1、 Recommendation ITU-R SM.2096-0 (08/2016) Test procedure for measuring direction finder sensitivity in the VHF/UHF frequency range SM Series Spectrum management ii Rec. ITU-R SM.2096-0 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical u
2、se 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 a
3、nd 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 t
4、he 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
5、ITU-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, radiodeterminatio
6、n, 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
7、news 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, 2016 ITU 2016 All rights reserved. No part of this publication
8、 may be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R SM.2096-0 1 RECOMMENDATION ITU-R SM.2096-0 Test procedure for measuring direction finder sensitivity in the VHF/UHF frequency range (2016) Scope The sensitivity of direction finding systems is an important con
9、sideration to regulatory authorities and others who have to locate emitters. It is often difficult to compare different systems due to a number of factors, such as the system architecture, typical use/purpose, size, installation requirements, and other issues. To facilitate comparison between direct
10、ion finding (DF) systems, this Recommendation provides guidance on a standard method of testing DF sensitivity and reporting of the results. Keywords DF sensitivity, measurement, test site, open-air-test-site, OATS Related ITU Recommendations, Reports Recommendation ITU-R SM.854 Recommendation ITU-R
11、 SM.2060 Recommendation ITU-R SM.2061 Recommendation ITU-R SM.2097-0 Report ITU-R SM.2125 NOTE In every case the latest edition of the Recommendation/Report in force should be used. The ITU Radiocommunication Assembly, considering a) that ITU-R published the typical specifications for direction find
12、ing (DF) sensitivity in the ITU Handbook on Spectrum Monitoring (Edition 2011); b) that the Handbook refers to Report ITU-R SM.2125 Parameters of and measurement procedures on H/V/UHF monitoring receivers and stations, which defines DF sensitivity and provides relevant test procedures; c) that the s
13、pecification of DF sensitivity strongly depends on the test procedures applied; d) that DF sensitivity may influence the suitability of a direction finder to fulfil certain monitoring tasks such as mobile or fixed use, or its ability to measure digital wideband signals, especially when used in typic
14、al operating environments; e) that a defined set of test procedures for DF sensitivity must be independent of the DF design; f) that a well-defined set of test procedures for DF sensitivity, if adopted by all manufacturers of DF intended for civil radio monitoring, will have the advantage for the us
15、ers of such DF, that an easier and more objective assessment of products from different manufacturers is possible; g) that performance data in specifications of DF systems usually show the performance under ideal test conditions or one specific condition, 2 Rec. ITU-R SM.2096-0 recommends 1 that the
16、 test procedure in Annex 1 should be used to determine and report the DF sensitivity; 2 that for each DF sensitivity performance specification, the test procedure and test conditions should be indicated by the manufacturer. Annex 1 Test procedure for measuring direction finder sensitivity in the VHF
17、/UHF frequency range 1 Introduction This Recommendation describes a general test procedure to evaluate the DF sensitivity of radio direction-finding systems. The aim of this document is to provide a definition of DF sensitivity and a standard method to conduct testing, so that administrations can ha
18、ve some basis for comparison of DF systems based on their requirements. The sensitivity of a direction finding system is defined as the minimum signal field strength (V/m) at the DF antenna that results in a suitable DF accuracy when receiving weak signals. The method described in this recommendatio
19、n is used to determine the “system sensitivity” in a defined set of test conditions simulated on a test range under ideal/controlled propagation conditions, and can be used, for example, for calibration purposes. 2 Principle of measurement The measurement will be conducted under simplified condition
20、s, thus permitting great simplicity of the tests and easy repeatability of the results at any time and at any site. Considering the objective to simplify the measurement, effects of modulation type (including phase and time variant signals), signal duty cycle, bandwidth, signal polarization, signal
21、duration, noise, effects from other signals and external uncontrollable conditions such as multi-wave/multipath propagation conditions, are intentionally ignored to reduce the complexity and duration of the test procedure. The measurement takes place in an otherwise reflection-free environment such
