1、 Report ITU-R RS.2185(10/2010)Study on compatibility between “arrival time difference” (ATD) stations of the meteorological aids service and stationsof the radionavigation service in the frequency band 9 to 14 kHzRS SeriesRemote sensing systemsii Rep. ITU-R RS.2185 Foreword The role of the Radiocomm
2、unication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulato
3、ry and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication Conferences and Radiocommunication 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/
4、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 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-
5、R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Reports (Also available online at http:/www.itu.int/publ/R-REP/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broa
6、dcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-
7、satellite and fixed service systems SM Spectrum management Note: This ITU-R Report was approved in English by the Study Group under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2011 ITU 2011 All rights reserved. No part of this publication may be reproduced, by any me
8、ans whatsoever, without written permission of ITU. Rep. ITU-R RS.2185 1 REPORT ITU-R RS.2185 Study on compatibility between “arrival time difference” (ATD) stations of the meteorological aids service and stations of the radionavigation service in the frequency band 9 to 14 kHz (2010) TABLE OF CONTEN
9、TS Page 1 Executive summary 2 2 ATD and radionavigation station deployments at June 2010 . 2 3 Geographical separation between stations 4 4 Typical radionavigation station parameters 4 4.1 RNAV transmitter characteristics . 4 4.2 RNAV antenna efficiency . 5 5 Typical ATD station parameters . 5 6 Con
10、siderations of atmospheric noise 6 7 Interference mitigation . 7 8 ATD receiver sensitivity and maximum permissible interference . 8 9 VLF propagation modelling . 10 9.1 VLF dominate mode theory 10 9.1.1 Historical VLF measurements deriving typical attenuation rates for various VLF path profiles 10
11、9.1.2 Generalizing attenuation as a factor of frequency and ground conductivity 11 9.1.3 Sharing analysis using dominate mode theory by Wait 10 . 12 9.1.4 Dominate mode graphs of predictive field-strength levels 12 9.1.5 Dominate mode sharing analysis results 16 2 Rep. ITU-R RS.2185 Page 9.2 Propaga
12、tion of paths based on published research as a basis for compatibility between radionavigation services and ATD sensor stations . 16 9.2.1 United States of America towards the Mediterranean . 17 9.2.2 CCIR measurements and empirical modelling 18 9.2.3 Recommendation ITU-R P.684 19 9.2.4 Predictions
13、using Recommendations ITU-R P.368 and ITU-R P.684 combined with results of historical measurements 20 9.2.5 VLF measurements in the Pacific 22 9.2.6 Atlantic measurements by the Naval Ocean Systems Center 23 9.2.7 Results of sharing analysis using published VLF propagation data 24 9.2.8 Published VL
14、F propagation data sharing analysis results . 26 10 Conclusions on sharing between the radionavigation services and ATD sensors of the meteorological aids service 27 References 28 1 Executive summary This Report outlines the results of studies into the work seeking to define sharing criteria to mana
15、ge compatibility between transmitting stations of the radionavigation services and passive arrival time difference (ATD) receivers operating in the meteorological service in the frequency band below 20 kHz. It discusses various issues and aspects of VLF propagation and concludes on the sharing and r
16、egulatory management aspects of ATD sensors and radionavigation services within the frequency band under discussion. The findings, reflecting the real life sharing environment for many years, are that sharing between both services is a high possibility and practicality. Notwithstanding the technical
17、 aspects discussed herein, this is partially due to the nature of deployment characteristics of both services, and interference mitigation implemented by the arrival time difference system of the meteorological aids service. 2 ATD and radionavigation station deployments at June 2010 Figure 1 shows t
18、he location of each of the existing ATD receiver locations (shown in green) and known RNAV transmitter locations (shown in red). Rep. ITU-R RS.2185 3 FIGURE 1 ATD receiver and RNAV transmitter locations Actual ATD and RNAV site locations are shown in Tables 1 and 2. TABLE 1 ATD receiver site locatio
19、ns Site name Latitude (decimal) Longitude (decimal) Valentia 51.939719N 10.244534W Norderney 53.712421N 7.152314E Exeter 50.728043N 3.475605W Lerwick 60.139419N 1.185009W Akrotiri 34.587151N 32.989052E Gibraltar 36.152706N 5.348185W Keflavik 63.968330N 22.614094W Helsinki 60.203932N 24.961027E La Re
