Figure 6 – Typical antenna positions for alternative test site – Vertical polarization NSA measurements ...24 Figure 7 – Typical antenna positions for alternative test site – Horizontal
Terms and definitions
3.1.1 antenna that part of a transmitting or receiving system that is designed to radiate or to receive electromagnetic waves in a specified way
NOTE 1 In the context of this standard, the balun is a part of the antenna
NOTE 2 This term covers various devices such as the wire antenna, free-space-resonant dipole, hybrid antenna and horn antenna
3.1.2 balun passive electrical network for the transformation from a balanced to an unbalanced trans- mission line or device or vice versa
CALTS open area test site with metallic ground plane and tightly specified site attenuation performance in horizontal and vertical E-field (electric field) polarization
NOTE 1 A CALTS is used for determining the free-space antenna factor of an antenna
Site attenuation measurements from a CALTS are utilized to compare with those from a compliance test site, enabling an assessment of the compliance test site's performance.
CMAD device that may be applied on cables leaving the test volume in radiated emission measurements to reduce the compliance uncertainty
COMTS environment that assures valid, repeatable measurement results of the disturbance field strength from equipment under test for comparison to a compliance limit
The cross-polar response measures how effectively an antenna rejects cross-polarized fields This evaluation occurs when the antenna is rotated within a linearly polarized electromagnetic field that maintains uniform phase and amplitude across its aperture.
FAR shielded enclosure, the internal surfaces of which are lined with radio-frequency-energy absorbing material (i.e RF absorber) that absorbs electromagnetic energy in the frequency range of interest
A free-space-resonant dipole wire antenna consists of two straight collinear conductors of equal length, positioned end to end with a small gap between them Each conductor is approximately a quarter-wavelength long, ensuring that at the specified frequency, the input impedance measured across the gap is purely real when the dipole is situated in free space.
In this standard, the wire antenna connected to the balun is referred to as the "test antenna," and it is also known as a "tuned dipole."
The hybrid antenna combines a conventional wire-element log-periodic dipole array (LPDA) with an extended boom at the open-circuit end, incorporating a broadband dipole such as a biconical or bow-tie design This configuration allows the infinite balun (boom) of the LPDA to function as a voltage source for the broadband dipole, enhancing its performance.
A common-mode choke is commonly employed at the boom's end to reduce unintended RF currents on the coaxial cable's outer conductor, preventing them from reaching the receiver.
Insertion loss refers to the reduction in signal strength that occurs when a device is inserted into a transmission line It is quantified as the ratio of the voltages measured immediately before and after the device's insertion, providing a clear indication of the device's impact on the transmission line's performance.
It is equal to the inverse of the transmission S-parameter, |1/S 21 |
The low-uncertainty antenna, specifically a robust biconical or log-periodic dipole array (LPDA) antenna, is designed to meet the stringent balance and cross-polar performance requirements of this standard It features an antenna factor with an uncertainty of less than ±0.5 dB, making it suitable for accurately measuring electric field strength at a specified point in space.
NOTE It is further described in A.2.3
3.1.12 quasi-free space test-site facility for radiated emission measurements, or antenna calibration, that is intended to achieve free-space conditions
Unwanted reflections from the surroundings are kept to a minimum in order to satisfy the site acceptance criterion applicable to the radiated emission measurement or antenna calibration procedure being considered
3.1.13 reflection coefficient ratio of a common quantity to both the reflected and incident travelling waves
The voltage reflection coefficient represents the ratio of the complex voltage of the reflected wave to that of the incident wave, and it is equivalent to the scattering parameter S11.
FAR shielded enclosure, the internal surfaces of which are lined with radio-frequency-energy absorbing material (i.e RF absorber) that absorbs electromagnetic energy in the frequency range of interest
A free-space-resonant dipole wire antenna consists of two straight collinear conductors of equal length, positioned end to end with a small gap between them Each conductor is approximately a quarter-wavelength long, ensuring that at the specified frequency, the input impedance measured across the gap is purely real when the dipole is situated in free space.
In this standard, the wire antenna connected to the balun is referred to as the "test antenna," and it is also known as a "tuned dipole."
