HP-AN1290-1_Cookbook for EMC Precompliance Measurements

8/14/2019 HP-AN1290-1_Cookbook for EMC Precompliance Measurements

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Precompl ianceMeasurements

Cookbookfor

EMC

A Guide to Making

Precompl iance Conducted and

Radiated Emiss ions Measurements

with Sp ectrum Analyzers

and EMC Analyzers


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Table of Conte nts 1. 0 Introduction to P recompliance Measurements 31.1 Precompliance Measurements versus Full Compliance

Measurements 5

2.0 EMI Precompliance Systems 5

3.0 Precompliance Measurements Process 64.0 Emissions Testing 9

4.1 Introduction 9

4.2 Conducted Emissions Measurements Preparat ion 9

4.3 Performing Conducted Emissions Measurements 13

4.4 Start ing the Conducted Measurements Process 13

4.4.1 Overload Test 14

4.4.2 Signal Measurements 14

4.5 Radiated Emissions Measurements Preparat ion 15

4.6 Measuring Radiated Emissions 17

4.7 Ambient Signal Measurements 17

4.8 Placement of EUT for Maximum Signals 18

4.9 Ambient Plus EUT Measurements 19

4.10 Evaluating Measurement Results 214.11 Report Development 22

5.0 Problem Solving and Trouble Shooting 24

5.1 Diagnostics Testing Setup 25

5.2 Problem Isolat ion 25

Appendix A

Line Impedance Stabilization Netw orks (LISN) 28

A1.0 Purpose of a LISN 28

A1.1 LISN Operat ion 28

A1.2 Types of LISNs 29

A2.0 Transient Limiter Operation 29

Appendix BAntenna Factors 30

B1.0 Field Strength Units 30

B1.1 Antenna Factors 30

B1.2 Types of Antenna s Used for Commercial

Radiated Measurements 31

Appendix C

Basic Electrical Relationships 32

Appendix D

Detectors Used in EMI Measurements 33

D1.0 Peak Detector 33

D1.2 Peak Detector Operat ion 33

D2.0 Quasi-Peak Detector 34D2.1 Quasi-Peak Detector Operat ion 34

D3.0 Average Detector 35

D3.1 Average Detector Operat ion 35

Appendix E

Regulatory Agency Addresses 36

Glossary 40


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Note: precomplia nce measurem ents can be mad e with a v ariety of

spectrum analyzers and EM C ana lyzers having th e appropriate

detectors an d band wid th filters. In th is application note, detailed

m easurement procedu res are provided for HP 8590EM series

EMC an alyzers. However, these procedu res can be adapted to other

instruments.

The concept of getting a pr oduct t o market on time an d within

budget is n othing new. However, compa nies h ave a dded some

new st eps t o the intr oduction process t o achieve t hose goals.

One of those steps in the process is the addition of an EMC (elec-

tro-ma gnetic compatibility) stra tegy. Man ufacturers ha ve rea lized

tha t in order to sell their electronic products on th e commer cial

market, they must pass EMC requirem ents. Waiting un til the end

of the development cycle to find out wh ether or not a product pass-es regulatory agency requirement s can be a costly gamble. Failing

to pass can result in costly redesign. Because of this, developers

are concerned about t he E MC performa nce of a n ew product from

design investigat ion to prepr oduction un its. Figure 1 below sh ows

a typical product development cycle.

Figure 1. A typical product development cycle .

Many manufacturers use EMI precompliance measurement sys-

tems t o perform conducted and r adiat ed EMI emissions t ests pr ior

to having the product sent to a test facility for full compliance test-

ing. Conducted emissions testing focuses on signa ls, present on t he

AC mains, tha t a re generated by the EU T (equipment u nder test).The test ra nge for t hese measurements are from 9 k Hz to

30 MHz depending on t he regulat ion.

1.0 Introduction to

Precompl iance

Measurements

Product Development Cycle

Initial Investigation

Design Breadboard

Lab Prototype

ProductionPrototype

ProductionUnit

R E D E S I G N

Production

Yespass pass pass passviable

No

NoNoNoNo

Yes


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Radiated emissions testing looks for signals broadcasted from t he

EUT through space. The frequency range for these measurements

is between 30 MHz and 1 GH z depending on t he r egulation.

Testing to higher frequencies may be required depen ding on thedevice a nd the intern al clock frequen cy. This pr elimina ry t esting

is called precompliance testing. Figure 2 illust rat es th e relation-

ship between ra diated emissions, radiated imm unity, conducted

emissions a nd condu cted imm unity. Radiated immu nity is the abil-

ity of a d evice or p roduct to withst an d ra diated electromagnetic

fields. Conducted immunity is the ability of a device or product to

withsta nd electr ical distur bances on power or data lines. In order

to experience an electromagnetic compatibility problem such as

when an electric drill int erferes with TV reception, th ere mu st be

a genera tor or source, a coupling pa th, a nd a receptor. An EMC

problem can be eliminated by removing one of the components,

generator, coupling path, or receptor.

Unt il recently, most of the concentra tion ha s been t o reduce the

generat or emissions t o remove an EMC problem. That is, reduce

the emissions from the source to an acceptable level.

With the advent of the new European requirements, there is

add itional focus on pr oduct imm un ity. The level of electr ical

field th at a r eceptor can withst an d before failur e is known as

the pr oduct immu nity. The term imm un ity and su sceptibility

are u sed interchan geably. Immu nity testing will not be covered

in this document.

Figure 2. Electromagnetic compatibi l ity between products.

Two Types of EMC Measurements

Emission Immunity = Susceptibility

ConductedRadiated


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5

1.1 Precomp liance Measurements versus

Full Compliance Measurements

Fu ll compliance measur ement s require th e use of a receiver th atmeets the r equirements set forth in the CISPR1 part 16 document,

a qualified open area test site, and an a ntenn a tower and tu rnta ble

to maximize the signals from the E UT. Great effort is ta ken t o get

the best a ccur acy and repeat ability. This can be very expensive.

The p hotograp h below shows a full compliance tes t facility.

Precompliance measurements are intended to give an approxima-

tion of the EMI performance of the EUT. The cost of performing

precompliance tests is a fraction of full compliance measurements.

The more att ention to detail, such as a good ground plane an d min-

imize th e nu mber of reflective objects in th e measu remen t a rea,

the better the a ccuracy of the measur ements.

The cont ents of a precompliance test system (the HP 84110EM pre-

production evalua tion system , for example) includes a n E MC ana -lyzer or spectru m a na lyzer, a line impeda nce stabilization n etwork

(LISN), antennas, close field probes, and interconnection cables

(Figure 3). The test environment for pr ecomplian ce test ing

is usually less controlled than full compliance testing, which is per-

formed on an open area test site (OATS).

