1 Scope
This standard provides procedures of measurement and calculation for shielding effectiveness of electromagnetic (EM) shielding enclosure whose each side is not smaller than 2.0. The standard is applicable to electromagnetic shielding enclosures at frequencies from 9 kHz to 18 GHz and as necessary, such frequencies may be extendable down to 50 Hz and up to 100 GHz.
If a shielding enclosure is used as fully-anechoic enclosure or semi-anechoic enclosure, its measurement for shielding effectiveness shall be conducted before the absorbing materials are mounted.
2 Normative References
The following standards contain provisions which, through reference in this text, constitute provisions of this standard. For dated reference, subsequent amendments to (excluding correction to), or revisions of, any of these publications do not apply. However, the parties whose enter into agreement according to these specifications are encouraged to research whether the latest editions of these labels are applied or not. For undated references, the latest edition of the normative document referred to applies.
GB/T 4365-2003 Electrotechnical terminology - Electromagnetic compatibility (idt IEC 60050 (161): 1990)
3 Terms and Definitions
For the purpose of this standard, the terms and definitions defined GB/T GB/T 4365-2003 and the following ones apply.
3.1
dynamic range (DR)
The range of amplitudes over which the receive system operates linearly (see B.6). If the signal amplitude is expressed by decibel (dB), the dynamic range is the difference between the maximum and minimum signal levels. For a measurement, the DR depends on the difference between the reference level and the minimum discernable signal above the noise floor. This should be verified during the DR validation step defined in 4.4. It represents the maximum SE measurable at that frequency with that particular equipment and settings.
3.2
shielding enclosure
A structure that protects its interior from the effect of an exterior electric or magnetic field, or, conversely, protects the surrounding environment from the effect of an interior electric or magnetic field. It is normally constructed of metal with provisions for continuous electrical contact between adjoining panels, including doors. A high-performance shielding enclosure is generally capable of reducing the effects of both electric and magnetic field strengths by one to seven orders of magnitude depending upon frequency.
3.3
shielding effectiveness (SE)
The ratio of the signal received (from a transmitter) without the shield, to the signal received inside the shield; the insertion loss when the shield is placed between the transmit antenna and the receiving antenna.
3.4
local source
An emitter located close enough to a shielding enclosure for its electromagnetic energy to illuminate only a localized portion of a shielding face.
3.5
owner
The individual, corporation, or organization that intends to use the shield and that is the ultimate source of the shielding requirement.
3.6
testing agency
The organization that actually performs the tests and records the data.
4 Preliminary procedures
4.1 Preparation
Reference level and dynamic range shall be measured before formal measurement.
4.2 Test plan
Foreword i
1 Scope
2 Normative References
3 Terms and Definitions
4 Preliminary procedures
4.1 Preparation
4.2 Test plan
4.3 Calibration
4.4 Reference level and dynamic range
4.5 Preliminary shield check procedures
4.6 Warning
5 Detailed procedure of measurement
5.1 Background
5.2 Recommended typical measurement frequencies
5.3 Criteria
5.4 Shielding effectiveness calculation
5.5 Preparation procedures
5.6 Low-frequency measurements: 9 kHz to 20 MHz
5.7 Resonant range measurements: 20 MHz to 300 MHz
5.8 High range measurement: 300 MHz ~ 18 GHz
6 Testing report
Annex A (Informative) Rationale
A. 1 Basis
A.2 Considerations
A. 3 Cavity resonances
A. 4 Measurement locations
A. 5 Measurement equipment
Annex B (Informative) Mathematical formulas
B.1 Specific mathematical formulas
B.2 Low range (50 Hz to 20 MHz) shielding effectiveness
B.3 Resonant range (20 MHz~300 MHz) shielding effectiveness
B.4 High range (300 MHz to 100 GHz) shielding effectiveness
B.5 Nonlinear (logarithmic) calculations
B.6 Dynamic range considerations
Annex C (Informative) Miscellaneous supporting information
C.1 Coplanar versus coaxial loops
C.2 Nonlinearity of high-permeability ferromagnetic enclosures
C.3 Selecting measurement frequencies
Annex D (Informative) Guidelines for the selection of measurement techniques
D.1 Types of enclosures
D.2 Performance requirement
D.3 Equipment requirements
Annex E (Informative) Preliminary measurements and repairs
E.1 Preparation
E.2 Frequencies for preliminary check
E.3 Preliminary check procedures
