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

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-Radio disturbance characteristics -Limits and methods

of measurement.

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measurement.

5. CISPR 16, Specification for radio disturbance and

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measurement.

7. ITU-T Recommendation K.11, Principles of

protection against overvoltages and overcurrents.

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9. ETSI EN 301 489-1 V1.8.1

( 2008-04) ,Electromagnetic compatibility and radio

spectrum Matters (ERM), Electromagnetic

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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

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receivers and associated equipment - Radio disturbance

characteristics - Limits and methods ofmeasurement.

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