1、Designation: E 1851 04Standard Test Method forElectromagnetic Shielding Effectiveness of Durable RigidWall Relocatable Structures1This standard is issued under the fixed designation E 1851; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method
3、covers the determination of the elec-tromagnetic shielding effectiveness of durable relocatableshielded enclosures.1.1.1 The intended application of this test method is forvirgin shielded enclosures that do not have any equipment orequipment racks. It is recommended that tests be conductedbefore the
4、 interior finish work begins. However, the shieldassembly including all enclosure penetrations shall be com-pleted and required penetration protection devices shall beinstalled in accordance with the design specification. The testmethod can also be used on existing shielded enclosures afterrepair wo
5、rk is done to verify workmanship, but it may benecessary to remove equipment or equipment racks to gainaccess to a test area.1.1.2 The test procedures delineated in this document arecomprehensive and may require several days to complete for aroom-size shielded enclosure.Auser can apply this test met
6、hodfor a first article test that requires proof of concept andvalidation of design and fabrication technique. Appendix X2provides guidance on choosing test points so shielding effec-tiveness tests on a room-size shielded enclosure may becompleted in about one-half day for which it applies toshielded
7、 enclosures coming off an assembly line.1.2 This test method is for use in the following frequencyranges: 140 to 160 kHz, 14 to 16 MHz, 300 to 500 MHz, 900to 1000 MHz, and 8.5 to 10.5 GHz. Specific test frequencieswithin these ranges are required (see 10.1.1 and 10.2.1).Additional measurements in th
8、e range of 10 kHz to 10.1.5.1GHz may be performed. For specific applications, the fre-quency range may be extended from 50 Hz to 40 GHz.Appendix X1 provides guidance on selecting measurementfrequencies.1.3 This test method is not applicable to individual compo-nents such as separate walls, floors, c
9、eilings, or shielded racks.1.4 This standard may involve hazardous materials, opera-tions, equipment, or any combination.1.5 The values stated in SI units are to be regarded as thestandard. The values in parentheses are for information only.1.6 This standard does not purport to address all of thesaf
10、ety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 IEEE Standards:2IEEE Std 299-1997, IEEE Standar
11、d Method for Measuringthe Effectiveness of Electromagnetic Shielding EnclosuresIEEE Std C95.1-1991, IEEE Standard for Safety Levelswith Respect to Human Exposure to Radio FrequencyElectromagnetic Fields, 3 kHz to 300 GHz2.2 Military Standard:3MIL-STD-188-125, High Altitude Electromagnetic Pulse(HEMP
12、) Protection for Ground Based C4I Facilities Per-forming Critical, Time-Urgent Missions2.3 OSHA Standard:4OSHA Regulation, 29 CFR 1910, Department of Labor,July 19923. Summary of Test Method3.1 Test ConfigurationA transmitting antenna is con-nected to an electromagnetic source set to a specific freq
13、uencyand amplitude. A receiving antenna is placed a specifieddistance from the transmitting antenna, and the receivedelectromagnetic field level is recorded as a reference orcalibration measurement. The transmitting antenna and elec-tromagnetic source are placed outside the shielded enclosure.The re
14、ceiving antenna and associated test equipment are placed1This test method is under the jurisdiction of ASTM Committee E06 onPerformance of Buildings and is the direct responsibility of Subcommittee E06.53on Materials and Processes for Durable Rigidwall Relocatable Structures.Current edition approved
15、 Nov 1, 2004. Published November 2004. Originallyapproved in 1997. Last previous edition approved in 2002 as E 1851 97.2Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE),445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331.3Available from Standardization Documents Order
16、 Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098.4Available from Occupational Safety and Health Administration (OSHA), 200Constitution Ave., NW, Washington, DC 20210.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Un
17、ited States.inside the shielded enclosure. The transmitting and receivingantennas separation, frequency, and amplitude are the refer-ence measurements. The transmitting and receiving antennasare at the same height for a given test point. The receivedelectromagnetic field level is recorded as the tes
18、t measurement.The ratio of the test measurement to the reference measurementis the electromagnetic shielding effectiveness of the shieldedstructure at the measurement location and frequency. Thelogarithm of this ratio is typically used in expressing theshielding effectiveness in decibels.3.2 Test Fr
