Iec 62153 4 5 2006

NORME INTERNATIONALECEI IEC INTERNATIONAL STANDARD 62153-4-5 Première éditionFirst edition2006-03 Méthodes d'essai des câbles métalliques de communication – Partie 4-5: Compatibilité

Equipement

Généralités

The test setup must have a background noise level at least 6 dB higher than the equipment measurement for the value to be considered valid This indicates that a test should be conducted using equipment with a dynamic range that exceeds this threshold.

115 dB pour mesurer l’affaiblissement de couplage ou l’affaiblissement d’écran jusqu’à environ

90 dB, lorsque l’on considère l’affaiblissement total d’une pince absorbante et d’un symétriseur normaux (le cas échéant) La précision des équipements doit être inférieure à ±1 dB

The equipment must be capable of measuring screen attenuation or coupling attenuation across the frequency range of 30 MHz to 1 GHz, unless otherwise specified in the relevant cable specifications.

Le montage de mesure peut être effectué en utilisant un analyseur de réseau vectoriel ou un générateur de signaux discrets et un récepteur de mesure sélectif

Une plaque de réflexion métallique verticale doit être placée directement devant le générateur

La hauteur et la largeur de la plaque doivent être chacune supérieure à 800 mm La plaque doit avoir un trou central pour accueillir le câble en essai

The measurement setup for maximum emitted power at the nearest end, utilizing discrete instruments, is illustrated in Figure 1 It includes an absorbing clamp with a minimum frequency range starting from 30 MHz.

1 GHz, se reporter à l’Annexe D de la CISPR 16-1-4 Une autre pince absorbante peut être nécessaire si des mesures sont effectuées en dehors de cette gamme de fréquences

LICENSED TO MECON Limited - RANCHI/BANGALORE FOR INTERNAL USE AT THIS LOCATION ONLY, SUPPLIED BY BOOK SUPPLY BUREAU.

The logarithmic ratio of the powers P 1 and P 2max is termed coupling attenuation, expressed in dB

In the case of unbalanced (coaxial) cables, the measurement yields the screening attenuation For balanced (symmetrical) cables, two scenarios must be considered: a) when disturbing power is introduced in differential mode, the measurement reflects the coupling attenuation, which encompasses both unbalance and screening attenuation; b) when disturbing power is applied in common mode, the measurement indicates the screening attenuation.

The surface current is measured on a swept-frequency basis with a stationary clamp

Taking into account the maximum effect of either near or far end surface waves, the coupling attenuation or screening attenuation a c is defined by:

P 1 is the input power of inner circuit of the sample;

P 2n is the maximum near end coupling peak power;

P 2f is the maximum far end coupling peak power

The test setup must achieve a noise floor that is at least 6 dB lower than the instrument reading necessary for reporting values For example, to measure coupling or screening attenuation up to about 90 dB, equipment with a dynamic range of at least 115 dB is essential, considering the full attenuation of a standard absorbing clamp and balun, if used Additionally, the precision of the equipment should exceed ±1 dB.

The equipment must measure coupling or screening attenuation across the full frequency range of 30 MHz to 1 GHz, unless otherwise specified in the relevant cable specifications.

The measurement set-up can be performed using a vector network analyser or alternatively a discrete signal generator and selective measuring receiver

A vertical metallic reflector plate, measuring at least 800 mm in both height and width, must be positioned directly in front of the generator This plate will feature a central hole designed to allow the cable under test to pass through.

The measurement setup for assessing maximum radiated power at the near end, utilizing discrete instruments, is illustrated in Figure 1 It includes an absorbing clamp that operates within a minimum frequency range of 30 MHz to 1 GHz, as detailed in Annex D.

CISPR 16-1-4 An alternative absorbing clamp may be required if measurements are performed outside this frequency range;

This document is licensed to MECON Limited for internal use in Ranchi and Bangalore, provided by the Book Supply Bureau It discusses the use of a symmetrizer to match the output signal impedance of an asymmetric generator to the characteristic impedance of a symmetric cable, applicable only for symmetric cables Additionally, it mentions a ferrite absorber with a minimum frequency range starting at 30 MHz.

To ensure optimal performance in signal testing, a minimum frequency of 1 GHz and a minimal attenuation of 10 dB are required Essential equipment includes a reflection plate measuring at least 800 mm × 800 mm, a signal generator or vector network analyzer with matching impedance to the asymmetric port of the balun, and a power amplifier if necessary for large dynamic ranges Additionally, a calibrated step attenuator or network analyzer should be used, coupled with a low-noise amplifier for enhanced dynamic range An appropriate printer and load resistor networks that terminate characteristic nominal impedances in differential and common mode are also necessary If equipment does not meet background noise level requirements, the dynamic range can be improved using an external amplifier, which must be properly shielded and connected to the reflection plate The amplifier's gain should be measured and adjusted in test results, taking care to avoid saturation An attenuator may be required at the receiver input during measurements, with its attenuation also measured and factored into the results.

0 Générateur de signaux, impédance de sortie Z 0

1 Câble en essai, impédance caractéristique nominale Z 1

2 Circuit externe du câble en essai, impédance Z 2

6 Transformateur de courant de la pince

7 Câble du récepteur de mesure (le même câble est utilisé pour les mesures et pour l’étalonnage)

8 Absorbeur (tube de ferrite) de la pince, pertes d’insertion >10 dB

9 Absorbeur (ou deuxième pince), pertes d’insertion >10 dB

10 Terminaison du câble en essai

11 Blindage du générateur de signaux et symétriseur si nécessaire pour les grandes plages dynamiques

Figure 1 – Mesure des ondes de surface au niveau de l’extrémité la plus proche de l’échantillon

This article outlines the essential equipment and requirements for effective signal measurement and analysis It specifies the need for a balun to match the impedance of unbalanced generator outputs to balanced cable characteristics, applicable for symmetrical cables Additionally, a ferrite absorber is required, with a frequency range of 30 MHz to 1 GHz and a minimum attenuation of 10 dB A reflector plate of at least 800 mm × 800 mm, along with a signal generator or vector network analyzer matching the balun's unbalanced port impedance, is necessary, potentially coupled with a power amplifier for high dynamic range A calibrated receiver, possibly with a low noise amplifier, is also essential The setup must include printing facilities and load resistance networks to terminate common and differential mode impedances If noise floor requirements are not met, an external amplifier may enhance dynamic range, provided it is well screened and connected to the reflector plate Care must be taken to measure and correct the amplifier's gain, and an attenuator may be required to prevent equipment overload during measurements.

