1、 I STD-CEPT ERC REPORT 63-FREN 1737 W 2326414 0016070 82T ERC REPORT 69 European Radiocommunications Committee (ERC) within the European Conference of Postal and Telecommunications Administrations (CEPT) PROPAGATION MODEL AND INTERFERENCE RANGE CALCULATION FOR INDUCTIVE SYSTEMS 10 KHZ - 30 MHZ Marbe
2、lla, February 1999 f STDeCEPT ERC REPORT bS-FREN Lqqq 2326414 001b071 7bb m Copyright 1999 the European Conference of Postal and Telecommuiiications .idministrations (CEPT) STDmCEPT ERC REPORT bS-FREN 1797 232b414 00Lb072 bT2 PROPAGATION MODEL AND INTERFERENCE RANGE CALCULATION FOR INDUCTIVE SYSTEMS
3、 10 KHZ . 30 MHZ 1 2 3 4 5 6 7 8 9 INTRODUCTION . 2 THE NEAR FIELD MODEL . 3 THE FAR FIELD MODEL . 5 THE ITU-R GROUNDWAVE PROPAGATION MODEL . 12 FREE SPACE PROPAGATION 14 INTERFERENCE RANGE 15 THE BANDWIDTH RATIO 16 THE INTERFERENCE RANGE CALCULATION 16 EXAMPLE OF A ROLL-OF“ CURVE FOR AN INDUCTIVE L
4、OOP SYSTEM . 20 ANNEX A DATA ACCORDING “0 ITU-R P.368-7 22 EXECUTIVE SUMMARY . 1 A“Ex B EXPECTED NOISE FELD STRENGTH LEVELS 26 STD-CEPT ERC REPORT b9-FREN 1999 W 232b4LY ERC REPORT 69 Page i EXECUTIVE SUMMARY Inductive short range radio systems are increasingly being introduced into the frequency ba
5、nds below 30MHz. These systems are normally allowed to operate on a non-interference basis to existing services, after appropriate compatibility studies have been made. The ERC could not identify a suitable propagation model for inductive systems which is necessary for the compatibility studies. The
6、re is no suitable model available in ITU-R, although there is some relevant information. With the assistance of manufacturers of inductive systems, the ERC has produced the following report on a propagation model and interference range calculation for use in compatibility studies concerning inductiv
7、e systems in the frequency range 10 kHz - 30 MHz. To assess the interference potential of an inductive system the field strength at a given distance is calculated, this may be compared to the protection requirements of a specific service, or to predicted noise levels, to determine the interference r
8、ange. The Biot-Savart law can be used to calculate the magnetic dipole moment, however this is only valid when calculating the field strength very close to the antenna within the near field range. For this study longer distances are considered anc so Maxwells equations are used to determine the magn
9、etic dipole moment from the expected field strength at 10m. The magnetic dipole moment is the product of the total current in the inductive loop, multiplied by the surface area; from this figure an effective radiated power level can be calculated; once this is known ITU-R Recommendation P.368-7 can
10、be used to determine the function of field strength with distance. The interfering range is the distance at which field strength decays to either the specified protection level or, where this is not available, to the noise level. Figure B1 contains a summary of ITU-R Recommendation P.372 for both at
11、mospheric and manmade noise. The methodology to determine the interference range can be found in Section 9. Section 9 contains a complete algorithm for the interference range calculation which can be implemented as a computer program. A sample program has been made to complement this report, a copy
12、is available from the ERO. STD-CEPT ERC REPORT by-FREN 3999 W 232b4114 00116074 475 ERC REPORT 69 Page 2 PROPAGATION MODEL AND INTERFERENCE RANGE CALCULATION FOR INDUCTIVE SYSTEMS 10 KHZ - 30 MHZ 1 INTRODUCTION The propagation model for inductive systems is split into four parts: 1. The near field m
13、odel. 2. The far field model. 3. The ITU-R groundwave propagation model. 4. The free space model. The near field model starts from the real antenna structure. The magnetic field strength is calculated using the Biot- Savart law. It is used to calculate the (effective) magnetic dipole moment from the
