Radio-frequency disturbance characteristics - Limits and methods of measurement engines - Radio disturbance characteristics - Limits and methods of measurement for the protection of of
Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC Guide 98-3 and ISO/IEC Guide 99, as well as the following apply
The definitions and terms related to uncertainty are outlined in ISO/IEC Guide 98-3, while general metrology definitions can be found in ISO/IEC Guide 99 This article does not reiterate the relevant basic definitions.
The MIU parameter characterizes the dispersion of values attributed to the measurand, reflecting the influence of all relevant input quantities related to the measurement instrumentation.
Symbols
For the purposes of this document, the symbols given in Clauses 3, 5, 6, 7 and 8 apply, as well as the following
The input quantity \( x_i \) is estimated as \( \hat{x}_i \) with a correction \( \delta x_i \) for accuracy The standard uncertainty of \( x_i \) is denoted as \( u(x_i) \), while the sensitivity coefficient is represented by \( c_i \) The measurement result \( y \), which is the corrected estimate of the measurand, is expressed in logarithmic units such as dB(àV/m) The combined standard uncertainty of \( y \) is indicated as \( u_c(y) \) in dB.
U(y) expanded uncertainty of y, in dB
U cispr CISPR criterion for the expanded MIU evaluated in this standard for each specific measurement method, in dB
U lab expanded MIU determined by the test laboratory, in dB k coverage factor a + upper abscissa of a probability distribution a - lower abscissa of a probability distribution
E disturbance electric field strength, in dB(àV/m)
I disturbance current, in dB(àA)
P disturbance power, in dB(pW)
V disturbance voltage, in dB(àV)
3.2.3 Symbols for input quantities common to all disturbance measurements a c attenuation of the connection between the receiver and the ancillary equipment
(e.g AMN, antenna etc.), in dB δ M correction for the error caused by mismatch, in dB
The receiver voltage reading, expressed in dB(àV), is subject to several corrections: δV sw accounts for inaccuracies in the sine wave voltage, δV pa addresses imperfections in the pulse amplitude response, δV pr corrects for the pulse repetition rate response, and δV nf compensates for the impact of the receiver's noise floor, all measured in dB.
Abbreviations
For the purposes of this document, the following abbreviations apply
NOTE Abbreviations not shown here are defined at their first occurrence in this document
AE associated equipment (equipment connected to the AE port of the ancillary equipment; ancillary equipment is a transducer, e.g an AAN; see definitions in CISPR 16-2-1)
FSOATS free-space OATS (refer to CISPR16-1-4)
LPDA logarithmic periodic (log-periodic) dipole array
OATS open area test site
VSWR voltage standing wave ratio
4 Compliance criterion for the MIU
General
MIU shall be taken into account, as described in this clause, when determining compliance or non-compliance of an EUT with a disturbance limit
The Measurement Uncertainty (MIU) for a test laboratory must be assessed for the measurements specified in Clauses 5 through 8, considering all relevant input quantities The standard uncertainty \( u(x_i) \) in decibels (dB) and the sensitivity coefficient \( c_i \) should be determined for each estimated quantity \( x_i \) Additionally, the combined standard uncertainty \( u_c(y) \) for the estimate \( y \) of the measurand must be calculated accordingly.
The expanded MIU U lab for a test laboratory shall be calculated for each type of measurement using
!CDNE coupling decoupling network for emission measurement"
If the value of U lab is less than or equal to U cispr as shown in Table 1, the test report can either specify the value of U lab or indicate that U lab is less than U cispr.