1 Cable under test, nominal characteristic impedance Z 1

2 Outer circuit of cable under test, impedance Z 2

6 Current transformer of the clamp

7 Measuring receiver cable (use the same in measurement and calibration)

8 Absorber (ferrite tube) of the clamp, insertion loss >10 dB

9 Absorber (or second clamp), insertion loss >10 dB

10 Termination of the cable under test

11 Shield of signal generator and balun if needed for very high dynamic range

Figure 1 – Measurement of surface waves at the near end of the sample

Exigences du symétriseur

To measure symmetrical cables, a balun is essential to convert the primary impedance of the asymmetric output from the signal generator into the nominal characteristic impedance of the symmetrical cable pair under test The minimum requirements for the balun are outlined in Table 1.

L’affaiblissement du symétriseur doit être maintenu aussi bas que possible parce qu’il limite la plage dynamique des mesures d’affaiblissement de couplage

Tableau 1 – Caractéristiques des performances du symétriseur (30 MHz à 1 GHz)

Perte d’insertion 3) (y compris les affaiblisseurs d'adaptation, le cas échéant) ≤ 10 dB

Puissance assignée Pour s’adapter à la puissance du générateur et de l’amplificateur (le cas échéant) Équilibre de tension de sortie 4) ≥ 50 dB de 30 MHz à 100 MHz

1) L’impédance primaire peut être différente si nécessaire pour s’adapter aux sorties de l’analyseur autres que 50 Ω

2) Les sorties symétriques des symétriseurs d’essai doivent être adaptées à l’impédance nominale de la paire de câbles symétriques Une résistance de 100 Ω doit être utilisée pour une terminaison de câbles de 120 Ω

3) L’affaiblissement opérationnel d’un symétriseur doit être soustrait mathématiquement des 3 mesures d’affaiblissement opérationnel avec 3 symétriseurs dos à dos

4) Mesuré selon les Recommandations ITU-T G.117 et O.9.

Echantillon en essai

Longueur du câble contrôlé

The effective length of the sample during testing is constrained by the absorbing clamp and the ferrite tube, as illustrated in Figure 1 This length must be maintained at 600 cm ±.

Préparation de l’échantillon en essai

If the hole of the absorbent clamp is smaller than the diameter of the sample being tested, it should be extended at both ends with smaller lines These extension lines must have significantly better screen attenuation than the sample under test Whenever possible, it is advisable to use lines with an external tubular conductor.

5.2.2.2.1 Préparation pour la mesure de l’affaiblissement de couplage

La longueur totale du câble doit être supérieure à 100 m La longueur du câble contrôlé (de la pince absorbante à l’absorbeur) doit être conforme à 5.2.1

To measure symmetrical cables, a balun is essential for converting the unbalanced output's primary impedance from the signal generator to the balanced cable pair's nominal characteristic impedance The minimum specifications for the balun are outlined in Table 1.

The attenuation of the balun shall be kept as low as possible because it will limit the dynamic range of the coupling attenuation measurements

Table 1 − Balun performance characteristics (30 MHz to 1 GHz)

Insertion loss 3) (including matching pads if used) ≤ 10 dB

Return loss, bi-directional ≥6 dB

Power rating To accommodate the power of the generator and amplifier (if applicable) Output signal balance 4) ≥ 50 dB from 30 MHz to 100 MHz

≥ 30 dB from 100 MHz to 1 GHz

1) Primary impedance may differ if necessary to accommodate analyser outputs other than 50 Ω

2) Balanced outputs of the test baluns shall be matched to the nominal impedance of the symmetrical cable pair 100 Ω shall be used for termination of 120 Ω cabling

3) The operational attenuation of a balun shall be mathematically deduced from 3 operational attenuation measurements with 3 baluns back-to-back

4) Measured per ITU-T Recommendations G.117 and O.9

The effective length of the test specimen is limited by the absorbing clamp and the ferrite tube, as shown in Figure 1 This length shall be 600 cm ± 10 cm

When the bore of the absorbing clamp is narrower than the diameter of the test specimen, it must be extended at both ends using smaller indicator lines These extension lines should provide significantly better screening attenuation than the test specimen itself Ideally, lines featuring a tubular outer conductor should be utilized for optimal performance.

5.2.2.2.1 Preparation for the measurement of the coupling attenuation

The entire length of the cable shall be at least 100 m The tested cable length (from absorbing clamp to the absorber) shall comply with 5.2.1

Analyseur de réseau ou générateur de signal

Figure 2 – Terminaison d’un câble symétrique blindé

A differential or common mode termination is essential for each pair at both the nearest and farthest ends of the cable, as illustrated in Figure 2 The terminations must be properly shielded to ensure that test results remain accurate and unaffected.

La valeur des résistances doit être la moitié de l’impédance caractéristique nominale du câble en essai

Les prises centrales des terminaisons doivent être connectées les unes aux autres Dans le cas de câbles blindés, les prises centrales doivent être connectées aux écrans

5.2.2.2.2 Préparation pour la mesure de l’affaiblissement d’écran (câbles blindés uniquement)

The total length of the cable must not exceed the length of the controlled cable plus the length of the plug and the absorber The length of the cable being tested (from the absorbing clamp to the absorber) must comply with section 5.2.1.

Shielded twisted pair cables are treated as a quasi-coaxial system, requiring that the conductors of all pairs be interconnected at both ends Additionally, all shields, including those of shielded pairs or quads, must also be connected at both ends The shields should be connected around the entire circumference.

Network analyser generator or signal generator

Figure 2 – Termination of a screened symmetrical cable

Each cable pair requires differential and common mode termination at both the near and far ends, as illustrated in Figure 2 It is essential that these terminations are well-screened to ensure the accuracy of test results.