The hybrid antenna combines a conventional wire-element log-periodic dipole array (LPDA) with an extended boom at the open-circuit end, incorporating a broadband dipole such as a biconical or bow-tie design This configuration allows the infinite balun (boom) of the LPDA to function as a voltage source for the broadband dipole, enhancing its performance.
A common-mode choke is commonly employed at the boom's end to reduce unintended RF currents on the coaxial cable's outer conductor, preventing them from reaching the receiver.
Insertion loss refers to the reduction in signal strength that occurs when a device is inserted into a transmission line It is quantified as the ratio of the voltages measured immediately before and after the device's insertion, providing a clear indication of the device's impact on the transmission line's performance.
It is equal to the inverse of the transmission S-parameter, |1/S 21 |
The low-uncertainty antenna, specifically a robust biconical or log-periodic dipole array (LPDA) antenna, is designed to meet the stringent balance and cross-polar performance requirements of this standard It features an antenna factor with an uncertainty of less than ±0.5 dB, making it suitable for accurately measuring electric field strength at a specified point in space.
NOTE It is further described in A.2.3
3.1.12 quasi-free space test-site facility for radiated emission measurements, or antenna calibration, that is intended to achieve free-space conditions
Unwanted reflections from the surroundings are kept to a minimum in order to satisfy the site acceptance criterion applicable to the radiated emission measurement or antenna calibration procedure being considered
3.1.13 reflection coefficient ratio of a common quantity to both the reflected and incident travelling waves
Abbreviations
The article discusses various types of equipment used for testing in electromagnetic environments, including EUT (Equipment Under Test), FSOATS (Free-space Open Area Test Site), and OATS (Open-Area Test Site) It also highlights specific antenna systems such as LAS (Loop Antenna System), LLA (Large-Loop Antenna), and LPDA (Log-Periodic Dipole Array) Additionally, the concept of NSA (Normalized Site Attenuation) is mentioned, emphasizing its importance in evaluating test conditions.
SA Site attenuation SAC Semi-anechoic chamber
S VSWR Site voltage standing wave ratio VSWR Voltage standing wave ratio
4 Antennas for measurement of radiated radio disturbance
General
Calibrated antennas used for radiated emission measurements must accurately measure field strength while considering their radiation patterns and surrounding mutual coupling It is essential that the antenna and the circuits connecting it to the measuring receiver do not significantly alter the receiver's overall characteristics Additionally, when the antenna is linked to the measuring receiver, the system must meet the bandwidth requirements specified by CISPR 16-1-1 for the relevant frequency band.
The antenna must be linearly polarized and adjustable in orientation to measure all incident radiation polarizations Additionally, the height of the antenna's center above the ground or absorber in a FAR may need to be modified based on specific testing procedures.
The field-strength measurement accuracy for a uniform sine-wave signal must exceed ±3 dB when utilizing an appropriate antenna and a measuring receiver that complies with CISPR 16-1-1 standards.
NOTE This requirement does not include the effect due to a test site
For additional information about the parameters of broadband antennas, see Annex A.
Physical parameter for radiated emission measurements
Radiated emission measurements are quantified in volts per meter, focusing on the E-field at a specific location relative to the equipment under test (EUT) For frequencies ranging from 30 MHz to 1,000 MHz, measurements are conducted on an Open Area Test Site (OATS) or in a Semi-Anechoic Chamber (SAC) The key parameter is the maximum field strength, assessed for both horizontal and vertical polarization at heights between 1 m and 4 m, and at a distance of 10 m from the EUT, which is rotated across all azimuth angles.
Remove the existing date and remove the two existing amendment references from the existing reference to CISPR/TR 16-3
3.1.12 quasi-free space test-site
Replace the existing term by the new term “quasi free-space test site”
The term "SAC" should be redefined as a shielded enclosure where all surfaces, except for the metal floor, are lined with materials that absorb electromagnetic energy, specifically RF absorbers, within the relevant frequency range.
