1、 Rec. ITU-R SM.328-11 1 RECOMMENDATION ITU-R SM.328-11 Spectra and bandwidth of emissions (Question ITU-R 222/1) (1948-1951-1953-1956-1959-1963-1966-1970-1974-1978-1982-1986-1990-1994-1997-1999-2006) Scope This Recommendation gives definitions, analytical models and other considerations of the value
2、s of emission components for various emission types as well as the usage of these values from the standpoint of spectrum efficiency. The ITU Radiocommunication Assembly, considering a) that in the interest of an efficient use of the radio spectrum, it is essential to establish for each class of emis
3、sion rules governing the spectrum emitted by a transmitting station; b) that, for the determination of an emitted spectrum of optimum width, the whole transmission circuit as well as all its technical working conditions, including other circuits and radio services sharing the band, the transmitter f
4、requency tolerances of Recommendation ITU-R SM.1045, and particularly propagation phenomena, should be taken into account; c) that the concepts of “necessary bandwidth” and “occupied bandwidth” defined in Nos. 1.152 and 1.153 of the Radio Regulations (RR), are the basis for specifying the spectral p
5、roperties of a given emission, or class of emission, in the simplest possible manner; d) that, however, these definitions do not suffice when consideration of the complete problem of radio spectrum efficiency is involved; and that an endeavour should be made to establish rules limiting, on the one h
6、and, the bandwidth occupied by an emission to the most efficient value in each case and, on the other hand, the amplitudes of the components emitted in the outer parts of the spectrum so as to decrease interference to adjacent channels; e) that with regard to the efficient use of the radio-frequency
7、 spectrum necessary bandwidths for individual classes of emission must be known, that in some cases the formulae listed in Recommendation ITU-R SM.1138, can only be used as a guide and that the necessary bandwidth for certain classes of emissions is to be evaluated corresponding to a specified trans
8、mission standard and a quality requirement; f) that the occupied bandwidth enables operating agencies, national and international organizations, to carry out measurements to quantify the bandwidth actually occupied by a given emission and thus to ascertain, by comparison with the necessary bandwidth
9、, that such an emission does not occupy an excessive bandwidth for the service to be provided and is, therefore, not likely to create interference beyond the limits laid down for this class of emission; g) that, in addition to limiting the spectrum occupied by an emission to the most efficient value
10、 in each case, rules have been established in Recommendation ITU-R SM.1541 to limit out-of-band emissions and in Recommendation ITU-R SM.329 to limit the amplitudes of the spurious emission components; 2 Rec. ITU-R SM.328-11 h) that there is a need to define the necessary bandwidth of a transmission
11、 to perform measurement of spurious emissions in accordance with Recommendation ITU-R SM.329; j) that methods of measurement for intermodulation distortion products have been established in Recommendation ITU-R SM.326 and that limits are to be found in Recommendation ITU-R SM.329; k) that in several
12、 cases, the use of systems employing necessary bandwidths much greater than the baseband bandwidth (e.g. systems which employ high modulation index FM or other bandwidth expansion techniques) potentially increase the number of users sharing a band, because the susceptibility of receivers to interfer
13、ence may be reduced sufficiently to more than compensate for the reduction in the number of channels available, thus increasing the efficiency of radio spectrum use, recognizing that the Radio Regulations (Article 1, Section VI) contain the following definitions of terms related to characteristics o
14、f emissions: “1.144 out-of-band emission*: Emission on a frequency or frequencies immediately outside the necessary bandwidth which results from the modulation process, but excluding spurious emissions. 1.145 spurious emission*: Emission on a frequency or frequencies which are outside the necessary
15、bandwidth and the level of which may be reduced without affecting the corresponding transmission of information. Spurious emissions include harmonic emissions, parasitic emissions, intermodulation products and frequency conversion products, but exclude out-of-band emissions. 1.146 unwanted emissions
16、*: Consist of spurious emissions and out-of-band emissions. 1.146A out-of-band domain (of an emission): The frequency range, immediately outside the necessary bandwidth but excluding the spurious domain, in which out-of-band emissions generally predominate. Out-of-band emissions, defined based on th
17、eir source, occur in the out-of-band domain and, to a lesser extent, in the spurious domain. Spurious emissions likewise may occur in the out-of-band domain as well as in the spurious domain. (WRC-03). 1.146B spurious domain (of an emission): The frequency range beyond the out-of-band domain in whic