If U lab exceeds U cispr of Table 1, then the test report shall contain the value of U lab (in dB) for the measurement instrumentation actually used for the measurements
NOTE Equation (2) means that a coverage factor k = 2 is applied that yields approximately a 95 % level of confidence for the near-normal distribution typical of most measurement results
Conducted disturbance at mains port using AMN (9 kHz to 150 kHz) 3,8 dB B.1
(150 kHz to 30 MHz) 3,4 dB B.2 Conducted disturbance at mains port using voltage probe (9 kHz to 30 MHz) 2,9 dB B.3
Conducted disturbance at telecommunication port using AAN (150 kHz to 30 MHz) 5,0 dB B.4
Conducted disturbance at telecommunication port using CVP (150 kHz to 30 MHz) 3,9 dB B.5
Conducted disturbance at telecommunication port using CP (150 kHz to 30 MHz) 2,9 dB B.6
Disturbance power (30 MHz to 300 MHz) 4,5 dB C.1
The electric field strength at an Open Area Test Site (OATS) or in a Semi-Anechoic Chamber (SAC) ranges from 30 MHz to 1,000 MHz, measuring 6.3 dB according to sections D.1 to D.4 Additionally, the radiated disturbance in a Fully Anechoic Room (FAR) within the same frequency range of 30 MHz to 1,000 MHz is recorded at 5.3 dB, as noted in sections D.5 to D.6 For frequencies between 1 GHz and 6 GHz, the electric field strength for radiated disturbance in a FAR is 5.2 dB, referenced in section E.1.
Radiated disturbance (electric field strength in a FAR) (6 GHz to 18 GHz) 5,5 dB E.2
The values of U cispr are determined based on the expanded uncertainties outlined in the annexes, which account for uncertainties related to the specific measurement quantities In cases where multiple values are presented in the annexes, the U cispr value is selected as the maximum from those listed, such as the highest value found in Tables D.1 through D.4.
In the frequency range below 1 GHz, U cispr values were determined using a quasi-peak detector, with the assumption that the average and r.m.s.-average detector values would not surpass these figures For frequencies above 1 GHz, U cispr values were calculated using a peak detector.
This clause does not override the necessity for measurement instrumentation to adhere to the specifications outlined in the CISPR 16-1 series, nor does it eliminate the obligation to comply with CISPR 16-4-3.
Compliance assessment
Compliance or non-compliance with a disturbance limit shall be determined in the following manner
If U lab is less than or equal to U cispr of Table 1, then:
– compliance is deemed to occur if no measured disturbance level exceeds the disturbance limit;
– non-compliance is deemed to occur if any measured disturbance level exceeds the disturbance limit
Conducted disturbance at mains port using CDNE (30 MHz to 300 MHz) 3,8 dB B.7
If U lab is greater than U cispr of Table 1, then:
– compliance is deemed to occur if no measured disturbance level, increased by (U lab − U cispr ), exceeds the disturbance limit;
– non-compliance is deemed to occur if any measured disturbance level, increased by (U lab − U cispr ), exceeds the disturbance limit
NOTE For the compliance assessment procedure described in this subclause, both the measured disturbance level and the disturbance limit are expressed in logarithmic units, e.g dB(μV/m)
Conducted disturbance measurements at a mains port using an AMN (see
5.1.1 Measurand for measurements using an AMN
V Unsymmetric voltage, in dB(àV), measured at the EUT port of the AMN relative to the reference ground plane
5.1.2 Symbols of input quantities specific to measurements using an AMN
The voltage division factor of the AMN is represented in dB as F AMN, while δF AMNf accounts for frequency interpolation errors in the voltage division factor Additionally, δD mains corrects for errors due to mains disturbances, and δV env addresses environmental effects Lastly, δZ AMN provides a correction for the imperfections in AMN impedance, all expressed in dB.
5.1.3 Input quantities to be considered for conducted disturbance measurements at a mains port using an AMN
– Attenuation of the connection between AMN and receiver
• Receiver sine-wave voltage accuracy
• Receiver pulse response variation with repetition frequency
– Mismatch effects between AMN receiver port and receiver
Conducted disturbance measurements at a mains port using a VP (see also B.2)
5.2.1 Measurand for measurements using a VP
V Unsymmetric voltage, in dB(àV), measured at the EUT power port – loaded with an impedance of 1 500 Ω – relative to the reference ground
5.2.2 Symbols of input quantities specific to measurements using a VP
The Voltage Division Factor (VDF) of the voltage probe is expressed in dB as F VP Additionally, δF VPf accounts for frequency interpolation errors in the VDF, while δD mains corrects for errors due to mains disturbances The correction for environmental effects is represented by δ V env, and δ Z VP addresses the inaccuracies stemming from imperfect voltage probe impedance Lastly, δZ mains corrects for errors related to mains impedance discrepancies.