Replace, in the existing definition of this term, “the FAR” by “a FAR”
Replace, in the existing Note of this term, “quasi-free space condition” by “quasi free-space condition”, and “the FAR” by “a FAR”
Add, after the existing definition 3.1.21, the following new terms and definitions 3.1.22, 3.1.23,
AF F a ratio of the electric field strength of an incident plane wave to the voltage induced across a specified load (typically 50 Ω) connected to the antenna
The load impedance connected to the antenna's radiating elements significantly influences the antenna's performance and is frequency dependent For instance, a biconical antenna can exhibit an impedance of up to 200 Ω, while antennas without a balun typically have an impedance that matches the load impedance, which is usually around 50 Ω.
NOTE 2 Usually, the AF is defined for the plane wave incident from the direction corresponding with the maximum gain of the antenna and at a specified point of the antenna
The AF is measured in inverse metres (m\(^{-1}\)) and is typically expressed in dB(m\(^{-1}\)) In radiated emission measurements, the strength of an incident field, E, can be estimated from the reading, V, of a measuring receiver connected to the antenna, provided that F\(_a\) is known.
E = V + F a where E is in dB(àV/m), V is in dB(àV) and F a is in dB(m -1 )
AF of an antenna located in a free-space environment
NOTE F a fs is a measurand for uncertainty calculation for antenna calibration For NSA measurements F a fs is an input quantity for uncertainty calculation
3.1.24 antenna pair reference site attenuation
The article presents a set of site attenuation measurement results obtained using a pair of antennas positioned at a defined distance in an ideal open-area test site One antenna is fixed at a specific height above the ground, while the other is scanned over a designated height range to record the minimum insertion loss for both vertical and horizontal polarizations.
NOTE 1 A APR is a measurand for uncertainty calculation
NOTE 2 A APR measurements are used for comparison to corresponding site attenuation measurements of a
COMTS to evaluate the performance of the COMTS
3.1.25 antenna reference point midpoint of an antenna from which the distance to the EUT or second antenna is measured
NOTE The antenna reference point is either defined by the manufacturer using a marker on LPDA antennas or by the calibration laboratory
3.1.26 ideal open-area test site open-area test site having a perfectly flat, perfectly conducting ground plane of infinite area, and with no reflecting objects except the ground plane
An ideal OATS is a theoretical concept essential for defining the measurand A APR and calculating the theoretical normalized site attenuation A N specifically for ground plane sites.
REFTS open-area test site with metallic ground plane and tightly specified site attenuation performance in horizontal and vertical electric field polarizations
Add, before the existing abbreviation EUT of this subclause, the following new sentence:
The following are abbreviations used in this standard that are not already given in 3.1
Add the following new abbreviation to the existing list:
Delete, in the existing list, the entire abbreviation SAC
Replace, in item c) 2) of the list, in the paragraph after the variable list of Equation (4), the existing text “corrections or as” by “a correction with associated”
Delete the existing NOTE 3 in the existing item c) 3) of the list
Replace, in the list of quantities below Equation (4), existing quantity "h 1 " by "h 2 " and replace existing quantity "h 2 " by "h 1 "
LPDA Log-periodic dipole array
OATS Open-area test site
S VSWR Site voltage standing wave ratio
VSWR Voltage standing wave ratio
4 Antennas for measurement of radiated radio disturbance
Calibrated antennas used for radiated emission measurements must accurately measure field strength while considering their radiation patterns and surrounding mutual coupling It is essential that the antenna and the circuits connecting it to the measuring receiver do not significantly alter the receiver's overall characteristics Additionally, when the antenna is linked to the measuring receiver, the system must meet the bandwidth requirements specified by CISPR 16-1-1 for the relevant frequency band.
The antenna must be linearly polarized and adjustable in orientation to measure all incident radiation polarizations Additionally, the height of the antenna's center above the ground or absorber in a FAR may need to be modified based on specific testing procedures.
For accurate field-strength measurement of a uniform sine-wave signal, the results must be within ±3 dB when utilizing an appropriate antenna and a measuring receiver that complies with CISPR 16-1-1 standards.
NOTE This requirement does not include the effect due to a test site
For additional information about the parameters of broadband antennas, see Annex A
4.2 Physical parameter for radiated emission measurements
Radiated emission measurements are quantified in volts per meter, focusing on the E-field at a specific location relative to the equipment under test (EUT) For frequencies ranging from 30 MHz to 1,000 MHz, measurements are conducted on an Open Area Test Site (OATS) or in a Semi-Anechoic Chamber (SAC) The key parameter is the maximum field strength, assessed for both horizontal and vertical polarization at heights between 1 m and 4 m, and at a distance of 10 m from the EUT, which is rotated across all azimuth angles.
