Rec. ITU-R SM.1541 1
*RECOMMENDATION ITU-R SM.1541
Unwanted emissions in the out-of-band domain
(Question ITU-R 211/1)
The ITU Radiocommunication Assembly,
a) that Recommendation ITU-R SM.329 – Spurious emissions, relates to the effects, measure-
ments and limits to be applied to unwanted emissions in the spurious domain; b) that Recommendations ITU-R SM.329 and ITU-R SM.1539 provide guidance for deter-mining the boundary between the out-of-band (OoB) and spurious domains in a transmitted radio frequency spectrum;
c) that considerations of out-of-band domain and necessary bandwidths are included by necessity in Recommendation ITU-R SM.328 – Spectra and bandwidth of emissions;
d) that unwanted emissions occur after a transmitter is brought into operation and can be reduced by system design;
e) that OoB limits have been successfully used as national or regional regulations in areas having a high radiocommunications density; such limits are generally designed according to specific and detailed local needs for coexistence with other systems;
f) that nevertheless there is a need, for each service, for a limited number of a more broadly generic ITU-R OoB limits, generally based on an envelope of the least restrictive OoB limits described in the above considering e);
g) that where frequency assignments are provided to the Radiocommunication Bureau (BR) in accordance with Appendix 4 of the Radio Regulations (RR), the necessary bandwidth of an emission with a single carrier is given by the bandwidth portion of the emission designator; h) that the necessary bandwidth, referred to in RR Appendix 4 is for a single carrier transmission, and may not adequately cover the case of systems with multiple carriers,
that the following terms are defined in the RR:
Unwanted emissions (RR No. 1.146)
Consist of spurious emissions and OoB emissions.
* This Recommendation should be brought to the attention of Radiocommunication Study Groups 4, 6, 7, 8 and 9.
2 Rec. ITU-R SM.1541
Spurious emission (RR No. 1.145)
Emission on a frequency or frequencies which are outside the necessary 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 OoB emissions.
Out-of-band emission (RR No. 1.144)
Emission on a frequency or frequencies immediately outside the necessary bandwidth which results from the modulation process, but excluding spurious emissions.
Occupied bandwidth (RR No. 1.153)
The width of the frequency band which is just sufficient 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.
Unless otherwise specified in an ITU-R Recommendation for the appropriate class of emission, the value of ；/2 should be taken as 0.5%.
Necessary bandwidth (RR No. 1.152)
For a given class of emission, the width of the frequency band which is just sufficient to ensure the transmission of information at the rate and with the quality required under specified conditions. Assigned frequency band (RR No. 1.147)
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 concerned, the assigned frequency band includes twice the maximum Doppler shift that may occur in relation to any point of the Earth's surface.
Assigned frequency (RR No. 1.148)
The centre of the frequency band assigned to a station,
a) that Recommendation ITU-R SM.1540 additionally covers cases of unwanted emissions in the OoB domain falling into adjacent allocated bands;
b) that the studies required by Question ITU-R 222/1, approved by Radiocommunication Assembly 2000, could have formal and substantial impact to basic definitions used in this Recommendation. It may be necessary to revise this Recommendation in the future to reflect the results of these studies,
Rec. ITU-R SM.1541 3
1 Terminology and definitions
that the following additional terms and definitions should be used:
11.1 Spurious domain
(of an emission): the frequency range beyond the OoB domain in which spurious emissions generally predominate.
11.2 OoB domain
(of an emission): the frequency range, immediately outside the necessary bandwidth but excluding the spurious domain, in which OoB emissions generally predominate.
1.3 dBsd and dBasd
dBsd: decibels relative to the maximum value of power spectral density (psd) within the necessary bandwidth. The maximum value of psd of a random signal is found by determining the mean power in the reference bandwidth when that reference bandwidth is positioned in frequency such that the result is maximized. The reference bandwidth should be the same regardless of where it is centred and is as specified in ? 1.6.
dBasd: decibels relative to the average value of psd within the necessary bandwidth. The average Maximum value of psd
value of psd of a random signal is found by computing the mean power in the reference bandwidth and averaging that result over the necessary bandwidth. The reference bandwidth is as specified in ? 1.6.