1. Comite Int erna tional Special des P ertu rbations Radioelectriques

2.0 EMI

Precompl iance Systems


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3.0 Precomp liance

Measurements Process

Figure 3. Components of a preproduction evaluation system.

The precompliance measu remen t pr ocess is fairly stra ight forwar d.

However, before measu remen ts can be performed on a product,

some preliminary questions must be answered.

1. Where is the product to be sold (i.e., United St ates, Eu rope,

Japan, etc.)?

2. What is the classification of th e product (i.e., inform ation

techn ology equipm ent [ITE] devices); indu str ial, scientific,

medical [ISM devices]; aut omotive or commu nicat ions)?

3. Where is the product to be used (i.e., home, commer cial,

light indust ry, or heavy indu str y)?

With th e answer s to the above questions, you can then determ ine

to which requirements your product mu st be tested. For example,

if you h ave determ ined th at your product is an ITE device an d you

are going to sell it in th e United Sta tes th en you n eed to test the pr oduct

to the FCC part 15 regulation. See Tables 1a, 1b, and 1c below to choose

the r equirement for your product. When in doubt, call the a ppropriateagen cy for final conforma tion of th e applicable requ iremen t. (A list of

phone nu mbers is included in th e Appendix E.)

HP 11947Transient Limiter

HP 11955A Biconical Antenna

HP 11956ALog Periodic Antenna

HP 11968CAntenna Tripod

HP 8447FPreamplifier

HP 11967DLISN

MONITOR

POWER OUTPUT

CAUTION

HIGH VOLTAGE GND

INPUTS OUTPUTS

LINE

OFFON

The HP 84110EM

EMC Preproduction Evaluation System

HP 8591EMEMC Analyzer

HP 11940A/11941AClose-Field Probe Set


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Table 1a. Comparison of regulatory agency requireme nts.

Table 1b. Major European requiremen ts.

European Norms Detai l Description

EN55011 (CISPR 11)

Indu stria l, Scientific, an d Medical P roducts.

Class A: Used in establishmen ts other t ha n domestic ar eas.

Class B: Suitable for use in domestic establishment s.

Group 1 Laboratory, medical, and scientific equipment.

(For exam ple: signal genera tors, mea sur ing receivers, frequen cy

counters , spectru m a na lyzers, switching mode power su pplies,

weighing machines, and electronic microscopes.)

Group 2 Indu strial induction heat ing equipment , dielectr ic heat ing

equipment, indu strial microwave heat ing equipment, domestic

microwave ovens, medical appa ra tu s, spark erosion equipmentan d spot welders. (For exam ple: meta l melting, billet hea ting,

component heat ing, soldering an d br azing, wood gluing, plastic

welding, food processing, food th awin g, paper dryin g, microwave

therapy equipment.)

EN55014 (CISP R 14)

Electric motor-operat ed an d th erma l appliances for household and

similar pur poses, electric tools, and electric appara tu s. Depending

on t he power ra ting of th e item being tested, u se one of the limits

shown in t he t able on th e following page.

7

International Regulations Summary(Emissions)

CISPR

11

12

13

14

15

16

22

FCC

Part 18

(SAE)

Part 15

Part 15

EN 55011

EN 55013

EN 55014

En 55015

EN 55022

EN 50081-1, 2

EN's Description

Industrial, Scientific and Medical

Automotives

Broadcast Receivers

Household Appliances/tools

Fluorescent lights/luminaries

Measurement apparatus/methods

Information technology equipment

Generic emissions standards

European Norms that Exist NowEquipment Type

sGeneric Equipment

s Residential

s Light Industrial

sIndustrial

sInformation Technology Equipment (ITE)

sIndustrial, Scientific, Medical Products (ISM)

EN 50081-1

EN 50081-2

EN 55022

EN 55011

Emissions


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(ROM card file names)

H ou seh old a nd sim ila r a pp lia nces (con du ct ed) E N014-H L

Household an d similar appliances (radiated) EN014-HHMotors < 700W (conducted) EN014-P1

Motors < 700W (radia ted) EN014-P4

Motors 1000W (radia ted) EN014-P6

Note: The condu cted ra nge is 150 kHz to 30 MHz an d th e radiat -

ed ra nge is 30 MHz to 300 MHz.

EN55022 (CISP R 22)

Information Technology Equipment

Equipmen t with t he prima ry fun ction of dat a ent ry, storage,displaying, retrieval, transmission, processing, switching, or con-

trolling. (For example, data processing equipment, office machines,

electr onic business equipment , telecommun ications equipment.)

Class A ITE: Not in tended for domest ic use.

Class B ITE: Intended for domest ic use.

Table 1c. FCC requireme nts sum mary.

Federal Communicat ions Commiss ion Equipment

Detai led Description

FCC Part 15

Radio frequen cy devicesuninten tiona l radiat ors (For example,TV broadcast receivers, FM broadcast receivers, CB receivers,

scann ing receivers, TV int erface device, cable system ter mina l

device, Class B personal compu ters an d peripher als, Class B

digita l devices, Class A digita l devices a nd p eriphera ls, extern al

switching power supplies.

Class A digital devices ar e ma rket ed for u se in a commer cial,

industrial, or business environment.

Class B digita l devices are m ar keted for u se in a r esidential

environment.

FCC

Equipment

s Broadcast receivers Part 15

s Household appliances/toolss Fluorescent lights/luminaries

s Information Technology Equipment (ITE)

s Industrial, Scientific, Medical Products (ISM) Part 18

s Conducted measurements: 450 kHz - 30 MHz

s Radiated measurements: 30 MHz - 1000MHz, 40 GHz

FCC

(Federal Communications Commission)


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4.0 Emissions Testing 4.1 Introduc tion

After t he ap propriate r egulations h ave been identified, th e next

step is to setup the test equipment a nd perform radiated an dcondu cted em issions t ests. The first gr oup of tests to perform ar e

cond ucted emissions t ests . The p rocess we will follow will be to

interconn ect th e equipment, load in t he appr opriate limit line

from th e ROM car d, correct for t he LISN a nd t ran sient limiter

(see Appendix A), and perform the tests.

4.2 Conducted Emissions Measurements Preparation

Em issions testing is divided into condu cted emissions and ra diated

emissions t esting. Condu cted emissions testing is th e easiest to

perform. Follow these steps t o setup t he equipment an d the equip-

ment under test .

Figure 4. Conducted measurements interconnection.

1. Int erconn ect th e EMC analyzer, limiter, LISN, and EU T

as sh own in Figure 4 (printer is optional).

(Operation of the LISN and the limiter is covered in Appendix A.)

2. Power up the EMC analyzer.

3. Setup t he correct frequency ra nge. Pr ess [SETUP ],

.

