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GB/T 12190-2021: Method for measuring the shielding effectiveness of electromagnetic shielding enclosures
Status: Valid GB/T 12190: Evolution and historical versions
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Method for measuring the shielding effectiveness of electromagnetic shielding enclosures
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GB/T 12190-2021
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| GB/T 12190-2006 | English | RFQ |
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Method for measuring the shielding effectiveness of electromagnetic shielding enclosures
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| GB/T 12190-1990 | English | 759 |
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Measurement of shielding effectiveness of high-performance shielding enclosures
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Basic data | Standard ID | GB/T 12190-2021 (GB/T12190-2021) | | Description (Translated English) | Method for measuring the shielding effectiveness of electromagnetic shielding enclosures | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | L06 | | Word Count Estimation | 34,387 | | Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration | GB/T 12190-2021: Method for measuring the shielding effectiveness of electromagnetic shielding enclosures
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(Measurement method of shielding effectiveness of electromagnetic shielding room)
ICS 33.100
CCSL06
National Standards of People's Republic of China
Replace GB/T 12190-2006
Measurement method of shielding effectiveness of electromagnetic shielding room
Released on 2021-05-21
2021-12-01 implementation
State Administration of Market Supervision and Administration
Issued by the National Standardization Management Committee
Table of contents
Foreword Ⅰ
1 Scope 1
2 Normative references 1
3 Terms and definitions 1
4 Initial test procedure 2
4.1 Preparation 2
4.2 Test plan 2
4.3 Equipment calibration 2
4.4 Reference level and dynamic range 2
4.5 Pre-check procedure for shielding effectiveness 2
4.6 Note 2
5 Detailed measurement procedures 3
5.1 Overview 3
5.2 Typical measurement frequency 3
5.3 Judgment Criteria 4
5.4 Measurement uncertainty 4
5.5 Preparation process 4
5.6 Low frequency band measurement (9kHz~20MHz) 4
5.7 Resonance frequency measurement (20MHz~300MHz) 7
5.8 High-frequency band measurement (300MHz~18GHz) 13
6 Test report 18
Appendix A (Informative) Measurement Technology Selection Guide 20
Appendix B (informative) Initial test and improvement 21
Appendix C (informative) SE Mathematical Formula 22
Appendix D (informative) Other relevant information 25
Appendix E (Informative) Basic Principles 27
Measurement method of shielding effectiveness of electromagnetic shielding room
1 Scope
This document describes the measurement method of the shielding effectiveness (SE) of electromagnetic shielding rooms, and the measurement frequency range is 9kHz~18GHz. As needed
If necessary, the frequency can be extended to 50Hz and 100GHz to both ends.
This document is applicable to electromagnetic shielding rooms with dimensions not less than 2.0m on each side.
2 Normative references
The contents of the following documents constitute the indispensable clauses of this document through normative references in the text. Among them, dated quotations
Only the version corresponding to the date is applicable to this document; for undated reference documents, the latest version (including all amendments) is applicable to
This document.
GB/T 4365-2003 Electrotechnical terminology electromagnetic compatibility (IEC 60050-161.1990, IDT)
3 Terms and definitions
The following terms and definitions defined in GB/T 4365-2003 apply to this document.
3.1
Accessible test location
No need to modify the mother body structure, the test antenna can reach the position.
3.2
Dynamic range; DR
The receiving system works in the amplitude range of the linear region (see C.6 of Appendix C).
Note 1.For SE measurement, DR is the difference between the reference level (see 4.4) and the minimum discernible signal above the noise floor.
Note 2.The minimum discernible signal is defined as the amplitude greater than the noise floor of the test system by at least 3dB.
3.3
Localsource
An emission source that is very close to the shielded room and whose electromagnetic energy only irradiates a local area on the surface of the shielded room.
3.4
Parent structure
A permanent enclosure or external room containing a shielded room.
3.5
Shielding effectiveness; SE
The ratio of the signal value received when there is no shield to the signal value received in the shield, that is, between the transmitting antenna and the receiving antenna
There is the insertion loss caused by the shield in the future.
3.6
Shielding enclosure
A structure that protects the inside from external electric and magnetic fields or protects the outside from the internal electric and magnetic fields.
Note. It is usually built of metal materials, and certain measures are taken at the seams of metal plates and doors to ensure continuous electrical connection. High-performance shielded room
The same frequency can suppress the electric field and magnetic field by one to seven orders of magnitude.
3.7
Shieldingenclosureowner
Individuals, companies, or organizations that put forward final shielding requirements and will use shielded rooms.
3.8
Testing agency
The organization that completed the measurement and issued a report.
4 Initial test procedure
4.1 Preparation
Before the formal measurement, the reference level and dynamic range (DR) need to be measured.
4.2 Test plan
Before the measurement, the owner of the shielded room and/or related parties should develop a test plan. When measuring, it should be carried out in accordance with the test plan. The test plan should
Including measurement frequency, measurement location, judgment criteria (ie SE limit) and a list of equipment used.