14、 measured magnetic field strength at the specified measuring distance. There is a need to use this model when the dimensions of the inductive loop are of the same order as that of the measuring range. When the dimensions of the loop are smaller (most often the case), a simplified formula can be used
15、 to calculate the magnetic dipole moment, or the far field model can be used. As the near field model is in principle a magneto static model it cannot be used for cases wherein the measuring distance is equal or larger than the radian wavelength (h1271). Only magnetic dipoles are considered, not the
16、 far field cancelling antennas as quadropole (e.g. figure of 8) antennas. For the purpose of estimating the far field radiation far field cancelling antennas can be considered as a magnetic dipole wherein the magnetic dipole moment is the nett result of the cancelling of separate magnetic dipoles in
17、 counterphase. In the compatibility studies the radiation and field strength is of interest at large distances only, and its relation to the field strength measurements at the specified measurement ranges. Studies have shown that for antenna dimensions up to 2 m, the specific quadropole effects can
18、be ignored at measuring distances of 10 m or more. For larger antenna dimensions the measuring distance of 30 m may be useful. The dipole moment is considered as the source of a radiated power Pd from where, according to the data from the recommendation ITU-R P.368-7, the field strength at 1 km or l
19、arger distances can be calculated. This data is accurate within 1 dB. For distances smaller than 1 km an estimated 40 dB/decade or 20 the lower diagram shows the situation when the transition distance lies within lkm. The value of the second asymptote at 1 km distance, EnFmp,o,r,JO, is shown in Tabl
20、e Al and in Figure Al of Annex A for frequencies between 10 kHz and 30 MHz, for the given types of ground. STD-CEPT ERC REPORT by-FREN 1999 m 2326434 OOLbOBb 177 ERC REPORT 69 Page 14 The transition point between ,the three regions depends completely on the frequency and on the conductivity ant: per
21、mittivity of the ground. The transition range, drransirion, can be calculated now from both asymptotic field strength values at 1 km distance, namely the field strength for the frequency under consideration at 1 km distance, according to the 40 dB/decade asymptote, Earymptote,do, and the value of th
22、e field strength according to the 20 dB/decade asymptote at 1 km distance, E-mp,o,e,20 (= 109.5 dBpV/m), both for a radiated power of 1 kW. 2 = Emymptore - 4010g(d/lOOO) (E2 on 2nd asymptote) (15) Ei = Easymptote,20 - 2010g(d/lOOO) (El on lSt asymptote) (16) (Emyiitptore2 - Easyinptore,d d = 1000*10
23、- 20 (d in meter) transition The far region. The roll-off increases to 150 dB/decade at distances greater than 100 - 3000 km. With the low radiated powers of the short range device (SRD) inductive systems the distances of concern are much less than100 km. This means that the far region in not of int
24、erest when considering SFWinductive systems. Note. Carefully inspecting the curves for frequencies = h/2 *2.354 k2d3 Jk4-k2d2 + d4 m = 1H/.47c. Thefield strength at the measuring position is maximal in the coplanar direction. OUTPUT Magnetic dipole moment, m, in Amz. CALCULATE 20 2 3c4 p = -.(m) rad
25、 OUTPUT Effective radiated power,Prd-dB. in dBkW Prd-nw,in nW. CALCULATE The interference level at a distance of 1 km is: Eint-lbn = Earymprotc,40 + Prd-dB The noise level is: EnOise = EnObez.i + 10*10glO(BW/2.7) The acceptable interference level is: Eintcercerrncc = EnOise + B WR IF groundwave is T