18、h spurious emissions generally predominate. (WRC-03). 1.147 assigned frequency band: The frequency band within which the emission of a station is authorized; the width of the band equals the necessary bandwidth plus twice the absolute value of the frequency tolerance. Where space stations are concer
19、ned, the assigned frequency band includes twice the maximum Doppler shift that may occur in relation to any point of the Earths surface. *The terms associated with the definitions given by Nos. 1.144, 1.145 and 1.146 shall be expressed in the working languages as follows: Numbers In French In Englis
20、h In Spanish 1.144 Emission hors bande Out-of-band emission Emisin fuera de banda1.145 Rayonnement non essentiel Spurious emission Emisin no esencial 1.146 Rayonnements non dsirs Unwanted emissions Emisiones no deseadas NOTE 1 In accordance with Resolution 115 (Marrakesh, 2002) the Table should be a
21、mended to present equivalents in Arabic, Chinese and Russian languages. Rec. ITU-R SM.328-11 3 1.148 assigned frequency: The centre of the frequency band assigned to a station. 1.149 characteristic frequency: A frequency which can be easily identified and measured in a given emission. A carrier freq
22、uency may, for example, be designated as the characteristic frequency. 1.150 reference frequency: A frequency having a fixed and specified position with respect to the assigned frequency. The displacement of this frequency with respect to the assigned frequency has the same absolute value and sign t
23、hat the displacement of the characteristic frequency has with respect to the centre of the frequency band occupied by the emission. 1.151 frequency tolerance: The maximum permissible departure by the centre frequency of the frequency band occupied by an emission from the assigned frequency or, by th
24、e characteristic frequency of an emission from the reference frequency. The frequency tolerance is expressed in parts in 106or in hertz. 1.152 necessary bandwidth: For a given class of emission, the width of the frequency band which is just sufficient to ensure the transmission of information at the
25、 rate and with the quality required under specified conditions. 1.153 occupied bandwidth: The width of a frequency band such that, below the lower and above the upper frequency limits, the mean powers emitted are each equal to a specified percentage /2 of the total mean power of a given emission. Un
26、less otherwise specified in an ITU-R Recommendation for the appropriate class of emission, the value of /2 should be taken as 0.5%”, recommends 1 Definitions That the following definitions should be used when dealing with bandwidth, channel spacing and interference problems: 1.1 Baseband The band of
27、 frequencies occupied by one signal, or a number of multiplexed signals, which is intended to be conveyed by a line or a radio transmission system. NOTE 1 In the case of radiocommunication, the baseband signal constitutes the signal modulating the transmitter. 1.2 Baseband bandwidth The width of the
28、 band of frequencies occupied by one signal, or a number of multiplexed signals, which is intended to be conveyed by a line or a radio transmission system. 1.3 Bandwidth expansion ratio The ratio of the necessary bandwidth to baseband bandwidth. 4 Rec. ITU-R SM.328-11 1.4 Out-of-band spectrum (of an
29、 emission) The part of the power density spectrum (or the power spectrum when the spectrum consists of discrete components) of an emission which is outside the necessary bandwidth and which results from the modulation process, with the exception of spurious emissions. 1.5 Permissible out-of-band spe
30、ctrum (of an emission) For a given class of emission, the permissible level of the power density (or the power of discrete components) at frequencies above and below the limits of the necessary bandwidth. NOTE 1 The permissible power density (or power) may be specified in the form of a limiting curv
31、e giving the power density (or power), expressed in decibels relative to the specified reference level, for frequencies outside the necessary bandwidth. The abscissa of the initial point of the limiting curve should coincide with the limiting frequencies of the necessary bandwidth. Descriptions of l
32、imiting curves for various classes of emissions are given in Annexes 1 to 6. 1.6 Out-of-band power (of an emission) The total power emitted at the frequencies of the out-of-band spectrum. 1.7 Permissible out-of-band power For a given class of emission, the permissible level of mean power emitted at
33、frequencies above and below the limits of necessary bandwidth. NOTE 1 The permissible level of out-of-band power should be determined for each class of emission and specified as a percentage of the total mean power radiated derived from the limiting curve fixed individually for each class of emissio