0 dBsd reference (a) maximum value of psd
0 dBasd reference (b) average value of psd
ReferenceMean powerReferenceMean power
Average value of psd
a) Maximum psd conceptb) Average psd concept
1 The terms “OoB domain” and “spurious domain” have been introduced in order to remove some inconsistency now existing between, on one hand, the definition of the terms “OoB emission” and “spurious emission” in RR Article 1 and, on the other hand, the actual use of these terms in RR
Appendix 3, as revised by World Radiocommunication Conference (Istanbul, 2000) (WRC-2000). OoB and spurious limits apply, respectively, to all unwanted emissions in the OoB and spurious domains.
4 Rec. ITU-R SM.1541
Decibels relative to the unmodulated carrier power of the emission. In the cases which do not have a carrier, for example in some digital modulation schemes where the carrier is not accessible for measurement, the reference level equivalent to dBc is dB relative to the mean power P.
Decibels relative to the maximum value of the peak power, measured with the reference bandwidth within the occupied bandwidth. The in-band peak power is expressed in the same reference bandwidth as the OoB peak power. Both the in-band and the unwanted emissions should be evaluated in terms of peak values. For radar systems, the reference bandwidth should be selected according to Recommendation ITU-R M.1177.
0 dBpp reference, maximum value of peak power
Peak to mean power ratioMean powerMaximum value of peak powerdisplay
Maximum value of mean power
Peak power concept1541-02
1.6 Reference bandwidth
The bandwidth required for uniquely defining the out-of-band limits. If not explicitly given with the OoB limit, the reference bandwidth should be 1% of the necessary bandwidth. For radar systems the reference bandwidth should be selected in line with Recommendation ITU-R M.1177. 1.7 Measurement bandwidth
The bandwidth which is technically appropriate for the measurement of a specific system. In common spectrum analysers this is generally referred as the resolution bandwidth. NOTE 1 – The measurement bandwidth may differ from the reference bandwidth, provided the results can be converted to the required reference bandwidth.
Rec. ITU-R SM.1541 5
For the purpose of this Recommendation, psd is the mean power per reference bandwidth. 1.9 Mean power
Power integrated over a specified frequency band using measurements of the psd or an equivalent method.
1.10 Adjacent channel mean power
Power integrated over the bandwidth of a channel adjacent to an occupied channel using measure-ments of the psd or an equivalent method.
1.11 Peak power
Power measured with the peak detector using a filter the width and shape of which is sufficient to accept the signal bandwidth.
1.12 Adjacent channel peak power
Peak power measured in the bandwidth of a channel adjacent to an occupied channel using a specified channel filter.
1.13 Total assigned band
Sum of contiguous assigned bands of a system consistent with the RR Appendix 4 data provided to the Radiocommunication Bureau and as authorized by an administration.
NOTE 1 – For space services, when a system has multiple transponders/transmitters that operate in adjacent bands separated by a guardband, the total assigned band should include the guardbands. In such cases, the guardbands should be a small percentage of the transponder/transmitter bandwidth.
1.14 Total assigned bandwidth
The width of the total assigned band;
2 Application of definitions
that, when applying this Recommendation, guidance should be taken from the following: 2.1 OoB domain emissions
Any emission outside the necessary bandwidth which occurs in the frequency range separated from the assigned frequency of the emission by less than 250% of the necessary bandwidth of the emission will generally be considered an emission in the OoB domain. However, this frequency separation may be dependent on the type of modulation, the maximum symbol rate in the case of digital modulation, the type of transmitter, and frequency coordination factors. For example, in the case of some digital, broadband, or pulse modulated systems, the frequency separation may need to differ from the 250% factor.
6 Rec. ITU-R SM.1541
Transmitter non-linearities may also spread in-band signal components into the frequency band of the OoB frequency ranges described in Annex 1, ? 1.3. Further, transmitter oscillator sideband noise also may extend into that frequency range described in Annex 1, ? 1.3. Since it may not be practical to isolate these emissions their level will tend to be included during OoB power measurements. 2.2 Spurious domain emissions
For the purpose of this Recommendation all emissions, including intermodulation products, conversion products and parasitic emissions, which fall at frequencies separated from the centre frequency of the emission by 250% or more of the necessary bandwidth of the emission will generally be considered as emissions in the spurious domain. However, this frequency separation may be dependent on the type of modulation, the maximum symbol rate in the case of digital modulation, the type of transmitter, and frequency coordination factors. For example, in the case of some digital, broadband, or pulse-modulated systems, the frequency separation may need to differ from the 250% factor.
