1、 Recommendation ITU-R SM.2061-0 (08/2014) Test procedure for measuring direction finder immunity against multi-path propagation SM Series Spectrum management ii Rec. ITU-R SM.2061-0 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use
2、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 regulatory and policy functions of the Radiocommunication Sector are performed by World and
3、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/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the
4、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-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU
5、-R Recommendations (Also 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,
6、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-satellite and fixed service systems SM Spectrum management SNG Satellite new
7、s gathering TF Time signals 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, 2014 ITU 2014 All rights reserved. No part of this publication ma
8、y be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R SM.2061-0 1 RECOMMENDATION ITU-R SM.2061-0 Test procedure for measuring direction finder immunity against multi-path propagation (2014) Scope The Recommendation provides test procedures for measuring the immunity
9、 against multi-path propagation of fixed and mobile direction finders (DF). Keywords DF, direction finder, test procedure, immunity, multi-path propagation, reflections, open-air-test-site, OATS Related ITU Recommendations, Reports Recommendation ITU-R SM.2060-0. NOTE In every case the latest editio
10、n of the Recommendation/Report in force should be used. The ITU Radiocommunication Assembly, considering a) that ITU-R has published the direction finder (DF) immunity against distorted wave fronts of different DF methods in the ITU Handbook on Spectrum Monitoring (Edition 2011); b) that the immunit
11、y against distorted wave fronts is an important specification of a DF since distorted wave fronts from multipath propagation are typical in practice; c) that the specification of DF immunity against distorted wave fronts strongly depends on the test procedures applied; d) that a test procedure for D
12、F immunity against distorted wave fronts must be independent of the direction finder design; e) that well-defined test procedures for DF immunity against distorted wave fronts to test the influence of multi-path propagation under approximated real-world conditions, if adopted by all manufacturers of
13、 direction finders intended for civil radio monitoring, will have the advantage for the users of such direction finders, that an easier and more objective assessment of products from different manufacturers is possible, recommends 1 that the measurement method in Annex 1 should be used to determine
14、and report the immunity against distorted wave fronts due to multi-path propagation on fixed and mobile direction-finding systems. 2 Rec. ITU-R SM.2061-0 Annex 1 Immunity against distorted wave fronts due to multi-path propagation: test procedure for fixed and mobile direction finder 1 General consi
15、derations Under normal circumstances, wave propagation between the emitter and DF is disrupted by buildings, mountains, hills, etc. Even if we have direct line of sight, secondary waves will still arise due to reflection, refraction and diffraction and superimpose the direct wave at the receiving lo
16、cation as interfering fields. If the interfering wave component has a lower power level than the desired wave component, the bearing error can be minimized by choosing suitable design parameters in the direction finder. This Recommendation serves to measure the DF immunity to distorted wave fronts c
17、aused by a secondary wave (reflection). It is meant to be used for an exemplary measurement of one single sample of the serial production version of the DF system under test. 2 Principle of measurement The measurement will be conducted under simplified conditions, thus permitting great simplicity of
18、 the tests and easy repeatability of the results at any time and at any site. In order to simulate a multipath environment, an arrangement of two transmitting antennas (two-wave field produced by a single transmitter) is proposed subsequently. Both antennas are connected to the test transmitter via
19、a power divider. By using an attenuator, the amplitude of the signal which represents the reflection (secondary wave) can be set, and hence determine the amplitude relation between direct (primary) and reflecting (secondary) path. The angle of arrival and the phase angle of the secondary wave is var
20、ied. Considering the objective to simplify the measurement, effects of modulation type (including phase and time variant signals), signal duty cycle, bandwidth, signal polarization, and signal duration, noise and other signal and DF quality parameters (e.g. DF sensitivity) are intentionally ignored
21、to reduce the complexity of the tests procedure and the time duration of the measurements. The measurement takes place in an otherwise reflection-free environment such as an open-air-test-site (OATS) or an anechoic chamber.1 In addition to the recommended measurement procedure described here, it is