The value of the resistors shall be one half the nominal characteristic impedance of the cable under test

The centre taps of the terminations shall be connected together In the case of screened cables, the centre taps shall be connected to the screens

5.2.2.2.2 Preparation for the measurement of the screening attenuation (screened cables only)

The total cable length should not exceed the tested cable length, which is measured from the absorbing clamp to the absorber, plus the lengths of the clamp and absorber It is essential that the tested cable length adheres to the specifications outlined in section 5.2.1.

Screened symmetrical cables function as a quasi-coaxial system, requiring that the conductors of all pairs be interconnected at both ends Additionally, all screens, including those of individually screened pairs or quads, must also be connected at both ends, ensuring a complete connection around the entire circumference.

Figure 3 – Préparation de l’échantillon en essai (câbles symétriques et multiconducteurs)

The quasi-coaxial system must be terminated at its nominal characteristic impedance, ensuring proper shielding to avoid skewed test results Impedance can be measured using a time-domain reflectometer (TDR) with a maximum rise time of 200 ps or through the method described below Additionally, an impedance adapter is required to match the generator's impedance with that of the quasi-coaxial system.

One end of the prepared sample is connected to a network analyzer, calibrated for impedance measurements at the reference plane of the connector interface The test frequency should be approximately at the point where the sample length is 1/8 of the wavelength, denoted as λ.

≈ × ó f test est la fréquence d’essai; c est la vitesse de la lumière, 3 × 10 8 m/s;

L sample est la longueur d’un échantillon; ε r 1 est la constante diélectrique du système interne

L’échantillon est en court-circuit à l’extrémité la plus éloignée L’impédance Z short est mesurée

L’échantillon est laissé ouvert à l’endroit ó il était en court-circuit L’impédance Z open est mesurée

L’impédance du système quasi coaxial Z 1 se calcule comme suit: open short

Si l’impédance du système interne Z 1 , et donc la résistance de charge R 1 , est inférieure à 50 Ω

(l’impédance du générateur), les formules ci-dessous sont utilisées:

Connector Well screened load resistor R 1

Figure 3 – Preparation of test sample (symmetrical and multi conductor cables)

The quasi coaxial system must be terminated with its nominal characteristic impedance, ensuring proper screening to avoid falsified test results Impedance can be measured using a TDR with a maximum rise time of 200 ps or through an alternative method Additionally, an impedance matching adapter is essential to align the generator's impedance with that of the quasi coaxial system.

The prepared sample is connected to a calibrated network analyser for impedance measurements at the connector interface reference plane The testing frequency is set to approximately correspond to a wavelength ($ \lambda $) such that the sample length is 1/8 of $ \lambda $.

≈ × where f test is the test frequency; c is the velocity of light, 3 × 10 8 m/s;

L sample is the length of sample; ε r 1 is the dielectric constant of the inner system

The sample is short circuited at the far end The impedance Z short is measured

The sample is left open at the same point where it was shorted The impedance Z open is measured

The impedance of the quasi coaxial system Z 1 is calculated as: open short

If the impedance of the inner system Z 1 and subsequently the load resistor R 1 is less than 50 Ω

(the generator impedance), the formulas below are used:

La configuration est illustrée à la Figure 4

Le gain en tension k m du circuit est: s 1 s p p

Si l’impédance du système interne Z 1 , et donc la résistance R 1 , est supérieure à 50 Ω

The configuration is depicted in Figure 4

The voltage gain k m of the circuit is: s 1 s p p

If the impedance of the inner system Z 1 and subsequently R 1 is greater than 50 Ω (the generator impedance) the formulas below are used:

Le gain en tension k m du circuit est:

The total length of the cable must not exceed the length of the tested cable plus the length of the connector and the absorber The length of the controlled cable, from the absorbing clamp to the absorber, must comply with section 5.2.1.

Le câble doit être terminé sur son impédance caractéristique nominale La terminaison doit être correctement blindée de telle sorte que les résultats des essais ne soient pas faussés.

Procédure d’étalonnage

Affaiblissement du montage de mesure

L’affaiblissement du montage de mesure est dộterminộ en commenỗant par mesurer la perte composite, puis en corrigeant la perte de réflexion dans le montage d’étalonnage, se reporter à la Figure 6

De cette manière, on trouve la réponse de la pince absorbante à la puissance d’une onde de surface incidente

The loss of reflection in the measurement setup, caused by the mismatch between the surface wave impedance, $ Z_2 $, and the clamp impedance, is not considered in the measurement The error resulting from neglecting this impedance can be deemed negligible.

Figure 5 − Impedance matching for Z 1 >50 Ω The voltage gain, k m , of the circuit is:

The cable shall be terminated with its nominal characteristic impedance The termination shall be well screened, so that the test results are not falsified

5.3.1 Attenuation of the measuring set-up

The attenuation of the measuring set-up is determined by first measuring the composite loss and then correcting for the reflection loss in the calibration set-up, see Figure 6

In this way, the response of the absorbing clamp to the power of an incident surface wave is found

The measurement setup does not account for the reflection loss resulting from the impedance mismatch between the surface wave, $ Z_2 $, and the clamp's impedance However, the error introduced by omitting this impedance mismatch is negligible.

5.3.1.2 Perte composite du montage de mesure

To determine the composite loss, the generator's output power is delivered directly to the external circuit, which consists of the cable screen (for shielded cables) or all conductors connected together (for unshielded symmetrical cables) and the surrounding environment The generator's termination directly on the cable screen under test (for shielded cables) or on all connected conductors (for unshielded symmetrical cables) is illustrated in Figures 6 and 7, using discrete instruments The composite loss of this calibration setup arises from measuring the output power of the absorbing clamp across the relevant frequency range The attenuation of the test wires must be included in the calibration of the network analyzer.

The resistance of the connection between the generator output and the cable screen or the interconnected conductors should be low, with a minimum copper cross-section of 0.75 mm² and a maximum length of 10 mm from the cable end Additionally, the cable end must be aligned within ±2 mm of the front side of the clamp.

The output cable screen from the signal generator must be connected to the reflection plate to provide a return path for the signal This can be achieved by installing a connector, such as a coaxial connector, on the reflection plate and connecting the generator to this connector using a low-loss cable, like a coaxial cable The cable connection is made at the central contact of the connector.