26、RUE CALCULATE IF rinterfercnce drronririon AND rintcrfcrence A271 *2-354 OUTPUT The interference range extends into the 40 dB/decade range. The groundwave interference range is rintrgerenre m. ELSE Cfronr formula (14) STD-CEPT ERC REPORT 69-FREN 1999 2326414 Lb91 554 m ERC REPORT 69 Page 19 IF rinre
27、derence u271 *2.354 OUTPUT The interference range is limited to the 20 dB/dec. roll-off range. The groundwave interference range is rjn,egerence m. ELSE (from formula (7) IF riruetferme U2n OUTPUT The interference range is close to the near field range. The groundwave interference range is rierferem
28、c m. ELSE (from formula (7) OUTPUT The interference range is inside the near field range. The groundwave interference range is rimetference m. IF fiee space is TRUE *O + 49.5 + dB - EinrerfcrLrpnrr 20 Cnnrerference - 10 (from formula (14) IF rinrerference *2.354 OUTPUT The interference range is limi
29、ted to the 20 dB/dec. roll-off range. The free space interference range is rinrerfrreme m. ELSE m Cnterjerencc - - J Hinrevcrenceun Ifrom formula (7) IF rinrer,ferencc OUTPUT The interference range is close to the near field range. The free space interference range is r,nrptfclpnce m. ELSE (from for
30、niula (7) STD-CEPT ERC REPORT bS-FREN LSSS 232b4L4 00Lb092 490 = ERC REPORT 69 Fage 20 OUTPUT The interference range is inside the near field range. The free space interference range is rinreqerencr m. 9 EXAMPLE OF A ROLL-OFF CURVE FOR AN INDUCTIVE LOOP SYSTEM Figure 9 gives an example of the roll-o
31、ff of an inductive loop system. In this example the radian wavelength U271 equals 10 m, and the field strength at the measuring distance of 10 m is 9 dBpAlm. For the type of ground “Land“ is assumed with o = 3 mS/m and E = 22. Figure Al in Annex A gives for Earympo,c,40 97 dBpV/m. Combined with an c
32、alculated radiated power Prod= -95 dBkW the field strength at 1 km distance will be 2 dBpV/m in the case of groundwave propagation. In the free space situation the field strength at 1 km is obtained by adding Prod= -95 dBkW to Eacynytotc, = 109.5 dBpV/m: 14.5 dBpV/m. From both field strength values
33、at 1 km the 20 dB/dec. and the 40 &/dec. curves are drawn. STDgCEPT ERC REPORT bS-FREN 1999 232b414 002b093 327 4 Inside ERC REPORT 69 Page 21 b4ciose+ 20 dB/decade + 40 dB/decade STD*CEPT ERC REPORT b9-FREN L977 232b414 0016094 263 ERC REPORT 69 Pagc 22 ANNEX A Data according to ITU-R P.368-7 Table
34、 Al. Table of the asymptotic value of field strength of 1 kW transmitter at 1 km distance E.lsywiotl, List of ground types according ITU-R PN.368-7: 1. Sea water, low salinity. 2. Sea water, average salinity. 3. Fresh water. 4. Land (very wet). 5. Wet ground. 6. Land. 7. Medium dry ground. 8. Dry gr
35、ound. 9. Very dry ground. 1 o. 11. Fresh water ice, -1 “C. Fresh water ice, -10 OC. o= 1 S/m, o = 5 S/m, o = 3 mS/m, o = 30 mS/m, o = 10 mS/m, o = 3 mS/m, o= 1 mS/m, o = 0.3 mS/m, o = 0.1 mS/m, o = 30 pS/m, o = 10 pS/m, E =80. E =70. E =80. E 40. E =30. E =22. E =15. E = 7. E = 3. E = 3. E = 3. STD-
36、CEPT ERC REPORT 69-FREN 3999 2326434 0036095 LTT ERC REPORT 69 Page 23 Figure Al. Field strength of the 40 dB/decade roll-off asymptote at 1 km distance form a 1 kW transmitter. STD-CEPT ERC REPORT 67-FREN 1999 m 2326414 001ibOSb 036 m ERC REPORT 69 Page 24 Table of 20 to 40 dB/decade roll-off trans
37、ition distance. accordina ITU-R P.368-7 km .d I Figure: 1 2 3 4 5 6 7 8 (3 S/m 1 5 3e-3 30e-3 10e-3 3e-3 le-3 3e-4 E 80 70 80 40 30 22 15 7 33 30e-6 10e-6 9 1 e-4 3 I Frequency 1 I l I I l I I I 51 O 370 260 140 100 30 44 13 24 8 90 55 15 . I 5.5 I 24 14 5.5 3.1 1.2 1.4 0.79 0.50 0.42 I 0.40 I 1 750
38、 I I170 It70 I 7 I65 I 22.5 I 7 I 2.2 I 0.75 0.28 0.27 1 0.27 I I 1 I MHz 1140 I150 I 4.8 I40 I 13 I 3.3 I 1.3 I 0.47 0.21 0.21 I 0.20 I I 1.5 I 1125 I140 I 2.7 I 18 I 6 I 1.6 I 0.71 I 0.27 0.1 3 0.14 I 0.13 I 0.094 0.067 0.050 0.038 0.027 0.050 0.050 1 0.040 0.042 0.027 1 0.027 1 0.021 I 0.021 1 0.
