1、 Recommendation ITU-R SM.1753-2(09/2012)Methods for measurementsof radio noiseSM SeriesSpectrum managementii Rec. ITU-R SM.1753-2 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectrum by all radiocommunic
2、ation 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 Radiocommunication Conferences and Radiocom
3、munication 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 statements and licensing declar
4、ations 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 available online at http:/w
5、ww.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 satellite services P Radiowave p
6、ropagation 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 signals and frequency standards
7、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, 2012 ITU 2012 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without wr
8、itten permission of ITU. Rec. ITU-R SM.1753-2 1 RECOMMENDATION ITU-R SM.1753-2 Methods for measurements of radio noise (2006-2010-2012) Scope For radio noise measurements there is a need to have a uniform, frequency-independent method to produce comparable, accurate and reproducible results between
9、different measurement systems. This Recommendation provides a set of processes or steps that need to be integrated in a measurement procedure resulting in these comparable results. The ITU Radiocommunication Assembly, considering a) that, due to the introduction of many types of electrical and elect
10、ronic equipment (producing radio noise) and radiocommunication networks (e.g. ultra-wide band (UWB), power line telecommunication (PLT) and computers), the radio noise levels stated in Recommendation ITU-R P.372 might increase; b) that, for efficient spectrum management, administrations need to know
11、 the exact noise levels; c) that there is a need to harmonize the measurement methods for noise measurements to achieve reproducible results that can be mutually compared; d) that, for noise measurements, certain minimum equipment specifications are required, recommends 1 that measurements of radio
12、noise should be carried out as described in Annex 1. Annex 1 Methods for measuring radio noise 1 Introduction This Annex describes methods for measuring and evaluating radio noise in practical radio applications. 2 Sources of radio noise Radiation from lightning discharges (atmospheric noise due to
13、lightning); Aggregated unintended radiation from electrical machinery, electrical and electronic equipment, power transmission lines, or from internal combustion engine ignition (man-made noise); Emissions from atmospheric gases and hydrometeors; The ground or other obstructions within the antenna b
14、eam; 2 Rec. ITU-R SM.1753-2 Radiation from cosmic radio sources. While noise due to natural causes is unlikely to change significantly over long periods of time, man-made noise (MMN) is often dominant in some parts of the radio spectrum and the intensity may change with increasing density of use of
15、electrical and electronic devices, with the introduction of new types of device, and with changes in measures intended to improve electromagnetic compatibility. Thus man-made noise is the type that is mainly of interest when performing radio noise measurements. TABLE 1 Relevant radio noise sources p
16、er frequency range Noise source Frequency range Atmospheric noise due to lightning 9 kHz to 30 MHz Cosmic noise 4 MHz to 100 MHz Man-made noise 9 kHz to 1 GHz Emissions from atmospheric gases, etc. Above 10 GHz 3 Components of radio noise Using the definition given in Recommendation ITU-R P.372, rad
17、io noise is the aggregate of emissions from multiple sources that do not originate from radiocommunication transmitters. If at a given measurement location there is no dominance of single noise sources, the characteristic of the radio noise often has a normal amplitude distribution and can be regard
18、ed as white Gaussian noise. However, with the high density of noise emitting devices especially found in cities and residential areas, it is virtually impossible to find a location that is not at least temporarily dominated by noise or emissions from a single source. These sources often emit impulse