LPDA Log-periodic dipole array
OATS Open-area test site
S VSWR Site voltage standing wave ratio
VSWR Voltage standing wave ratio
4 Antennas for measurement of radiated radio disturbance
Calibrated antennas used for radiated emission measurements must accurately measure field strength while considering their radiation patterns and surrounding mutual coupling It is essential that the antenna and the circuits connecting it to the measuring receiver do not significantly alter the receiver's overall characteristics Additionally, when the antenna is linked to the measuring receiver, the system must meet the bandwidth requirements specified by CISPR 16-1-1 for the relevant frequency band.
The antenna must be linearly polarized and adjustable in orientation to measure all incident radiation polarizations Additionally, the height of the antenna's center above the ground or absorber in a FAR may need to be modified based on specific testing procedures.
For accurate field-strength measurement of a uniform sine-wave signal, the results must be within ±3 dB when utilizing an appropriate antenna and a measuring receiver that complies with CISPR 16-1-1 standards.
NOTE This requirement does not include the effect due to a test site
For additional information about the parameters of broadband antennas, see Annex A
4.2 Physical parameter for radiated emission measurements
Radiated emission measurements are quantified in volts per meter, focusing on the E-field at a specific location relative to the equipment under test (EUT) For frequencies ranging from 30 MHz to 1,000 MHz, measurements are conducted on an Open Area Test Site (OATS) or in a Semi-Anechoic Chamber (SAC) The key parameter is the maximum field strength, assessed for both horizontal and vertical polarization at heights between 1 m and 4 m, and at a distance of 10 m from the EUT, which is rotated across all azimuth angles.
The following are abbreviations used in this standard that are not already given in 3.1. EUT Equipment under test
LPDA Log-periodic dipole array
OATS Open-area test site
S VSWR Site voltage standing wave ratio
VSWR Voltage standing wave ratio
Frequency range 9 kHz to 150 kHz
General
Experience has shown that, in this frequency range, it is the magnetic field component that is primarily responsible for observed instances of interference.
Magnetic antenna
To measure the magnetic component of radiation, one can utilize either an electrically-screened loop antenna, which fits within a square of 60 cm sides, or a suitable ferrite-rod antenna.
The magnetic field strength is measured in microamperes per meter (μA/m), and in logarithmic terms, it is represented in decibels (dB) as 20 times the logarithm of the field strength level Emission limits must also be stated in these same units.
Direct measurements of the magnetic component's strength can be conducted in dB(μA/m) or μA/m for radiated fields in both near and far field conditions Many field strength measuring receivers, however, are calibrated to reflect the equivalent plane wave E-field strength in dB(μV/m), based on the assumption that the ratio of the E and H components is either 120 π Ω or 377 Ω Calculations for the H component are provided accordingly.
H E (1) where H is typically in μA/m and E in μV/m
H (2) where H is in dB(μA/m) and E in dB(μV/m)
The impedance used in the above conversions, Z = 377 Ω , with 20 log Z = 51,5 dB(Ω), is a constant originating from the calibration of field strength measuring equipment indicating the magnetic field in μV/m [or dB(μV/m)].
Shielding of loop antenna
Inadequate shielding of a loop antenna can lead to an E-field response To evaluate the E-field discrimination, the antenna should be rotated in a uniform field while keeping the loop's plane parallel to the E-field vector When the loop's plane is initially perpendicular to the magnetic flux and then rotated to align with it, the measured response should decrease by at least 20 dB.
Frequency range 150 kHz to 30 MHz
Electric antenna
To measure the electric component of radiation, either a balanced or unbalanced antenna can be utilized When employing an unbalanced antenna, the measurement will specifically reflect the influence of the E-field on a monopole (rod) antenna It is essential to specify the type of antenna used alongside the measurement results.
