1、 ECMA TR/94 1stEdition / December 2007 Assessment of the Human Exposure to Electromagnetic Fields for Low Power Electronic and Electrical Apparatus according to EN 50371:2002 Ecma International Rue du Rhne 114 CH-1204 Geneva T/F: +41 22 849 6000/01 www.ecma-international.org IW TR-094.doc 11.12.2007
2、 11:09:00 Assessment of the Human Exposure to Electromagnetic Fields for Low Power Electronic and Electrical Apparatus according to EN 50371:2002 Technical Report ECMA TR/94 1stEdition / December 2007 . Introduction Assessing compliance with a new standard usually requires additional measurements, w
3、hich increase cost and time-to-market. Compliance with EMF standards is now required under EU Directives. For low power electronic devices covered by EN 50371, there is an alternative way to demonstrate compliance, usually without additional measurements, provided that the product has previously pas
4、sed EMC measurements. This Ecma Technical report outlines the computations that allow determining compliance of a low power electronic device, based on an assessment of already available EMC measurement results. This Ecma Technical Report has been adopted by the General Assembly of December 2007. -
5、i - Table of contents 1 Scope 1 2 References 1 3 Acronyms 2 4 Assessment of the total emitted power (to be 1 GHz. 2 References EN 50371:2002 Generic standard to demonstrate the compliance of low power electronic and electrical apparatus with the basic restrictions related to human exposure to electr
6、omagnetic fields (10 MHz 300 GHz) General public EN 55011:1998 Limits and methods of measurement of radio disturbance characteristics of industrial, scientific and medical (ISM) radio-frequency equipment EN 55013:2001 Sound and television broadcast receivers and associated equipment. Radio disturban
7、ce characteristics. Limits and methods of measurement EN 55014-1:2007 Electromagnetic compatibility Requirements for household appliances, electric tools and similar apparatus Part 1: Emission EN 55016-1-3:2007 Specification for radio disturbance and immunity measuring apparatus and methods Part 1-3
8、: Radio disturbance and immunity measuring apparatus Ancillary equipment Disturbance power EN 55016-2-1:2005 Specification for radio disturbance and immunity measuring apparatus and methods Part 2-1: Methods of measurement of disturbances and immunity Conducted disturbance measurements EN 55022:1998
9、 Information technology equipment Radio disturbance characteristics Limits and methods of measurement EN 61000-6-3:2001 Electromagnetic compatibility (EMC) - Part 6-3: Generic standards - Emission standard for residential, commercial and light-industrial environments EN 61000-6-4:2001 Electromagneti
10、c compatibility (EMC) - Part 6-4: Generic standards - Emission standard for industrial environments ETSI TR 102273-2 V1.2.1:2001 Electromagnetic compatibility and Radio spectrum Matters (ERM); Improvement on Radiated Methods of Measurement (using test site) and evaluation of the corresponding measur
11、ement uncertainties; Part 2: Anechoic chamber ETSI TR 102273-3 V1.2.1.2001 Electromagnetic compatibility and Radio spectrum Matters (ERM); Improvement on Radiated Methods of Measurement (using test site) and evaluation of the corresponding measurement uncertainties; Part 3: Anechoic chamber with a g
12、round plane EU Council Recommentadion 1999/519/EC ICNIRP Guidelines (4-98) - 2 - 3 Acronyms CEN Comit Europen de Normalisation (in English: European Committee for Standardization) CENELEC Comit Europen de Normalisation Electrotechnique (in English: European Committee for Electrotechnical Standardiza
