1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T K.62TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2004) SERIES K: PROTECTION AGAINST INTERFERENCE System level radiated emissions compliance using mathematical modelling ITU-T Recommendation K.62 ITU-T Rec. K.62 (02/2004) i ITU-T Recommendation K.62
2、 System level radiated emissions compliance using mathematical modelling Summary This Recommendation supports telecommunication operators in demonstrating the compliance of the radiated emissions generated by telecommunication systems. Telecommunication operators typically construct their systems fr
3、om many items of equipment that are each engineered to individually meet EMC requirements, including radiated emissions. This means that a system will typically contain a number of emissions sources (i.e., separate equipment items) at a number of common frequencies. This is true if the system contai
4、ns many items of the same equipment or many items of different equipment. For such a system, the superposition of these multiple emissions has the potential to produce a system emission level that is greater than the system emission limit. This is of fundamental concern for telecommunication operato
5、rs seeking to demonstrate the compliance of the radiated emissions of their systems. This Recommendation introduces a statistical approach to systems radiated emission compliance. By applying a statistical approach to the treatment of basic variables that are not known by the operator, a method is p
6、resented that allows the system emission level to be described statistically in terms of a probability and cumulative probability distributions. These distributions allow the compliance of the system emission level, with respect to a limit, to be expressed as a statistical confidence level (rather t
7、han as a simple “Pass“ or “Fail“ statement). It is proposed that the 80% confidence level be used for compliance to align with the approach taken for series production equipment within CISPR 22. The method presented may also be used by other organizations that either build or operate other systems t
8、hat are formed from the integration of many items of digital electronic equipment that each individually comply with their own radiated emissions limit. Source ITU-T Recommendation K.62 was approved on 29 February 2004 by ITU-T Study Group 5 (2001-2004) under the ITU-T Recommendation A.8 procedure.
9、ii ITU-T Rec. K.62 (02/2004) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operat
10、ing and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, pro
11、duce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In th
12、is Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. int
13、eroperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest
14、that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence
15、, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may b
16、e required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2004 All rights reserved. No part of this publication may be reproduced, by any means whatsoeve
17、r, without the prior written permission of ITU. ITU-T Rec. K.62 (02/2004) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Terms and definitions . 2 4 Abbreviations and acronyms 3 5 General principles. 3 6 Method 5 6.1 System map 6 6.2 System composure 7 6.3 Equipment emissions 7 6.4 Common emissions f
18、requencies. 8 6.5 Evaluation points 8 6.6 Separation matrix 8 6.7 Evaluation method 8 Appendix I Example distributions 11 I.1 N = 2. 11 I.2 N = 3. 12 I.3 N = 4. 13 I.4 N = 5. 14 I.5 N = 10. 15 I.6 N = 100. 16 I.7 Review of probability distributions 17 iv ITU-T Rec. K.62 (02/2004) Introduction Teleco
19、mmunication operators typically construct their systems from many items of equipment that are each engineered to individually meet EMC requirements, including radiated emissions. This means that a system will typically contain a number of emissions sources (i.e., separate equipment items) at a numbe
20、r of common frequencies. This is true if the system contains many items of the same equipment or many items of different equipment. The system as a whole will generally be expected to comply with a radiated emissions limit. This may be the same or different to the limit applicable to the individual
21、constituent equipment. For each common emission frequency, the presence of many individual sources within the system means that the system emission level may be higher than that of the individual equipment. A method is presented that allows the radiated emissions to be assessed without performing pr
22、actical measurement. The method presented is particularly suited to the analysis of systems that are physically very large, for which practical testing is both prohibitively expensive and practically difficult to perform. ITU-T Rec. K.62 (02/2004) 1 ITU-T Recommendation K.62 System level radiated em
23、issions compliance using mathematical modelling 1 Scope This Recommendation provides a procedure for demonstrating the compliance of the radiated RF emissions from telecommunication systems. Telecommunication operators typically construct their systems from many items of equipment that are each engi
24、neered to individually meet EMC requirements, including radiated emissions. This means that a system will typically contain a number of emissions sources (i.e., separate equipment items) at a number of common frequencies. This is true if the system contains many items of the same equipment or many i
25、tems of different equipment. For such a system, the superposition of these multiple emissions has the potential to produce a system emission level that is greater than the system emission limit. This is of fundamental concern for telecommunication operators seeking to demonstrate the compliance of t
26、he radiated emissions of their systems. This Recommendation introduces a statistical approach to systems radiated emission compliance. By applying a statistical approach to the treatment of basic variables that are not known by the operator, a method is presented that allows the system emission leve
27、l to be described statistically in terms of a probability and cumulative probability distributions. These distributions allow the compliance of the system emission level with respect to a limit to be expressed as a statistical confidence level (rather than as a simple “Pass“ or “Fail“ statement). It