19、equenciesA summary of nominal test frequen-cies and corresponding test configurations is shown in Table 1.4. Significance and Use4.1 This standard provides measurement procedures fordetermining the electromagnetic shielding effectiveness ofdurable rigid wall relocatable shielded enclosures. This sta
20、n-dard specifies a method for comparing the shielded enclosureperformance of structures provided by different suppliers. Inaddition, this standard is written to minimize variations inmeasured shielding effectiveness at a given frequency and testpoint regardless of test personnel, equipment, and test
21、 site.Therefore, the shielding effectiveness of a durable rigid wallrelocatable shielded enclosure of any size from any suppliercan be determined. This standard specifies a minimum set ofmeasurements at a given frequency and a minimum set offrequencies to determine shielding effectiveness.4.2 Source
22、 FieldsPerformance of a shielded enclosure isto be assessed for two source fields: magnetic and plane wave.4.2.1 Magnetic Field MeasurementsThe attenuation pro-vided by a shielded enclosure is assessed by using a localsource to generate the near field. The magnetic field measure-ments are specified
23、for two narrow frequency bands: 140 to160 kHz and 14 to 16 MHz.4.2.2 Plane Wave MeasurementsThe attenuation providedby a shielded enclosure is assessed by using a locally generateddistant source or plane wave field. The plane wave measure-ments are specified for three narrow frequency bands: 300 to5
24、00 MHz, 900 to 1000 MHz, and 8.5 to 10.5 GHz.5. Interferences5.1 Interference with Electronic EquipmentCare shall betaken to avoid interference with other electronic equipmentoperating in the vicinity.5.2 Operational Impact Analysis and RiskThe electro-magnetic barrier must remain intact during the
25、shieldingeffectiveness measurement sequence, and use of electricallynoisy equipment must be restricted. Therefore, constructionactivity or unusual operations (facility modification or mainte-nance) may be affected. Radiated signal levels should presentno hazard to equipment, but frequency adjustment
26、s may berequired to avoid self interference or interference with nearbyfacilities. Record the actual test frequencies. Normal electricalsafety precautions apply.6. Apparatus6.1 The required apparatus is identified in Table 2. Choosetest equipment that provides a dynamic range of at least 10 dBin exc
27、ess of the shielding effectiveness requirement at the testfrequency.7. Hazards7.1 For human exposure to electromagnetic energy in con-trolled environments, the maximum permissible exposure toelectric and magnetic field strengths shall be minimized to themaximum extent possible. Acceptable levels can
28、 be found inIEEE C95.1-1991 and OSHA Regulation 29 CFR.8. Preparation of Apparatus8.1 New and Existing Durable Relocatable EnclosureTestingTesting of new durable rigid wall relocatable shieldedenclosures can be conducted at the manufacturing site. Manu-facturing site testing can locate structural de
29、fects or weak-nesses or both and corrections may be easily implemented. Forexisting structures, weaknesses can be determined and cor-rected during maintenance or periodic retesting.8.2 Movable EquipmentMoveable equipment containingmetal, not normally housed in the enclosure or attached outsidethe en
30、closure, shall be removed from the enclosure prior tomaking measurements.TABLE 1 Test Frequencies and Test ConfigurationsNominal Test FrequencyCorresponding TestConfiguration150 kHz and 14 MHz Fig. 1400 MHz, 1000 MHz, and 10 GHz Fig. 2TABLE 2 Test ApparatusEquipment CharacteristicsOscillator(s) 140
31、to 160 kHz, 14 to 16 MHz, 300 to 500 MHz,900 to 1000 MHz, 8.5 to 10.5 GHzPower Amplifier(s) 140 to 160 kHz, 14 to 16 MHz, 300 to 500 MHz,A900 to 1000 MHz,A8.5 to 10.5 GHz, amplificationand noise figures as required for dynamic rangePreamplifier(s) 140 to 160 kHz, 14 to 16 MHz, 300 to 500 MHz,900 to
32、1000 MHz, 8.5 to 10.5 GHz, amplificationand noise figures as required for dynamic rangeReceiver(s)/SpectrumAnalyzer(s)140 to 160 kHz, 14 to 16 MHz, 300 to 500 MHz,900 to 1000 MHz, 8.5 to 10.5 GHzAntenna Kit 140 to 160 kHz,B14 to 16 MHz,B300 to 500MHz,C900 to 1000 MHz,C8.5 to 10.5 GHzDMiscellaneous C
33、ables andAttenuators as RequiredEAThe power amplifier output is usually matched to an unbalanced to balanced(balun) transformer; the balanced output is matched to a balanced dipole.BCircular loop antenna whose diameter is 30 cm (1 ft) shall be used. Theshielded circular receiving antenna can have mu
34、ltiple turns, but the total length ofwire forming the loop shall be less than16 wavelength.CAny antenna that radiates at the prescribed frequencies may be used.However, antennas that require a large clear space in the direction of wavepropagation shall not be used where clear space is limited for te