Annex B provides details on calculating the performance characteristics of a monopole (rod) antenna and its matching network It highlights that the antenna factor obtained through the Equivalent Capacitance Substitution Method (ECSM) exhibits increased uncertainties for monopole lengths exceeding one-eighth of a wavelength.
The electric field strength is measured in microvolts per meter (μV/m), and in logarithmic terms, it is represented as dB(μV/m), calculated as 20 times the logarithm of the measured field strength level Emission limits are also expressed in these same units.
Magnetic antenna
For the measurement of the magnetic component of the radiation, an electrically-screened loop antenna, as described in 4.3.2 shall be used
Tuned electrically balanced loop antennas can measure magnetic field strengths as low as -51.5 dB(μA/m) using QP detection within the frequency range of 1.6 MHz to 30 MHz This sensitivity is significantly better than untuned electrically-screened loop antennas, which have a noise level approximately 25 dB higher.
Balance/cross-polar performance of antennas
If a balanced E-field antenna is used, it shall comply with the requirement of 4.5.4 If a balanced magnetic field antenna is used, it shall comply with the requirement of 4.3.3.
Frequency range 30 MHz to 1 000 MHz
General
In this frequency range, E-field measurements are conducted using dipole-like antennas, excluding magnetic field antennas The antennas utilized include tuned dipole antennas, which feature either straight rod or conical elements, log-periodic dipole array (LPDA) antennas with staggered straight rod elements, and hybrid antennas, all employing the free-space antenna factor for accurate measurement.
Antenna characteristics
Replace, in item c) 2) of the list, in the paragraph after the variable list of Equation (4), the existing text “corrections or as” by “a correction with associated”
Delete the existing NOTE 3 in the existing item c) 3) of the list
Replace, in the list of quantities below Equation (4), existing quantity "h 1 " by "h 2 " and replace existing quantity "h 2 " by "h 1 "
LPDA Log-periodic dipole array
OATS Open-area test site
S VSWR Site voltage standing wave ratio
VSWR Voltage standing wave ratio
4 Antennas for measurement of radiated radio disturbance
Calibrated antennas used for radiated emission measurements must accurately measure field strength while considering their radiation patterns and surrounding mutual coupling It is essential that the antenna and the circuits connecting it to the measuring receiver do not significantly alter the receiver's overall characteristics Additionally, when the antenna is linked to the measuring receiver, the system must meet the bandwidth requirements specified by CISPR 16-1-1 for the relevant frequency band.
The antenna must be linearly polarized and adjustable in orientation to measure all incident radiation polarizations Additionally, the height of the antenna's center above the ground or absorber in a FAR may need to be modified based on specific testing procedures.
The field-strength measurement accuracy for a uniform sine-wave signal must exceed ±3 dB when utilizing an appropriate antenna and a measuring receiver that complies with CISPR 16-1-1 standards.
NOTE This requirement does not include the effect due to a test site
For additional information about the parameters of broadband antennas, see Annex A
4.2 Physical parameter for radiated emission measurements
Radiated emission measurements are quantified in volts per meter, focusing on the E-field at a specific location relative to the equipment under test (EUT) For frequencies ranging from 30 MHz to 1,000 MHz, measurements are conducted on an Open Area Test Site (OATS) or in a Semi-Anechoic Chamber (SAC) The key parameter is the maximum field strength, assessed for both horizontal and vertical polarization at heights between 1 m and 4 m, and at a distance of 10 m from the EUT, which is rotated across all azimuth angles.
LPDA Log-periodic dipole array
OATS Open-area test site
S VSWR Site voltage standing wave ratio
VSWR Voltage standing wave ratio
4 Antennas for measurement of radiated radio disturbance
Calibrated antennas used for radiated emission measurements must accurately measure field strength while considering their radiation patterns and surrounding mutual coupling It is essential that the antenna and the circuits connecting it to the measuring receiver do not significantly alter the receiver's overall characteristics Additionally, when the antenna is linked to the measuring receiver, the system must meet the bandwidth requirements specified by CISPR 16-1-1 for the relevant frequency band.
The antenna must be linearly polarized and adjustable in orientation to measure all incident radiation polarizations Additionally, the height of the antenna's center above the ground or absorber in a FAR may need to be modified based on specific testing procedures.