5.2.3 Input quantities to be considered for conducted disturbance measurements at a mains port using a VP
– Attenuation of the connection between VP and receiver
• Receiver sine-wave voltage accuracy
• Receiver pulse response variation with repetition frequency
– Mismatch effects between VP receiver port and receiver
– Effect of mains impedance when compared with AMN
Conducted disturbance measurements at a telecommunication port using an
The term "asymmetric artificial network (AAN)" is defined in CISPR 16-1-2 and is also known as an impedance stabilization network (ISN) in CISPR 22 This designation as a Y-network distinguishes it from V- and Δ-networks.
5.3.1 Measurand for measurements using an AAN
V Asymmetric (common mode) voltage, in dB(àV), measured at the EUT port of the AAN referred to the reference ground plane
5.3.2 Symbols of input quantities specific for measurements using an AAN
The Voltage Division Factor (VDF) of the AAN is expressed in dB as \$F AAN\$ Additionally, the correction for the VDF frequency interpolation error is denoted as \$\delta F AANf\$ in dB The correction for disturbances from the AE is represented by \$\delta D AE\$ in dB Furthermore, the environmental effect is accounted for with the correction \$\delta V env\$ in dB The correction for the imperfect longitudinal conversion loss of the AAN is indicated as \$\delta a LCL\$ in dB, while the correction for the imperfect asymmetric (common mode) impedance of the AAN is represented by \$\delta Z AAN\$ in dB.
5.3.3 Input quantities to be considered for conducted disturbance measurements at a telecommunication port using an AAN
– Attenuation of the connection between AAN and receiver
• Receiver sine-wave voltage accuracy
• Receiver pulse response variation with repetition frequency
– Mismatch effects between AAN receiver port and receiver
– Asymmetric impedance of the AAN
– Longitudinal conversion loss (LCL) of the AAN
– Effect of disturbances from the AE
Conducted disturbance measurements at a telecommunication port using a
5.4.1 Measurand for measurements using a CVP
V Asymmetric (common mode) voltage, in dB(àV), measured at the telecommunication port referred to the reference ground
5.4.2 Symbols of input quantities specific for measurements using a CVP
The CVP Voltage Division Factor (VDF) is expressed in dB and is subject to various corrections These include the frequency interpolation error correction (δF CVPf), the disturbance error correction from the AE (δD AE), and the environmental effect correction (δ V env) Additionally, adjustments are made for the cable's position within the CVP aperture (δ F c pos) and its radius (δ F c rad), both of which impact the VDF Furthermore, corrections for imperfect termination of the telecommunication port by the AE (δZ AE) and the CVP load impedance (δZ CVP) are also necessary.
5.4.3 Input quantities to be considered for conducted disturbance measurements at a telecommunication port using a CVP
– Attenuation of the connection between CVP and receiver
• Receiver sine-wave voltage accuracy
• Receiver pulse response variation with repetition frequency
– Effect of cable position inside the CVP aperture on VDF
– Effect of cable radius on VDF
– Effect of disturbances from the AE
– Effect of the AE impedance when compared with AAN
– Mismatch effects between CVP receiver port and receiver
Conducted disturbance measurements at a telecommunication port using a
5.5.1 Measurand for measurements using a CP
I Asymmetric (common mode) current, in dB(àA), measured on the cable connected to the telecommunication port of the EUT
5.5.2 Symbols of input quantities specific for measurements using a CP
The transfer admittance of the CP is represented in dB(S) as \$Y_T\$ Corrections are applied for various factors: \$\delta Y\$ accounts for the frequency interpolation error of the CP transfer admittance, while \$\delta D\$ addresses disturbances from the AE Additionally, \$\delta I\$ corrects for environmental effects, \$\delta Z\$ compensates for errors due to the CP insertion impedance, and \$\delta Z_{AE}\$ adjusts for imperfect termination of the telecommunication port by the AE, all expressed in dB.