1 Ecran ou conducteur externe de l’échantillon en essai

3 Connecteur installé dans la plaque de réflexion

5.3.1.2 Composite loss of the measuring set-up

To calculate the composite loss, the generator's output power is directly connected to the outer circuit, which consists of the cable screen for screened cables or all conductors joined together for unscreened balanced cables This setup involves terminating the generator directly to the cable screen for screened cables or to the combined conductors for unscreened balanced cables, as illustrated in Figure 6.

The composite loss of the calibration setup is determined by measuring the output power from the absorbing clamp across the full frequency range of interest Additionally, the attenuation of the test leads must be factored into the calibration of the network analyzer.

The connection from the generator output to the cable screen or conductors connected together shall be of low resistance (minimum 0,75 mm 2 copper cross section) and short

(maximum 10 mm from the cable end) The cable end shall be in line (±2 mm) with the front side of the clamp

To ensure a proper return path for the signal, the output cable's screen from the signal generator must be connected to the reflector plate This can be achieved by installing a coax connector on the reflector plate and linking the generator to this connector using a low-loss coax cable The connection is made to the center contact of the connector.

1 Screen or outer conductor of test sample

3 Connector mounted in reflector plate

Connexion entre écran et plaque de réflexion

Câble provenant du générateur de signaux

5.3.1.3 Perte de réflexion de la pince absorbante dans le montage d’étalonnage

The measurement of the composite loss in section 5.3.1.2 includes the reflection loss caused by the mismatch between the generator and the cable sample placed in the clamp during the calibration setup.

L’affaiblissement de la pince, y compris l’affaiblissement des fils d’essai, a cl , se calcule comme suit: a cl = a cal – a rfl ó a cal est la perte composite; a rfl est la perte de réflexion

S 21 est le paramètre de diffusion mesuré lorsque la puissance est délivrée directement au circuit externe et la puissance de sortie de la pince absorbante est mesurée

La perte de réflexion, a rfl , est déterminée en mesurant les coefficients complexes de réflexion de la pince dans le montage d’étalonnage et en calculant a rfl comme suit:

S 11 est le paramètre de diffusion mesuré lorsque la puissance est délivrée directement au circuit externe et la puissance réfléchie est mesurée

The measurement is typically conducted by assessing the diffusion parameter S11 using a vector network analyzer S11 represents the reflection coefficient, and the calibration point for this S11 measurement is the interface where the test cable connects to the output of the generator, such as the output pin of the connector on the reflection plate.

Connection between screen and reflector plate

5.3.1.3 Reflection loss of the absorbing clamp in the calibration set-up

The composite loss measurement of 5.3.1.2 includes the reflection loss caused by the mismatch between the generator and the cable sample positioned in the clamp in the calibration set-up

The clamp's attenuation, which includes the attenuation of the test leads, is calculated using the formula: \$ a_{cl} = a_{cal} - a_{rfl} \$ In this equation, \$ a_{cal} \$ represents the composite loss, while \$ a_{rfl} \$ denotes the reflection loss.

S 21 is the measured scattering parameter when the power is fed directly to the outer circuit and the output power of the absorbing clamp is measured

The reflection loss, a rfl , is determined by measuring the complex reflection coefficients of the clamp in the calibration set-up and calculating a rfl as:

S 11 is the measured scattering parameter when the power is fed directly to the outer circuit and the reflected power is measured

The measurement is normally performed by measuring the scattering parameter S 11 with a vector network analyser S 11 is equal to the reflection coefficient The calibration point for this

The S 11 measurement serves as the interface connecting the cable under test to the generator output, specifically at the output pin of the connector located on the reflector plate.

The measurement setup's attenuation, denoted as \$a_m\$, can be calculated by the formula: \$a_m = a_{cal} - a_{rfl} + a_{balun}\$ (if applicable) Here, \$a_{cal}\$ represents the composite loss measured from the setup, \$a_{balun}\$ is the attenuation from the balun used (if applicable), and \$a_{rfl}\$ is the reflection loss due to impedance mismatch between the generator and the external circuit during calibration.

Perte d’insertion des absorbeurs

The absorber's insertion loss must ensure that the reflected waves from the cable section behind the absorber are eliminated, requiring a value greater than 10 dB The measurement setup is illustrated in Figure 8.

The measuring absorber should be positioned as close as possible to connection point number 4, as shown in Figure 8 The space must be significantly less than 1/4 of the wavelength in the secondary system at the highest frequency to be measured.

Directly behind the tested absorber, as observed from the generator, the current in the external cable conductor (using a coaxial cable) or the cable shield (using a symmetrical cable) is measured in the absorbing clamp, as shown in Figure 8a.

The termination of the external cable conductor or cable shield at the generator output is described in section 5.3.1.2 The test absorber is then removed, and without changing the position of the absorbing clamp, the current in the clamp is measured again, as shown in Figure 8b The difference in levels indicates the insertion loss of the absorber.

Figure 8a – Mesure avec l’absorbeur en essai Figure 8b – Mesure sans l’absorbeur en essai

4 Connexion du conducteur externe isolé de câble coaxial ou de l’écran de câble symétrique (échantillon 1) sur le conducteur interne du générateur

Figure 8 – Mesure de la perte d’insertion d’un absorbeur

The attenuation of the measuring set-up, denoted as \$a_m\$, is calculated by the formula: \$a_m = a_{cal} - a_{rfl} + a_{balun}\$ (if applicable) In this equation, \$a_{cal}\$ represents the measured composite loss of the measuring set-up, \$a_{rfl}\$ accounts for the reflection loss due to mismatches between the generator and the outer circuit during calibration, and \$a_{balun}\$ is the attenuation of the balun used, if applicable.

5.3.2 Insertion loss of the absorbers

To effectively suppress waves reflected by the cable section behind the absorber, an insertion loss greater than 10 dB is essential The measuring arrangement is illustrated in Figure 8.

The absorber to be measured is to be positioned as close as possible to connection point 4 in

Figure 8 The gap shall be much smaller than 1/4 of the wavelength in the secondary system at the highest frequency to be measured

To measure the insertion loss of the absorber under test, the current in the outer cable conductor or cable screen is recorded using an absorbing clamp positioned directly behind the absorber, as shown in Figure 8a The connection of the outer cable conductor or cable screen to the generator output follows the procedure outlined in section 5.3.1.2 After removing the absorber, the clamp current is measured again in the same position, as illustrated in Figure 8b The difference in current levels indicates the insertion loss of the absorber.

