EN 50083-3:2002

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Kabelska omrežja za televizijske in zvokovne signale ter interaktivne storitve - 3. del: Aktivna širokopasovna oprema za koaksialna kabelska omrežjaKabelnetze für Fernsehsignale, Tonsignale und interaktive Dienste -- Teil 3: Aktive Breitbandgeräte für koaxiale KabelnetzeRéseaux de distribution par câbles pour signaux de télévision, signaux de radiodiffusion sonore et services interactifs
-- Partie 3: Matériels actifs à large bande utilisés dans les réseaux de distribution coaxialeCable networks for television signals, sound signals and interactive services -- Part 3: Active wideband equipment for coaxial cable networks33.120.10Koaksialni kabli. ValovodiCoaxial cables. Waveguides33.060.40Kabelski razdelilni sistemiCabled distribution systemsICS:Ta slovenski standard je istoveten z:EN 50083-3:2002SIST EN 50083-3:2003en01-december-2003SIST EN 50083-3:2003SLOVENSKI
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EUROPEAN STANDARDEN 50083-3NORME EUROPÉENNEEUROPÄISCHE NORMApril 2002CENELECEuropean Committee for Electrotechnical StandardizationComité Européen de Normalisation ElectrotechniqueEuropäisches Komitee für Elektrotechnische NormungCentral Secretariat: rue de Stassart 35, B - 1050 Brussels© 2002 CENELEC -All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.Ref. No. EN 50083-3:2002 EICS 33.060.40Supersedes EN 50083-3:1998English versionCable networks for television signals,sound signals and interactive servicesPart 3: Active wideband equipment for coaxial cable networksRéseaux de distribution par câblespour signaux de télévision,signaux de radiodiffusion sonoreet services interactifsPartie 3: Matériels actifs à large bandeutilisés dans les réseaux de distributioncoaxialeKabelnetze für Fernsehsignale,Tonsignale und interaktive DiensteTeil 3: Aktive Breitbandgerätefür koaxiale KabelnetzeThis European Standard was approved by CENELEC on 2001-10-01. CENELEC members are bound tocomply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration.Up-to-date lists and bibliographical references concerning such national standards may be obtained onapplication to the Central Secretariat or to any CENELEC member.This European Standard exists in three official versions (English, French, German). A version in any otherlanguage made by translation under the responsibility of a CENELEC member into its own language andnotified to the Central Secretariat has the same status as the official versions.CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.SIST EN 50083-3:2003

EN 50083-3: 2002- 2 -ForewordThis European Standard was prepared by CENELEC Technical Committee TC 209, "Cable networks fortelevision signals, sound signals and interactive services" on the basis of EN 50083-3:1998 and the firstamendment to EN 50083-3.The text of this first amendment was submitted to the Unique Acceptance Procedure and was approved byCENELEC on 2001-10-01 to be published as part of a second edition of EN 50083-3.The following dates were fixed:–latest date by which the EN has to be implementedat national level by publication of an identicalnational standard or by endorsement(dop)2002-10-01–latest date by which the national standards conflictingwith the EN have to be withdrawn(dow)2004-10-01Annexes designated "normative" are part of the body of the standard.Annexes designated "informative" are given for information only.In this standard, Annexes A, B, C and D are normative and Annexes E and F are informative.__________SIST EN 50083-3:2003