5.5.3 Input quantities to be considered for conducted disturbance measurements at a telecommunication port using a CP
– Attenuation of the connection between CP and receiver
– Transfer admittance of the CP
– CP transfer admittance frequency interpolation
• Receiver sine-wave voltage accuracy
• Receiver pulse response variation with repetition frequency
– Mismatch effects between CP and receiver
– Effect of the CP insertion impedance
– Effect of disturbances from the AE
– Effect of the termination impedance of the telecommunication cable by the AE
5.6 Conducted disturbance measurements using a CDNE (see also B.7)
5.6.1 Measurand for measurements using a CDNE
V Asymmetric (common-mode) disturbance voltage, in dB(àV), measured on the connection lead of the EUT through a CDNE referred to reference ground
5.6.2 Symbols of input quantities specific to CDNE measurements
F CDNE Voltage division factor (VDF) of the CDNE, in dB
F CDNE δ Correction for VDF frequency interpolation error, in dB
Z CDNE δ Correction for the imperfect common mode impedance of the CDNE, in dB
D amb δ Correction for the effect of ambient disturbances, in dB
The clamp factor, as defined in CISPR 16-1-3, is crucial for accurate measurements The correction for the clamp factor frequency interpolation error, denoted as \$\delta F\$, is expressed in decibels (dB) Additionally, \$\delta D\$ represents the correction for errors caused by mains disturbances, also measured in dB Lastly, \$\delta P\$ accounts for the environmental effects, providing another necessary correction in dB.
6.3 Input quantities to be considered for disturbance power measurements
– Attenuation of the connection between absorbing clamp and receiver
– Clamp factor (original) of the absorbing clamp (as defined in CISPR 16-1-3)
• Receiver sine-wave voltage accuracy
• Receiver pulse response variation with repetition frequency
– Mismatch effects between absorbing clamp receiver port and receiver
6 Disturbance power measurements (see also C.1)
Measurand for disturbance power measurements
P Disturbance power, in dB(pW), measured on a power lead at the clamp position of maximum indication of emission
Symbols of input quantities specific for disturbance power measurements
F AC Clamp factor (original) of the absorbing clamp, in dB(pW/àV)
V env δ Correction for the effect of the environment, in dB
5.6.3 Input quantities to be considered for conducted disturbance measurements at a mains port using a CDNE
– Cable attenuation between CDNE and receiver
• Receiver sine wave voltage accuracy
• Receiver pulse repetition rate response
– Mismatch effects between CDNE receiver port and receiver
" grounding δV Correction for the effect of imperfect grounding, in dB
Input quantities to be considered for disturbance power measurements
– Attenuation of the connection between absorbing clamp and receiver
– Clamp factor (original) of the absorbing clamp (as defined in CISPR 16-1-3)
• Receiver sine-wave voltage accuracy
• Receiver pulse response variation with repetition frequency
– Mismatch effects between absorbing clamp receiver port and receiver
6 Disturbance power measurements (see also C.1)
6.1 Measurand for disturbance power measurements
P Disturbance power, in dB(pW), measured on a power lead at the clamp position of maximum indication of emission
6.2 Symbols of input quantities specific for disturbance power measurements
F AC Clamp factor (original) of the absorbing clamp, in dB(pW/àV)
V env δ Correction for the effect of the environment, in dB
5.6.3 Input quantities to be considered for conducted disturbance measurements at a mains port using a CDNE
– Cable attenuation between CDNE and receiver
• Receiver sine wave voltage accuracy
• Receiver pulse repetition rate response
– Mismatch effects between CDNE receiver port and receiver
" grounding δV Correction for the effect of imperfect grounding, in dB
– Attenuation of the connection between antenna and receiver
• Receiver sine-wave voltage accuracy
• Receiver pulse response variation with repetition frequency
– Mismatch effects between antenna port and receiver
– Antenna factor variation with height
– Site attenuation of the test site
– Separation between EUT and measurement antenna
– Height of table supporting the EUT
– Effect of setup table material supporting the EUT
Ambient noise significantly impacts measurements at an Open Area Test Site (OATS) Corrections must be applied for various factors: the distance of the antenna, denoted as \$\delta d\$ in dB, accounts for any imperfections in antenna placement Additionally, the height of the test table above the ground plane requires a correction, represented as \$\delta h\$ in dB Lastly, the effect of ambient noise itself is quantified by \$\delta E_{amb}\$ in dB, ensuring accurate assessments in testing environments.
