1、 Recommendation ITU-R BT.1195-1(01/2013)Transmitting antenna characteristics at VHF and UHFBT SeriesBroadcasting service (television)ii Rec. ITU-R BT.1195-1 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency sp
2、ectrum 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 regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunicati
3、on 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/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent stat
4、ements 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-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Recommendations (Also
5、available online at http:/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 satel
6、lite 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-satellite and fixed service systems SM Spectrum management SNG Satellite news gathering TF Time signa
7、ls and frequency standards 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, 2013 ITU 2013 All rights reserved. No part of this publication may be reproduced, by any m
8、eans whatsoever, without written permission of ITU. Rec. ITU-R BT.1195-1 1 RECOMMENDATION ITU-R BT.1195-1 Transmitting antenna characteristics at VHF and UHF (Question ITU-R 30/6) (1995-2013) The ITU Radiocommunication Assembly, considering a) that, by Resolution 76-1, the ex-CCIR has decided that t
9、he results of the studies carried out by Radiocommunication Study Group 10 and the related antenna diagrams should be contained in ITU-R Recommendations separately published; b) that comprehensive information on the characteristics of transmitting and receiving antenna systems at VHF and UHF is requ
10、ired for frequency planning; c) that computer-based procedures are required to give, in a standardized form, the gain and directivity patterns of transmitting and receiving antenna systems; d) that it is essential to verify both the antenna system element radiation pattern and the overall antenna sy
11、stem radiation pattern by measurements; e) that standardized measurement methods are required to verify the radiation patterns mentioned in considering d); f) that differences are to be expected between theoretical and measured performance due to practical aspects of VHF and UHF antennas, recommends
12、 1 that the formulae contained in Part 1 of Annex 1 and the associated computer programs described in Part 3 of Annex 1 should be used to evaluate VHF and UHF antenna systems performances for planning purposes; 2 that the measurement methods contained in Part 2 of Annex 1 should be used to verify th
13、e practical performances of the antenna system elements and of the overall antenna system. 2 Rec. ITU-R BT.1195-1 Annex 1 PART 1 VHF and UHF transmitting antenna pattern calculation Table of Contents Page 1 Introduction 4 1.1 Reference frames 4 2 Geometrical representation of antenna radiation patte
14、rns 5 3 Radiation patterns and gain calculation 6 4 Radiating elements . 7 4.1 Point sources . 7 4.2 Arrays of point sources . 9 4.2.1 Pattern multiplication . 9 4.2.2 Vectorial pattern addition . 9 4.3 VHF and UHF elementary radiators . 10 5 Polarization . 11 5.1 Elliptical polarization 11 5.2 Hori
15、zontal and vertical polarization . 12 5.3 Slant polarization 12 5.4 Circular polarization . 12 6 Antenna arrays 13 6.1 Broadside arrays . 13 6.1.1 Linear antenna arrays with parasitic elements . 16 6.2 The amplitude and phase radiation patterns . 18 6.3 Calculation of the radiation pattern of antenn
16、a arrays 20 6.4 VHF and UHF antenna arrays 21 6.4.1 Panel type antennas 21 6.4.2 Yagi antennas . 24 6.4.3 Other types of antenna array 24 7 Antenna systems . 24 Rec. ITU-R BT.1195-1 3 Page 7.1 The antenna system pattern 25 7.1.1 Null filling 25 7.1.2 Beam tilting 28 7.2 Antenna system radiation patt
17、erns 29 7.3 Examples of antenna system pattern . 32 7.3.1 Dipole antenna systems 32 7.3.2 Yagi antenna systems . 33 7.3.3 Panel antenna systems 34 4 Rec. ITU-R BT.1195-1 PART 1 to Annex 1 VHF and UHF transmitting antenna pattern calculation 1 Introduction This Part briefly summarizes the basic theor
18、etical principles of VHF and UHF antennas and the general characteristics of antenna systems realized by a number of individual radiators. Some examples of antenna systems are also given in order to show their performance and orientate the user in selecting the configuration that best suits the requ
19、irements. In particular 6.4 and 7.2 give the analytical procedure to calculate the overall radiation pattern of an antenna system. The aim of this section is to provide a recommended unified approach to evaluate the performance of an antenna system in ideal conditions. However, it is to be borne in