- 3 -EN 50083-3: 2002Content1Scope.51.1General.51.2Specific scope of this part 3.52Normative references.63Terms, definitions, symbols and abbreviations.73.1Terms and definitions.73.2Symbols.113.3Abbreviations.124Methods of measurement.134.1Linear distortion.134.2Non-linear distortion.144.3Automatic gain and slope control step response.244.4Noise figure.254.5Cross talk attenuation.264.6Signal level for digitally modulated signals.274.7Method of measurement for non-linearity of return path equipment carrying only digitalmodulated signals [Measurement of composite intermodulation noise ratio (CINR)].275Equipment requirements.295.1General requirements.295.2Safety.295.3Electromagnetic compatibility (EMC).295.4Frequency range.295.5Impedance and return loss.295.6Gain.295.7Flatness.305.8Test points.305.9Group delay.305.10Noise figure.305.11Non-linear distortion.305.12Automatic gain and slope control.315.13Hum modulation.315.14Power supply.325.15Environmental.325.16Marking.325.17Mean operating time between failure (MTBF).335.18Requirements for multiswitches.33AnnexesAnnex A (normative)
Test carriers, levels and intermodulation products.42Annex B (normative)
Checks on test equipment.44Annex C (normative)
Table C.1
-
Frequency allocation plan.45Annex D (normative)
Special national conditions.46Annex E (informative)
Measurement errors which occur due to mismatched equipment.47Annex F (informative)
Examples of signals, methods of measurement and network design
for return paths.48TablesTable 1
-
Return loss requirements for all equipment.34Table 2
-
Correction factors where the modulation used is other than 100%.34Table 3
-
Notch filter frequencies.35Table C.1
-
Frequency allocation plan.45Table F.1
-
Application of methods of measurement in EN 50083-3 for return path equipment.48Table F.2
-
Application of methods of measurement in EN 50083-6 for return path equipment.49SIST EN 50083-3:2003

EN 50083-3: 2002- 4 -FiguresFigure 1
-
Measurement of return loss.35Figure 2
-
Maximum error a for measurement of return loss using V.S.W.R. bridge with directivity
D = 46 dB
and 26 dB test port return loss.35Figure 3
-
Basic arrangement of test equipment for evaluation of the ratio of signal
to intermodulation product.36Figure 4
-
Connection of test equipment for the measurement of non-linear distortion by composite beat.36Figure 5
-
Connection of test equipment for the measurement
of composite crossmodulation.37Figure 6
-
Carrier/hum ratio = 20lgdBAa.37Figure 7
-
Test set-up for local-powered objects.38Figure 8
-
Test set-up for remote-powered objects.38Figure 9
-
Oscilloscope display.38Figure 10
-
Measurement of AGC step response.39Figure 11
-
Time constant Tc.39Figure 12
-
Measurement of noise figure.39Figure 13
-
Presentation of the result of CINR.40Figure 14
-
Characteristic of the noise filter.40Figure 15
-
Test setup for the non-linearity measurement.41Figure 16
-
Measurement of cross talk attenuation for loop trough ports of multiswitches.41Figure A.1
-
An example showing products formed when 2A
> B .42Figure A.2
-
An example showing products formed when 2A
< B.42Figure A.3
-
Products of the form A
B
C .43Figure E.1
-
Error concerning return loss measurement.47Figure E.2
-
Maximum ripple.47Figure F.1
-
Spectrum of a QPSK-modulated signal.48Figure F.2a
-
Loading with digital channels can be simulated with wideband noise.50Figure F.2b
-
Non-linearity decreases the S/N at high levels.50Figure F.3
-
Network used in the design example.50Figure F.4
-
A test result measured from a real 20 dB return amplified.51Figure F.5
-
The CINR curve of one amplifier is modified to represent the CINR of the whole
coaxial section of the network.52Figure F.6
-
The CINR of an optical link as a function of OMI, example.53SIST EN 50083-3:2003

- 5 -EN 50083-3: 20021 Scope1.1 GeneralStandards of EN 50083 series deal with cable networks for television signals, sound signals andinteractive services including equipment, systems and installations for headend reception, processing and distribution of television and sound signals andtheir associated data signals and for processing, interfacing and transmitting all kinds of signals for interactive services using all applicable transmission media. All kinds of networks like CATV-networks, MATV-networks and SMATV-networks, Individual receiving networks and all kinds of equipment, systems and installations installed in such networks, are within thisscope. The extent of this standardisation work is from the antennas, special signal source inputs to theheadend or other interface points to the network up to the system outlet or the terminal input,where no system outlet exists. The standardisation of any user terminals (i.e. tuners, receivers, decoders, multimedia terminalsetc.) as well as of any coaxial and optical cables and accessories therefor is excluded.1.2 Specific scope of this part 3 This standard applies to all broadband amplifiers used in cable networks; covers the frequency range 5 MHz to 3000 MHz; applies to one-way and two-way equipment; lays down the basic methods of measurement of the operational characteristics of theactive equipment in order to assess the performance of this equipment; identifies the performance specifications that shall be published by the manufacturers; states the minimum performance requirements of certain parameters.Amplifiers are divided into the following two quality levels:Grade 1:Amplifiers typically intended to be cascaded.Grade 2:Amplifiers for use typically within an apartment block, or within a single residence, tofeed a few outlets.Practical experience has shown these types meet most of the technical requirements necessary forsupplying a minimum signal quality to the subscribers. This classification shall not be consideredas a requirement but as the information for users and manufacturers on the minimum qualitycriteria of the material required to install networks of different sizes. The system operator has toselect appropriate material to meet the minimum signal quality at the subscriber´s outlet, and tooptimise cost/performance, taking into account the size of the network and local circumstances.All requirements and published data are understood as guaranteed values within the specifiedfrequency range and in well matched conditions.SIST EN 50083-3:2003