7.1.3 Input quantities to be considered for radiated disturbance measurements at an
7 Radiated disturbance measurements in the frequency range 30 MHz to
Radiated disturbance measurements at an OATS or in a SAC (see also D.1)
7.1.1 Measurand for radiated disturbance measurements at an OATS or in a SAC
The maximum electric field strength, expressed in dB(µV/m), is measured in both horizontal and vertical polarizations at a specified horizontal distance from the Equipment Under Test (EUT) These measurements are taken at a height ranging from 1 m to 4 m above a reflecting ground plane, with the EUT being rotated 360° in azimuth.
7.1.2 Symbols of input quantities specific for radiated disturbance measurements
The antenna factor, measured in dB(1/m), is influenced by several correction factors These include the correction for frequency interpolation error (\$δF_{af}\$), height variation (\$δF_{ah}\$), directivity (\$δF_{adir}\$), and phase center location (\$δF_{aph}\$) Additionally, adjustments for cross-polarization response (\$δF_{acp}\$) and unbalance (\$δF_{abal}\$) are necessary Furthermore, corrections for imperfect normalized site attenuation (\$δA_{N}\$) and the impact of setup table material on measurement results (\$δA_{NT}\$) are also critical for accurate antenna performance assessment.
• Receiver sine-wave voltage accuracy
• Receiver pulse response variation with repetition frequency
– Mismatch effects between antenna port and receiver
– Antenna factor variation due to FAR influence
– Site attenuation of the test site (FAR)
– Separation between EUT and measurement antenna
– Effect of setup table material supporting the EUT
– Effect of imperfect table height
7.2.3 Input quantities to be considered for radiated disturbance measurements in a
– Attenuation of the connection between antenna and receiver
Radiated disturbance measurements in a FAR (see also D.2)
7.2.1 Measurand for radiated disturbance measurements in a FAR
E Maximum electric field strength, in dB(àV/m), measured in horizontal and vertical polarizations at the specified horizontal distance from the EUT which is rotated 360° in azimuth
7.2.2 Symbols of input quantities specific for radiated disturbance measurements
The antenna factor, measured in dB(1/m), is influenced by several corrections: δF af accounts for frequency interpolation errors, δF ah addresses variations due to FAR influence, and δF adir corrects for directivity Additionally, δF aph adjusts for the phase center location, while δF acp considers cross-polarization response and δF abal addresses unbalance Corrections for site attenuation include δA N for imperfect normalization and δA NT for the impact of setup table material Finally, δd and δh correct for inaccuracies in antenna distance and table height, respectively.
– Effect of preamplifier gain instability
– Attenuation of the connection between preamplifier output and receiver
– Receiver sine-wave voltage accuracy
– Mismatch effects between antenna port and preamplifier input
– Mismatch effects between preamplifier output and receiver
– Site voltage standing wave ratio of the test site (FAR)
– Separation between EUT and measurement antenna
– Effect of setup table material supporting the EUT
– Effect of imperfect table height
8.3 Input quantities to be considered for radiated disturbance measurements in a FAR
– Attenuation of the connection between antenna port and preamplifier input
8 Radiated disturbance measurements in the frequency range 1 GHz to 18 GHz (see also E.1)
Measurand for radiated disturbance measurements in a FAR (FSOATS)
NOTE 1 A FAR is a practical approximation of an FSOATS (see CISPR 16-1-4)
The maximum electric field strength, expressed in dB(µV/m), is measured in both horizontal and vertical polarizations at the designated antenna height and specified horizontal distance from the Equipment Under Test (EUT), which is rotated 360° in azimuth.