20、mind that deviations from the patterns calculated according to the above procedure can be encountered in practical situations as described in Part 2. 1.1 Reference frames In the Radio Regulations, the horizontal angle of the “beam” of an antenna (the “beam tilt”) is specified in degrees relative to
21、the horizontal; a downward tilt being a negative angle. Beam azimuth is specified in degrees measured clockwise from true north. For regulatory purposes, it is essential that a common frame of reference, such as that enshrined in these definitions, is used to ensure that the effect of the beam of on
22、e antenna is properly considered in relation to the intended service area of another. This Recommendation, however is concerned with the properties of the antenna itself and the mathematical formulae are more tractable and less cumbersome if: a reference frame related to the antenna itself is used;
23、and all angles are in radians rather than degrees. Throughout the Recommendation both polar and Cartesian coordinates are used as appropriate. Polar coordinates use: r distance from the origin, elevation angle, and azimuth angle Cartesian co-ordinates use: x arbitrary horizontal axis, y arbitrary ho
24、rizontal axis (orthogonal to x), and z vertical axis The “x” axis is frequently the axis of the main beam of the antenna. Where these coordinate systems are “overlaid”, the common reference (r, = 0, = 0) is taken to be the x-axis. It is important to note that when considering the service area of the
25、 antenna and its potential effects on the service area of others, the beam direction must be referenced back to true north. Rec. ITU-R BT.1195-1 5 2 Geometrical representation of antenna radiation patterns An antenna can consist of a single element or an array of radiating elements. The spatial radi
26、ation distribution, or pattern, of an antenna can be represented by a three-dimensional locus of points, with each point having a value of cymomotive force (c.m.f.)*, based on a sphere centred at the electrical centre of the antenna and of radius which is large compared to the physical and electrica
27、l dimensions of the antenna. The c.m.f. at a point on the sphere is indicated in dB below the maximum c.m.f., which is labelled 0 dB. The three-dimensional radiation pattern is based on the reference coordinate system of Fig. 1. The following parameters are defined: : elevation angle from the horizo
28、ntal (/2 /2) negative angles represent downward beam tilt; : azimuthal angle from an x-axis (0 2); r : distance between the origin and the observation point; Q : observation point. The x, y and z axes are a set of orthogonal Cartesian coordinates over which the polar coordinates are sometimes laid t
29、o aid the mathematical representation of certain of the properties of the antenna. While the z axis is always vertical, the x and y axes are chosen to best represent the antenna and its characteristics. *Definition of cymomotive force and specific cymomotive force (see Recommendation ITU-R BS.561).
30、The cymomotive force at a given point in space is the product of the electric field strength at that point produced by the antenna and the distance from that point to the antenna. This distance must be large enough for the reactive components of the field to be negligible. The c.m.f (V) is numerical
31、ly equal to the electric field strength (mV/m) at a distance of 1 km. The specific cymomotive force at a point in space is the c.m.f. at that point when the power radiated by the antenna is 1 kW. 6 Rec. ITU-R BT.1195-1 FIGURE 1 The reference coordinate system BT.1195-01Observation pointzOyrQx3 Radia
32、tion patterns and gain calculation In the reference coordinate system of Fig. 1, the magnitude of the electrical field contributed 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 : nor
33、malizing factor to set E (, ) max= 1, i.e. 0 dB. Expressing the total electrical field in terms of its components in a spherical coordinate system, gives: E (, ) = E (, )2+ E (, )2(2) The directivity, D, of a radiating source is defined as the ratio of its maximum radiation intensity (or power flux-
34、density) to the radiation intensity of an isotropic source radiating the same total power. It can be expressed by: null= 4|nullnull,null|nullnullnullnullnullnull|null null,null|2cos ddnull/nullnullnull nullnullnullnull(3) When equation (1) is applied, D can be expressed in terms of the normalized ra