HP 11947Transient Limiter

HP 11967DLISN

MONITOR

POWER OUTPUT

CAUTION

HIGH VOLTAGE GND

Conducted EMI: Measurement Setup

HP 8591EMEMC Analyzer Printer

EUT


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4. Select an d load t he limit line from th e ROM car d supplied

based on the type of equipment a nd t he regulat ory agency

requirements. Selecting and loading limit lines is accomplished

by pressing the following butt ons on t he E MC ana lyzer:

[SETUP], , , ,

scroll down and highlight the required limit line (i.e.,

lEN022_BC which is the conducted limits for Class B

products). Press . (See Figures 5a an d 5b)

Figure 5a. Partial l ist of regu latory limits.

Figure 5b. Regulatory limits displayed.


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6. Correct the display for the HP 11947A tran sient l imiter by

pressing the following buttons:

[SETUP], , , ,, select HP 11947A and .

( See Figures 7a an d 7 b)

12

Figure 7a. List of amplifiers and limiter.

Figure 7b. Display corrected for l imiter losses.


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4.3 Performing Conducte d Emissions Measu remen ts

At this point t he EMC an alyzer is setup with a ll th e correct par a-

meter s including band width, frequency ran ge, LISN an d limitercompensa tion, a nd limit line. Ther e is one more th ing to consider

before st ar ting condu cted measu remen ts th e effect of the am bi-

ent en vironmen t on the r esults. The power cable between th e LISN

and t he EUT can act as an a ntenna which can cause false EUT

responses on th e display. To test th at th is phenomenon is not

occurring, switch the power of the EUT off and check the display

to ensure that the noise floor and ambient signals are at least 6 dB

below the limit line (see Figure 8).

Figure 8. Noise picked up by power cord with EUT off .

If signals app ear above th e limit line on t he display, the int er-

conn ecting power cord m ay need t o be shorten ed or a sh ield ma y

be needed around t he cord. Do not u se a ferrite core around th e

power cord because the common mode signals coming from the

EU T can a lso be att enua ted giving false indications.

4.4 Starting the Condu cted Measu remen t Proce ss

Tur n on t he E UT power an d observe th e display. Ifn o signals

appea r a bove the limit line, the pr oduct passes t he condu cted

emissions limit and your job is done. Most of the time, testers

ar e not so lucky. There ar e usua lly signals above the limit th at

need closer analysis.

Condu cted em issions u sua lly occur in th e lower end of the band.

One of th e ways to ta ke a closer look a t t he lower en d of the band

is to switch to log frequency sweep. Log sweep expands the lower

decades.

Press [FREQUENCY],

The display is in a log frequency format. As you can see on the dis-

play, th e signals at th e lower frequencies are m ore defined in

log swept mode th an in linear frequency mode.


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4.4.1 Overlo ad Tes t

Before sta rting th e measurement s, you sh ould test t o ensure tha t

the EMC analyzer is not in overload. An overload condition occurswhen t he energy level at th e input m ixer of th e EMC ana lyzer very

high causing errors in amplitu de measu remen ts. To test for th is

cond ition do t he following: Pr ess [AMPLITUD E], ,

up arrow which increases the attenuation before the input mixer

of the EMC analyzer. If the signal does not cha nge position on th e

display then th e mixer is not over loaded. If the amp litu de of th e

signal does cha nge then th e input is overloaded an d additional

attenu ation mu st be added.

4.4.2 Signal Measureme nts

The next step is to perform a qua si-peak m easur ement on signa ls

above the limit line. One meth od is to use the measu re at mar kfunction.

To measur e th e peak an d qua si-peak level of a signal (see Appendix

D), perform th e following:

Pr ess [SETUP ], , , un derline

. Press [WINDOWS ON], use and to show the signa ls of int erest

in th e active trace. (See Figure 9)

To measur e th e peak an d qua si-peak level of a signal of interest

press [TEST] th en use t he kn ob or the u p/down keys to place th e

mark er on the signal.

Pr ess . After th e measu remen t is

completed, th e signal frequency, peak, a nd quasi-peak

am plitudes will appear in t he box above th e display.

Pr ess

Figure 9. Conducted emissions from EUT in log format.


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Repeat the measurement procedure until all the signals above the

limit line have been measu red.

At this point , all the m easur ed signa l values ar e in the int erna l listof th e EMC a na lyzer. To view th e list an d deter min e which signa ls

quasi-peak levels are above the limit do the following.

Press

Pr ess un til VIEW QP LIM 1 is shown.

(See Figure 10)

Figure 10. List of meas ured signals .

If there a re n o quasi-peak values above the limit line (positive

values) then your job is done an d th e product passes condu cted

emissions t ests.

If some of the qua si-peak values ar e above the limit line,

troubleshooting an d redesign are requ ired.

4.5 Radiated Emissions Measureme nts Preparation

Performing radiated emissions measurements is not as straight for-

ward as performing conducted EMI measurements. There is theadded complexity of the a mbient environm ent which could interfere

with th e emissions from the E UT. There ar e meth ods to different ial

between a mbient environmen t signals (TV, FM, a nd cellular rad io).

1. Arra nge the antenn a, EUT, and the EMC an alyzer as shown

in Figure 11. Separate the ant enna an d the EUT by 3 meters

(10 meters if it is called out in the regulation. If space is limited,

correct the results for the difference in distance from 3 to 10

meters which is 10.45 dB). It is important that the antenna is

not pla ced in th e nea r field which is /2 away from the EUTor closer.


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Figure 11. Radiated emissions test setup.

2. Setup th e EMC analyzer for the correct span , anten na correction

factors, and limit line with a mar gin. Load in the appr opriate

limit line using the following steps:

Pr ess [SETUP], , , an d


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Typical an tenn a factors a re n ow loaded into the E MC ana lyzer.

The display is now corrected for t he loss of th e ant enna an d th e

level is measu red in dBuV/m which is a field str ength m easur e-

ment. (See Appendix B for more information on field strength.)

4. If an amplifier is used between the antenna and the EMC analyzer

to improve sensitivity, correction factor for the amplifier also must

be loaded in the analyzer. To do this, press

[SETUP], , , ,

Scroll to 8447HI a nd press .

Your displa y should look similar to Figur e 12.

Figure 12. Display with limit l ine and correction factors.

4.6 Measuring Radiated Emissions

Now you can star t evaluat ing the ra diated emissions your product

produces.

With th e EU T off, sweep the frequency ran ge of int erest t o survey

am bient environment levels. The ideal situa tion would be to ha ve

all the a mbient signals below th e limit line. In ma ny cases, ambient

signals will be above th e limit, so you sh ould mea sur e th em a nd

place th e results in th e intern al list of th e EMC ana lyzer.