NOTE 2 Antenna height variation is applied if the EUT is not encompassed by the antenna vertical-plane beamwidth.
Symbols of input quantities specific for radiated disturbance measurements
G p Preamplifier gain δ G p Correction for instability of preamplifier gain, in dB
The antenna factor, measured in dB(1/m), is influenced by several correction factors These include the correction for antenna factor interpolation error (\$δF_{af}\$), the correction for antenna directivity (\$δF_{adir}\$), and the correction for the phase center location of the antenna (\$δF_{aph}\$) Additionally, the correction for cross-polarization response (\$δF_{acp}\$) and the voltage standing wave ratio at the site (\$δS_{VSWR}\$) also play significant roles Other important corrections involve the effects of the setup table material on measurement results (\$δA_{NT}\$), as well as adjustments for imperfect antenna distance (\$δd\$) and table height (\$δh\$).
Input quantities to be considered for radiated disturbance measurements in a
– Attenuation of the connection between antenna port and preamplifier input
8 Radiated disturbance measurements in the frequency range 1 GHz to 18 GHz (see also E.1)
8.1 Measurand for radiated disturbance measurements in a FAR (FSOATS)
NOTE 1 A FAR is a practical approximation of an FSOATS (see CISPR 16-1-4)
The maximum electric field strength, expressed in dB(µV/m), is measured in both horizontal and vertical polarizations at the designated antenna height and specified horizontal distance from the Equipment Under Test (EUT), which is rotated 360° in azimuth.
NOTE 2 Antenna height variation is applied if the EUT is not encompassed by the antenna vertical-plane beamwidth
8.2 Symbols of input quantities specific for radiated disturbance measurements
G p Preamplifier gain δ G p Correction for instability of preamplifier gain, in dB
The antenna factor, measured in dB(1/m), is influenced by several correction factors These include the correction for antenna factor interpolation error (\$δF_{af}\$), the correction for antenna directivity (\$δF_{adir}\$), and the correction for the phase center location of the antenna (\$δF_{aph}\$) Additionally, the correction for cross-polarization response (\$δF_{acp}\$) and the voltage standing wave ratio at the site (\$δS_{VSWR}\$) also play significant roles Other important corrections involve the impact of the setup table material on measurement results (\$δA_{NT}\$), as well as adjustments for imperfect antenna distance (\$δd\$) and table height (\$δh\$).
Basis for U cispr values in Table 1, general information and rationale for input quantities common to all measurement methods
Annexes A through E outline the approach used to determine U cispr for the measurement methods specified in the CISPR 16-2 series
Each annex begins with the model equation for the measurand, which encapsulates the primary sources of Measurement Uncertainty (MIU) linked to the measurement instrumentation chain This equation, derived from the measurement model, offers a mathematical definition of the measurand.
The article presents tables that outline the estimated values of each input quantity used to calculate the U cispr values in Table 1 of Clause 4 It is important to note that the values in the tables found in Annexes B through E are merely examples based on the CISPR 16-1 series requirements and do not represent mandatory requirements.
All assumptions for determining estimated values are thoroughly documented and referenced with superscripts Superscripts labeled "A" indicate sources of Measurement Uncertainty (MIU) that are applicable to multiple measurement methods, with detailed documentation found in section A.2 Superscripts "B" through "E" denote MIU sources specific to individual measurement methods, and their corresponding assumptions are outlined in the relevant annex subclauses following the tables Additionally, notes provided after comments offer further guidance for test laboratories facing data or situations that differ from those assumed in this document.
The uncertainty for each input quantity estimate \( x_i \) in Annexes B through E represents the maximum likely value within the table's frequency range, ensuring consistency with the measuring apparatus specifications outlined in the CISPR 16-1 series standards.
Measurement uncertainty terms and their definitions, along with guidance on evaluating and expressing measurement uncertainty, can be found in references [2] to [5] of the bibliography and in ISO/IEC Guide 98-3.