EN 50083-3: 2002- 6 -2 Normative referencesThis European Standard incorporates, by dated or undated reference, provisions from otherpublications. These normative references are cited at the appropriate places in the text and thepublications are listed hereafter. For dated references, subsequent amendments to or revision ofany of these publications apply to this European Standard only when incorporated in it byamendment or revision. For undated references, the latest edition of the publication referred toapplies.EN 50083Cable networks for television signals, sound signals andinteractive servicesEN 50083-1+ A1+ A2199319971997Part 1:Safety requirementsEN 50083-22001Part 2:Electromagnetic compatibility for equipmentEN 50083-41998Part 4: Passive wideband equipment for coaxial cablenetworksEN 50083-52001Part 5:Headend equipmentEN 50083-61997Part 6: Optical equipmentEN 50083-102002System performance for return pathsEN 60068 /HD 323seriesEnvironmental testing/Basic environmental testingproceduresEN 60169-241993Radio frequency connectors – Part 24: Radio frequencycoaxial connectors with screw coupling, typically for usein 75 ohm cable distribution systems (Type F)(IEC 60169-24:1991)EN 60417seriesGraphical symbols for use on equipment(IEC 60417 series)EN 60529+ A119912000Degrees of protection provided by enclosures (IP Code)(IEC 60529:1989 + A1:1999)EN 61319-1+ A1119961999Interconnections of satellite receiving equipmentPart 1: Europe (IEC 61319-1:1995)EN 80416seriesBasic principles for graphical symbols for use onequipment (EIC 80416 series)HD 134.2.S21984Radio frequency connectors – Part 2: Coaxialunmatched connector (IEC 60169-2:1965 + A1:1982)ES 200 800V1.3.12001Digital Video Broadcasting (DVB); DVB interactionchannel for Cable TV distribution systems (CATV)ETS 300 1581992Satellite Earth Stations and Systems (SES) - TelevisionReceive Only (TVRO-FSS) Satellite Earth Stationsoperating in the 11/12 GHz FSS bandsETS 300 2491993Satellite Earth Stations and Systems (SES) - TelevisionReceive Only (TVRO) equipment used in theBroadcasting Satellite Service (BSS)SIST EN 50083-3:2003

- 7 -EN 50083-3: 20023 Terms, definitions, symbols and abbreviations3.1 Terms and definitionsFor the purpose of this standard, the following definitions apply.3.1.1 equalisera device designed to compensate over a certain frequency range for the amplitude/frequencydistortion or phase/frequency distortion introduced by feeders or equipmentNOTE
This device is for the compensation of linear distortions only.3.1.2 feedera transmission path forming part of a cable network. Such a path may consist of a metallic cable,optical fibre, waveguide or any combination of them. By extension, the term is also applied to pathscontaining one or more radio links3.1.3 decibel ratioten times the logarithm of the ratio of two quantities of power P1 and P2, i.e.10lgPP12(dB)3.1.4 standard reference power and voltageIn cable networks the standard reference power, P0, is 1/75 pWNOTE
This is the power dissipated in a 75 ohm resistor with a voltage drop of 1VRMS across it.The standard reference voltage, U0, is 1V3.1.5 levelthe level of any power P1 is the decibel ratio of that power to the standard reference power P0, i.e.01PPlg10the level of any voltage U1 is the decibel ratio of that voltage to the standard reference voltage U0,i.e.01UUlg20This may be expressed in decibel (relative to 1V in 75 ohm) or more simply in dB (V) if there isno risk of ambiguity.3.1.6 attenuationratio of the input power to the output power of an equipment or system, usually expressed indecibel3.1.7 gaindecibel ratio of the output power to the input powerSIST EN 50083-3:2003