For multichannel or multicarrier transmitters/transponders, where several carriers may be transmitted simultaneously from a final output amplifier or an active antenna, the centre frequency of the emission is taken to be the centre of either the assigned bandwidth of the station or of the –3 dB bandwidth of the transmitter/transponder, using the lesser of the two bandwidths. 2.3 Necessary bandwidth and OoB domain
In the case of narrow-band or wideband emissions (as defined in Recommendation ITU-R SM.1539, the extent of the OoB domain should be determined by using Table 1.
Start and end of OoB domain
Offset (?) from the If necessary Frequency separation between Type of centre of the necessary bandwidth the centre frequency and the emission bandwidth for the start B is: spurious boundary Nof the OoB domain
Narrow-band < B(see Note 1) 0.5 B 2.5 B L NL
Normal B to B 0.5 B 2.5 B LUNN
Wideband > B 0.5 B B + (1.5 B) UNUN
NOTE 1 – When B < B, no attenuation of unwanted emissions is recommended at frequency NL
separations between 0.5 B to 0.5 B. NL
NOTE 2 – B and B are given in Recommendation ITU-R SM.1539. LU
Rec. ITU-R SM.1541 7
2.3.1 Single carrier emissions
The value of necessary bandwidth that should be used for checking whether a single carrier emission complies with limits in the OoB domain should coincide with the value in the emission designator provided to the BR in accordance with RR Appendix 4.
Some systems specify the OoB mask in terms of channel bandwidth or channel separation. These may be used as a substitute for necessary bandwidth provided they are found in ITU-R Recommen-dations or in relevant regional and national regulations.
2.3.2 Multicarrier emissions
Multicarrier transmitters/transponders are those where multiple carriers may be transmitted simul-taneously from a final amplifier or an active antenna.
For systems with multiple carriers, the OoB domain should start at the edges of the total assigned bandwidth. For satellite systems, the necessary bandwidth used in the OoB masks provided in Annex 5 of this Recommendation and to determine the width of the OoB domain should be taken to be the lesser of 3 dB transponder bandwidth or the total assigned bandwidth (Annex 2 provides two examples showing how to calculate the start and end of the OoB domain for multicarrier systems with single and multiple transponders per satellite).
For space services, the above definition of necessary bandwidth applies when all or some of the carriers are being transmitted simultaneously.
2.4 Considerations on dBsd, dBc, and dBpp
2.4.1 Positive and negative signs for dBsd, dBc, and dBpp
Since dBsd is defined as relative to some reference power spectral density, the OoB dBsd value is expressed using a negative number (for the usual case where the OoB psd is lower than the reference psd). However, if a term such as “dBsd below” or “Attenuation (dBsd)” is used, then the OoB domain emission value is expressed using a positive number.
Since dBc is defined as relative to some reference power, the OoB dBc value is expressed using a negative number. However, if a term such as “dBc below” or “Attenuation (dBc)” is used, then the OoB domain emission value is expressed using a positive number.
Since dBpp is defined as relative to some reference peak power, the OoB dBpp value is expressed using a negative number. However, if a term such as “dBpp below” or “Attenuation (dBpp)” is used, then the OoB domain emission value is expressed using a positive number. Annex 3 provides the way to label X and Y axes on dBc and dBsd masks.
2.4.2 Comparisons of dBsd and dBc
Since dBsd and dBc do not have the same 0 dB reference, the same numeric dB value may cause dBsd emission limits that are more stringent than dBc emission limits. The chosen reference bandwidth will affect the amount of this difference. Thus, the type of mask, reference bandwidth, and mask values need to be established together.
8 Rec. ITU-R SM.1541
2.4.3 Practical application of dBsd, dBc, and dBpp limits
dBsd may be more practical for the following applications:
– digital modulation;
– modulation formats in which measurement of the carrier is impractical.
dBc may be more practical for the following applications:
– analogue modulation;
– specific digital modulation systems;
– subsidiary limits for discrete emissions contained in the OoB domain when spectral density
is specified in dBsd values.
dBpp may be more practical for the following applications:
– specific pulsed modulation systems, e.g. radar, and certain specific analogue transmission
3 Methods to determine conformance to OoB limits
that the adjacent channel and alternate adjacent channel power method or the OoB spectrum mask method described in Annex 1 should be used to determine conformance to OoB domain emission requirements;
24 OoB limits for transmitters in the range of 9 kHz to 300 GHz
that the spectrum limits specified in this Recommendation should be regarded as generic limits, which generally constitute the least restrictive OoB emission limits successfully used as national or regional regulations. These are sometimes called safety net limits. They are intended for use in bands where tighter limits are not otherwise required to protect specific applications (e.g. in areas having a high radiocommunications density).
