1、 Rec. ITU-R BS.1386-1 1 RECOMMENDATION ITU-R BS.1386-1*LF and MF transmitting antennas characteristics and diagrams*(Question ITU-R 201/10) (1998-2001) The ITU Radiocommunication Assembly, considering a) that Recommendations ITU-R BS.705 and ITU-R BS.1195 are defining respectively HF and VHF, UHF br
2、oadcasting antenna diagrams together with other relevant information; b) that the diagrams published in this Recommendation should be easy to be understood and used by the planning and designing engineers, while retaining all necessary useful information; c) the experience gained with the previous e
3、ditions of Recommendations on antennas; d) that the characteristics of the LF and MF antennas as contained in Annex 1 to this Recommendation have a wide application, recommends 1 that the formulae as illustrated by sample diagrams and contained in Annex 1 to this Recommendation together with the cor
4、responding computer programs should be used to evaluate the performance of LF and MF transmitting antennas; particularly for planning purposes. NOTE 1 Part 1 of Annex 1 gives comprehensive and detailed information on the theoretical characteristics of LF and MF transmitting antennas. Computer progra
5、ms have been developed from the theory to calculate the radiation patterns and gain for the various included antenna types. The real performance of antennas encountered in practice will deviate to a certain extent from its analytically calculated characteristics. To this purpose Part 2 gives advice
6、about this deviation on the basis of the results of a comprehensive set of measurements carried out by various administrations with modern techniques. _ *Radiocommunication Study Group 6 made editorial amendments to this Recommendation in 2002 in accordance with Resolution ITU-R 44. *Chapter 2 of Pa
7、rt 2 of Annex 1 should be brought to the attention of the International Electrotechnical Commission (IEC). 2 Rec. ITU-R BS.1386-1 ANNEX 1 CONTENTS PART 1 LF AND MF TRANSMITTING ANTENNA CHARACTERISTICS AND DIAGRAMS 1 Introduction 2 Radiation patterns and gain calculation 2.1 General considerations 2.
8、2 Radiation patterns 2.2.1 Graphical representation 2.2.2 Tabular representation 2.3 Directivity and gain 2.4 Effect of the ground 2.4.1 Wave reflection on imperfect ground 2.5 Antenna designation 3 LF-MF antenna systems 3.1 General considerations 3.2 Radiating element cross-section 3.3 Frequency of
9、 operation 3.4 Earth system and ground characteristics 3.5 Omnidirectional antenna types 3.5.1 Vertical monopoles 3.5.2 Types of vertical monopoles 3.6 Directional antennas 3.6.1 Arrays of active vertical elements 3.6.2 Arrays of passive vertical elements 3.7 Other types of antennas 3.7.1 T-antennas
10、 3.7.2 Umbrella antennas 3.7.3 Angle radiator cage antennas 4 Calculation of radiation patterns and gain 4.1 General considerations 4.2 Currently available analytical approaches Annex 1 The calculation procedure Rec. ITU-R BS.1386-1 3 PART 2 PRACTICAL ASPECTS OF LF AND MF TRANSMITTING ANTENNAS 1 Int
11、roduction 2 Measurements of antenna radiation patterns 2.1 Methods of measurement 2.1.1 Ground-based measurement of horizontal radiation pattern 2.1.2 Helicopter-based measurement of radiation pattern 2.2 Measurement equipment 2.3 Measurement procedures 2.3.1 Ground 2.3.2 Helicopter 2.4 Processing t
12、he measured data 2.4.1 Ground 2.4.2 Helicopter 3 Comparison of theoretical and measured radiation patterns 3.1 Far field 3.2 Variations in practical antenna performance 3.2.1 Influence of surrounding environment on radiation patterns 3.2.1.1 Ground conductivity 3.2.1.2 Ground topography and other si
13、te structures 3.2.2 Feeding arrangements and guy wires PART 1 LF AND MF TRANSMITTING ANTENNA CHARACTERISTICS AND DIAGRAMS 1 Introduction Efficient spectrum utilization at LF and MF demands for both omnidirectional and directional antennas whose characteristics and performance should be known as accu
14、rately as possible. Therefore, a unified approach to evaluate the antenna gain and radiation pattern should be made available to the engineer both for national planning and for international coordination. In the past the former CCIR responded to such a requirement by preparing Manuals of Antenna Dia
15、grams (ed. 1963, 1978 and 1984), which included graphical representations of the radiation patterns of some of the most commonly used antenna types at MF and HF. For the sake of simplicity, the patterns were calculated assuming a sinusoidal current distribution and using computer facilities as 4 Rec
16、. ITU-R BS.1386-1 available at that time. Today modern antenna theories and powerful computing means allow the planning engineer to determine the antenna characteristics with far better accuracy and perform the relevant calculation on low cost computers. The application of digital techniques to soun
