1、 Recommendation ITU-R P.534-5(02/2012)Method for calculatingsporadic-E field strengthP SeriesRadiowave propagationii Rec. ITU-R P.534-5 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectrum by all radioco
2、mmunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication Conferences and Ra
3、diocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent statements and licensing
4、declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Recommendations (Also available online at h
5、ttp:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related satellite services P Radio
6、wave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite news gathering TF Time signals and frequency stan
7、dards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2012 ITU 2012 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, with
8、out written permission of ITU. Rec. ITU-R P.534-5 1 RECOMMENDATION ITU-R P.534-5 Method for calculating sporadic-E field strength (Question ITU-R 221/3) (1978-1982-1986-1990-1999-2012) The ITU Radiocommunication Assembly, considering a) that propagation by sporadic E is an important source of interf
9、erence at low VHF; b) that the calculation method of sporadic-E field strength given in Annex 1 to this Recommendation has been proved to be practical and reliable; c) that there exists no other practical method, recommends 1 that the calculation method in Annex 1 be adopted as the method to be used
10、 for estimation of sporadic-E field strength for the low- and mid-dip latitudes; 2 that more foEs and sporadic-E field strength data be collected, particularly in the high latitude regions. In the meantime, caution should be exercised if the method in Annex 1 is used in these regions. Annex 1 Propag
11、ation by sporadic E 1 Introduction The present text sets out a statistical method for calculating the field strength of signals propagated by means of ionospheric sporadic E (Es) at VHF and, possibly, at higher portions of the HF bands, for distances up to 4 000 km. The calculation is based upon the
12、 fact that the field strength is very closely correlated with foEs, that is to say, the critical frequency of sporadic-E layer at vertical incidence at the path mid-point. It should be noted that the method is suitable for application to an ionospheric radio circuit in the case where the regular pro
13、pagation mode via the E or F2 layer does not exist. When using the method at HF therefore, caution should be exercised if the possibility of regular layer propagation exists. (See Recommendation ITU-R P.533 for regular-layer propagation.) The data provided by the Recommendation are restricted to geo
14、magnetic latitudes between 60. 2 Rec. ITU-R P.534-5 In the equatorial region some sky-wave paths of medium distance propagation (500-2 000 km), clearly indicate Es propagation, which must be distinguished from the much more important effects of trans-equatorial propagation (TEP) in the area. Low lat
15、itude Es propagation field strength is approximately the same as estimates for mid-latitudes in this Annex. However the parameter showing the greatest change is the percentage of time as a function of the vertical incidence critical frequency (foEs) (Figs. 2 to 6 for middle magnetic latitudes). Ther
16、efore, alternative Figs. 16 to 21 are provided for use in the low magnetic latitude region. The method has the following features: Es field strength is predicted by means of the statistical correspondence of a value of ionospheric attenuation to that of foEs at a given rate of occurrence; the ionosp
17、heric attenuation of the Es signal is represented by a function of the ratio of the signal frequency f to foEs and the surface distance between the transmitting and receiving stations; some useful probability charts and world maps of foEs are provided for quick and easy evaluation of the Es field st
18、rength. 2 Formula for sporadic-E field strength Es field strength or receiver input voltage can be expressed as follows: E = E0+ P + Gt Lt dB (1) E0= 104.8 20 log l dB (1a) V = V0+ P + Gt+ Gr Lt Lr (2) V0= 133 20 log l 20 log f (2a) where E : predicted field strength (dB(V/m) E0: theoretical inverse
19、 distance field strength (dB(V/m), for 1 kW radiated power and isotropic transmitting antenna V : median voltage developed across receiver input terminals (dB(V) V0 : theoretical inverse distance receiver input voltage, for 1 kW radiated power and isotropic transmitting and receiving antenna matched