4.7 Ambient Signal Measu remen ts

The pr ocess for m easur ing th e am bient signals is a s follow:

1. Perform a m aximum h old on th e signals in the band by pressing

the following:

[TRACE],

(This function capt ur es most signals including low PRF signals)

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2. Turn WINDOW function on by pressing [ON] un der t he

[WINDOWS ] ar ea.

3. Adjust th e with th e knob to display no moreth an 20 signa ls above the limit line on t he bottom active tr ace.

4. Use the au tomeasur e function to automat ically measu re the

signals above the limit line.

Press [TEST], , , .

At this point , the EMC an alyzer is performing peak an d quasi-peak

measu remen ts on all signals above the limit line. The signa ls

measu red ar e the a mbients (signa ls produced by other sources)

with E UT off. These signals ar e placed in t he int erna l list. Move

the zone mar ker t o the next group of signals on t he top tr ace

using the function a nd r epeat th e aut omat icmeasurements in Step 4 above. Make sur e tha t a ll the signals that

are a bove the limit on the u pper broad span trace are measu red.

Pr ess [ON] under th e WINDOW area to view the menu with

. Pr ess an d use th e knob

to move the zone mar ker t o the next group of signals and r epeat

Step 4 above.

4.8 Place men t of EUT for Maximum Signals

Radiated emissions from electronic devices are not uniform. The

strongest emissions m ay be from th e rear pan el or front pan el or

slots in th e shielding. To ensur e tha t you are mea sur ing the worst

case em issions from your device, do th e following:

1. Pr ess [SETUP ] and t he frequency band of your a nten na (i.e.,

for a biconical antenna).

2. At each 45-degree step, note the amp litu de of the largest signals.

(A screen out put t o a print er can be very useful. With a pr inter

connected to the IO port, press [COPY].)

3. On each screen outpu t, mar k th e position of th e EUT.

After a ll the screens have been captu red, compar e them to find th e

position of the worst case emissions. In some cases, you may findtha t t here a re worst case emissions for different frequencies at

different positions. For example, 100 MHz may be worst case

emissions at 90 degree an d 200 MHz may be worst case emissions

at 270 degrees. In th is case, the emissions test s must be performed

at both positions. A typical screen output is shown in Figure 13.


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If you are n ot sure wh ether the signa l you a re looking at is an

am bient or EUT signal, switch t he power off on the E UT. If the

signal remains, th en it is an a mbient signal. Repeat th is process

for the other polarization of the antenna (i.e., vertical or horizontal).

Figure 13. Radiated emission s display.

4.9 Ambient Plus EUT Measureme nts

With t he EU T tur ned on and oriented to the worst case position,

perform au tomat ed tests a gain as sh own below.

1. Press [NEXT] un der [WINDOW] (This activates the

upper tr ace to captur e the additiona l emissions from theEUT.) Press [NEXT] again to activate the lower window.

2. Adjust t he with the k nob to display no

more th an 20 signa ls above th e limit line on t he bottom

active trace. This gives the best frequency accuracy.

3. Use the aut o measu re fun ction to au tomatically measu re

the signals above th e limit line (above th e ma rgin if it wa s

initiated).

Pr ess [TEST], , , .

At this point , the EMC an alyzer is performin g a peak a nd qua si-peak on a ll signals a bove the limit line or mar gin which is within

th e zone spa n a rea. If necessary, move the zone span to the n ext

group of signals above th e limit or m argin a nd per form an oth er

automeasure as in Step 2 above.

The signals measur ed are th e ambients and the E UT signals. These

signals are also placed in th e intern al list. Now that you h ave the

ambient signals from the first test and the ambient signals plus the

EU T signa ls from t he second group of test s. You can per form a sort

on the list looking for duplicates which will be the ambient signals.

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To remove the ambient signals from the measurement results,

perform th e following:

Press [TEST], , , ,,

, and .

(See Figure 14)

Figure 14. Radiated emissions measurement l i st .

At this point, most of the ambient signals ha ve been deleted from

your list. Some ambients ma y still be present in t he inter na l list

becau se they appea red dur ing only one of th e aut omatic measu re-

ments which means t hat they would not have had duplicatesignals and t hu s would not ha ve been deleted.

The signals in the list are t he peak a nd qua si-peak values of the

EUT emissions and r emaining am bient signals. Next, find signals

tha t a re a bove the limit. To do th is first sort th e list by quasi-peak

values with t he highest levels at th e top of the list:

Pr ess [TEST], , , ,

.

Next, switch t he column on wh ich indicates t he value of the

quasi-peak measurement versus the limit line.

Press [TEST], ,

Press until VIEW QP LIM 1 is indicated at the t op

of the right column. (See Figure 15)

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Figure 15. Measuremen ts l ist compared to l imit.

4.10 Evaluating Measurem ent Results

If all the values in th e right ha nd column of th e intern al list ar e

negative, the product emissions are below the limitand your

product passes the radiated emissions requirements and your

job is completed.

If some of th e values are positive th en th e quasi-peak measu re-

ment s are above th e quasi-peak limit and th e product fails

radiated emissions measurements. To be sure that signals are not

am bients, each signal should be remeasur ed. Use the demodulation

function to listen to the signa l. AM/FM dem odulat ion is a good toolto use to determine whether or not a signal is an ambient.

To listen to a signa l do th e following:

Press [TEST], ,

With th e signal list on, highlight the signal of int erest with

th e up/down k eys.

Press [DEMOD], , .

Adjust th e volume t o listen to th e signal. If the signal is a local

AM, FM, TV, or cellular phone you should be able to demodulatean d listen t o the signal. The demodulation function will enable the

opera tor to hear t he au dio par t of th e tra nsmission by dwelling at

the marker for a specified length of time (usually 500 msec).

If there is any doubt about the signal being an ambient or an EUT

signal, remove the power to the E UT an d observe the signa l. If th e

signal rema ins, it is an a mbient. Note: It may not be convenient

to remove the p ower from th e EU T, so using th e demodulation

function may be th e preferred m ethod of identifying ambients.

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If you have determined that a signal is an ambient, the next step

is to delete th e signal.

Press [TEST], , , ,highlight the a mbient signal to be deleted and pr ess

.

After t he am bient signals ha ve been deleted from t he list, the next

step is t o develop a report.

4.11 Re port Dev elopm en t

The end r esult of all the a bove testing is a report. The report is

used by t he design en gineer to correct a ny pr oblems which is foun d

dur ing the t est process. You can assemble a r eport using th e

[OUTPU T] functions. The conten ts of th e report can include a list

of signals, graphical representa tion of the signals, an d up to twopages of text wh ich can be generat ed using a common P C key

board which conn ects to the rear of th e EMC a na lyzer. To creat e

the text, press the following:

[OUTPU T] an d

If unwanted text exists in the annotation area, press . Type in th e desired text for your report . You ma y

want to include th e dat e, location of the test ing, who perform ed th e

tests, pr oduct d escription, design engineer, and t o which r egulatory

agency product is tested. Some genera l comments a bout th e test

results is usu ally helpful. After th e text development is completed,

press .