17、d broadcasting at LF and MF is envisaged in the near future and relevant studies are already being carried out by the ITU-R. The advantages of such techniques combined with the propagation characteristics at LF and MF in comparison to broad-casting at VHF (such as larger coverage areas and more stab
18、le reception in mobile conditions, etc.) will make the new services not only more spectrum efficient but also more attractive from the economical point of view. However, the introduction of digital techniques to broadcasting at LF and MF, will put an emphasis on the use of advanced planning tools, s
19、uch as the calculation of the antenna patterns, to be made available to future planning Conferences as well as to assess more precisely the performance of existing transmitting systems. This Recommendation has been deve-loped to respond timely to such requirements providing, as in the case of the co
20、mpanion Recommendations ITU-R BS.705 and ITU-R BS.1195, that the associated computer program to be used to perform the relevant calculations. 2 Radiation patterns and gain calculation 2.1 General considerations An LF-MF antenna system may consist of a single element or an array of radiating elements
21、. Radiation patterns of an antenna system can be represented by a three-dimensional locus of points. The three-dimensional radiation pattern is based on the reference coordinate system of Fig. 1, where the following parameters can be defined: : elevation angle from the horizontal (0 90) : azimuth an
22、gle with respect to the North direction, assumed to coincide with the y-axis (0 360) r : distance between the origin and distant observation point where the far field is calculated. 2.2 Radiation patterns In the reference coordinate system of Fig. 1, the magnitude of the electrical field contributed
23、 by an antenna is given by the following expression: |E (,)| = K |f(,)| (1) where: |E (,)| : magnitude of the electrical field |f(,)| : radiation pattern function K : normalizing factor to set |E (,)|max= 1, i.e. 0 dB. Expressing the total electrical field in terms of its components in a spherical c
24、oordinate system, gives: |E (,)|2= |E(,)|2+ |E (,)|2 (2) Rec. ITU-R BS.1386-1 5 1386-01zPOxryFIGURE 1Reference coordinate systemNorth direction2.2.1 Graphical representation A set of particular sections of the radiation pattern at specific elevation angles (azimuthal patterns) and at specific azimut
25、hal angles (vertical patterns) is used to describe the full radiation pattern. The most important sections are the azimuthal patterns at the elevation angle at which the maximum cymomotive force (c.m.f.) occurs and the vertical pattern at the azimuthal angle at which the maximum c.m.f. occurs. These
26、 are referred to as the horizontal radiation pattern (HRP) and the vertical radiation pattern (VRP) respectively. 2.2.2 Tabular representation A tabular representation of the full antenna pattern may be found to be a useful application when antenna data is integrated into a planning system. A resolu
27、tion which is considered suitable for such a purpose consists of pattern values evaluated at each 2 for elevation angles and each 5 for azimuthal angles. 2.3 Directivity and gain The directivity, D, of a radiating source is defined as the ratio of its maximum radiation intensity (or power flux-densi
28、ty) to the radiation intensity of an isotropic source radiating the same total power. It can be expressed by: =202/2/ddcos),(),(422EEDmax(3) 6 Rec. ITU-R BS.1386-1 When equation (1) is applied, D can be expressed in terms of the normalized radiation pattern function of the source, |f(,)|: =202/2/ddc
29、os),(f),(f422maxD(4) The above definition of directivity is a function only of the shape of the source radiation pattern. The antenna efficiency is defined as a ratio of radiated power, radP , to the power at the input of antenna :inputP inputradPP=(5) The antenna gain, G, is expressed as a ratio of
30、 its maximum radiation intensity to the maximum radiation intensity of a reference antenna with the same input power. When a lossless isotropic antenna is taken as the recommended reference antenna, the gain, Gi, is expressed by: dBlog1010DGi= (6) Other expressions used are the gain relative to a ha
31、lf-isotropic antenna, Ghi, that is: dB01.3=ihiGG (7) and the gain, Gv, relative to a short vertical monopole: dB77.4=ivGG (8) 2.4 Effect of the ground Using the assumptions given in 2.1, and also the assumption that the antenna is located in the coordinate system of Fig. 1, where the x-y plane repre
32、sents a flat homogeneous ground, the far field produced at the observation point P(r, , ), including the ground reflected part, can be derived as follows. If the incident radiation on the ground is assumed to have a plane wavefront, the following two different cases can be considered. a) horizontal
33、polarization; b) vertical polarization. In the case of horizontal polarization, the incident (direct) electric vector is parallel to the reflecting x-y plane (and hence perpendicular to the plane of incidence, i.e. the plane containing the direction of propagation and the perpendicular to the reflec