19、s or single carriers. Since radiocommunication equipment has to operate in such an environment, it may be unrealistic to exclude these components from radio noise measurements. Rec. ITU-R SM.1753-2 3 TABLE 2 Components of radio noise Noise component Properties Sources (examples) White Gaussian noise
20、(1)(WGN) Uncorrelated electromagnetic vectors Bandwidth equal to or greater than receiver bandwidth Spectral power level increases linear with bandwidth Computers, power line communication networks, wired computer networks, cosmic noise Impulsive noise (IN) Correlated electromagnetic vectors Bandwid
21、th greater than receiver bandwidth Spectral power level rises with square of bandwidth Ignition sparks, lightning, gas lamp starters, computers, ultra wideband devices Single carrier noise (SCN) One or more distinct spectral lines Bandwidth smaller than receiver bandwidth Spectral power level indepe
22、ndent of bandwidth Wired computer networks, computers, switched mode power supplies (1)In the context of this Annex to Recommendation ITU-R SM.1753, WGN is considered to represent a continuous noise signal which exhibits a nearly flat power spectral density in the frequency ranges around the measure
23、ment bandwidth. While the WGN component is sufficiently characterized by the r.m.s. value, this is much more difficult for the IN. Modern digital communication services almost always apply error correction, making it more immune especially against impulsive noise. However, when certain pulse lengths
24、 and repetition ratios are reached, IN can significantly interfere with the operation of such a service. It is therefore desirable to measure radio noise in a way that gives not only the level of IN but also certain information about the statistical distribution of pulse parameters. Single carrier n
25、oise (SCN) is only detected as such when it comes from a single source near the measurement location. Multiple sources emitting single carriers quickly add up to a noise-like spectrum as their numbers increase. Recommendation ITU-R P.372 defines radio noise as the aggregated unintended radiation fro
26、m various sources and specifically excludes emissions from single, identifiable sources. It is therefore necessary to select measurement locations and/or frequencies that are not dominated by emissions from these single sources which makes further consideration of SCN unnecessary in the context of M
27、MN measurements. 4 Key parameters The measurement procedures described here will deliver results for the following parameters of radio noise: WGN: r.m.s. level, presented as a single value or hourly medians over the day. IN: Peak level, presented as a distribution; 4 Rec. ITU-R SM.1753-2 Impulse/bur
28、st lengths, presented as a distribution; Impulse/burst period, presented as a distribution. 5 Measurement principles The White Gaussian noise component (WGN) can be measured using an r.m.s. detector. This measurement method is herein referred to as the “r.m.s.-method”. Using the 20% reduction descri
29、bed in 10.3, it is possible to obtain the r.m.s. noise value directly from a frequency scan, even if some of the frequencies are occupied with wanted signals. IN, however, can only be measured by fast sampling of the momentary RF amplitude values. These values are stored for off-line evaluation to o
30、btain the impulse parameters. The measurement is preferably done on a single frequency that is free of wanted signals and continuous carriers. The maximum time between two consecutive samples is: RBWTs*21 (1) where: Ts: time between two consecutive samples RBW: filter bandwidth used for measurement.
31、 This measurement method is herein referred to as the “raw data sampling method”. 6 Measurement type Determining the true MMN level and characteristics including IN for all frequency ranges can be a very time consuming complex measurement task. However, when only the WGN component is of interest, or
32、 only certain frequency ranges have to be investigated, the measurements can be simplified significantly without losing important information or reducing accuracy. For this reason, the following three different methodologies are recommended when performing radio noise measurements: Type A: WGN only.