To define the report content press , then choose

the items you would like t o have in t he r eport . Your r eport can

include a nn otation, log graph ics, linear graph ics, instru ment

settings, an d signal list informa tion. Examples of log graph an d

linear graph ar e shown in Figures 16a an d 16b on t he following

page.


23/44

23

Figure 16a. Line ar graph

Figure 16b. Log graph

List definition is a separate category. To define the list press

an d choose th e items t o be included in t he list su ch

as detector results, limit compar isons, correction factors u sed, an d

show marked signals. With the printer attached, press . All th e item s selected un der report definition will be

print ed sequ entially.


24/44

24

5.0 Problem Solving and

Trouble Sho oting At this point , after the pr oduct is tested an d the r esults ar e record-

ed an d pr inted your pr oduct is eith er r eady for full compliance

testing a nd pr oduction or it mu st go back to th e bench for furt herdiagnosis an d repa ir.

If the product needs furth er r edesign, t he following process is

recommended.

1. Connect th e diagnostic tools as shown in th e Figure 17 below.

2. Fr om th e report, locat e the pr oblem frequen cies.

3. Use th e probe to locate th e source or sour ces of th e problem

frequencies.

4. With th e probe placed to give the maximu m am plitudes, recordthe r esults on a RAM car d.

5. Make circuit changes as n ecessary to reduce the emissions.

6. Remeasur e the circuit using the sam e settings as before.

7. Recall the previous measur ement st ored on the RAM car d and

compare t he results to the curr ent measu rement.

Figure 17. Diagnostics setup interconnection.

EMI Diagnostic Measurement Setup

HP 8447FPreamplifier

Circuit Under Test

INPUTS OUTPUTS

LINE

OFFON

HP 8591EMEMC Analyzer

Close-Field Probe


25/44

5.1 Diagnostics Testing Setup

As with emissions t esting, the EMC an alyzer mu st be setup t o

perform diagnostics testing. Corrections for the probe and amplifi-er mu st first be loaded into the EMC an alyzer. The HP 11945A

probe kit cont ains t wo probes one for t he 9 kHz t o 30 MHz fre-

quency ran ge and one for the 30 MH z to 1 GHz frequen cy ran ge.

Conn ect th e probe for t he a ppropriate frequency range an d load

in the correction factors by pressing the following:

[SETUP], more, , ,

and .

Scroll down t o the probe number which was insta lled an d

press .

The next step is to load in the correction factors for the amplifier

by press ing th e following:

[SETUP], more, , , and

.

Scroll down to th e HP 8447F HI or LO depending on th e

probe used a p ress .

The EMC a na lyzer is now calibrated in dBA/m wh ich is m agneticfield strength units.

5.2 Problem Isolation

Using the report generated from the conducted and radiated

emissions t est, tu ne t he E MC an alyzer t o one of th e problem

frequen cies with na rr ow enough span to give adequat e different ia-

tion between signals.

Move th e close field probe slowly over t he device un der test .

Observe the display for m aximum emissions a s you isolat e th e

source of the emissions. After you have isolated the source of the

emissions, record t he location an d store th e display to a card.

To store t he display insert a forma tted RAM car d into th e card

reader an d press t he following:

[SAVE/RECALL], , , CARD>,

an d .

Select a register n umber (i.e., 5) and pr ess [ENTER].

25


26/44

Figure 18 below is th e tr ace saved into register 5 on th e RAM car d.

The prefix na me TRACE was genera ted using t he Cha nge Prefix

functions.

Figure 18. Isolated signal source display.

The next st ep is to make design changes to reduce the emissions.

This can be accomplished by adding or changing circuit compo-

nent s, redesign t he pr oblem circuit, or a dd sh ielding.

After t he redesign, remeasu re th e results compa ring th e old tra ce

before redesign to new trace by recalling the saved trace off the

card. To recall the trace in register 5 press the following:

[SAVE/RECALL], , , a nd .

Scroll down t o the t ra ce you previously stored an d pr ess

.

The tr ace is recalled into the TRACE B ar ea in th e VIEW mode.

The curren t tr ace is in TRACE A in the CLEAR WRITE mode.

Figure 19 below shows th e active trace and th e recalled tr ace.

26


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27

Figure 19. Emission s reduc tion comparison display.

As you can see from t he delta ma rker m easurement the n ew trace

after t he pr oduct r edesign is 10 dB below th e previously stored

trace. There is a one-to-one correlation between changes is close

field measurements an d cha nges in far field measu remen ts. For

example if you n ote a 10 dB cha nge in measu remen ts m ade by a

close field probe you will note a 10 dB cha nge wh en you per form a

far field measurement u sing an ant enna a nd an EMC ana lyzer.

Conversely, if you find t ha t t he r adiat ed emissions from your E UT

is failing a limit by 10 dB, then you will need to do some redesign

to reduce the em issions by a t least 10 dB. A good indication t ha t

you have accomplished your goal is to make a 10 dB change with

close field measu remen ts.


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A1.0 Pu rpose of a LISNA line impedan ce sta bilization net work serve thr ee purpose:

1. The LISN isolates th e power mains from the equipment

un der test . The power supplied to th e EUT mu st be as clean

as possible. Any noise on th e line will be coupled to th e EMC

analyzer and interpreted as noise generated by the EUT.

2. The LISN isolates an y noise genera ted by the EUT from

being coupled to the power mains. Excess noise on the power

main s can cause inter ference with th e proper operat ion of

other devices on the line.

3. The signals generated by the EUT ar e coupled to the

EMC an alyzer u sing a high pa ss filter which is part of th e

LISN. Signa ls which a re in th e pass ban d of th e high pass

filter see a 50 load which is the input to the EMC

analyzer.

A1.1 LISN Opera tion

The diagram in Figure A-1 below show the circuit for one side of

the line relative to earth ground.

Figure A-1. Typical LISN circuit diag ram.

28

Appen dix ALine Impedance Stabil ization

Netw ork (LISN)

Line Impedance Stabilization

Network (LISN)

605040302010

.01 .1 1 10 100

Impedance(ohms)

Frequency (MHz)

0.1 F

1000W

From PowerSource

ToEUT

ToReceiver or EMC Analyzer

(50 )

50 H

1 F


29/44

The 1 F in combinat ion with th e 50 H indu ctor is the filter t ha t

isolates th e mains from th e EUT. The 50 H indu ctor isolates th enoise generat ed by the EUT from the ma ins. The 0.1 F couples

the n oise generat ed by the EU T to the E MC ana lyzer or receiver.At frequencies above 150 kHz, the EU T signa ls are pr esented with

a 50 impedance.