Figure 8a – Measurement with absorber under test Figure 8b – Measurement without absorber under test

4 Connection of insulated outer conductor of coax cable or screen of balanced cable (sample 1) to inner conductor of generator

Figure 8 – Measurement of the insertion loss of an absorber

Si les exigences ne peuvent pas être satisfaites à de basses fréquences (en dessous de

At frequencies of 100 MHz, the results must be substituted with those obtained at higher frequencies that meet the requirements Extrapolation should be conducted using a horizontal straight line.

Montage d’essai

Vérification du montage d’essai

5.4.1.1 Détermination de la sensibilité des mesures du montage

Avant les mesures, la sensibilité des mesures du montage doit être déterminée

This is achieved by measuring the screen attenuation or coupling attenuation of a cable that has a screen attenuation or coupling attenuation higher than that of the test cable The cable used to determine the measurement sensitivity must be of the same type (coaxial or symmetrical) as the test cable.

Le montage de mesure doit être exactement identique au montage pour le câble en essai

The screen attenuation or coupling attenuation measured for this cable, used to determine measurement sensitivity, defines the highest screen attenuation or coupling attenuation that can be measured by the setup This is also represented by the background noise of the setup.

A reliable method to determine the background noise of a test setup is to use a bare copper tube containing one or more twisted pairs, terminated in either common mode or differential mode The theoretical coupling attenuation of this device exceeds 100 dB across the entire frequency range from 30 MHz to 1,000 MHz.

Ainsi, l’affaiblissement de couplage mesurée reflète précisément la qualité de la fabrication de la connexion et le niveau de bruit de fond restant

5.4.1.2 Vérification de l’étalonnage du montage d’essai

Pour les fréquences ó les absorbeurs disponibles ne sont pas conformes aux exigences de

10 dB de pertes d’insertion, typiquement en dessous de 100 MHz, l’incertitude peut être plus élevée

L’incertitude peut être réduite en soudant soigneusement les écrans au niveau de la plaque de réflexion et la terminaison des paires inutilisées.

Force de traction sur le câble

La force de traction maximale doit être de 20 N

For the keys to the figure, refer to Figure 1

Figure 12 – Measurement of surface wave at far end of sample

5.4.1.1 Determination of measurement sensitivity of the set-up

Before measurements are performed, the measurement sensitivity of the test set-up shall be determined

To ensure accurate measurement sensitivity, it is essential to use a cable with higher coupling or screening attenuation than the cable being tested The measurement cable must be of the same type, either coaxial or symmetrical, as the cable under evaluation.

The measurement set-up shall be exactly as the measurement set-up for the cable under test

The coupling or screening attenuation of this cable, which is essential for assessing measurement sensitivity, establishes the maximum attenuation that can be detected by the setup This value is commonly referred to as the noise floor of the system.

A reliable method to assess the noise floor of a test setup involves using a simple copper tube containing one or more twisted pairs with differential and common mode termination This device offers a theoretical coupling attenuation exceeding 100 dB across the frequency range of 30 MHz to 1,000 MHz Consequently, the measured coupling attenuation accurately indicates the quality of the connecting workmanship and the level of the residual noise floor.

5.4.1.2 Verification of test set-up calibration

For frequencies where the available absorbers do not comply with the requirement of 10 dB insertion loss, typically below 100 MHz, a higher uncertainty may be expected

By carefully bonding of screens at the reflector plate and termination of unused pairs the uncertainty can be minimised

The maximum pulling force shall be 20 N

Procédure de mesure

A symmetrical cable under test must be connected to the generator through a suitable impedance matching device In contrast, an asymmetrical (coaxial) cable should be directly connected to the generator, ensuring that the generator's impedance matches the cable's nominal impedance If the impedances do not match, an impedance adapter must be utilized.

Pour les câbles symétriques, toutes les paires doivent être mesurées individuellement

The test cable is positioned in an aerial span It is essential that no metallic objects or individuals are located within 600 mm of the test cable in any direction perpendicular to the cable's axis, as illustrated in Figure 13.

Les légendes sur la Figure sont les mêmes que pour la Figure 1

Figure 13 – Disposition de blindage pour une mesure d’extrémité la plus éloignée

La pince absorbante est placée aussi près que possible de la plaque de réflexion pour une mesure d’extrémité la plus proche

For the most distant endpoint measurement, the absorbing clamp and the absorber must be swapped In both scenarios, the current probe of the absorbing clamp should be directed towards the absorber.

The output power ratio of the absorbing clamp to the generator is measured using a linear frequency sweep across the specified frequency range, matching the frequencies used during the calibration procedure This measurement can be conducted either directly with a network analyzer or by utilizing a discrete signal generator along with a measurement receiver.

To test a balanced (symmetrical) cable, it must be connected to the generator using an impedance matching balun In contrast, an unbalanced (coaxial) cable should be connected directly to the generator only when the generator impedance matches the nominal cable impedance If there is a mismatch, an impedance matching adapter is required.

For symmetrical cables, all pairs shall be individually measured

When testing the cable, it must be positioned in an aerial span, ensuring that no metallic objects or individuals are within 600 mm of the cable in any direction perpendicular to its axis, as illustrated in Figure 13.

For the keys to the figure, refer to Figure 1

Figure 13 – Shielding arrangements for a far end measurement

The absorbing clamp is placed as near as practically possible from the reflector plate for a near end measurement

For a far end measurement, the absorbing clamp and the absorber shall be interchanged In both cases, the current probe of the absorbing clamp shall be directed towards the absorber

The output power ratio from the absorbing clamp to the generator is assessed through a linear frequency sweep across the designated frequency range, using the same frequency points as in the calibration process Measurements can be conducted directly with a network analyzer or via a discrete signal generator paired with a measuring receiver.

Surface current is measured using a fixed clamp based on a frequency sweep Measurements are taken at both the nearest and farthest end positions The position yielding the worst measurement is used to determine the total measurement.