13、tion) EMF Electromagnetic Fields ETSI: European Telecommunications Standards Institute ICNIRP International Commission on Non-Ionizing Radiation Protection SAR Standard Absorption Rate 4 Assessment of the total emitted power (to be 1000 MHz limit: D class A: 60 / class B: 54 dbV/m (d) The total emit
14、ted power is assessed under the theoretical assumption that the EUT radiates with an equal distance between the spectral lines, which leads to following equations: Figure 5 Spectral lines and spectral line distance 10 MHz to 30 MHz In band a) a receiver (EN 55016) resolution bandwidth of 9kHz as the
15、 spectral line distance dsleads to the following maximum number of spectral lines: LinesSpectralkHzMHzMHz_222291030=30 MHz to 230 MHz and 230 MHz to 1000 MHz In bands b) and c) a receiver (EN 55016) resolution bandwidth of 120kHz as spectral distance ds leads to the following maximum numbers of spec
16、tral lines: LinesSpectralkHzMHzMHz_166712030230=Spectral line distance ds- 10 - And LinesSpectralkHzMHzMHz_64171202301000=1 GHz to 300 GHz In band d) a receiver (EN 55016) resolution bandwidth of 1 MHz as spectral distance dsleads to the following maximum number of spectral lines: LinesSpectralMHzGH
17、zGHz_29900011300=Under this assumption, over the whole frequency band from 10 MHz to 300 GHz; the total power of 309306 (= 299000 d + 6417c + 6417 b + 2222 a) spectral lines has to be determined. The radiated power is to be determined as follows: =nSLTotalPP1(7) PSL = EIRP of a single spectral line
18、n = total No of spectral lines EMC measurements provide electrical field strength measured at a given distance from the source of radiation. The relationship between field strength and source power is as follows: 64.1210=ZPsrE (8) The above equation is valid for far field free space conditions. The
19、electrical field strength Eris the field strength present at distance r from an RF power source. Here the RF power is given as ERP through dissipation by a /2 Dipole which has a numeric gain of 1.64. When radiated EMC measurements are performed above a metallic ground plane, both direct and reflecte
20、d RF wave reach the receiving antenna. By 360 rotation of the EUT and positioning the receiving antenna between 1 m and 4 m height, an attempt is made to maximise field strength. In-phase adding of both waves can lead to an increase of Field strength of up to 6 dB compared to free space conditions.
21、For the further analysis this is neglected, which results in an additional margin to the limit. Then the logarithmic equation for the determination of the substituted ERP is: =rEPrERP3log204.7 (9) With ERPP in dBpW , rE in dBV/m , distance r in m If reference is EIRP, combination of (2) and (9) give
22、s: =rEPrEIRP3log2025.5 (10) - 11 - Table 1 shows the results at a given distance r of 3 m or as power line conducted over 50 Ohm for Class B equipment. Table 2 Class B Band a) 10 30 MHz over 50 Ohm Band b) 30230 MHz Band c) 230-1000 MHz Band d) 1 300 GHz Power Sum a) d) EMC limit (dBV/50Ohm) 60 (dBV
23、/50Ohm) EMC limit (dBV/m) 40 dBV/m 47 dBV/m 54 dBV/m PEIRP per spectral line (dBm) - 47 dBm PEIRP per spectral line (dBpW) 34.75 dBpW 41.75 dBpW 48.75 dBpW PEIRP per spectral line (mW) 0.00002 PEIRP per spectral line (mW) 0.00000299 0.00001496 0.00007499 max number of spectral lines 2222 max number
24、of spectral lines 1667 6417 299000 max Total Power 2 x lines inside Band (mW) 0.089 Total Power inside Band (b-d); (mW) 0.00498 0.096 22.42 22.61 Total Power for 2 x lines inside Band (dBm) - 10.05 Total Power inside Band (b-d); (dBm) - 23.03 - 10.18 13.51 13.54 overestimated real number of spectral
25、 lines 500 overestimated real number of spectral lines 400 1000 1000 overestimated real Power for 2 x lines inside Band a); (mW) 0.02 overestimated real Power inside Band (b-d); (mW) 0.001196 0.01496 0.07499 0.1111 overestimated real Power for 2 x lines inside Band a); (dBm) -16.989 overestimated re