20、 to 50 feeder for a signal frequency of f (MHz) P : transmitter power (dB(1 kW) Gt: gain of the transmitting antenna relative to an isotropic antenna, (dB) Gr: gain of the receiving antenna relative to an isotropic antenna, (dB) Lt: losses including feeder loss and mismatch loss of the transmitting
21、antenna, (dB) Lr: losses including feeder loss and mismatch loss of the receiving antenna, (dB) : ionospheric attenuation (dB) as shown by the broken line curves in Fig. 1 l : transmission path length (km), (see equation (5) f : signal frequency (MHz). Rec. ITU-R P.534-5 3 For the calculation by com
22、puter, for single-hop propagation signal, (1 hop)(d ), is given approximately by: +=2806601expfoEs60022.0250130140)(222)1(dfddddhop(3) and for double-hop propagation signal, (2 hop)(d ) approximately by: =26.2)()1()2(ddhophop(4) and l : transmission path length (km) is given by: 2/10002020)2/(cos()(
23、2)(2 RdhRRhRRl +=(5) where: R0: effective radius of the Earth, 8 500 kmh : height of Es layer, 120 km d : surface distance between the transmitting and receiving stations (km) f : signal frequency (MHz) foEs : critical frequency of sporadic-E at vertical incidence at a given rate of occurrence (MHz)
24、. The accuracy with which equations (3) and (4) reproduce the measured values of is indicated in Fig. 1 where they are plotted as the broken line curves. The use of equation (3) should be restricted to distances less than 2 600 km with the values of f/foEs between 1 and 8, where the error is less th
25、an 5 dB. The use of equation (4) should be restricted to distances between 2 600 and 4 000 km, and to values of f/foEs between 2 and 5.5; the error will then be less than 10 dB. 4 Rec. ITU-R P.534-5 FIGURE 1 Chart of ionospheric attenuation for Es propagation 0 1 000 2 000 3 000 4 000010203040506070
26、Surface distance (km)dfrom observed valuesfrom empirical formulae (3) and (4)Ionospheric attenuation(dB)Single-hop propagation Double-hop propagationf/foEs=1f/foEs=25.54.53.52.53 A procedure for calculating sporadic-E field strength A procedure for calculating Es field strength is as follows: Step 1
27、 : calculate a value of E0(or V0) corresponding to given value of l using equation (1a) (or equation (2a). Step 2a : (path mid-point dip latitude outside 20) : read off a value of foEs at a given time percentage of occurrence in the desired region and season using one of Figs. 2 to 6. If a more accu
28、rate prediction is required, read off a value of the percentage of time that foEs exceeds 7 MHz at the path mid-point using a pertinent map of Figs. 12 to 15 and determine a value of foEs by drawing a new line on the relevant one of Figs. 2 to 6 as described in 4.1. If a prediction of diurnal variat
29、ion is required, read off a value of foEs on a pertinent figure of Figs. 7 to 11. Step 2b : (path mid-point dip latitude within 20) : determine the dip angle for the ionospheric reflection point and read off a value of foEs at a given percentage of time of occurrence under the desired region and sea
30、son using Figs. 16 to 21. Step 3 : calculate f/foEs. Step 4 : using the broken line curves in Fig. 1, read off a value of corresponding to the given value of d and the calculated f/foEs, or, for an approximate value, calculate using equations (3) and (4). Rec. ITU-R P.534-5 5 Step 5 : calculate the
31、predicted value of E (or V) by equation (1) (or (2), using given values of P, Gt, Gr, Lt, Lrand the value obtained for . 4 Probability of occurrence of foEs It is necessary to clarify the statistical characteristics of foEs since it undergoes sporadic behaviour changes with location and time. The wo
32、rld map of foEs, such as that in Recommendation ITU-R P.1240, can be used for high accuracy of prediction. On the other hand, simplified statistical data of foEs are also very useful in cases where the general tendency of temporal variation is to be obtained. For the purpose of predicting the averag
33、e Es field strength, probability curves of foEs have been prepared for the five mid-latitude regions of Europe and North Africa, North America, Asia (Far East), South America and a buffer region between these regions as shown in Figs. 2 to 11. For low latitudes, probability curves of foEs have been
34、prepared for America, Asia and Africa as shown in Figs. 16 to 21. The high latitude region characteristics need to be further clarified in the future. 4.1 Mid-latitudes To provide detailed geographic characteristics of foEs, the world maps of the percentage of time for which foEs is equal to or grea