34、n. 1.8 x dB bandwidth The width of a frequency band such that beyond its lower and upper limits any discrete spectrum component or continuous spectral power density is at least x dB lower than a predetermined 0 dB reference level. The definition of x dB bandwidth may vary according to the determinat
35、ion of 0 dB (see Recommendation ITU-R SM.1541): x dBsd bandwidth: x dB bandwidth in a situation where the reference level is chosen to the maximum value of power spectral density (psd) within the necessary bandwidth; x dBc bandwidth: x dB bandwidth in a situation where the reference level is chosen
36、to the unmodulated carrier power of the emission. When the carrier is not accessible for measurement, the reference level is the mean power; x dBpp bandwidth: x dB bandwidth in a situation where the reference level is chosen to the maximum value of the peak power, measured with the reference bandwid
37、th within the occupied bandwidth. NOTE 1 The x dB bandwidth method gives results acceptable for the estimation of the 99% occupied bandwidth as defined in RR Article 1, No. 153, under the appropriate choice of x dB and 0 dB reference levels. Rec. ITU-R SM.328-11 5 1.9 Build-up time of a telegraph si
38、gnal The time during which the telegraph current passes from one-tenth to nine-tenths (or vice versa) of the value reached in the steady state; for asymmetric signals, the build-up times at the beginning and end of a signal can be different. 1.10 Relative build-up time of a telegraph signal Ratio of
39、 the build-up time of a telegraph signal defined in 1.9 to the half-amplitude pulse duration. 1.11 Modulation rate The modulation rate (Bd), B, used in the following text is the maximum speed used by the corresponding transmitter. For a transmitter operating at a speed lower than this maximum speed,
40、 the build-up time should be increased to keep the occupied bandwidth at a minimum, to comply with RR No. 3.9. 2 Emission of a transmitter, optimum from the standpoint of spectrum efficiency That an emission should be considered optimum from the standpoint of spectrum efficiency when its occupied ba
41、ndwidth coincides with the necessary bandwidth for the class of emission concerned. An optimum bandwidth from the standpoint of spectrum efficiency may not be optimum from the standpoint of spectrum usage in a sharing situation. 2.1 The following are examples of spectra illustrating the definitions
42、of out-of-band power, necessary bandwidth and x dB bandwidth. 6 Rec. ITU-R SM.328-11 3 Limits for out-of-band emissions that this Recommendation could be used as guidance in deriving the limits for out-of-band emissions. Such limits should be defined considering the degradation caused by modulation
43、imperfections, phase noise, intermodulation and practical limitations on filter implementation. Rec. ITU-R SM.328-11 7 4 Calculation of emitted spectra that values for emission components can be calculated for the emission types identified in RR Appendix 1. Annexes 1 to 6 should be used to calculate
44、 the following emissions types which contain the analytical models and other considerations which may be utilized as the basis determining the values in measurement of occupied bandwidth: emissions designated Type A (see Annex 1); emissions designated Types B and R (see Annex 2); emissions designate
45、d Type F (see Annex 3); emissions designated Type G (see Annex 4); emissions designated Type J (see Annex 5); digital phase modulation (see Annex 6). 4.1 Approximation of out-of-band spectra envelopes for analytical calculations For an approximation of out-of-band spectra envelopes by power function
46、s the following formula should be used: =fffSfSmm)()(1(1) = 0.33 N where S(fm) is the power on a given frequency fm, and N is a number of dB by which the spectrum envelope is reduced within a single octave of band widening. For another approximation of out-of-band spectra envelopes by exponential fu
47、nctions the following formula should be used: = )(23.0exp)()(12 mmmfffNfSfS (2) where N1represents the number of dB corresponding to the first octave of band widening. For the most common values of N = 12 to 20 dB/octave, it is sufficient to carry out the power comparison at a very low accuracy of a
48、bout 15% to 20% to ensure an occupied bandwidth measurement accuracy of 3% to 7%*. These methods consist in comparing the total power of the emission with the power remaining after filtering, either by means of two low-pass filters or two high-pass filters, or by a high-pass filter, or by a high-pas
49、s and a low-pass filter, the cut-off frequencies of which can be shifted at will with respect to the spectrum of the emission. Alternatively, the relevant power constituents can be determined by evaluating the power spectrum as obtained by a spectrum analyser. *Note by the Secretariat: The relationship between the percentage error in measuring the occupied bandwidth and the percentage error in the power comparison, for different values of N is shown in Fig. 71 of the ITU-R Spectrum Monitoring Handbook (Geneva, 1995). 8 Rec. ITU-R SM