22、as an open-air-test-site (OATS) or an anechoic chamber.1 Measurements in an OATS shall be conducted under sufficiently low levels of external noise. 3 Measurement set up The measurement setup is shown in Fig. 1. To ensure a well-defined propagation scenario, the environment of the DF and transmittin
23、g antennas should be free of reflecting obstacles and interferences as indicated in Recommendation ITU-R SM.2060. 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 reflectio
24、n and far-field (Fraunhofer Region). Rec. ITU-R SM.2096-0 3 The test frequency selection, the distances between the DF antenna and the transmitting antennas, as well as the height of all antennas involved should be in line with Recommendation ITU-R SM.2060. Frequencies with sufficiently low external
25、 noise levels should be selected as test frequencies for measurement in an OATS. The attenuator of the DF system should be set to the minimum attenuation. The bandwidth of the DF system should be set to 1 kHz for the narrowband unmodulated signal (if the DF system does not support this setting, choo
26、se the nearest value which is higher than the default parameter value). The integration time of the DF system should be set to 1 second for the narrowband unmodulated signal (if the DF system does not support this setting, choose the nearest value which is lower than the default parameter value). Se
27、t the default 0 degree bearing of the DF system directly facing the transmitting antenna by adjusting the angle of the turn table. Other settings should be the optimal settings for the DF system. All the relevant settings should be specified in the data sheet. All test equipment (including transmitt
28、er, transmitting antennas and turntable) should be calibrated. 4 Measurement procedure Adjust the signal level of the test transmitter to make sure that the DF antenna receives a strong signal with SNR of at least 20 dB. Record the angle of arrival 0 (it must be stable). Note the signal level of the
29、 transmitter and perform a field measurement at the position of the direction-finding antenna E0 (V/m). In the next step, measure the DF bearing fluctuation (RMS value) after incrementally reducing the signal level of the test transmitter until DF bearing fluctuation reaches a certain value (nominal
30、 3 degrees RMS). The RMS value for DF bearing fluctuation should be calculated described as follows: = (0)2 where: : RMS value between the measurement at the sensitivity limit and the measurement at the high level with at least 20 dB SNR (degrees) 0: azimuth measured with a strong signal with at lea
31、st 20 dB SNR mes: azimuth measured for each level of the signal generator (degrees) N: number of readings of the azimuth for each level of the signal generator. A minimum of 10 consecutive readings of the azimuth for each level of the signal generator should be used. In order to allow for automated
32、measurements, out of these readings, 10% could be discarded to exclude outliers, e.g. from short duration interferers. Record the signal level of the transmitter and the field strength at the position of the direction-finding antenna E(V/m). 4 Rec. ITU-R SM.2096-0 Change the test frequency and repea
33、t the above procedure until all the frequencies are completed.2 The final result is presented as a table or chart indicating the field strength for each measurement frequency as indicated in Table 1. It should be noted that the recommended measurement procedure is focused on narrowband unmodulated s
34、ignals. However, it would be agreed that different types of signals are measured according to specific test conditions. If such specific test conditions are applied, it should be indicated in the test reports. All measurement parameters should be compliant with the Spectrum Monitoring Handbook (Band
35、width, etc.), with results specified in V/m so they are comparable. FIGURE 1 DF sensitivity measurement setup for a direction finding system at an OATS S M . 2 0 9 6 - 0 1T ran s i t an t en n as (T x )T u rn t ab l ePC co n t ro l s y s t emD F rec ei v er an dp ro ce s s o rD F an t en n as (Rx )A
36、 mp l i fi er an ds w i t chSi g n alg en era t o rTABLE 1 Sample test data table Signal modulation: _ Signal polarization: _ Frequency (MHz) True Azimuth (degree) Field Strength E (V/m) 1 2 3 Example for a specification in a data sheet of DF sensitivity: Frequency f1 f2 f3 fN DF sensitivity DF sensitivity at f1 DF sensitivity at f2 DF sensitivity at f3 DF sensitivity at fN 2 This kind of repeated testing can be efficiently conducted using software to control the transmitter and DF system, and collect and report the results. The test efficiency can be improved dramatically.