EN 50083-3: 2002- 8 -3.1.8 amplitude frequency responsegain or loss of an equipment or system plotted against frequency3.1.9 slopedifference in gain or attenuation at two specified frequencies between any two points in anequipment or system3.1.10 crossmodulationundesired modulation of the carrier of a desired signal by the modulation of another signal as aresult of equipment or system non-linearities3.1.11 carrier to noise ratiodifference in decibel between the vision or sound carrier level at a given point in an equipment orsystem and the noise level at that point (measured within a bandwidth appropriate to the televisionor radio system in use)3.1.12 noise factor/noise figurenoise factor/noise figure are used as figures of merit describing the internally generated noise of anactive deviceThe noise factor (F) is the ratio of the carrier to noise ratio at the input, to the carrier to noise ratioat the output of an active device, assuming the incoming carrier is noise free.2211//NCNCFwhereC1=signal power at the inputC2=singal power at the outputN1=noise power at the input (ideal thermal noise)N2=noise power at the outputIn other words, the noise factor is the ratio of noise power at the output of an active device to thenoise power at the same point if the device had been ideal and added no noise.idealactualNNF22The noise factor is dimensionless and is often expressed as noise figure (NF) in dBNF
=10 lg F (dB)SIST EN 50083-3:2003

- 9 -EN 50083-3: 20023.1.13 ideal thermal noisenoise generated in a resistive component due to the thermal agitation of electronsThe thermal power generated is given by:P=4 x B x k x TwhereP=noise power in wattsB=bandwidth in hertzk=Boltzmann's constant=1,38 x 10-23 J/KT=absolute temperature in kelvinsIt follows that:UR2=4 x B x k x Tand U=4xRxBxkxTwhere:U = noise voltageR = resistance in ohmsIn practice it is normal for the source to be terminated with a load equal to the internal resistancevalue, the noise at the input is then U/2.3.1.14 chrominance / luminance delay inequalitydelay inequality in nanoseconds, between the luminance and chrominance (4,43 MHz) within asingle PAL/SECAM television channel. The worst case channels shall be identified by frequency.3.1.15 well-matchedmatching condition when the return loss of the equipment complies with the requirements ofTable 1.NOTE
Through mismatching of measurement instruments and the measurement object measurement errors arepossible. Comments to the estimation of such errors are given in Annex E.3.1.16 multiswitchequipment used in distribution systems for signals that are received from satellites and convertedto a suitable IF. The IF signals that are received from different polarisations, frequency bands andorbital positions are input signals to the multiswitch. Subscriber feeders are connected tomultiswitch output ports. Each output port is switched to one of the input ports, depending oncontrol signals that are transmitted from the subscriber equipment to the multiswitch. Beside asplitter for each input port and a switch for each output port a multiswitch can contain amplifiers tocompensate for distribution or cable losses.3.1.17 multiswitch loop through portone or more ports to loop through the input signals through a multiswitch. This enables largernetworks with multiple multiswitches, each one installed close to a group of subscribers. Themultiswitches are connected in a loop through manner. The IF signals that are received by anoutdoor unit from different polarisations, frequency bands and orbital positions are input signals toa first multiswitch. Cables connect the loop through ports of this multiswitch to the input ports of asecond multiswitch and so on.SIST EN 50083-3:2003