35、sting. Examples ofsuch antennas are linearly polarized log periodic dipole and circularly polarizedconical spiral antennas. Procedures are written assuming use of dipole antennasfor plane wave measurements. If a dipole antenna is used as a receiving antenna,its length shall be less than16 of wavelen
36、gth. The receiving antenna is usuallyconnected to a balun then to an attenuator.DAny antenna that radiates at the prescribed frequencies may be used excepta linearly polarized log periodic dipole antenna or circularly polarized conical spiralantenna. Procedures are written assuming use of aperture a
37、ntennas for highfrequency plane wave measurements. An isolator is usually used between thesource and its antenna to minimize variation of power between reference and testmeasurements.EWell shielded coaxial cable such as flexible semi-rigid coaxial cable, RG-214or RG-223, shall be used.E18510428.3 Pr
38、eliminary ProceduresPerform the following pre-liminary test on all accessible shielding faces to detect weakpoints and to permit remedy of shielding defects caused byfaulty assembly and poor workmanship prior to actual mea-surement.8.3.1 With the transmitting antenna turned off, perform acontinuous
39、wave (cw) measurement at each frequency to beused for testing to ensure that no emitters are nearby that maycause interference. Frequency adjustments may be necessary toavoid interference. Setup for this measurement is the referencemeasurement (see Section 9 and Fig. 1a and Fig. 2a).8.3.2 Additional
40、ly, perform a receiving equipment couplingmeasurement. The setup for this measurement is the referencemeasurement (Section 9) with the following exceptions. Dis-connect the receiving antenna from the nearest cable andreplace the receiving antenna with a dummy load (resistiveload matched to the chara
41、cteristic impedance of the receivingsystem) as shown in Fig. 3. Measured levels shall be negligibleso the required dynamic ranges are maintained. If the measuredlevels are larger than expected, determine the penetrationpoints and correct the identified leakage points. Repeat thereceiving equipment c
42、oupling measurements until negligiblelevels are maintained.8.3.3 Perform a noise measurement with the followingequipment setup. Place the receiving antenna and equipmentinside the enclosure and turn off the transmitting antennaplaced outside the enclosure (see Fig. 4).The receiving antennacan be pla
43、ced outside the enclosure. When this is done anE1851043attenuator shall be inserted between the receiving antenna andreceiving equipment, and it shall be set to a shielding effec-tiveness level of the enclosure being tested. Measure the noiselevel at each frequency to be used for testing.8.3.4 After
44、 noise levels have been found negligible (or thetest equipment has been modified to make the penetrationnegligible), position the transmitting and receiving antennas inaccordance with the procedures detailed in Section 10. Foreach location, use the receiving antenna as a probe to locateareas of maxi
45、mum penetration. Alternatively, a commercialleak detector may be used. Check all penetrations such asdoors, power line filters, air vents, seams, and coaxial cablefittings. If the performance of the enclosure appears to beinadequate for its design, remedial measures are suggestedprior to complete te
46、sting. Identify regions of significantlygreater field penetration for later measurements.9. Calibration Procedures9.1 Magnetic Field Calibration ProcedureConduct thecalibration for magnetic field measurements for each magneticfield test frequency as shown in Fig. 1a. Choose test equipmentthat provid
47、es a dynamic range of at least 10 dB in excess of theshielding effectiveness requirement at the test frequency. Placethe loops of the transmitting and receiving antennas in acoplanar configuration. Place the transmitting and receivingantennas so the distance between them is 90 cm (3 ft) plus thethic
48、kness of the enclosure (see Fig. 1a). If an attenuator is usedas the basis for the desired measurement, the attenuator shall becalibrated and the results shall be documented. The attenuatorimpedance shall match the system transmission line imped-ance. Place the receiving system, but not the receivin
49、g antenna,inside the enclosure.9.1.1 During calibration no other equipment or electromag-netic reflectors (except ground) shall be closer than three timesthe antenna separation. The antennas shall be at least 1 m (3.3ft) above the ground.9.1.2 Record the received signal strength for each frequencyand transmitting antenna polarization as the calibration signal(Vc) for that configuration. Record all equipment settings,including generator loop current or transmit power.9.2 Plane Wave Calibration ProcedureConduct the cali-bration for plane wave measurements for each plane wa
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