For a shielded room used in a full anechoic chamber (FAR) or a semi-anechoic chamber (SAC), the SE measurement should be carried out before the installation of the absorbing material
OK; if not, perform SE measurement on FAR or SAC, and the measurement location shall be specified in the test plan.
See Appendix A for the selection guide for measurement techniques.
4.3 Equipment calibration
Any measuring equipment that can affect the measured value of SE should be calibrated. The latest calibration date traceable to the national standard shall be provided.
4.4 Reference level and dynamic range
The reference level should be determined in accordance with the description in the measurement clauses for the low-frequency band (magnetic field), resonance band, and high-frequency band (plane wave) (see 5.6.4,
5.7.4, 5.8.5). The reference level should be re-determined when the measurement arrangement is changed. The reference level should be re-measured after the end of each frequency measurement.
If the re-measured reference level value has a change of more than ±3dB from the previous reference level value, the measurement should be performed again.
It should be ensured that each measurement arrangement has a suitable DR. This can be determined by the following method. Excite the receiving device with the relevant transmitting device, and prove
The receiving equipment maintains the linear calibration state for all the various emission and reception levels that may be encountered during the measurement. In the receiving system, use the school
The calibrated attenuator changes the input of the receiver. If the decibels of the two changes are the same, it means that the system is working in a linear calibration state. This kind of
The verification should be performed at least once at each measurement frequency point.
The DR should be at least 6dB greater than the SE of the shielded room under test. It is best to determine the DR when measuring the reference level. The surrounding environment should be minimized
(Such as walls, buildings).
4.5 Pre-check procedures for shielding effectiveness
See Appendix B for the pre-check procedure of SE.
4.6 Matters needing attention
The emission source should be operated by experienced surveying personnel.
During the measurement process in accordance with this document, the personnel concerned shall be protected from radio frequency radiation, and the attachment of the measurement site shall be avoided.
Near other electronic devices cause interference.
5.8.6 Measurement method
5.8.6.1 Overview
After determining the relative position of the transmitting antenna and the receiving antenna from the shielding wall, measure the amplitude of the maximum signal. Whether it is measured with a dipole antenna
Still use horn antenna to measure, the method is the same.
5.8.6.2 Transmitting antenna position
According to Figure 7 and Figure 8, select some measurement points according to the test plan, and the selected transmitting antenna position and polarization should be able to cover the shielding room respectively
The walls.
The measurement was carried out under the horizontal polarization and vertical polarization of the antenna. The horizontal distance between adjacent measuring points should not be greater than 2.6m. but if
When measuring the reference level, the distance between the transmitting antenna and the receiving antenna is less than 2m, and the horizontal distance between adjacent measurement points should not be greater than 1.3m. Such as
If the height of the shielding wall is not more than 3m, place the center of the antenna at half the height of the shielding wall. If the height of the shielding wall exceeds
3m, the measuring point should be added in the vertical direction. The distance between the measuring points in the vertical direction should not be greater than 2m, and the antenna should be located in each vertical segment.
center. However, if the distance between the transmitting antenna and the receiving antenna is less than 2m when measuring the reference level, the vertical distance between adjacent measurement points should not be large
At 1m. The distance between the transmitting antenna and the measuring wall is at least 1.7m (excluding the thickness of the shielding wall); and the distance from the ground is at least 0.3m. If because of
Due to the limitation of physical size, the distance between the two antennas is less than 2m, then the distance between the transmitting antenna and the shielding wall is the reference distance and 0.3m.
Difference.
When measuring, the power applied to the transmitting antenna should be equal to the power used when measuring the reference level in 5.8.5.
5.8.6.3 Location and data recording of the receiving antenna
The receiving antenna should look for the maximum response in each position and polarization direction in the shielded room. Use the recorded maximum value to calculate the mask
The minimum SE of the room. The closest distance between the receiving antenna and the shielding wall should not be less than 0.3m.
5.8.6.4 Measuring point
Using the method specified in the test plan, repeat 5.8.6.3.at all transmitting antenna positions, measuring frequencies, and on each wall of the shielding room. test
Personnel should perform measurements in the order of measurement parameters (frequency, antenna position) in order to shorten the measurement time.
5.8.7 Calculation of shielding effectiveness
If the measured value uses linear units, the calculation of SE is shown in formula (C.2), formula (C.3) or formula (C.4); if logarithmic unit is used
For calculation of SE, see formula (C.5), formula (C.7) or formula (C.8).
6 Test report
The test report should include at least the following.
a) Customer's name;
b) The name of the testing organization;
c) The name and brief description of the shielded room;
d) Test location;
e) test personnel;
f) test date;
g) Measuring frequency point;
h) Specific measurement location;
i) Measuring instruments used. including manufacturer, model, serial number, and calibration date;
j) Measurement method and test arrangement;
k) SE calculation method, and the difference from standard measurement method;
l) SE results and limits (if any);
m) Measurement uncertainty.