Expression

Les puissances mesurées (indiquées par le récepteur de mesure, équipement n° 4 de la

Figure 1) sont P 4,n (extrémité la plus proche) et P 4,f (extrémité la plus éloignée) respectivement En considérant uniquement le cas le plus défavorable de la puissance mesurée (P 4,n ou P 4,f ), nous avons:

P o est la puissance du générateur radio-fréquence; a m est l’affaiblissement en dB du montage de mesure; k m est le gain en tension du circuit d’adaptation d’impédance (1 si aucun gain n’est utilisé), ó     [ 4, n 4, f ]    

P est directement lu sur un analyseur de réseau comme a c(meas)

(c’est-à-dire la plus mauvaise parmi les mesures de l’extrémité la plus proche ou de l’extrémité la plus éloignée)

Les données d’étalonnage doivent être enregistrées pour corriger rapidement les résultats d’essai

The screen attenuation or coupling attenuation significantly varies at a specific frequency, even for repeated measurements on the same cable after handling Therefore, the worst-case value of coupling attenuation or screen attenuation should be specified over a certain frequency range This range must cover at least 200 MHz to smooth out normal frequency variations.

Compte rendu d’essai

Généralités

L’affaiblissement d’écran ou l’affaiblissement de couplage du câble en essai doit être au moins

The report must indicate that the screen attenuation or coupling attenuation is better than the measured value of the tested cable if it is 6 dB below the sensitivity of the test setup.

In the case of coaxial cables, the screen attenuation is typically frequency-independent The worst-case scenario corresponds to the maximum peak value across the entire frequency range.

Dans le cas de câbles symétriques, l’affaiblissement de couplage augmente normalement avec la fréquence d’environ 20 dB par décade

It is important not to measure the internal pairs of a multi-pair cable that are completely enclosed by other pairs along their entire length All other pairs should be measured, and the worst-case value for any pair should be considered as the coupling loss of the cable.

The surface current is measured on a swept frequency basis with a stationary clamp

Measurements are performed in both the near and far end position The position at which the worst measurement occurs is used for the full measurement

The measured powers (indicated by the measuring receiver, equipment n° 4 of Figure 1) are

P 4,n (near end) and P 4,f (far end) respectively Considering only the worst case of measured power (P 4,n or P 4,f ) we have:

The power of the radio frequency (r.f.) generator is denoted as \$P_o\$, while \$a_m\$ represents the attenuation in decibels (dB) of the measurement setup The voltage gain of the impedance matching circuit is indicated by \$k_m\$, which equals 1 if no circuit is utilized.

P is directly read on a network analyser as a c(meas) (i.e the worst of the near end or far end measurements)

Calibration data shall be stored to allow for fast correction of test results

Coupling attenuation and screening attenuation can fluctuate considerably at specific frequencies, particularly after handling the same cable multiple times To ensure accuracy, it is essential to specify the worst-case values of coupling or screening attenuation across a defined frequency range This range should encompass at least 200 MHz to account for typical frequency variations.

The cable under test must exhibit coupling or screening attenuation that is at least 6 dB lower than the measurement sensitivity of the test setup If this condition is not met, the report should indicate that the coupling or screening attenuation is superior to the measured value of the cable.

In the case of coaxial cables, the screening attenuation is normally independent of frequency

The worst-case value corresponds to the maximum peak value over the entire frequency range

In the case of symmetrical cables, the coupling attenuation normally increases with frequency by approximately 20 dB per decade

In a multi-pair cable, the inner pairs that are completely surrounded by other pairs throughout their entire length should not be measured Instead, all other pairs must be assessed, and the worst-case value among these pairs will be considered the coupling attenuation of the cable.

Si cela est nécessaire dans les spécifications des câbles appropriées, l’enregistrement de a c en fonction de la fréquence dans n’importe quelle gamme continue spécifiée de fréquences doit être rapporté.

Evaluation des résultats d’essai pour l’affaiblissement de couplage de câbles symétriques (informatif)

Il convient de soustraire la valeur du cas le plus défavorable, A dB, en dessinant une courbe dérivée des informations suivantes:

100 MHz 1 GHz: (A – 20 log f/100) dB ó f est la fréquence en MHz

Il convient de tracer la courbe jusqu’à ce que la première crête soit rencontrée Se reporter aux exemples de la Figure 14 et de la Figure 15

La valeur A dB correspond à l’intersection de la courbe et de l’axe Y.

Equipment

General

The test setup must achieve a noise floor that is at least 6 dB lower than the instrument reading necessary for accurate reporting For example, to measure coupling or screening attenuation up to about 90 dB, equipment with a dynamic range of at least 115 dB is essential, considering the full attenuation of a standard absorbing clamp and balun, if used Additionally, the precision of the equipment should be within ±1 dB.

The equipment must measure coupling or screening attenuation across the entire frequency range of 30 MHz to 1 GHz, unless otherwise specified in the relevant cable specifications.

The measurement set-up can be performed using a vector network analyser or alternatively a discrete signal generator and selective measuring receiver

A vertical metallic reflector plate, measuring at least 800 mm in both height and width, must be positioned directly in front of the generator This plate will feature a central hole designed to allow the cable under test to pass through.

The measurement setup for assessing the maximum radiated power at the near end, utilizing discrete instruments, is illustrated in Figure 1 This setup includes an absorbing clamp that operates within a minimum frequency range of 30 MHz to 1 GHz, as detailed in Annex D.

CISPR 16-1-4 An alternative absorbing clamp may be required if measurements are performed outside this frequency range;

This document is licensed to MECON Limited for internal use in Ranchi and Bangalore, as supplied by the Book Supply Bureau It includes a symmetrical adapter to match the output signal impedance of the asymmetric generator to the characteristic impedance of symmetrical cables, applicable only for symmetrical cables Additionally, it features a ferrite absorber with a minimum frequency range starting from 30 MHz.