22、possible to measure the DF immunity against distorted wave fronts by means of multi-channel emulators which can simulate the propagation effects of a real environment, in situations where an OATS or anechoic chamber is not readily available. 3 Measurement set up The proposed measurement setup is sho
23、wn in Fig. 1. In order to ensure a well-defined dual-path propagation scenario, the environment of the DF and transmitting antennas should be free of reflecting obstacles and interferences as indicated in Recommendation ITU-R SM.2060-0. The distances between the DF antenna and both transmitting ante
24、nnas, as well as the height of all antennas involved should be in line with Recommendation ITU-R SM.2060-0. 1 OATS definition can be found in a number of standards documents such as ANSI C63.7, CISPR or EN55 022. The OATS is considered as line-of sight with no interference signal, no reflection and
25、far-field (Fraunhofer Region). Rec. ITU-R SM.2061-0 3 4 Measurement procedure In order to simulate a basic multipath wave environment (two-wave field produced by a single transmitter), an experimental test bed as shown in Fig. 1 is recommended: an un-modulated continuous wave input signal S on vario
26、us measurement frequencies within the operational frequency range of the DF is generated using a signal generator; the input signal S is divided into S1 and S2 signals by means of a power divider; the S1 signal is transmitted by transmit antenna 1; and attenuation and phase shift is added to the S2
27、signal before it is transmitted by transmit antenna 2 from a different angle than S1. Both S1 and S2 signals must have a power level high enough to ensure a minimum S/N of 20 dB (in order to ensure that system noise does not affect the measurement results). Due to the fact that the DF immunity to di
28、storted wave fronts tends to vary with frequency it is required to repeat the measurement for various measurement frequencies. The measurement frequencies are selected in line with Recommendation ITU-R SM.2060-0. For each measurement frequency, the S2 signal from antenna A2 (the “reflected” signal)
29、is varied in azimuth, amplitude and phase shift as follows: the angle of arrival difference between the reflected wave S2 and the main wave S1 is set to 20, 60 and 90; the amplitude ratio of the reflected wave S2 and the main wave S1 is set so that the power level of S2 is 0.25 (6 dB) with respect t
30、o S1 at the DF antenna. Note that takes into account all gains and losses over cables, antennas and air; the positive time delay difference of the reflected wave S2 is set so that a phase difference of 05, 905 and 2005 between S1 and S2 occurs at the DF antenna. Note that takes into account all prop
31、agation delays over cables, antennas and air. Note further that the phase shift can be applied by a variable phase shifter or a delay line, besides 5 have been included to consider uncertainties of the setup configuration, e.g. small variations of the antenna locations during placement. For all diff
32、erent settings described above, the bearing error is measured and the RMS bearing error is calculated with the formula stated in Recommendation ITU-R SM.2060-0, resulting in one RMS bearing error per measurement frequency. The final result is presented as a table or chart indicating the RMS bearing
33、error for each measurement frequency as indicated in Table 1. It should be noted that the recommended measurement procedure is focused on a single angle of arrival of the primary wave. However, it would be desired in specific cases that different angles of arrival of the primary wave are measured by
34、 rotating the antenna. If such specific test conditions are applied, this should be indicated in the test reports. 4 Rec. ITU-R SM.2061-0 FIGURE 1 Measurement setup for determining the direction finder immunity to distorted wave fronts S M . 2 0 6 1 - 0 1Refl ect eds i g n al : V a r i a bl ede l a
35、y s hi f t e r : V a r i a bl ea t t e nua t orP ow e r di vi de rC om m on t e s tt r a ns m i t t e rI nput s i gna l ( )StC ont r ol l e r D F pr oc e s s orDFA nt e nnaM a i nw a ve1( t )SA ngl er e s ol ut i onD F a nt e nnai n t hedi r e c t i onof A 1Q3 dBT r a ns m i ta nt e nna A 1f or m a
36、i n w a ve : V a r i a bl e a ngl eM a i n s i gna lT r an s mi t a n te n n aA 2f o r r e f l ec t e d w a v eR e f le c t e dw a ve2 ( t )= . 1 ( t- )SS C l e a r t e st a re aTABLE 1 Sample test data table Signal modulation:_Signal polarization: _ S2 relative power level at the DF antenna: _ (dB)
37、 True Frequency 1 Frequency 2 Frequency 3 Frequency M Index Azimuth DF DF DF DF 1 0 20 0 2 90 3 200 60 0 90 200 90 0 90 200 Note that is the difference between the true azimuth (angle of the transmitters test antenna) and the displayed bearing on the DF equipment. Example for a specification in a data sheet of DF immunity against multi-path propagation conditions: Rec. ITU-R SM.2061-0 5 Frequency f1 f2 f3 fN RMS DF error RMS DF error at f1 RMS DF error at f2 RMS DF error at f3 RMS DF error at fN