Appendix A
(Informative)
Measurement technology selection guide
A.1 Classification of shielded rooms
Shielded rooms are usually classified according to their construction methods, shielding materials, and intended use.
The construction method refers to and is not limited to. single-layer shielding, double-layer shielding, double-layer electrical isolation shielding, bolt fastening, fixed, detachable and welding
Connection type; shielding material refers to but not limited to. copper (non-mesh and mesh), steel (strip and plate), aluminum or metalized textile; it can be divided into uses
It is not limited to. military standard compliance measurement anechoic chamber, semi-anechoic chamber and full anechoic chamber for commercial EMC compliance measurement, reverberation chamber; R&D test
Inspection and use facilities, radio frequency equipment production and maintenance facilities, medical imaging and treatment facilities, and scientific research facilities.
After determining the purpose of the shielded room, and taking into account the above-mentioned classification, this can be appropriately applied when selecting the measurement method and measurement frequency.
file. In some cases, it may be necessary to use special techniques, such as sweeping over a range of frequencies. See other appendices for details.
The following are some examples in practical applications.
a) The military welding shielded room needs to be measured on each frequency band. SE requirements are also relatively high, usually above 100dB.
b) The single-shielded, screw-connected copper shielded room used in medical applications for magnetic resonance imaging (MRI) can only be within the magnetic resonance frequency range
For measurement, the SE is usually required to be between 80dB and 100dB.
c) The steel shielded room used for the measurement and repair of very high frequency (VHF) or ultra high frequency (UHF) radio frequency equipment is usually only in the high frequency range
Measure within.
d) The portable measurement chamber made of metalized fabric or mesh material does not require high performance in the resonance or high frequency range.
A.2 Performance requirements
In the process of designing, ordering and constructing the shielded room, it is necessary to put forward clear requirements for its SE. The purpose of this document is to
The type of shielded room proposes a unified measurement method. However, the choice and use of measurement methods are still at the discretion of the owner of the shielded room. If this document
The required methods and techniques are not compatible with the special shielded room, so all measurements cannot be carried out in accordance with this document.
A.3 Requirements for equipment
The instrument used when measuring SE must meet the needs of the measurement. The frequency range and measurement method determine the signal generation that needs to be used
And antenna type. It is necessary to ensure that the frequency range and DR of the instrument meet the corresponding requirements. The DR of the measurement system needs to be better than specified or expected
SE is greater than 6dB. Within the frequency range of this document, radio frequency power amplifiers or pre-amplifiers can be selected as required during measurement.
Appendix B
(Informative)
Initial test and improvement
B.1 Overview
Before the formal measurement of SE, small-scale improvements can be made, and large-scale rectifications can also be made if necessary. In order to improve efficiency, in accordance with Chapter 5
A rough inspection is performed before the measurement. However, a cursory inspection is not necessary.
B.2 Preparation
Although the initial test before the start of the formal measurement is not mandatory, it is still beneficial. It can find those with serious leakage
area.
B.3 Frequency of initial measurement
The frequency of the initial measurement can be within the frequency range of the normal measurement, or within the extended frequency range.
In the low frequency frequency band (9kHz~20MHz), choose the loop antenna (with a diameter of less than 1m) as the transmitting antenna and the receiving antenna.
In the resonant frequency band (20MHz~300MHz), it is advisable to use biconical antennas and dipole antennas.
Dipole antennas, horn antennas and similar antennas are used in the high frequency band (300MHz~18GHz).
The measurement shall be carried out in accordance with the test plan (see 4.2). Select a single frequency point for measurement in the following frequency bands. 9kHz~
16kHz, 140kHz~160kHz, 14MHz~16MHz, 50MHz~100MHz, 300MHz~400MHz, 600MHz~
1000MHz, 8.5GHz~10.5GHz, 16GHz~18GHz. The frequency unique to the facility also needs to be considered.
B.4 Initial test method
Before the initial test starts, the leakage of the measuring equipment needs to be measured.
When measuring, the auxiliary equipment that usually exists in the shielding room, such as fans or fans, needs to be arranged in normal use; and the shielding room is normal
Excess equipment that is not needed during use needs to be removed from the shielded room before measurement.
The positions of the transmitting antenna and the receiving antenna need to be approximately the same as the measurements in Chapter 5 (see Figure 1, Figure 2, Figure 4, Figure 7 and Figure 8), but for the initial
The position and direction of the antenna can be adjusted to get the maximum response, and the accessible surface of the shielded room can be scanned once to detect the leakage.
The most serious area of leakage.
Doors, power filters, ventilation holes, gaps, coaxial cables and observation windows, communication filters, waveguide devices, escape ports, and liquid pipes are required
Measure at the connection port, etc., and then according to the measurement result and the size of the leak area, the owner of the shielded room and the testing agency can decide whether it is advanced
To improve or continue to measure.
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