The chart in Figure A-1 above represent s th e impedance of the

EUT port versu s frequency.

A1.2 Typ es of LISNs

Figure A-2. Three different types of LISNs.

The most common t ype of LISN is the V-LISN. It measu res t he

un symmetr ic voltage between line a nd ground. This is done for

both t he hot an d th e neut ral lines or for a t hr ee-pha se circuit in a

Y configuration, between each line and ground. There are some

other specialized types of LISNs. A delta LISN m easur es th e line

to line or symmetric emissions voltage. The T-LISN, sometimes

used for telecommunications equipment, measures the asymmetric

voltage, which is the potential difference between the midpoint

potential between two lines a nd ground.

A2.0 Transient Limiter Operation

The pu rpose of the limiter is to protect t he inpu t of the EMCan alyzer from large tr an sients when conn ected to a LISN.

Switching E UT power on or off can cause lar ge spikes generat ed

in the LISN.

The HP 11947A tran sient l imiter incorporates a l imiter, high pass

filter, and an at tenu at or. It can with stan d 10 kW for 10 sec an d

ha s a frequency ra nge of 9 kH z to 200 MHz. The h igh pa ss filter

reduces th e line frequen cies coupled to th e EMC a na lyzer.

29

Types of LISNs

V-LISN:-LISN:

T-LISN:

Unsymmetric emissions (line-to-ground)Symmetric emissions (line-to-line)Asymmetric emissions (mid point line-to-line)

V-LISN Vector Diagram

V symmetric

Ground

H N

V unsymmetric

1

V2uns

ymme

tric

1/2Vsymmetric 1/2Vsymmetric

V unsymmetric

1

V unsymmetric2

V asymmetric


30/44

30

Appen dix BAntenna Factors

B1.0 Field Strength Units

Radiated E MI emissions measur ement s measu res th e electric field.

The field strengt h is calibra ted in dBV/m. F ield st rength indBV/m is der ived from t he following :

P t = total power radiat ed from a n isotropic radiator

PD = the power density at a dista nce r from the isotropicradiator (far field).

PD = Pt /4r2 R = 120

PD = E2/R

E2 /R = Pt /4r2

E = (Pt x 30)1/2 /r (V/m)

Fa r field* is consider ed t o be >/2

*Far field is the m inimum distan ce from a r adiat or where th e field

becomes a plana r wa ve.

B1.1 Anten na Fac tors

The definition of antenna factors is the ratio of the electric field in

volts per meter present at the plane of the antenna versus the volt-

age out of the a nt enna conn ector. Note: an tenn a factors a re not th e

same as antenna gain.

Figure B-1. Typical anten na factor shape s.

Antenna Factors

Linear Units:

dB/m

Frequency, MHz

5

10

15

20

25

0 200 400 600 800 1000

Biconical@ 10m

Log Periodic@ 1m

AF = Antenna Factor (1/m)E = Electric Field Strength (V/m)V = Voltage Output from Antenna (V)

Log Units: AF(dB/m) = E(dBV/m) - V(dBV)

E(dBV/m) = V(dBV) + AF(dB/m)

AF = EinV out

30


31/44


32/44

Basic Electrical Relationsh ips

The decibel is used extensively in electr omagnetic measur ement s.

It is t he log of th e ra tio of two amplitudes. The am plitudes ar e inpower, voltage, amps, electric field units, and magnetic field units.

dec ibel = dB = 10 log (P 2/P 1)

Data is sometimes expressed in volts or field strength un its.

In this case, replace P with V2/R.

If the impedances are equa l, the equat ion becomes:

dB = 20 log(V2/V1)

A unit of measure used in EMI measurements is dBV or dBA.

The r elationsh ip of dBV and dBm is a s follows:

dBmV = 107 + P dBmThis is tru e for a n impeda nce of 50

Wave length (l) is determined using the following relationship:

= 3x108 / f (Hz) or = 300/f (MHz)

32

Appen dix C


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33

Appen dix DDetec tors Used in EMI

MeasurementsPeak,

Quasi-Pea k, an d AverageD1.0 Peak Detector

Initial EMI measurements are made u sing the peak detector.

This mode is much fast er th an quasi-peak, or a verage modes of

detection. Signals ar e norma lly displayed on spectrum an alyzers

or EMC ana lyzers in peak m ode. Since signa l measur ed in peak

detection m ode always have am plitude values equa l to or h igher

th an quasi-peak or average detection m odes, it is a very easy

process to take a sweep and compa re th e results t o a limit line.

If all signa ls fall below the limit, th en th e product passes an d no

further testing is needed.

D1.2 Peak Detector Operation

The EMC an alyzer ha s an en velope or peak detector in th e IF

chain which h as a t ime constan t such th at t he voltage at the

detector outpu t follows th e peak value of th e IF signa l at all

times. In other words, t he detector can follow th e fastest possible

changes in th e envelope of th e IF signal, but not th e instan ta-

neous value of the IF sine wave. (See Figure D-1)

Figure D-1. Peak detecto r diagram.

Output of the Envelope DetectorFollows the Peaks of the IF Signal


34/44

D2.0 Quasi-Pea k Dete ctor

Most r adiat ed an d condu cted limits ar e based on quasi-peak

detection mode. Quasi-peak detectors weighs signals according totheir r epetition ra te, which is a way of measu ring th eir ann oyan ce

factor. As th e repetition ra te increases, t he qu asi-peak detector

does not ha ve time to discha rge as mu ch r esulting in a higher

volta ge outpu t. (See Figur e D-2 below.) For contin uous wave (CW)

signals the peak a nd th e quasi-peak are t he same.

Since the quasi-peak detector a lways gives a reading less th an or

equal to peak detection, why n ot use qua si-peak d etection a ll the

time? Wont th at m ake it easier to pass E MI tests? Its tru e tha t

you can pa ss th e tests easier, however, quasi-peak measu remen ts

are much slower by 2 or 3 orders of magn itude compa red t o using

the peak d etector.

Figure D-2. Quasi-peak detector respo nse diagram.

D2.1 Quasi-Peak Detector Operation

The quasi-peak detector has a charge rat e much faster t han the

discha rge rate th erefore the higher th e repetition ra te of th e sig-

na l the higher th e outp ut of the qu asi-peak det ector. The qua si-

peak det ector also responds to different am plitu de signals in alinear fashion. H igh amp litu de low repetition ra te signals could

produce the same output as low amplitude high repetition rate

signal.

