EMCperformance should analyze systemic equipmentfunction and application environments. Inaccordance with relevant international anddomestic standards, the applicationelectromagnetic environment of radio andtelevision equipments are typically divided into
Proceedings
the following categories:E1: residential areas such as urban or rural residential
areas, etc
E2: commercial or light industrial areas, such as
theater, room, studio, etc.
E3: urban outdoor areas such as transportation, etc.
E4: controlled EMC environment and rural outdoor
environment, such as the engine room, studio and so
on.
E5: heavy industry or the environment near radio and
television transmitters.
In the perspective of specific equipments, as for
the mobile multimedia radio and television headend
equipments, with reference to the division principle of
GB9254 and the analysis of the actual test results, it
should be vested in A-type equipments, and for the
Mobile Multimedia Broadcasting and television
supplement coverage transmission equipments (such
as the repeater amplifier) should be vested in Class B
equipments. Certainly, as a result of related system
equipment being continually improved, limits have
not yet developed, so the method of division may
change.
The study of limits of Mobile Multimedia
Broadcasting system headend and supplement
coverage transmission equipments' EMC performance
mainly in the following fields (or parameters) focus on:
1) Characteristics of radiated disturbance including
radiated disturbance field strength.
2) Characteristics of conductive disturbance including
power supply terminal disturbed voltage, voltage
fluctuation, scintillation Properties, emission
characteristics of harmonic currents, voltage changes
characteristics.
3) Immunity characteristics including immunity to
radio frequency electromagnetic field radiation,
immunity to conductive disturbance induced by radio
frequency field, electric fast transient pulse group
characteristics, electrostatic discharge (ESD)
characteristics, immunity to voltage changes, voltage
dips and voltage short interruptions.
The above mentioned radiated disturbance,conducted disturbance, immunity characterristics will be studied in following issues:
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CEEM'2009/Xi'an
1. Propose and determine the classification of
equipments (level) by testing and research.
2. Achieve the disturbance and immunity
characteristics by testing and the actual measurement.
3. Give some advice on the equipments'
characteristics limits by data analysis and research.
4. Propose the characteristics limits of the
headend equipments and supplement coverage
transmission equipments step by step on the based on
the research ,analysis and coordination.
2. The method of measurement of limits of Mobile
Multimedia Broadcasting system headend and
supplement coverage transmission equipments' EMC
performance.
The study of Mobile MultimediaBroadcasting system headend and supplementcoverage transmission equipments' EMCperformance and the study of limits aresynchronized. In the study of methods ofmeasurement, we need to focus on the issuesmentioned as following.1. The study and the establishment of test andmeasurement systems. The study of test andmeasurement systems should be taken intoconsideration in fields of disturbance fromradiation, conduction disturbance, disturbancepower, immunity and so on.2. To disturbance for radiated, conducteddisturbance, disturbance power, it's necessaryto study the type of disturbance and make surewhich the disturbance belongs to, narrow-bandcontinuous disturbance, broadband continuousdisturbance or broadband discontinuousdisturbance.3. Conducting research in the connectionbetween test equipment and test measurementequipment, test equipment and auxiliary testequipment (such as artificial power network),test measurement equipment and auxiliary testequipment as well as reference groundingmethods, and give suggestion on test methodand operation.4. Study the conditions of test measurementand requirements, analyze the test site, the
Proceedings
environment level, operating conditions andexporting method in details, and give testguidelines.5. Study and analyze the measurementuncertainty of tests.
REFERENCE.S
1. Clayton R. Paul, Introduction to Electromagnetic
Compatibility (2nd edition), 2005.
2. ITU-T Recommendation K.60, Emission levels
and test methods for wire-line telecommunication
networks in case of radio interference.
3. CISPR22, Information technology equipment
-Radio disturbance characteristics -Limits and methods
of measurement.
4. CISPR20, Sound and television broadcast
receivers and associated equipment immunity
characteristic limits and methods of methods of
measurement.
5. CISPR 16, Specification for radio disturbance and
immunity measuring apparatus and methods.
6. CISPR13, Sound and television broadcast
receivers and associated equipment radio disturbance
characteristic limits and methods of methods of
measurement.
7. ITU-T Recommendation K.11, Principles of
protection against overvoltages and overcurrents.
8. ITU-T Recommendation K.61, Guidance to
measurement and numerical prediction of
electromagnetic fields for compliance with human
exposure limits for telecommunication installations.
9. ETSI EN 301 489-1 V1.8.1
( 2008-04) ,Electromagnetic compatibility and radio
spectrum Matters (ERM), Electromagnetic
compatibility (EMC) standard for radio equipment and
services; Part 1: common technical requirements.
10. EN 55103-1:1997, electromagnetic compatibility
- Product family standard for audio, video,
audio-visual and entertainment lighting control
apparatus for professional use; Part 1:Emission.
11. EN 55103-2:1997, electromagnetic compatibility
- product family standard for audio, video,
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CEEM'2009/Xi'an
audio-visual and entertainment lighting control
apparatus for professional use; Part 2:Immunity.
12. Bai Tongyun. ElectroMagnetic compatibility
Design. Beijing: China Dianli Press, 2007.
13. GB9254-1998: information technology equipment
radio disturbance characteristics- limits and methods of
measurement.
14. GB13836-2000: Cabled distribution systems for
television and sound signals - Part2: Electromagnetic
compatibility of equipment.
15. GB13837-1997: Sound and television broadcast
receivers and associated equipment - Radio disturbance
characteristics - Limits and methods ofmeasurement.
16. GB/Z19871-2005: Digital television broadcast
receivers - Electromagnetic compatibility - Request and
methods of measurement.
17. GB17625.1-2003: .Electromagnetic compatibility
Limits - Limits for harmonic current emissions
(equipment input currentss 16Aper phase).
18. GB/T17626.2-2006: Electromagnetic compatibility
- Testing and measurement techniques - Electrostatic
discharge immunity test.
19. GB/Z18039.1-2000: Electromagnetic compatibility
Environment Electromagnetic environment
classification.
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