EN 50083-3: 2002- 10 -3.1.18 multiswitch port for terrestrial signalsA network can be used to distribute terrestrial signals in addition to the signals received fromsatellites. The terrestrial antennas are connected to an optional terrestrial input port of amultiswitch. On each output port the terrestrial signals are available in addition to the satellite IFsignals. Since the usual frequency ranges for terrestrial signals and satellite IF signals do notoverlap, both can be carried on the same cable.For large networks with loop through connected multiswitches, two possibilities exist to carry theterrestrial signals from one multiswitch to another multiswitch:a) To use a specialised cable for the terrestrial signal, in addition with the cables used for thesatellite IF signals and then, on each output port the terrestrial signal is combined with the selectedsatellite IF signal.b) To combine the terrestrial signal with each satellite IF signal before the first multiswitch inorder to minimise the number of cables between multiswitches.NOTE
The signal coming from an outdoor unit for satellite reception may contain unwanted signal-components withfrequencies below the foreseen satellite IF frequency range. These signal-components overlap with the frequency rangeof terrestrial signals. For example, an outdoor unit that converts the frequency band 11,7 to 12,75 GHz to the satellite IFfrequency range may convert signals in the 10,7 to 11,7 GHz band to frequencies below the satellite IF frequency range.These frequencies have to be filtered out sufficiently to avoid interference with terrestrial signals on the same cable.3.1.19 cross talk attenuationunwanted signals beside the wanted signal on a lead caused by electromagnetic coupling betweenleads. Cross talk attenuation is the ratio of the wanted signal power to the unwanted signal power,while equal signal powers are applied to the leads. Cross talk attenuation is usually expressed indecibel.3.1.20 composite intermodulation noise (CIN)sum of noise and intermodulation products from digital modulated signals3.1.21 composite intermodulation noise ratio (CINR)ratio of the signal level and the CIN level.SIST EN 50083-3:2003

- 11 -EN 50083-3: 20023.2 SymbolsSymbolsTermsSymbolsTermsAamperemeterVvoltmeterWpower meteroscilloscopeGsignal generatorGvariable signal generatorGkTnoise generatorlow pass filterhigh pass filterbandpass filterstop band filterDUTdevice under TestAx dBattenuatorAvariable attenuatorcombinertap-off-boxdouble tap-off-boxOEoptical receiveramplifier with return pathamplifierspectrum analyserdetector with LF-amplifieradjustable AC voltage sourcegroundcapacitorRF chokevariable resistorSIST EN 50083-3:2003

EN 50083-3: 2002- 12 -3.3 AbbreviationsACalternating currentAFaudio frequencyAGCautomatic gain controlAMamplitude modulationCATVcommunity antenna television (system)CINComposite intermodulation noiseCINRComposite intermodulation noise ratioCSOcomposite second orderCTBcomposite tripple beatCWcontinous waveDUTdevice under testEMCelectromagnetic compatibilityHPhigh passIFintermediate frequencyIPinternational protectionLFlow frequencyLPlow passMATVmaster antenna television (system)MTBFmeantime between failureOMIOptimum Modulation IndexPALphase alternating lineRFradio frequencyRMSroot mean squareRSrotary switchSECAMséquenciel couleur a mémoireSGsignal generatorSMATVsatellite master antenna television (system)TVtelevisionVSWRvoltage standing wave ratioXMODcross modulationNOTE
Only the abbreviations used in the English version of this part of EN 50083 are mentioned in this subclause. TheGerman and the French versions of this part may use other abbreviations. Refer to 3.3 of each language version fordetails.SIST EN 50083-3:2003

- 13 -EN 50083-3: 20024 Methods of measurementThis clause defines basic methods of measurement. Any equivalent method that ensures the sameaccuracy may be used for assessing performance.Unless stated otherwise, all measurements shall be carried out with 0 dB plug-in attenuators andequalisers. The position of variable controls used during the measurements shall be published.The test set-up shall be well matched over the specified frequency band.For measurements on multiswitches it is necessary that control signals be fed to the output portsthat are involved in the measurement. Therefore, a bias-tee has to be connected between themultiswitch output port and the measurement set. The DC port of the bias-tee is connected to astandard receiver that generates the required control signals. Care has to be taken that theinfluence of the bias-tee on the measurement result is insignificant. This can be achieved byincluding it into the calibration or using a network analyser with a built in bias-tee.4.1 Linear distortion4.1.1 Return lossThe method described is applicable to the measurement of the return loss of equipment operatingin the frequency range 5 MHz to 3 000 MHz.All input and output ports of the unit shall meet the specification under all conditions of automaticand manual gain controls and with any combination of plug-in equalisers and attenuators fitted.4.1.1.1 Equipment requireda)A signal generator or sweep generator, adjustable over the frequency range of the equipmentto be tested;Care must be taken to ensure that the signal generator or sweep generator output does nothave a high harmonic content as this can cause serious inaccuracy.b)A voltage standing wave ratio bridge with built-in or separate RF detector;The accuracy of measurement is dependent on the quality of the bridge; in particular on thedirectivity and on the return loss of the test port of the bridge. For example Figure 2 shows themaximum accuracy achieved by a bridge with 46 dB directivity and 26 dB return loss.c)An oscilloscope;d)Calibrated mismatches;4.1.1.2 Connection of equipmentThe equipment shall be connected as in Figure 1.4.1.1.3 Measurement procedureNOTE 1
All coaxial input and output ports, other than those under test, shall be terminated in 75 .NOTE 2
Ensure that there is no supply voltage on the port being measured as this could damage the bridge. If it isnecessary to use a voltage blocking device, use one with a good return loss (10 dB above requirement).NOTE 3
Only good quality calibrated connectors, adaptors and cables shall be used.The measurement procedure comprises the following steps:a)Connect the equipment as shown in Figure 1;b)Set the signal generator output level such that the device under test is not overloaded;c)Use calibrated mismatches to calibrate the display on the oscilloscope;d)Connect the device under test as shown in Figure 1 and check the return loss over thespecified frequency range;SIST EN 50083-3:2003