For accurate field-strength measurement of a uniform sine-wave signal, the results must be within ±3 dB This accuracy is achievable when using an antenna that complies with specified requirements alongside a measuring receiver that meets the standards of CISPR 16-1-1.
NOTE This requirement does not include the effect due to a test site
For additional information about the parameters of broadband antennas, see Annex A
4.2 Physical parameter for radiated emission measurements
Radiated emission measurements are quantified in volts per meter, focusing on the E-field at a specific location relative to the equipment under test (EUT) For frequencies ranging from 30 MHz to 1,000 MHz, measurements are conducted on an Open Area Test Site (OATS) or in a Semi-Anechoic Chamber (SAC) The key parameter is the maximum field strength, assessed for both horizontal and vertical polarization at heights between 1 m and 4 m, and at a distance of 10 m from the EUT, which is rotated across all azimuth angles.
The following are abbreviations used in this standard that are not already given in 3.1. EUT Equipment under test
LPDA Log-periodic dipole array
OATS Open-area test site
S VSWR Site voltage standing wave ratio
VSWR Voltage standing wave ratio
4.3 Frequency range 9 kHz to 150 kHz
Experience has shown that, in this frequency range, it is the magnetic field component that is primarily responsible for observed instances of interference.
To measure the magnetic component of radiation, one can utilize either an electrically-screened loop antenna, which fits within a square of 60 cm sides, or a suitable ferrite-rod antenna.
The magnetic field strength is measured in microamperes per meter (μA/m) In logarithmic terms, it is represented in decibels (dB) as dB(μA/m), calculated as 20 times the logarithm of the measured field strength Emission limits must also be stated in these same units.
Direct measurements of the magnetic component's strength can be conducted in dB(μA/m) or μA/m for a radiated field in both near and far field conditions Many field strength measuring receivers, however, are calibrated to reflect the equivalent plane wave E-field strength in dB(μV/m), based on the assumption that the ratio of the E and H components is either 120 π Ω or 377 Ω Calculations for the H component are provided accordingly.
H E (1) where H is typically in μA/m and E in μV/m
H (2) where H is in dB(μA/m) and E in dB(μV/m)
The impedance used in the above conversions, Z = 377 Ω , with 20 log Z = 51,5 dB(Ω), is a constant originating from the calibration of field strength measuring equipment indicating the magnetic field in μV/m [or dB(μV/m)]
Inadequate shielding of a loop antenna can lead to an E-field response To evaluate the E-field discrimination, the antenna should be rotated in a uniform field while keeping the loop's plane parallel to the E-field vector When the loop's plane is initially perpendicular to the magnetic flux and then rotated to align with it, the measured response should decrease by at least 20 dB.
4.4 Frequency range 150 kHz to 30 MHz
To measure the electric component of radiation, either a balanced or unbalanced antenna can be utilized When employing an unbalanced antenna, the measurement will specifically reflect the influence of the E-field on a monopole (rod) antenna It is essential to specify the type of antenna used alongside the measurement results.
Annex B provides details on calculating the performance characteristics of a monopole (rod) antenna and its matching network It highlights that the antenna factor obtained through the Equivalent Capacitance Substitution Method (ECSM) exhibits increased uncertainties for monopole lengths exceeding one-eighth of a wavelength.
The electric field strength is measured in microvolts per meter (μV/m), and in logarithmic terms, it is represented in decibels (dB) as 20 times the logarithm of the measured field strength Emission limits are also expressed in these same units.
For the measurement of the magnetic component of the radiation, an electrically-screened loop antenna, as described in 4.3.2 shall be used
Cross-polar response of antenna
Replace, in the third paragraph of this subclause, “quasi-free space conditions” by “quasi free-space conditions”, and “high-quality anechoic chamber” by “high-quality fully anechoic room”
Replace the existing text of this subclause by the following new text:
To ensure accurate and consistent measurement results of disturbance field strength from an Equipment Under Test (EUT), a suitable environment is essential In cases where the EUT can only be tested at its intended location, alternative methods must be employed, such as the in-situ measurement techniques outlined in CISPR 16-2-3.