On this basis, the OoB domain emissions, to be applied to transmitters in the range of 9 kHz to 300 GHz, should be limited as given in Table 2.
The applicability of Recommendations ITU-R SM.1541 and ITU-R SM.1540 is described in Annex 14.
The development of more specific OoB limits for each system and in each frequency band should be encouraged by administrations. These limits would take into account the actual application, modulation, filtering capabilities of the system and would take care about co-frequency or adjacent bands operating systems, with a view to enhancing compatibility with other radio services. Examples of ITU-R Recommendations providing such more specific OoB emission limits for some systems in some frequency bands are listed in Annex 4.
2 OoB limits apply to unwanted emissions (both OoB and spurious emissions) in the OoB domain.
Rec. ITU-R SM.1541 9
OoB domain emission spectrum limiting curves
Service category in accordance with Emission mask RR Article 1, or equipment type
Space services (earth and space stations) See Annex 5
Broadcast television See Annex 6
Sound broadcasting See Annex 7
Radar See Annex 8
Amateur services See Annex 9
Land mobile service See Annex 10
Maritime and aeronautical mobile services See Annex 11
Fixed service See Annex 12
Compliance with emission limits contained in this Recommendation may not preclude the occurrence of interference. Therefore, compliance with the standard does not obviate the need for cooperation in resolving and implementing engineering solutions to harmful interference problem; 5 Adaptation of OoB masks provided in Annexes 5 to 12 in the cases of
narrow-band and wideband systems
a) that in cases where the necessary bandwidth B is less than B as defined in Recommen-NL
dation ITU-R SM.1539, the OoB mask should be scaled. This can be done by replacing B N
by B; L
b) in cases where the necessary bandwidth B is greater than B as defined in Recommen-NU
dation ITU-R SM.1539, the value of B will remain unchanged in the application of the N
OoB mask but the mask should be truncated. Accordingly, the OoB mask will only be
applicable from 50% of B to (150 ？ 100 B/B)% of B; NU NN
6 Measurement methods
that the methods for measurement of OoB described in detail in Annex 13 should be used.
Methods to determine conformance to OoB limits
Two possible methods can be used to quantify the OoB emission energy. Section 1 provides a method by which the power is measured in an adjacent channel. Section 2 discusses a method of assessment based on the determination of the power spectral density in the OoB domain.
10 Rec. ITU-R SM.1541
1 Adjacent channel and alternate adjacent channel power method
This methodology is based on the concept defined in Recommendation ITU-R SM.328 – Spectra
and bandwidth of emissions, ? 1.12 and has become popular since the commercial availability of spectrum analysers with digital signal processing capability which can perform numerical inte-gration within a specified bandwidth.
A limit for permissible OoB domain power can be derived from the limits imposed by a permissible OoB spectrum mask by integrating the mathematical expression for the curve over a specified frequency band. An example of this translation is provided in Appendix 1 for an example emission mask used in the land mobile service, the primary user of this method. Comparisons of limits so derived with actual limits adopted in mobile service standards reveal that mobile radio industry practice has been to establish limits significantly more stringent than those derived from an OoB mask in order to achieve spectrum efficiency.
One key advantage of this method in a defined bandwidth approach is that the same approach is defined in Recommendation ITU-R SM.329 for limits of the power of spurious domain emissions displaced relatively far in the frequency spectrum from a transmitter's assigned frequency band (i.e. channel).
Another advantage is that it tends to facilitate frequency management if the reference bandwidth is chosen comparable to that of receivers used in the assigned frequency bands adjacent to that of a transmitter as this leads to more efficient use of the electromagnetic spectrum. This can be especially significant in new channel splitting “refarming” environments wherein the close packing of channels in an allocated band has resulted in frequency assignment co-ordination based on adjacent channel considerations in addition to co-channel considerations. It also provides a convenient means of assessing the interference potential between two different modulation methods used on adjacent channels or bands. This has proved useful in spectrum allocation planning in various countries to determine compatible neighbouring technologies and link directions. 1.1 Parameters to be measured
The parameters to be measured are the occupied bandwidth of an emission, and the mean power in several defined bands. The same modulation condition is employed for all measurement bands. The maximum value of 99% power occupied bandwidth permitted by a particular emission mask can be determined by calculating the frequency difference between the 23 dB attenuation levels for any emission mask.
1.2 Units of measurement
The units of power measurement are the same as those used for measurement of spurious domain emissions, as given in Annex 1 of Recommendation ITU-R SM.329 (mean power is specified for