EN 50083-3: 2002- 14 -4.1.2 FlatnessMethods of measurement are well known and a full description of the procedure is not necessary.Measurement is commonly made with a 75
scaler or vector network analyser. Care must betaken that all equipment used (connectors, adaptors, cable etc.) are well matched.4.1.3 Chrominance / luminance delay inequality for PAL/SECAM onlyThe well known 20T pulse method of measurement is used as described in EN 50083-5.4.2 Non-linear distortion4.2.1 General4.2.1.1 FundamentalsIn a non-linear device, the expression for the output signal will, in general, have an infinity of terms,each generated from one or more of the (assumed sinusoidal) terms in the input, and particularlyby the interaction of two or more terms. The transfer function of the device can be expressed as:Vout
=
a0 + a1Vin
+
a2V 2in
+
a3V 3in
+
....anV nin
+
.... etc.If the input signal Vin has m sinusoidal terms, then this can be expressed as:Vin =
V1sin(1t + 1)
+
V2sin(2t + 2)
+
.....Vmsin(mt + m)The output signal is then a series of terms each of which can be expressed in the general form:CVi an sin( it +
i)where:
i is the sum or difference of integral positive multiples of one or more of the inputfrequencies, for example:42, 21 - 3, 41 + 2, 21 + 2 + 3 .This may be written in a general form as: i
=
p11
p22
p33
.....pmmwhere:
i is the angular velocity 2fi ;p1, p2, .pm are positive integers (including 0); i is the relative phase of the output signals;an is a coefficient of the transfer function;Vi is a term dependent on the product of powers of the amplitudes of theinput signals (V1, V2, etc.) where the sum of the powers equals n;C is a numerical multiplier.It should be noted that terms at the same frequency may arise from several different terms in thetransfer function, i.e. for several different values of n.Each component of the output signal represented by such an expression with n > 1 is a non-lineardistortion product, where
i is an integral multiple of a single term in the input signal, e.g. 42, theproduct is regarded as a harmonic distortion product. If it is formed from two or more terms, e.g.21 - 3, it is known as an intermodulation distortion product.Since the values of a1, a2, a3, etc., usually decrease relatively rapidly with increasing values of n, itis found that the predominant non-linear output signals arise from the terms in the transfer functionin such a way that the sum p1+p2+ .pm = n, and n is defined as the order of the non-lineardistortion product, e.g. 31-23 is a fifth order product arising from the term aVin55.SIST EN 50083-3:2003