To ensure optimal performance, the setup requires a minimum frequency of 1 GHz and a minimal attenuation of 10 dB Essential components include a reflection plate measuring at least 800 mm × 800 mm, a signal generator or vector network analyzer with matching impedance to the asymmetric port of the balun, and a power amplifier if needed for large dynamic ranges Additionally, a receiver with a calibrated step attenuator or network analyzer, coupled with a low-noise amplifier, may be necessary for extensive dynamic ranges An appropriate printer and load resistor networks that terminate characteristic nominal impedances in differential and common mode should also be included If equipment does not meet background noise level requirements, the dynamic range can be enhanced using an external amplifier, which must be properly shielded and connected to the reflection plate The amplifier's gain should be measured and adjusted in test results, taking care to avoid saturation An attenuator may be required at the receiver input during measurements, with its attenuation also measured and factored into the results.

0 Générateur de signaux, impédance de sortie Z 0

1 Câble en essai, impédance caractéristique nominale Z 1

2 Circuit externe du câble en essai, impédance Z 2

6 Transformateur de courant de la pince

7 Câble du récepteur de mesure (le même câble est utilisé pour les mesures et pour l’étalonnage)

8 Absorbeur (tube de ferrite) de la pince, pertes d’insertion >10 dB

9 Absorbeur (ou deuxième pince), pertes d’insertion >10 dB

10 Terminaison du câble en essai

11 Blindage du générateur de signaux et symétriseur si nécessaire pour les grandes plages dynamiques

Figure 1 – Mesure des ondes de surface au niveau de l’extrémité la plus proche de l’échantillon

This article outlines the necessary equipment and specifications for effective signal measurement and analysis Key components include a balun for impedance matching of unbalanced generator outputs to balanced cable characteristics, a ferrite absorber with a frequency range of 30 MHz to 1 GHz and a minimum attenuation of 10 dB, and a reflector plate measuring at least 800 mm × 800 mm Additionally, a signal generator or vector network analyzer with matching characteristic impedance is required, potentially coupled with a power amplifier for high dynamic range needs A calibrated receiver or vector network analyzer, possibly paired with a low noise amplifier, is also essential The setup should include printing facilities and load resistance networks to terminate common and differential mode impedances If noise floor requirements are not met, an external amplifier may enhance dynamic range, provided it is well screened and connected to the reflector plate Care must be taken to measure and correct the amplifier's gain, and an attenuator may be necessary to prevent equipment overload during measurements.

1 Cable under test, nominal characteristic impedance Z 1

2 Outer circuit of cable under test, impedance Z 2

6 Current transformer of the clamp

7 Measuring receiver cable (use the same in measurement and calibration)

8 Absorber (ferrite tube) of the clamp, insertion loss >10 dB

9 Absorber (or second clamp), insertion loss >10 dB

10 Termination of the cable under test

11 Shield of signal generator and balun if needed for very high dynamic range

Figure 1 – Measurement of surface waves at the near end of the sample

To measure symmetrical cables, a balun is required to convert the primary impedance of the asymmetric output from the signal generator into the nominal characteristic impedance of the symmetrical cable pair under test The minimum requirements for the balun are outlined in Table 1.

L’affaiblissement du symétriseur doit être maintenu aussi bas que possible parce qu’il limite la plage dynamique des mesures d’affaiblissement de couplage

Tableau 1 – Caractéristiques des performances du symétriseur (30 MHz à 1 GHz)

Perte d’insertion 3) (y compris les affaiblisseurs d'adaptation, le cas échéant) ≤ 10 dB

Puissance assignée Pour s’adapter à la puissance du générateur et de l’amplificateur (le cas échéant) Équilibre de tension de sortie 4) ≥ 50 dB de 30 MHz à 100 MHz

1) L’impédance primaire peut être différente si nécessaire pour s’adapter aux sorties de l’analyseur autres que 50 Ω

2) Les sorties symétriques des symétriseurs d’essai doivent être adaptées à l’impédance nominale de la paire de câbles symétriques Une résistance de 100 Ω doit être utilisée pour une terminaison de câbles de 120 Ω

3) L’affaiblissement opérationnel d’un symétriseur doit être soustrait mathématiquement des 3 mesures d’affaiblissement opérationnel avec 3 symétriseurs dos à dos

4) Mesuré selon les Recommandations ITU-T G.117 et O.9

The effective length of the sample during testing is constrained by the absorbing clamp and the ferrite tube, as illustrated in Figure 1 This length must be maintained at 600 cm ±.

5.2.2 Préparation de l’échantillon en essai

If the opening of the gripping clamp is smaller than the diameter of the sample being tested, it should be extended at both ends with smaller lines These extension lines must have significantly better screen attenuation than the sample under test Whenever possible, it is advisable to use lines with an external tubular conductor.

5.2.2.2.1 Préparation pour la mesure de l’affaiblissement de couplage

La longueur totale du câble doit être supérieure à 100 m La longueur du câble contrôlé (de la pince absorbante à l’absorbeur) doit être conforme à 5.2.1

Balun requirements

To measure symmetrical cables, a balun is essential for converting the unbalanced output's primary impedance from the signal generator to the balanced cable pair's nominal characteristic impedance The minimum specifications for the balun are outlined in Table 1.

The attenuation of the balun shall be kept as low as possible because it will limit the dynamic range of the coupling attenuation measurements

Table 1 − Balun performance characteristics (30 MHz to 1 GHz)

Insertion loss 3) (including matching pads if used) ≤ 10 dB

Return loss, bi-directional ≥6 dB

Power rating To accommodate the power of the generator and amplifier (if applicable) Output signal balance 4) ≥ 50 dB from 30 MHz to 100 MHz

≥ 30 dB from 100 MHz to 1 GHz

1) Primary impedance may differ if necessary to accommodate analyser outputs other than 50 Ω

2) Balanced outputs of the test baluns shall be matched to the nominal impedance of the symmetrical cable pair 100 Ω shall be used for termination of 120 Ω cabling

3) The operational attenuation of a balun shall be mathematically deduced from 3 operational attenuation measurements with 3 baluns back-to-back

4) Measured per ITU-T Recommendations G.117 and O.9.

Test sample

Tested cable length

The effective length of the test specimen is limited by the absorbing clamp and the ferrite tube, as shown in Figure 1 This length shall be 600 cm ± 10 cm.

Preparation of test sample

When the bore of the absorbing clamp is narrower than the diameter of the test specimen, it must be extended at both ends using smaller indicator lines These extension lines should provide significantly better screening attenuation than the test specimen itself Whenever feasible, lines featuring a tubular outer conductor are recommended for optimal performance.