26、al Power inside Band b-d) (dBm) -29.22 - 18.25 -11.25 -9.54 With (7) the maximum total emitted power(P EIRP) when all spectral lines are measured up to its EMC-limit is: +=3093061) dcbaSLTotalPPPPPP = 22.61 mW (11) The maximum emitted overestimated real power(P EIRP) is: 0.1111 mW for Class B produc
27、ts. The following table 2 shows the results at a given distance r of 3 m or as power line conducted over 50 Ohm for Class A equipment. - 12 - Table 3 Class A Band a) 10 30 MHz over 50 Ohm Band b) 30230 MHz Band c) 230-1000 MHz Band d) 1 300 GHz Power Sum a) d) EMC limit (dBV/50Ohm) 73 (dBV/50Ohm) EM
28、C limit (dBV/m) 50 dBV/m 57 dBV/m 60 dBV/m PEIRP per spectral line (dBm) - 34 dBm PEIRP per spectral line (dBpW) 44.75 dBpW 51.75 dBpW 54,75 dBpW PEIRP per spectral line (mW) 0.0004 PEIRP Per spectral line (mW) 0.0000299 0.0001496 0.000298 max number of spectral lines 2222 max number of spectral lin
29、es 1667 6417 299000 max Total Power 2 x lines inside Band (mW) 1,78 Total Power inside Band (b-d); (mW) 0.049 0.96 89.40 92.189 Total Power for 2 x lines inside Band (dBm) 2.50 Total Power inside Band (b-d); (dBm) -13.09 -0,177 19.51 19.65 overestimated real number of spectral lines 500 overestimate
30、d real number of spectral lines 400 1000 1000 overestimated real Power for 2 x lines inside Band a); (mW) 0.4 overestimated real Power inside Band (b-d); (mW) 0.012 0.1496 0.299 0.861 overestimated real Power for 2 x lines inside Band a); (dBm) -3.979 overestimated real Power inside Band (b-d); (dBm
31、) -19.21 -8.25 -5.24 -0.65 With (7) the maximum total emitted power (PEIRP) when all spectral lines are measured up to its EMC-limit is: +=3093061) dcbaSLTotalPPPPPP = 92.189 mW (12) The maximum emitted overestimated real power (PEIRP) is 0.861 mW for Class A products. The emitted power calculated b
32、y this way is overestimated for Class B as well as Class A products, but is still lower than 1/20 of the of 20 mW limit of EN 50371. This assumption is very conservative because all the different frequencies radiate in different directions and will never reach at the same time any 10 g of human tiss
33、ue. - 13 - Conclusion Compliance with EN 50371 may be demonstrated based on EMC standard measurements and an EMF assessment based on this Technical Report. Such assessment takes the power line Conducted Emissions and the Radiated Electromagnetic Emissions in the frequency range between 10 MHz to 40
34、GHz (300 GHz at later stage) in consideration and proofs that the total emitted power is less than the 20 mW limit. The following steps should be performed to assess the EUT emitted power based on the EMC limits shown in Figure 5. 1) If all the frequencies are measured within the limits and an engin
35、eering analysis according to the number of measured emissions shows that the total of emitted power is clearly below the 20 mW limit, compliance with EN 50371 can be concluded without the need of substitution measurements. 2) If the limits as shown above are exceeded and if these emissions are found
36、 to be significant with respect to the definition in 5.2, then for those frequencies the emitted power has to be evaluated by applying the substitution method (simplified substitution, if the site fulfils free space conditions). If results show that the total emitted power is less than 20 mW, compli
37、ance with EN 50371 can be concluded. 6.1 Measurement method and uncertainties to determine the emitted power All measurement should be done as described within the referenced standards. Consideration of measurement uncertainties Measurements uncertainties are well described within EN 55016. NOTE The uncertainty can increase if the margin of the results of an assessment to any limit also increases.