- 15 -EN 50083-3: 2002The m input signals represented in the expression are not necessarily distinct signals. Any periodicsignal may be represented by a series of sinusoidal terms as in the expression for Vin. For thepredominant non-linear output signals it is found that:mpmpppiVVVVV.321321so that if the amplitudes of all the input signals are multiplied by a common factor K, the amplitudeof the nth order distortion products will be multiplied by Kn (since p1+p2+p3+.pm = n). When thelevels of all input signals are raised by 1 dB, the level of any signal nth order distortion product willincrease by n dB, and the resultant signal/distortion ratio will decrease by (n-1) dB. Thisrelationship will be referred to as the "standard level variation" of a distortion product.If a distortion product is due to components of different order, and/or different order products occurwithin the bandwidth of the device used to measure the level of distortion products, then themeasured level will not follow a standard level variation.In principle, an infinite number of terms is necessary for a complete description of a non-linearcharacteristic. However, considering the standard level variation of terms of different order, therelative contribution of higher-order terms increases with the level of input signals. Conversely, ifsignal levels are low enough, only a few of the lowest order terms will produce significantcontributions at the output.If all input signals are limited to a frequency band of less than one octave, the frequencies of allsecond-order terms will fall outside the band limits. Signal frequencies can also be allocated in twoor more non-contiguous bands in a manner that will place all second-order products outside thebands.Third-order distortion products, in particular some of the products that occur at frequenciesrepresented by 1
3 cannot be kept out of the band that contains the input signals. Theaccumulation of third-order distortion products may therefore be a limiting factor in the performanceof a wideband multi-channel distribution system.4.2.1.2 MeasurementMeasurements related to the following phenomena are described: intermodulation between two or three single frequency signals; composite beats produced by a number of single frequency signals; composite crossmodulation between a number of single frequency signals.A proper specification shall include at least the following details:a)the particular effect that is measured;b)the required signal to distortion ratio.The result of the measurement shall be given as the worst case maximum signal level at theequipment output that allows the required signal to distortion ratio to be met. If the output level issloped with frequency, this shall be defined.The effect shall be defined as being of a particular order (e.g. "third-order intermodulation").4.2.2 Intermodulation4.2.2.1 IntroductionThe two equal carrier and the three equal carrier methods described are applicable to themeasurement of the ratio of the carrier to a single intermodulation product at a specified pointwithin the cable network. The methods can also be used to determine the intermodulationperformance of individual items of equipment.NOTE 1
It should be especially noted that the simultaneous use of many channels spaced by the same frequencyinterval results in a large number of intermodulation products (particularly those of the third-order) falling near the visioncarrier of a wanted television channel.SIST EN 50083-3:2003

EN 50083-3: 2002- 16 -In these cases, the resultant interference is of an extremely complex nature and an alternativemeasurement procedure will be needed. This is covered in 4.2.3 and 4.2.4.Examples of second-order and third-order intermodulation products are given in Annex A.Second-order products are encountered only in wideband equipment and systems, covering morethan one octave, and shall be measured using two signals (see A.1).Third-order products are encountered in wideband and narrowband equipment and systems andshall be measured using three signals (see A.2).NOTE 2
If the unequal carrier method of measurement, as described in EN 50083-5, is used, the output level giving theappropriate signal to distortion ratio must be decreased by 6 dB to obtain the correct result for the equal carrier methoddescribed here.4.2.2.2 Equipment requireda) A selective voltmeter covering the frequency range of the equipment or system to be tested.This may be a spectrum analyser;b) The appropriate number of signal generators covering the frequencies at which the tests are tobe carried out;c) A variable attenuator with a range greater than the signal to intermodulation ratio expected, ifnot incorporated in the voltmeter described in 4.2.2.2 a);d) A combiner will be required for tests on equipment and systems with a single input (Figure 3);NOTE
Additional items may be necessary, for example to ensure that the measurements are not affected by spurioussignals generated in the test equipment itself (Annex B).4.2.2.3 Connection of equipmentThe equipment shall be connected as shown in Figure 3.4.2.2.4 Measurement procedureThe measurement procedure comprises the following steps:a)GeneralUnless otherwise required, the reference output levels used in the measurements shall be thenominal output levels for the equipment. It shall be quoted whether the signal output levels areconstant over the frequency range or not. If the specified output levels are not constant overfrequency range then the output levels off all the test signals shall be quoted in the results.Measurements of both second-order and third-order products shall be carried out with the testsignals widely and closely spaced over each band of interest at frequencies capable of producingsignificant products within the overall frequency range.Where the equipment to be measured includes automatic gain control, tests shall be carried out atthe nominal operating signal input levels.b)Calibration and checksA check shall be made to determine if the harmonics and other spurious signals at the outputs ofthe signal generators are likely to affect materially the results of the measurements (see Annex B).The selective voltmeter shall be calibrated and checked for satisfactory operation (see Annex B).A check shall be made for possible intermodulation between the signal generators at the outputlevels to be used for the tests (see Annex B).c)MeasurementSet the signal generators, in CW mode, to the frequencies of the test signals (see 4.2.2.4 a) andAnnex A) and adjust their outputs and that of the different points of the system as far as the pointof measurement to obtain the specified system operating levels throughout.SIST EN 50083-3:2003