28、 is proposed that the 80% confidence level be used for compliance to align with the approach taken for series production equipment within CISPR 22. The method presented may also be used by other organizations that either build or operate other systems that are formed from the integration of many ite
29、ms of digital electronic equipment that each individually comply with their own radiated emissions limit. This Recommendation does not define radiated emissions limits or methods of measurement for telecommunication systems. 2 References The following ITU-T Recommendations and other references conta
30、in provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the
31、 possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a R
32、ecommendation. 1 CISPR 22 (1997), Information technology equipment Radio disturbance characteristics Limits and method of measurement. 2 ITU-R Recommendation P.525-2 (1994), Calculation of free-space attenuation. 3 ITU-R Recommendation P.526-8 (2003), Propagation by diffraction. 2 ITU-T Rec. K.62 (0
33、2/2004) 3 Terms and definitions This Recommendation defines the following terms: 3.1 equipment: Within this Recommendation, the term “equipment“ applies to an item that forms a basic building block of a system. An equipment is generally supplied to the telecommunication operator by a third-party man
34、ufacturer and is placed on the market as a separate item. As a result, an equipment will have been engineered to meet local EMC requirements, including radiated emissions. 3.2 system: Within this Recommendation, the term “system“ applies to that item formed from the integration of many items of equi
35、pment, all at the same physical location, to deliver a defined function. All cables used to interconnect the constituent equipment that together form the system, are also part of the system. All interconnect cables that connect a system with other systems are not considered part of the system. 3.3 s
36、ystem emission level: The emission level of the system, generated through the superposition of the emissions radiated at the common frequency by the systems constituent equipment. Within this Recommendation, this term is represented mathematically as ES. 3.4 probability distribution: The probability
37、 distribution of an unknown, continuous variable, x, that exists within the range xmin x xmaxis written as p(x). The probability distribution quantifies the probability (i.e., the relative frequency of occurrence) with which the variable will exist within the range x and x + dx. By definition, =maxm
38、inxxdxxp 1)( 3.5 cumulative probability distribution: The cumulative probability distribution of an unknown, continuous variable, x, that exists within the range xmin x xmaxis written as CP(x). The cumulative probability distribution quantifies the probability (i.e., the relative frequency of occurr
39、ence) with which the variable x exists within the range: xmin x x where the value x falls within the range xmin x xmaxBy definition, =)()(xxmindxxpxCP 3.6 compliance probability: The probability (i.e., the relative frequency of occurrence) with which the system emission level, ES, will exist within
40、the range: ESmin ES ELwhere: ESminis the lower limit (i.e., minimum value) of the system emission level ELis the system emission limit The compliance probability is, therefore, the probability with which the system emission level will meet the system emission limit. ITU-T Rec. K.62 (02/2004) 3 The c
41、ompliance probability is the cumulative probability value for ES= EL, i.e., =LSminEESSdE)p(Eyprobabilitcompliance 4 Abbreviations and acronyms This Recommendation uses the following abbreviations: CPD Cumulative Probability Distribution EMC Electromagnetic Compatibility ITE Information Technology Eq
42、uipment PD Probability Distribution RF Radio Frequency 5 General principles When a system contains a number of equipment items that individually emit at a common frequency, the superposition of these multiple emissions has the potential to produce a system emission level that is greater than the typ
43、ical equipment emission level. This is a concern for telecommunication operators seeking to act responsibly and manage the EMC of their systems. If the individual equipment emission levels are known (at some known measurement distance) for each common emission frequency, mathematical tools do exist
44、to predict the radiated emissions level of the system at this common frequency. Imagine that a number, N, of radiated RF emissions at some common frequency, f, are incident at some point of measurement. It is possible to represent each radiated emission at the point of measurement in the time-domain
45、 as a simple cosine function. The ith radiated emission may be written as: )cos()(0tEtEii= (1) where: )(tEiis the instantaneous radiated emission level due to the ith radiated emission at time, t, at the point of measurement iE0is the amplitude of the ith radiated emission at the point of measuremen
46、t iis the phase difference between the ith radiated emission and some agreed reference at the point of measurement f= 2The combination of these radiated emissions at the point of measurement can also be expressed as a simple cosine function at the same frequency, viz: )cos()(00tEtE = (2) 4 ITU-T Rec
47、. K.62 (02/2004) where: )(0tE is the instantaneous combined radiated emission level at time, t, at the point of measurement 0E is the amplitude of the combined radiated emission level is the phase difference between the combined radiated emission level and some agreed reference at the point of measu
48、rement and =+=NijNijijiNiiEEEE10012020)cos(2 (3) Careful examination of this equation indicates that, to know the amplitude of the combined radiated emission level, E0, two pieces of information are required for each radiated emission: the amplitude, E0i; the phase, i , with respect to some referenc
49、e. While the telecommunication operator can generally have knowledge of the amplitude, E0i, at the point of measurement, the operator cannot have knowledge of the phase value at the point of measurement. This means that the operator has only half the information required to use this equation. Hence, the conventional mathematical tools are not ideally suited to this problem. It is possible for the telecommunication operator to use the conventional mathematical tools to determine the upper limit to the system emission level. This is the