34

Quasi-Peak Detector Output

Varies with Impulse Rate

t

Peak ResponseQuasi-Peak

Detector ReadingQuasi-Peak

Detector Response

t

Test Limit

Test Limit


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35

D3.0 Average Detec tor

The average detector is required for some conducted emissions

tests in conjunction with using the quasi-peak det ector. Also,radiated emissions measurements above 1 GHz are performed

using avera ge detection. The average detector outpu t is always

less tha n or equal t o peak d etection.

D3.1 Avera ge D ete ctor Opera tion

Average detection is similar in ma ny r espects t o peak det ection.

Figure D-3 below shows a signal that has just passed through the

IF a nd is a bout to be detected. The outpu t of the envelope detector

is th e modulation envelope. Peak detection occurs wh en t he post

detection bandwidth is wider than the resolution bandwidth.

For avera ge detection to take place, the peak det ected signal

must pass th rough a filter whose bandwidth is much less tha n t heresolut ion ban dwidth. The filter avera ges the h igher frequen cy

components, su ch as noise, at th e output of the en velope detector.

Figure D-3. Average detection respons e diagram.

Average Detection

A

t

Envelope Detector

Filters

Average Detector


36/44

36

Appen dix EEMC Regulatory Agencie s The following is a listing of addr ess an d ph one nu mbers for obta in-

ing EMC regulat ion information.

IE C

CISPR

Sales De partmen t of the Central Office of the IEC

PO B ox 131

3, Rue de Verem be

1121 Geneva 20, Switzerland

CCIR

ITU, Gene ral Secretariat , Sales S ervice

Place de Na tion

1211 Geneva, Switzerland

Australia

Austral ia Electromechanical Committee

Stand ards Association of Austral ia

PO B ox 458

North Sydney N.S.W. 2060

Teleph on e: +61 2 963 41 11

Fax: +61 2 963 3896

Belgium

Comite Electrotechnique Belge

3 Galerie Ravenstein, Boite 11

B-1000 Bru xelles

Teleph on e: +32 2 512 00 28Fax: +32 2 511 29 38

Canada

Stand ards Council of Canada

Standards Sales Divis ion

350 Sparks Street, Suite 1200

Ottawa, Ontar io K1P 6N7

Teleph on e: 613 238 3222

Fax: 613 995 4564

Canadians Stand ards Association (CSA)

178 Rexdale Boulevard

Rexdale (Toronto), Ont ar io MSW 1R3Teleph on e: 416 747 4044

Fax: 416 747 2475

Denmark

Dansk Elektroteknisk Komite

Stran dgade 36 st

DK-1401 Kobenha vn K

Teleph on e: +45 31 57 50 50

Fax: +45 31 57 63 50


37/44

37

France

Comite E lectrotechnique Fr an cais

UTE CE dex 64

F-92052 Pa ris la DefenseTeleph on e: +33 1 47 68 50 20

Fax: +33 1 47 89 47 75

Germany

VDE CERLAG GmbH

Austieferungsstelle

Merianstr asse 29

D-6050 OFFE NBACH a.M.

Teleph on e: + 49 69 8306-1

Fax: + 49 69 83 10 81

India

Bureau of Indian Standards , Sales De partmentManak Bhavan

9 Bahadur Sh ah Zafar Marg.

New Delh i 110002

Teleph on e: + 91 11 331 01 31

Fax: + 91 11 331 40 62

Italy

Cometato Eletrotecnico Ital iano

Viale Monza 259

1-20126 Milan o MI

Teleph on e: + 39 2 25 77 31

Fax: + 39 2 25 773 222

Japan

Japane se Standards Associat ion

1-24 Akasa ka 4

Minato-Ku

Tokyo 107

Teleph on e: + 81 3 583 8001

Fax: + 81 3 580 14 18

Netherlands

Nederlands Normalisatie-Instituut

Afd. Verdoop en Informa tie

Kalfjeslaan 2, PO Box 5059

2600 GB DelftNL

Teleph on e: + 31 15 69 03 90

Fax: + 31 15 69 01 90

Norway

Norsk Elektroteknisk Komite

Ha rbizalleen 2A

Postboks 280 Skoyen

N-0212 Oslo 2

Teleph on e: + 47 2 52 69 50

Fax: + 47 2 52 69 61


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38

South Africa

South African Bureau o f Standards

Electronic Engineering Department

Pr ivate Bag X191Pretoria

0001 Republic of South Africa

Spain

Comite Na cional Espa nol de la CEI

Fr an cisco Gervas 3

E-28020 Ma drid

Teleph on e: + 34 1 270 44 00

Fax: + 34 1 270 28 55

Sweden

Svenka Elecktr i ska Kommiss ionen

PO Bow 1284S-164 28 Kista -Stockh olm

Teleph on e: + 48 8 750 78 20

Fax: + 46 8 751 84 70

Switzerland

Swiss Electromechanical Committee

Swiss E lectr omechan ical Associat ion

Seefeldstrasse 301

CH-8008 Zur ich

Teleph on e: + 41 1 384 91 11

Fax: + 41 1 55 14 26

United Kingdom

British Standards Institution

BSI Sales Departm ent

Lin ford Wood

Milton Keynes MK14 GLE

Teleph on e: +44 908 22 00 22

Fax: +44 908 32 08 56

Briti sh Defence Standards

DEF STAN

Ministr y of Defence

Northumberland House

North umber land AveLondon WC2N 5 BP

Teleph on e: + 01 218 9000

United States of America

America National Standards Institute Inc.

Sales Dept.

1430 Broadwa y

New York, NY 10018

Teleph on e: 212 642 49 00

Fax: 212 302 12 86


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39

FCC Rules and Reg ulations

Tech nical Standards Branc h

2025 M Street N.W.

MS 1300 B4Washington DC 20554

Teleph on e: 202 653 6288

FCC Equipme nt Authorization Branch

7435 Oaklan d Mills Road

MS 1300-B2

Columbia, MD 21046

Teleph on e: 301 725 1585


40/44

Ambient Level

1. The values of ra diated an d conducted signa l and noise existing

at a specified test location a nd t ime when t he test sample is notactivated.

2. Those levels of ra diated a nd condu cted signal an d noise existing

at a specified test location a nd t ime when t he test sample in inop-

erative. Atmospherics, interference from other sources, and circuit

noise, or other int erference generated with in the m easur ing set

compose the ambient level.

Amplitude Modulation

1. In a signal tr an smission system, the process, or th e result of th e

process, where t he a mplitude of one electr ical qua ntity is va ried in

accordance with some selected characteristic of a second quantity,which n eed not be electr ical in na tu re.

2. The process by which t he am plitude of a carr ier wave is varied

following a specified law.