5.2.2.2.1 Preparation for the measurement of the coupling attenuation

The entire length of the cable shall be at least 100 m The tested cable length (from absorbing clamp to the absorber) shall comply with 5.2.1

Analyseur de réseau ou générateur de signal

Figure 2 – Terminaison d’un câble symétrique blindé

A differential or common mode termination is essential for each pair at both the nearest and farthest ends of the cable, as illustrated in Figure 2 It is crucial that the terminations are properly shielded to ensure that test results remain accurate.

La valeur des résistances doit être la moitié de l’impédance caractéristique nominale du câble en essai

Les prises centrales des terminaisons doivent être connectées les unes aux autres Dans le cas de câbles blindés, les prises centrales doivent être connectées aux écrans

5.2.2.2.2 Préparation pour la mesure de l’affaiblissement d’écran (câbles blindés uniquement)

The total length of the cable must not exceed the length of the controlled cable plus the length of the plug and the absorber The length of the cable being tested (from the absorbing clamp to the absorber) must comply with section 5.2.1.

Shielded twisted pair cables are treated as a quasi-coaxial system, requiring that the conductors of all pairs be interconnected at both ends Additionally, all shields, including those of shielded pairs or quads, must also be connected to each other at both ends The shields should be connected around the entire circumference.

Network analyser generator or signal generator

Figure 2 – Termination of a screened symmetrical cable

Each cable pair requires differential and common mode termination at both the near and far ends, as illustrated in Figure 2 It is essential that these terminations are well-screened to ensure the accuracy of test results.

The value of the resistors shall be one half the nominal characteristic impedance of the cable under test

The centre taps of the terminations shall be connected together In the case of screened cables, the centre taps shall be connected to the screens

5.2.2.2.2 Preparation for the measurement of the screening attenuation (screened cables only)

Screened symmetrical cables function as a quasi-coaxial system, requiring the conductors of all pairs to be interconnected at both ends Additionally, all screens, including those of individually screened pairs or quads, must also be connected at both ends, ensuring a complete connection around the entire circumference.

Figure 3 – Préparation de l’échantillon en essai (câbles symétriques et multiconducteurs)

The quasi-coaxial system must be terminated at its nominal characteristic impedance, ensuring proper shielding to avoid skewed test results Impedance can be measured using a time-domain reflectometer (TDR) with a maximum rise time of 200 ps or through the method outlined below Additionally, an impedance adapter is required to match the generator's impedance with that of the quasi-coaxial system.

One end of the prepared sample is connected to a network analyzer, calibrated for impedance measurements at the reference plane of the connector interface The test frequency should be approximately at the point where the sample length is 1/8 of the wavelength (\$λ\$).

≈ × ó f test est la fréquence d’essai; c est la vitesse de la lumière, 3 × 10 8 m/s;

L sample est la longueur d’un échantillon; ε r 1 est la constante diélectrique du système interne

L’échantillon est en court-circuit à l’extrémité la plus éloignée L’impédance Z short est mesurée

L’échantillon est laissé ouvert à l’endroit ó il était en court-circuit L’impédance Z open est mesurée

L’impédance du système quasi coaxial Z 1 se calcule comme suit: open short

Si l’impédance du système interne Z 1 , et donc la résistance de charge R 1 , est inférieure à 50 Ω

Connector Well screened load resistor R 1

Figure 3 – Preparation of test sample (symmetrical and multi conductor cables)

The quasi coaxial system must be terminated with its nominal characteristic impedance to ensure accurate test results, which requires proper screening Impedance can be measured using a TDR with a maximum rise time of 200 ps or through an alternative method Additionally, an impedance matching adapter is essential to align the generator's impedance with that of the quasi coaxial system.

The prepared sample is connected to a calibrated network analyser for impedance measurements at the connector interface reference plane The test frequency is set to approximately correspond to a wavelength (\$λ\$) such that the sample length is 1/8 of \$λ\$.

≈ × where f test is the test frequency; c is the velocity of light, 3 × 10 8 m/s;

L sample is the length of sample; ε r 1 is the dielectric constant of the inner system

The sample is short circuited at the far end The impedance Z short is measured

The sample is left open at the same point where it was shorted The impedance Z open is measured

The impedance of the quasi coaxial system Z 1 is calculated as: open short

If the impedance of the inner system Z 1 and subsequently the load resistor R 1 is less than 50 Ω

(the generator impedance), the formulas below are used:

Le gain en tension k m du circuit est: s 1 s p p

Si l’impédance du système interne Z 1 , et donc la résistance R 1 , est supérieure à 50 Ω

The voltage gain k m of the circuit is: s 1 s p p

If the impedance of the inner system Z 1 and subsequently R 1 is greater than 50 Ω (the generator impedance) the formulas below are used:

Le gain en tension k m du circuit est:

The total length of the cable must not exceed the length of the tested cable plus the length of the plug and the absorber The length of the controlled cable, from the absorbing clamp to the absorber, must comply with section 5.2.1.

Le câble doit être terminé sur son impédance caractéristique nominale La terminaison doit être correctement blindée de telle sorte que les résultats des essais ne soient pas faussés

5.3.1 Affaiblissement du montage de mesure

L’affaiblissement du montage de mesure est dộterminộ en commenỗant par mesurer la perte composite, puis en corrigeant la perte de réflexion dans le montage d’étalonnage, se reporter à la Figure 6

De cette manière, on trouve la réponse de la pince absorbante à la puissance d’une onde de surface incidente

The loss of reflection in the measurement setup, caused by the mismatch between the surface wave impedance, $ Z_2 $, and the clamp impedance, is not considered in the measurement The error resulting from neglecting this impedance can be deemed negligible.

Figure 5 − Impedance matching for Z 1 >50 Ω The voltage gain, k m , of the circuit is:

The cable shall be terminated with its nominal characteristic impedance The termination shall be well screened, so that the test results are not falsified.

Calibration procedure

Test set-up

Test report

Tiêu đề	Cease 62153-4-5:2006
Chuyên ngành	Electromagnetic compatibility
Thể loại	standard
Năm xuất bản	2006

Định dạng
Số trang	58
Dung lượng	0,98 MB