39、021 I 15 I I 6.5 1 28 I 0.251 0.18 I 0.10 I 0.067 I 0.047 I 0.025 0.01 3 0.013 I 0.013 1 I I 20 I I 3.4 I 17 I 0.191 0.12 I 0.071 1 0.053 I 0.035 I 0.019 0.011 I 0.011 I 0.01 1 0.007 I 30 I I 1.7 I 7.5 I 0.13 I 0.07 I 0.047 I 0.035 I 0.02410.013 0.007 I 0.007 -1 _ _ Table A2. Table of 20 to 40 dB/de
40、cade roll-off transition distance. STD CEPT ERC REPORT 69-FREN 232b414 Distance for the transition from 20 dB/decade 0036097 T72 ERC REPORT 69 Page 25 to 40 dB/decade roll-off. STD-CEPT ERC REPORT b7-FREN 1977 232b414 OOLb09 707 ERC REPOR 69 Page 26 ., ANNEX B Expected noise field strength levels In
41、troduction In this Annex a study is made into the noise levels that primary radio users will encounter. Three sources of noise will be taken into account: the atmospheric noise, the galactic noise and manmade noise. Together they form the absolute lower sensitivity limit which a receiving station ha
42、s to cope with. This goal can be achieved by using the information of the ITU-R Recommendation P.372 and converting noise powers to noise field strength levels, depending on frequency and statistical distribution. The Recommendation gives atmospheric noise data due to lightning as a function of: the
43、 geographical position, the four seasons of the year, six blocks of 4 hours a day, and the frequency. Three curves are derived, which give probabilities of 20 %, 50 %, and 80 % that the actual noise level will be lower than the indicated field strength (distribution function of the field strength).
44、A receiver bandwidth of 2.7 kHz is assumed, field strength values for various bandwidths can be calculated from this curves. The Recommendation also gives the relationships between the levels of manmade noise in four environments, such as: quiet rural, rural, residental, business, and the frequencie
45、s are given. A relationship for the galactic noise level is also given. Estimation of the atmospheric noiselevels. Atmospheric noise is the result of natural electrical activity (thunderstorms) in the earths atmosphere, propagated over long distances. Thousands of lightning discharges per minute res
46、ult in a EM field with a nature of noise. As well as the location of the electrical activity the propagation to the receiver location is strongly dependendent on the season of the year as well as on the time of the day. Also the geographical location of the receiver is relevant. ITU-R P.372 gives th
47、e noise figure (Fa) lines mapped on the earths surface for every season and for every 4 hour block of the day. These noise figures are valid for the frequency of 1 MHz. Additional graphs show the noise figures for other frequencies, 10 kHz to 100 MHz, using the 1 MHz value as a parameter. The noise
48、figures are estimated for the European area and collected in Table B 1 of this Report for frequencies between 10 and lo00 kHz, and in Table B2 for frequencies between 1 and 20 MHz. STD-CEPT ERC REPORT b9-FREN 1999 2326434 00Lb099 845 Winter ERC REPORT 69 Page 27 hLT 10 20 00-04 157 145 Season I peri
49、od 1 30 138 136 124 F /dB over kTo) 50 70 128 122 124 117 118 99 08-12 12-16 104-08 I158 I144 153 135 155 136 120-24 1154 I142 1134 1123 Ill6 I Spring 100-04 I157 I146 I138 I128 I122 88 i68 i56 144 135 1 123 I108 197 187 169 159 146 139 108 114 I I I I I I 116-20 1154 (140 Il31 Il18 (110 92 83 74 67 62 . 98 89 79 74 68 I 104-08 1157 1146 1137 (127 1119 I 108-12 1151 1141 1131 1118 1109 104-08 I157 I142 I134 I121 I112 1 I 112-16 (158 Il43 I133 I121 I112 116-20 1164 1151 1142 1131 (123 99 101 120-24 I160 1148 1141 I131 1124 78 66 52 4