35、ter than 7 MHz during the months of May-August (northern summer), November-February (southern summer), the months of March, April, September and October (equinoctial months, north and south) and for twelve months, are specifically included as Figs. 12-15. As may be seen in these world maps, contours
36、 of time percentage are shown between 60 geomagnetic (or dipole) north and south latitudes. A low latitude region around the dip equator is excluded. Figures 2 to 6 show the relation between the value of foEs and the time percentage of its occurrence. In these figures, curves for the summer months,
37、winter months and equinoctial months are all represented by straight lines connecting two points corresponding to values of time percentage exceeding 7 MHz and 10 MHz, respectively, of foEs. These are subject to the so-called Phillips frequency-dependence rule. This rule is a strictly empirical one
38、which works quite well at mid-latitudes for percentages of time less than about 30% and for frequencies above foE, the critical frequency of the normal E layer. Caution should be exercised in the use of the Phillips rule for frequencies above about 100 MHz and for equatorial and high latitudes. The
39、Phillips rule is: log p = a + b f (6) where: p : probability of occurrence of foEs f f : frequency (MHz) a and b : adjustable constants, such that b is the slope in a plot of log p as a function of f. A curve showing the annual average, has values of time percentage of about one third of the corresp
40、onding values for the summer months in the low percentage of time ranges. For reference, probability curves are added to the respective figures for the period of daytime (0800-2300 h) in the summer months, when the most intense sporadic E is observed. When there exists a difference between a value o
41、f time percentage of foEs for 7 MHz, as obtained by the world maps in Figs. 12, 13, 14 or 15 and that obtained by the average probability curve for a Region, as seen in Figs. 2 to 6, a value of foEs may be determined for a given percentage of time, by using a new probability curve redrawn so as to b
42、e parallel to the original curve in the respective region and displaced by an amount equal to the difference of those values. 6 Rec. ITU-R P.534-5 Figures 7 to 11 exhibit diurnal variations of occurrence of foEs in a time block of 4 h in the above four regions for the summer and non-summer months, a
43、ccording to their distinctive characteristics. It is noticeable that a definite minimum of foEs is observed shortly after midday in regions B and C, particularly in summer. For the purpose of predicting the detailed behaviour of Es signal strength, it may be necessary to show the diurnal variations
44、of foEs in terms of a time block smaller than 4 h. 4.2 Low latitudes Figures 16 to 21 show the relation between the value of foEs and the time percentage of its occurrence for low latitudes. In these figures, a clear difference is observed between a very narrow belt around the dip equator ( 6 dip an
45、gle) and the adjacent region up to 20 dip, which might be called equatorial and sub-equatorial regions respectively. As seen from comparison with Figs. 2 to 6, the sub-equatorial region, but not the equatorial one, is subject to the Phillips law. FIGURE 2 Values of foEs equalled or exceeded for indi
46、cated percentage of time for region A 2 4 6 8 10 12 14 16 1810210125110225525foEs (MHz)PercentageoftimeEurope and North AfricaMay to August (0800-2300 h)May to Augustannual averageMarch, April, September and OctoberNovember to FebruaryRegion A:I:II:III:IV:V:Rec. ITU-R P.534-5 7 FIGURE 3 Values of fo
47、Es equalled or exceeded for indicated percentage of time for region B 2 4 6 8 10 12 14 16 1810210125110225525foEs (MHz)PercentageoftimeNorth AmericaMay to August (0800-2300 h)May to Augustannual averageMarch, April, September and OctoberNovember to FebruaryRegion B:I:II:III:IV:V:8 Rec. ITU-R P.534-5
48、 FIGURE 4 Values of foEs equalled or exceeded for indicated percentage of time for region C 2 4 6 8 10 12 14 16 1810210125110225525foEs (MHz)PercentageoftimeAsia (Far East)May to August (0800-2300 h)May to Augustannual averageMarch, April, September and OctoberNovember to FebruaryRegion C:I:II:III:I
49、V:V:Rec. ITU-R P.534-5 9 FIGURE 5 Values of foEs equalled or exceeded for indicated percentage of time for region D 2 4 6 8 10 12 14 16 1810210125110225525foEs (MHz)PercentageoftimeSouth AmericaMay to Augustannual averageMarch, April, September and OctoberNovember to FebruaryNovember to February (0800-2300 h)Region D:II:III:IV:V:VI:10 Rec. ITU-R P.534-5 FIGURE 6 Values of foEs equalled or exceeded for indicated percentage of time 2 4 6 8 10 12 14 16