Anechoic Chamber

1. A shielded room which is lined with ra dio absorbing material to

reduce reflections from all internal surfaces. Fully lined anechoic

chambers h ave such m at erial on all intern al sur faces: wall ceiling

an d floor. Its also called a fully anechoic cham ber. A semi-an e-

choic chamber is a shielded room wh ich h as a bsorbing ma terial on

all su rfaces except t he floor.

Antenna (Aerial)

1. A mean s for ra diated or receiving radio waves.

2. A tra nsdu cer which either emits radio frequency power into

space from a signal source or int ercepts an ar riving electr oma gnet-

ic field, convert ing it in to an electr ical signa l.

Antenna Factor

The factor wh ich, when properly applied to the voltage at th e input

term inals of the measu ring instr um ent, yields th e electric fieldstrength in volts per meter and a magnetic field strength in

amperes per m eter.

Antenna Ind uced Voltage

The volta ge which is measu red or calculat ed to exist across the

open circuited antenna terminals.

Antenna Terminal Conduc ted Interference

Any undesired volta ge or curr ent generat ed within a receiver,

tran smitter, or t heir associated equipment a ppearing at th e ant en-

na terminals.

40

Glossary of Acronym sand Def ini t ions


41/44

41

Auxil iary Equipment

Equipment not under test that is nevertheless indispensable for

setting u p all the functions a nd a ssessing the correct performa nce

of th e EUT dur ing its exposure to the distur bance.

Balun

A balun is an an tenn a balan cing device, which facilitates use of

coaxial feeds with symm etrical ant enna such as a dipole.

Broadband emiss ion

Broadband is the definition for an int erference am plitu de when

several spectra l lines a re within th e RFI r eceivers specified ban d-

width.

Broadband Interference (Measurements)

A distur bance that h as a spectral energy distribution sufficiently

brad, so tha t t he response of th e measu ring receiver in use doesnot var y significan tly when tu ned over a specified num ber of

receiver bandwidth s.

Conducted Interference

Int erference resu lting from conducted ra dio noise or u nwan ted sig-

na ls enter ing a tra nsdu cer (receiver) by direct coupling.

Cross Coupling

The coupling of a signal from one channel, circuit, or conductor to

an other, where it becomes an un desired signa l.

Decoupl ing Network

A decoupling net work is an electr ical circuit for preventing t est-sig-

na ls which ar e applied to th e EU T from a ffecting other devices,

equipment, or systems th at are n ot u nder test . IEC 801-6 states

th at t he coupling and decoupling network systems can be integrat -

ed in one box or t hey can be in separa te net works.

Dipole

1. An anten na consisting of a str aight condu ctor usu ally not more

than a half-wavelength long, divided at its electrical center for con-

nection t o a tra nsm ission line.

2. Any one of a class of an tenn as pr oducing a radiat ion pa tter n

appr oximating t ha t of an elementar y electr ic dipole.

Electromagne tic Compatibi l i ty (EMC)

1. The capability of electr onic equipm ent of system s to be opera ted

within a defined ma rgins in of safety in t he int ended operational

environment at designed levels of efficiency without degradation

due t o interference.

2. EMC is the ability of equipm ent t o function sat isfactorily in its

electromagn etic environment without intr oducing intolerable dis-

turbances into that environment or into other equipment.


42/44

42

Electromagnet ic interference

Electr omagnetic int erference is the impa irment of a wa nt ed elec-

tr omagnetic signal by an electromagn etic distu rban ce.

Electromagnet ic w ave

The r adian t en ergy produced by th e oscillation of an electric

charge characterized by oscillation of the electric and magnetic

fields.

Emission

Electr omagnetic energy propagated from a sour ce by radiation or

conduction.

Far Field

The region wher e the power flux density from an an tenn a a pprox-

imat ely obeys an inverse squ ar es law of the distan ce. For a d ipole

th is corr esponds t o distan ces greater tha n l/2 where l is th e wavelength of th e radiat ion.

Ground Plane

1. A conducting surface of plat e used as a common r eference point

for circuit retu rn s an d electric or signal potentials.

2. A meta l sheet or plate used a s a common reference point for

circuit ret ur ns a nd electr ical or signal potentials.

Immunity

1. The property of a receiver or any other equipmen t or system

enabling it to reject a ra dio distur bance.

2. The ability of electr onic equipment to with sta nd r adiat ed elec-

tr omagnetic fields with out pr oducing un desirable responses.

Intermodulation

Mixing of two or more signals in a nonlinear element, producing

signals at frequencies equal t o the su ms a nd differences of int e-

gral m ultiples of th e original signals.

Isotropic

Isotropic mean s h aving properties of equal values in all directions.

Monopole

An an tenn a consisting of a st raight condu ctor, usua lly not more

th an one-quart er wave length long, mounted immediat ely above,

an d norma l to, a ground plan e. It is connected to a tr an smissions

line at its base an d beha ves, with its image, like a dipole.

Narrowband Emiss ion

That which h as its principal spectra l energy lying with in the

band pass of the m easur ing receiver in use.


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43

Open Area

A site for ra diated electroma gnetic interference measu remen ts

which is open flat t erra in at a dista nce far enough awa y from

buildings, electric lines, fences, trees, underground cables, and pipelines so that effects due to such are negligible. This site should

have a sufficiently low level of ambient interference to permit test-

ing to the required limits.

Polarization

A term used t o describe the orienta tion of the field vector of a ra di-

ated field.

Radiated Interference

Radio int erference resu lting from r adiat ed noise of unwan ted sig-

nals. Compare radio frequency interference below.

RadiationThe emission of energy in the form of electromagnetic waves.

Radio Frequency Interference

RFI is t he h igh frequency int erference with ra dio reception. This

occur s wh en un desired electroma gnetic oscillations find entr an ce

to the h igh frequency input of a receiver or an tenn a system .

RFI Source s

Sources ar e equipment a nd systems a s well as t heir components

which can cau se RFI.

Shie lded Enclosure

A screened or solid met al housing designed expressly for the pur -

pose of isolating t he int erna l from th e externa l electromagn etic

environm ent. The pur pose is to prevent outside ambient electro-

magn etic fields from causing perform an ce degrada tion an d to pr e-

vent emissions from causing interference to outside activities.

Stripl ine

Parallel plate transmission line to generate an electromagnetic

field for testing purposes.

Susceptibi l i ty

Susceptibility is the cha ra cteristic of electronic equipment tha t

permits u ndesirable responses when su bjected to electromagn eticenergy.


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of f i ce l is t ing , v i s i t our web s i t e ,http :/ /ww w.hp.com/go/tmdir . Youcan also contact one of the followingc e n t e r s a n d a s k f o r a t e s t a n dmeasurement sales representative .

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Documents

HP-AN1290-1_Cookbook for EMC Precompliance Measurements