- 17 -EN 50083-3: 2002Connect the variable attenuator and selective voltmeter and other items if required (see Annex B)to the output of the device under test. Tune the meter to each test signal and note the attenuatorvalue a1 required to obtain a convenient meter reading R for the reference signal. The attenuatorvalue a1 should be slightly greater than the signal to intermodulation ratio expected at the point ofmeasurement.Tune the meter to the intermodulation product to be measured and reduce the setting of thevariable attenuator to the value a2 required to obtain the same meter reading R.NOTE
When measuring levels of intermodulation products, it may be necessary to insert a filter at the input to the meter(see Annex B). In such instances the insertion loss (in dB) of the filter at the frequency of the products shall be added tothe attenuator value.The signal to intermodulation product ratio in dB is given by:S / I
=
a1 - a2where: a1=attenuator value for the test signal used as a reference in dBa2=attenuator value for the intermodulation product in dB.4.2.3 Composite triple beat4.2.3.1 IntroductionThe method of measurement of composite triple beat using CW signals is applicable to themeasurement of the ratio of the carrier to composite triple beat at a specified point in a cablenetwork. The method can also be used to determine the composite triple beat intermodulationperformance of individual items of equipment.When the input signals are at regularly spaced intervals (as is common in most allocations for TVchannels), the various distortion products tend to cluster in groups, close to the TV channels. Thenumber of different products in each cluster increases rapidly with the number of channels, andthey combine in different ways, depending on the degree of coherence between generatingsignals, and the relative phases of the different distortion products.The method described in this subclause measures the non-linear distortion of a device or systemby the composite effect of all the beats clustered within
15 kHz of the vision carrier of a TVchannel. During the measurement, the vision carrier of that channel shall be turned off, so that thecomposite triple beat measured is that generated by all the carriers except that of the measuredchannel.The method is used to support a specification of the following general format:"The composite triple beat ratio for groups of carriers in channel (A) at (B) dB(V) is (C) dB."where:(A)designates the channel in which the test is made. If omitted, the specification is understoodto be a minimum specification for measurements at all the channels specified by the list ofcarriers;(B)is the reference level at which all the carriers should be set during the measurement, unlessotherwise specified. If all the carriers are not at the same level, the specification shouldclearly indicate the level of each carrier relative to the reference level;(C)is the composite triple beat ratio, usually given as a minimum specification.Because of the large variety of frequency plans in use throughout Europe and the need to comparereadily performance specifications of different manufacturer's equipment, the measurement shallbe made with the carriers listed in Annex C (the carriers are all in an 8 MHz raster, except for thespecial case of 48,25 MHz).The vision carrier frequencies are arranged in groups and only complete groups shall be used,except as stated below. If an amplifier is specified up to 450 MHz, group A shall be used. Ifspecified up to 550 MHz, groups A and B shall be used. If specified up to 862 MHz, all groups A, B,C, D and E shall be used.SIST EN 50083-3:2003

EN 50083-3: 2002- 18 -Group A can also be used in part, dependent on the specified bandwidth of the equipment undertest. The frequencies deleted shall be stated. If the carrier 48,25 MHz is not used in case of theforward path starts with 85 MHz, than the results of measurements shall be published including thenotice "without Band I". If the equipment can operate at all frequencies in group A this result shallbe quoted together with the result where only a part of group A is used.For all passbands, the performance shall be quoted for the maximum possible number of completegroups. The manufacturer may, in addition, provide a performance figure for a larger number ofcarriers. The frequencies deleted shall be stated.4.2.3.2 Equipment requireda)A spectrum analyser with 30 kHz intermediate frequency (IF) bandwidth and 10 Hz videobandwidth capability;NOTE
When using a spectrum analyser with minimum
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