20、union 20.896791S 55.485258E Azores 38.658939N 27.223078W Payerne 46.812123N 6.943854E Camborne 50.218553N 5.327223W 4 Rep. ITU-R RS.2185 TABLE 2 Radionavigation site locations Site name Latitude (decimal) Longitude (decimal) Komsomolsk Na Amure 50.5667N 136.96667E Krasnodar 45.0333N 38.65E Novosibir
21、sk 55.0667N 82.9667E 3 Geographical separation between stations The physical separation distance between each ATD receiver and each of the RNAV transmitters is also shown in Table 3. TABLE 3 Separation distances between ATD and RNAV site locations Separation distance to RNAV site (km) ATD receiver s
22、ite Komsomolsk Na Amure Krasnodar Novosibirsk Valentia 8 216 3 616 5 707 Norderney 7 520 2 453 4 668 Exeter 8 156 3 613 5 445 Lerwick 7 154 3 106 4 705 Akrotiri 7 994 1 259 4 428 Gibraltar 9 701 3 798 6 699 Keflavik 7 164 4 263 5 343 Helsinki 6 289 1 917 3 388 La Reunion 11 222 7 535 8 850 Azores 9
23、985 5 357 7 685 Payerne 8 185 2 446 5 141 Camborne 8 262 3 300 5 581 4 Typical radionavigation station parameters The following section outlines various technical parameters of the radionavigation service. 4.1 RNAV transmitter characteristics The parameters in Table 4 were used as being representati
24、ve of a typical RNAV transmitter. Rep. ITU-R RS.2185 5 TABLE 4 Radionavigation stations parameters Name of transmitting station Occupied bandwidth (Hz) Transmitting centre frequency (kHz) Antenna input power (dBW) Komsomolsk Na Amure 100, 200 11.905, 12.500, 12.649, 13.281, 14.881, 15.625 57 Krasnod
25、ar 100, 200 11.905, 12.500, 12.649, 13.281, 14.881, 15.625 57 Novosibirsk 100, 200 11.905, 12.500, 12.649, 13.281, 14.881, 15.625 57 4.2 RNAV antenna efficiency The efficiency of a typical RNAV transmitting antenna at these frequencies is not known and is likely to be very small. Work by Raghuram et
26、 al. 1974, cites efficiencies of VLF transmitting antennas as low as 6 to 8% over a 3 000 m thick ice sheet, whereas over a conducting earth it is as low as 0.1% 1. However references in declassified documents on the historical Omega system 2 provides efficiency values of the order of 10%. For these
27、 studies the radionavigation services have an assumed radiated power of 40 dBW. For radiated powers greater than 40 dBW, the required separation distances between stations shown in this study would be greater. 5 Typical ATD station parameters Typical ATD station parameters are presented in Table 5.
28、TABLE 5 Typical ATD system parameters Technical characteristics of the ATD system Receiver centre frequency 9.766 kHz Receiver (sensor unit) amplifier gain 12 dB if switched on by control software (normally the case) otherwise zero 3 Measurement bandwidth 3 kHz Total “pass-band” 6.87 to 20.6 kHz Ant
29、enna type and directivity 2 m vertical polarization, omnidirectional whip Software filter Broad-band high-pass filter (3 dB at 2.0 kHz), cascaded with low-pass filter (0.28 dB pass-band limit at 17.75 kHz) Software narrow-band pass filter 3 dB bandwidth 2.5 kHz 10 dB bandwidth 4.3 kHz 20 dB bandwidt
30、h is 5.7 kHz Typical receiver noise floor 70.4 dBm in a 5 kHz reference bandwidth 6 Rep. ITU-R RS.2185 6 Considerations of atmospheric noise Recommendation ITU-R P.372-9 gives typical values for radio noise between 0.1 Hz and 100 GHz. Noting that in case of a ATD receiver the antenna is a 2 m monopo
31、le, used at frequencies where equates to between 25 to 38 km; equation (7) in this recommendation gives a suitable method to use to approximate levels of atmospheric noise at the input to this type of antenna. Equation (7) provides the method, for a short (h 2 000 km, the r.m.s. vertical electric fi
32、eld-strength field E at a great circle distance d from a transmitter, radiating power P(kW) is given by: meadPhEmvad2/1)/(sin300where: a: the radius of the Earth h: the height of the ionosphere reflecting layer (km) : the wave length (km) : the attenuation factor (dB). As the attenuation factor is t
33、he only unknown factor for calculation of relative field-strength at d for a given transmitted power, by using data derived from real measurements, typical propagation attenuation factors for values d 2 000 km can be derived. 9.1.1 Historical VLF measurements deriving typical attenuation rates for v
34、arious VLF path profiles Using dominate mode theory and comparing empirical measurements work published by James R. Wait 5, A. P. Nickolaenko 6, Round, Eckersley, Tremellen the other curves are displaced20 dB from each other.It can be seen that for a pure sea path over the Pacific at night, for dist