33、 This Type delivers only WGN levels, disregarding IN. It only requires measurements of the remaining r.m.s. level on a “free” frequency. Both r.m.s. and raw data sampling methods can be applied. Evaluation of data is relatively simple. Type B: WGN and IN. This Type delivers WGN levels and characteri
34、stics of the important IN parameters of radio noise. It requires fast data sampling (raw data sampling method). Data evaluation is more complex and requires extensive post-processing, most of which can only be performed by computers. Type C: WGN, IN and separation of MMN. In addition to WGN level an
35、d IN characteristics, this Type separates MMN, IN from atmospheric noise to a large extent which may be important in the HF frequency range. The measurement process is equal to measurement Type B, but it has to be performed at two different locations and the equipment of both locations has to be tim
36、e synchronized. The selection of the adequate measurement Type depends on the requirements, environmental category and frequency range. If measurement results should be for general use, the recommended Type is underlined in Table 3. Rec. ITU-R SM.1753-2 5 TABLE 3 Recommended measurement types Freque
37、ncy range Outdoor measurements Indoor measurements 9 kHz 300 kHz (LF) A, B A, B 300 kHz 3 MHz (MF) A, B, C A, B 3 MHz 30 MHz (HF) A, B, C A, B 30 MHz 300 MHz (VHF) A, B A, B 300 MHz 3 GHz (UHF) A, B A, B 3 GHz (SHF) A A 7 Equipment specifications 7.1 Receiver and preamplifier The measurement receive
38、r should be a standard transportable measurement receiver or spectrum analyser and any additional pre-amplification such as LNA must exhibit a low equipment noise figure together with high gain stability which is essential for the performance of noise measurements. To guarantee an acceptable measure
39、ment accuracy it is required to keep the measured noise at least 10 dB above the equipment noise floor if an r.m.s. detector is used. An external low noise amplifier (LNA) can assist in this goal. It is essential for frequencies 20 MHz. Care should be taken to use a measurement receiver with a built
40、-in correction for the error that is imposed on the result when measuring at low S/N ratios. If this noise correction is switchable, it can be turned on. However, in this case no additional correction as described in 10.2 is applicable. The requirements for the measurement system are given in Table
41、4 which does not describe a new set of measurement receivers or LNA specifications but only points out the additional or specific requirements necessary for a receiver and LNA used for noise measurements. Also the frequency band designations are based on the practical implementation of a noise measu
42、rement system and do not point to a specific receiving system. TABLE 4 Noise measurement system (receiver/LNA) requirements Function Frequency range Frequency range 9 kHz 30 MHz 30-500 MHz 0.5-3 GHz Input (antenna input) VSWR 50 , nominal 3 MHz) 10 dBm 0 dBm 2nd order intercept 60 dBm ( 3 MHz) 50 dB
43、m 40 dBm Preselection Set of sub-octave band filters or tracking filter Tracking or fixed filter Low pass/high pass filter Total noise figure 15 dB ( 2 MHz) 2 dB(1)( 20 MHz) 2 dB(1)6 Rec. ITU-R SM.1753-2 TABLE 4 (end) Function Frequency range IF rejection 80 dB 90 dB 100 dB Image rejection 80 dB 90
44、dB 100 dB LNA gain 18 dB 25 dB 25 dB LNA gain stability 0.7 dB at 20-30C LNA gain flatness over the frequency range of interest 10 dB below the average noise to be measured (1)This noise figure applies to the LNA. When an LNA is used, the requirements in Table 4 have to be met by the whole combinati
45、on of receiver and LNA. The system noise figure of the combination is dominated by the noise figure of the LNA. Care should be taken not to overload the receiver or the LNA. An external band pass filter has to be applied to prevent overloading. Below 30 MHz, signals with the highest input level orig
46、inate from broadcast stations. The attenuation of the band pass filter throughout the broadcast bands should be at least 20 dB. The IF selectivity between 6 and 60 dB should be accurately known to calculate the equivalent noise bandwidth when measurements with different IF filters have to be compare
47、d. If specified, the noise bandwidth can be taken out of the receiver specifications. This is the bandwidth of a (theoretical) rectangular filter that passes the same noise power as the filter of the receiver or analyser. 7.2 Antennas According to Recommendation ITU-R P.372, the noise level is state
48、d as a noise figure (in dB above thermal noise) rather than field strength. This noise figure is per definition referenced to a “lossless” antenna. Regarding noise sources that are evenly spread over the horizontal plane or that are received under relatively small vertical angle, the most commonly u
49、sed antenna is a vertical tuned dipole. However, a tuned ground plane antenna and a sleeve antenna are preferable for noise measurements above 30 MHz to avoid the influence of a coaxial cable and a metallic antenna mast on the isotropy of the radiation pattern. Below 30 MHz, vertical dipoles are not practical as they become too big in size. Also, they are only ideal if they are far enough away from the ground which again would be hard to realize. Recommendation ITU-R P.372 therefore uses a short vertical monopole on perfectly con