35、diation pattern function of the source, f (, ) : null= 4|f null,null|nullnullnullnullnullnull|f null,null|nullnull/nullnullnull/nullcosd dnullnullnull(4) The above definition of directivity is a function only of the shape of the source radiation pattern. Rec. ITU-R BT.1195-1 7 To take into account t
36、he antenna efficiency, it is necessary to define its gain G, expressed as a ratio of 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
37、expressed by: Gi= 10 log10D dB (5) Another expression used in practice is the gain relative to a half-wave dipole, Gd, that is: Gd= Gi 2.15 dB (6) 4 Radiating elements 4.1 Point sources When the radiation from an antenna is in the far field condition (Fraunhofer zone), i.e. when the distance from th
38、e antenna is such that its electromagnetic fields can be taken as being orthogonal to the direction of propagation, the antenna can be considered as a point source. At VHF and UHF, this distance is usually so small that, particularly in the service area, any radiating element can be considered as a
39、point source, regardless of its size and complexity. Furthermore, the radiation pattern of these point sources, used as an approximation of typical VHF and UHF radiating elements, is usually directional. In far field conditions the power flux from a point source is always radial. The Poynting vector
40、 results therefore only from two transverse electrical field components Eand Eas shown in Fig. 2. FIGURE 2 Relation of the Poynting vector and the electrical far field components BT.1195-02zyxPrEE8 Rec. ITU-R BT.1195-1 When the spherical wave front is at a sufficiently large distance that it can be
41、considered as a plane, the average Poynting vector (radial component only) Pris given by: 022ZEPr= (7) where: E 2= E 2+ E 2(8) and: Z0 : intrinsic impedance of free space E: total electrical field intensity. Considering the variation of the total electrical field strength at a constant radius, the r
42、esulting pattern will be a function of and . Normalizing the pattern values with respect to its maximum value (assumed in the direction of maximum radiation) the resulting pattern is called a relative amplitude radiation pattern. The electrical field strength E generated at a distance r by an isotro
43、pic source radiating a power Pisis given by (see also Recommendation ITU-R P.525): E = 30 Pis/ r2V/m (9) where: Pis : isotropic power (W) r : distance (m) The above relation is also known as the free-space propagation condition. Referring the isotropic radiated power Pis to the half-wave dipole radi
44、ated power P, i.e., Pis = 1.64 P, the expression of the electrical field strength becomes: E = 7.014 P / r V/m (10) Expressing E in mV/m and r in m: E = 7.014 103P / r V/m (11) or, expressing E in dB(V/m) E = 20 log10P / r + 136.9 dB(V/m) (12) Considering a non-isotropic point source, the electrical
45、 field strength Eni radiated in the different directions will be affected by the radiation pattern, so that Eni= f (, ) Eis(13) where: Eni : electrical field strength generated at the observation point Q (r, , ) by a non-isotropic point source radiating power P f (, ): relative amplitude radiation p
46、attern function of the non-isotropic point source Eis : electrical field strength generated at the observation point Q by an isotropic point source radiating the same power P Rec. ITU-R BT.1195-1 9 4.2 Arrays of point sources When considering arrays of point sources such as those normally encountere
47、d at VHF and UHF where complex antenna systems are often required, the following two cases are of immediate interest: a) arrays of non-isotropic, similar point sources; b) arrays of non-isotropic and dissimilar point sources. Case a) refers to arrays whose elements have equal relative amplitude radi
48、ation patterns (same shape) oriented in the same direction. This is normally the case of an array of vertically stacked panel antennas (see 6.4.1) beaming toward the same direction. Case b) is the most general case where no correlation exists between the relative amplitude radiation patterns of the
49、array sources which may arbitrarily be oriented. 4.2.1 Pattern multiplication For arrays of non-isotropic but similar point sources (case a) of 4.2), the principle of pattern multiplication applies. According to this principle, the relative amplitudes of the radiation pattern of an array of non-isotropic but similar point sources is the product of the amplitude pattern of the individua