34、ting surface, as shown in Fig. 2a). In the case of vertical polarization, the incident electric vector is parallel to the plane of incidence while the associated incident magnetic vector is parallel to the reflecting surface, as shown in Fig. 2b). Rec. ITU-R BS.1386-1 7 1386-02HiEi ErHrzHrErEiHizFIG
35、URE 2Wave reflection on imperfect grounda) Horizontal polarization b) Vertical polarization2.4.1 Wave reflection on imperfect ground The total far-field components above ground in Fig. 2 can then be expressed as follows: a) Horizontal polarization )()()()(2121rERrErErEEihirih+=+= (9) where: Eh : tot
36、al horizontal component r1: direct distance between the antenna and the observation point r2: distance from the image of the antenna to the observation point Ei : direct electric field Er : reflected electric field Rh : complex reflection coefficient for horizontally polarized waves defined as: 2/1M
37、Hz22/1MHz2.00018j)cos(sin.00018j)cos(sin+=ffRh(10) and : grazing angle : relative permittivity (or dielectric constant) of the ground : conductivity of the ground (S/m) fMHz: operating frequency (MHz). 8 Rec. ITU-R BS.1386-1 b) Vertical polarization )()()()(2121rERrEErERrEEivivivih+=(11) where: hE :
38、 total horizontal component Ev :total vertical component Rv :complex reflection coefficient for vertically polarized waves defined as: 2/1MHz2MHz2/1MHz2MHz.00018j)cos(sin.00018j.00018j)cos(sin.00018j+ =ffffRv(12) 2.5 Antenna designation In consideration of the variety of LF-MF antenna systems, a sui
39、table antenna designation based only on the electrical length might not be feasible. Therefore, such a designation will have to be implemented on a case-by-case basis. 3 LF-MF antenna systems 3.1 General considerations LF and MF antennas have in general few radiating elements. The height and the spa
40、cing of these elements are not restricted to /2. The radiation pattern of these antennas is a function of: radiating element cross-section; frequency of operation; earth system and ground characteristics; number of elements and their spacing; height of elements above the ground; orientation; feeding
41、 arrangement; characteristics of environment. 3.2 Radiating element cross-section Various radiating structures are in common use, such as self-supporting towers, guyed masts and wire elements. Therefore, the cross-section and, as a consequence, the current in the radiating element vary considerably,
42、 affecting its radiation pattern and gain. In the case of radiating towers or masts, triangular or square cross-section are in common use, whilst wire structures are characterized by circular cross-sections. To simplify the calculation of LF-MF antenna patterns and gain for Rec. ITU-R BS.1386-1 9 pl
43、anning purposes, each element of the antenna system is assumed to have the same cross-section. In addition the calculation procedure developed according to the theory included in Annex 1, automatically transforms any triangular or square section into an equivalent circular cross-section. 3.3 Frequen
44、cy of operation The operating frequency of a given antenna system has an impact on the resulting radiation pattern. In some cases a given structure is used to operate on more than one channel or may be used to radiate on a channel different from the design frequency. In this case the pattern has to
45、be evaluated at the actual operating frequency to get consistent results. 3.4 Earth system and ground characteristics As mentioned in 2.4, antenna systems at LF-MF are normally placed on an imperfect ground whose characteristics in terms of reflection coefficients, are specified by the dielectric co
46、nstant and conductivity of the ground. However, efficient antenna systems at LF-MF require an earth system. An ideal earth system would consist of a perfectly conducting circular surface surrounding the base of the antenna. In practice an earth system is realized by a network of radial conductors of
47、 suitable length and diameter that can only be an approximation of an ideal perfectly conducting surface. The length of radials varies from 0.25 to 0.50 and the number of radials varies from 60 to 120, whilst their diameter is of the order of a few mm. A typical earth system configuration consists o
48、f a circular mesh of 120 wires 0.25 long having a diameter of 2.7-3 mm. As usual it is necessary to optimize systems both from the technical and economical point of view. In the case of directional vertical antennas (see 3.2.2) each radiating element is normally provided with an individual earth sys
49、tem suitably connected to the others. To simplify the calculation of LF-MF antenna patterns and gain for planning purposes, the earth system is assumed to be represented by a circular wire network centred on the base of the radiating element. In the case of arrays of radiating elements it is also assumed that the earth system parameters of each of the radiating elements are t