The standard uncertainty \( u(x_i) \) is determined by dividing the uncertainty value associated with \( x_i \) by a factor that reflects the probability distribution of the input quantity and the confidence level For U-shaped, rectangular, or triangular distributions, where \( X_i \) is estimated to lie between \( (x_i - a_-) \) and \( (x_i + a_+) \) with 100% confidence, \( u(x_i) \) is set to 2, 3, or 6 respectively, with \( a = (a_+ + a_-)/2 \) representing the half-width of the distribution In the case of a normal distribution, the divisor is 2 for a 95% confidence level (twice the experimental standard deviation) and 1 for a 68% confidence level (the experimental standard deviation) For non-symmetrical distributions, if significant, the value \( \delta x_i = c_i (a_+ - a_-)/2 \) should be used to correct the measurement result; if insignificant, the average of the two limits is acceptable.
A correction compensates for systematic errors and can be identified through calibration reports or internal evaluations of the test laboratory When the magnitude of a correction is unknown and equally likely to be positive or negative, it is assumed to be zero All known corrections are applied according to the model, as indicated in the model equations preceding the tables Additionally, each correction functions as an input quantity with an associated uncertainty.
The assumptions leading to the values in the tables of Annexes B through E may not be appropriate for a particular test laboratory When a test laboratory evaluates its expanded MIU
In evaluating its measuring system, a test laboratory should consider equipment characteristics, validation data from test sites, calibration data quality, and internal measurement procedures It may be beneficial for the laboratory to assess uncertainties across specific subranges of the frequency spectrum, especially when a key input quantity shows significant variation throughout the entire frequency range.
The frequency step size of a measuring receiver is not considered a source of uncertainty, as it can be minimized by reducing the step size or eliminated through final frequency adjustments Guidance for selecting the step size is provided in CISPR 16-2-1, CISPR 16-2-2, and CISPR 16-2-3, with final adjustments typically made at critical frequencies related to disturbance limits If neither reduction of step size nor final adjustments are implemented, it may need to be treated as an additional input quantity, akin to antenna height and EUT azimuth adjustments in radiated emission measurements Further discussions on these effects can be found in CISPR 16-4-1.
Sensitivity coefficients are the partial derivatives of the model equations for measurands, specifically the left-hand sides of these equations, concerning the varying input quantities Given that all model equations are linear in logarithmic units, the sensitivity coefficients \( c_i \) are derived accordingly.
1 (c i = 1) and are therefore not listed in the tables
Repeatability of cable connections is considered negligibly small compared to the other sources of uncertainty Therefore it is not included as a relevant input quantity
A.2 Rationale for the estimates of input quantities common to all disturbance measurements (“A” comments)
The following comments are applicable to the input quantities that are common to more than one measurement method, being those marked with the superscript “A” (e.g A1) )
A1) Receiver readings will vary for reasons that include measuring system instability and meter scale interpolation errors
The estimate of V r is the mean of many readings (sample size larger than 10) of a stable signal, with a standard uncertainty given by the experimental standard deviation of the mean (k = 1)
When estimating attenuation (\$a_c\$) from manufacturer data for cables or attenuators, it is appropriate to assume a rectangular probability distribution with a half-width corresponding to the specified tolerance on the attenuation In cases where a cable and attenuator are connected in tandem, and data is available for both, \$a_c\$ consists of two components, each represented by its own rectangular probability distribution.
NOTE 2 This uncertainty contribution is not applicable if the absorbing clamp is calibrated together with the cable
An estimate of the attenuation coefficient (\$a_c\$) for the connection between the receiver and various components such as the AMN, AAN, CDNE, CP, CVP, VP, absorbing clamp, or antenna is typically provided in a calibration report This report also includes an expanded uncertainty and a coverage factor.
In uncertainty budgets, a normal distribution function is typically employed unless specified otherwise in the tables To obtain a more accurate estimate of this uncertainty contribution, utilizing a vector network analyzer for cable calibration is recommended.
A3) An estimate of the correction δV sw for receiver sine-wave voltage accuracy is assumed to be available from a calibration report, along with an expanded uncertainty and a coverage factor