Replace the existing text of this subclause by the following new text:
An Open Area Test Site (OATS) is defined by its flat, cleared terrain and the inclusion of a metallic ground plane to meet validation standards It is essential that the test site remains unobstructed by buildings, electric lines, fences, trees, and underground utilities, except those necessary for the operation of the Equipment Under Test (EUT) For detailed construction guidelines for an OATS aimed at disturbance field-strength measurements between 30 MHz and 1,000 MHz, please refer to Annex D.
The equation \(2\phi (4)\) involves key parameters such as \(h_1\), the height of the equipment being tested, \(h_2\), the height of the measurement antenna, and \(d\), the horizontal distance from the phase center of the measurement antenna to the device under test.
To minimize associated uncertainties, it is essential to employ antenna down-tilting; otherwise, the reduction in received signal must be calculated from the radiation patterns and applied as corrections or directivity uncertainties Example uncertainty budgets can be found in CISPR 16-4-2.
NOTE 1 Assuming an E-field radiation pattern normalised to unity on boresight (= peak of mainlobe) read the E-field at the angles of declination from the antenna for the direct, E D, and reflected rays, E R The error, compared to an E-field of unity magnitude for each of the direct and reflected rays, is given in decibels by 20 log [2/(E D + E R )]
NOTE 2 The reduction in signal strength caused by reduced directivity at angles off antenna boresight is a systematic error and therefore can be corrected If a correction is applied, from knowledge of the radiation patterns at each frequency and polarization, the uncertainty in emitted signal strength can be reduced accordingly
3) For broad beamwidth antenna types used for radiated emission testing, such as biconical, LPDA and hybrid antennas, the beamwidth is inversely related to antenna directivity An alternative to the criterion based on beamwidths in items 1) and 2), is to specify the maximum gain of an antenna and to refer to generic uncertainty tolerances for the directivity component in the uncertainty budget for an emission test The generic uncertainties, based on the narrowest beamwidths in the frequency range used for a given antenna, are given in CISPR 16-4-2 The maximum isotropic antenna gain for biconical antennas shall be 2 dB, and shall be 8 dB for log-periodic dipole array (LPDA) and hybrid antennas For V-type LPDA antennas, whose H-plane beamwidth is equalised to the E-plane beamwidth, the maximum permissible isotropic gain shall be
NOTE 3 The directivity uncertainties given in CISPR 16-4-2 can be used for a 10 m separation, but revised uncertainties are needed for a 3 m separation d) The return loss of the antenna with the antenna feeder connected shall not be less than
To meet the 10 dB requirement, a matching attenuator may be included in the feeder cable for antennas Additionally, a calibration factor must be provided to ensure compliance with the specified requirements.
In radiated emission measurements, common-mode (CM) currents on the antenna cable can generate electromagnetic fields that affect the receiving antenna As a result, these CM currents can influence the accuracy of radiated emission measurement results.
The primary sources of common mode (CM) currents in antenna cables are twofold: first, the electric field produced by the equipment under test (EUT) when it has a component aligned with the antenna cable; second, the transformation of the differential mode (DM) antenna signal, which is the intended signal, into a CM signal due to imperfections in the balun of the receiving antenna.
The equation \(2\phi (4)\) involves key parameters such as \(h_1\), the height of the equipment being tested, \(h_2\), the height of the measurement antenna, and \(d\), the horizontal distance from the phase center of the measurement antenna to the device under test.
To minimize associated uncertainties, it is essential to employ antenna down-tilting; otherwise, the reduction in received signal must be calculated from radiation patterns and applied as corrections or directivity uncertainties Example uncertainty budgets can be found in CISPR 16-4-2.
NOTE 1 Assuming an E-field radiation pattern normalised to unity on boresight (= peak of mainlobe) read the E-field at the angles of declination from the antenna for the direct, E D, and reflected rays, E R The error, compared to an E-field of unity magnitude for each of the direct and reflected rays, is given in decibels by 20 log [2/(E D + E R )]
NOTE 2 The reduction in signal strength caused by reduced directivity at angles off antenna boresight is a systematic error and therefore can be corrected If a correction is applied, from knowledge of the radiation patterns at each frequency and polarization, the uncertainty in emitted signal strength can be reduced accordingly