35、ances greater than 2 000 km the attenuation is approximately 10 dB over 8 000 km, equating to an average of 1.25 dB per 1 000 km. These figures agree with the values given in Tables 7 and 8. 9.2.3 Recommendation ITU-R P.684 This section outlines specific night time plots made from a transmitter base
36、d at Halifax in Canada on a bearing of 340 taken from Recommendation ITU-R P.684. 20 Rep. ITU-R RS.2185 FIGURE 15 Field-strength verses distance taken from Recommendation ITU-R P.684 This north westerly path from Halifax at 340 is 1 000 km over a path with poor conductivity. The impact of the poor c
37、onducting land can be seen in the decrease of field-strength and high rate of attenuation. 9.2.4 Predictions using Recommendations ITU-R P.368 and ITU-R P.684 combined with results of historical measurements An evaluation of the field-strength was performed on the basis of Recommendation ITU-R P.368
38、 Ground-wave propagation curves for frequencies between 10 kHz and 30 MHz. Figure 16 shows the calculation results of Alpha system signal field strength (E, dB(V/m) subject to distance (R) to receiving point. The results shown above were obtained for ground wave propagation in accordance with Recomm
39、endation ITU-R P.368 for propagation over the land. These plots assume a transmitter e.r.p. of 57 dBW for frequencies of 10 kHz and 15 kHz. Other calculation results were also assessed for propagation over sea and mixed paths, all of which were shown to be very similar for distances greater than 1 0
40、00 km. The differences between the obtained results were shown to be not greater than 3 dB. Rep. ITU-R RS.2185 21 FIGURE 16 Alpha system signal field-strength as a function of distance from transmitting antenna (R) for ground-wave propagation case 10Distance (Mm)(dB(V/m)E100302040605070801 000 2 000
41、 3 000 4 000 5 000 6 000 7 000R, km10 kHz 15 kHzFigures 17 and 18 show the calculation results obtained for field-strength prediction using skywave propagation based on Recommendation ITU-R P.684 methodology combined with data from historical measurements. Assessment was made for frequencies of 10 k
42、Hz (see Fig. 17) and 15 kHz (see Fig. 18). Each frequency was assessed for day time and night time prediction shown in Figs (a) and (b) respectively. In Figs 17 and 18, curve 1 represents the ground-wave component, curves 2, 3 and 4 represent skywave prediction, using assumptions of 4, 5 and 6 hops
43、respectively. 22 Rep. ITU-R RS.2185 FIGURE 17 Alpha system signal field-strength as a function of distance from transmitting antenna (R) for ground and ionosphere waves propagation case at 10 kHz a)(dB(V/m)E200406080R, km R, km1423( dB(V/m)E2004060800 2 000 4 000 6 000 8 000b)0 2 000 4 000 6 000 8 0
44、004231FIGURE 18 Alpha system signal field-strength as a function of distance from transmitting antenna (R) for ground and ionosphere waves propagation case at 15 kHz a)(dB(V/m)E200406080R, km1423( dB(V/m)E2004060800 2 000 4 000 6 000 8 000b)0 2 000 4 000 6 000 8 0004231R, km9.2.5 VLF measurements in
45、 the Pacific The following plot outlines a path from a theoretical transmitter based at Hawaii on an east to west path to Tokyo 12 generated by Garner for northerly mixed paths (land sea land), the separation distances are of the order of 2 500-3 000 km at 1 kHz frequency offset, 1 800-2 100 km at 2
46、 kHz and 100 km at 3 kHz respectively; for easterly sea paths the separation distances are of the order of 6 250-6 800 km at 1 kHz frequency offset, 4 600-4 700 km at 2 kHz respectively; for westerly sea paths the separation distance are of the order of 2 900-3 600 km at 1 kHz frequency offset, 2 50
47、0 km at 2 kHz and 100 km at 3 kHz respectively. Additionally, through the selective selection of ATD sensor sites, this could reduce the necessary separation distances between stations further. Even in cases where 90% of a path exceeds the ATD sensor threshold selective selection of a sensor locatio
48、n would make compatibility a possibility (locating of sensors at nulls formed due to modal interaction within the Earth-ionosphere waveguide). 10 Conclusions on sharing between the radionavigation services and ATD sensors of the meteorological aids service Co-existence and sharing between the radion
49、avigation service and ATD sensors has been shown to be possible, not only from a theoretical basis as seen in this document but in practice also. From a technical perspective the necessary separation distances are found to be of the following order: TABLE 13 Necessary separation distances based on 10 kW radionavigation e.i.r.p. Path dielectric Frequency offset from ATD measurement frequency (kHz) Separation distance (km) Land Good (Good, G/H = 105) 1 2 500-3 850* Land Poor (G/H = 104) 1 1 600-3 500* Sea (westerly)
