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ITU and CEPT studies on Unwanted Emissions |
Over the past few years a technological battle has been quietly raging in the Study Groups of ITU and Project Teams of CEPT concerning the suppression of unwanted emissons from transmitters. All transmitters produce unwanted emissions of some kind, the most familiar being spurious emissions, such as the harmonics of the transmitted frequency, however new digital systems and wide band satellite transponders have brought a range of new problems, especially from out-of -band emissions that result from the modulation process. There are a variety of technical and operational means to reduce the level of unwanted emissions but all have cost penalties and, generally, the greater the degree of reduction, the greater the cost. In most cases, unwanted emissions rarely cause interference to the operator of the transmitter, it is usually another service that suffers and it is particularly unfortunate that the passive services, without transmitters but with very sensitive receivers, such as radio astronomy, are especially vulnerable to unwanted emissions. However, it is recognised that all services benefit from unwanted emission controls and it is a question of balancing the needs of rapidly developing telecommunications with the protection requirements of the passive and safety services.
The Spectrum Engineering section has lead the international technical studies through the chairmanship of a CEPT Project Team responsible for coordinating the European position, and chairmanship of an ITU Task Group responsible for developing international recommendations, some of which may be incorporated into the Radio Regulations as mandatory requirements. At a recent ITU-R Study Group 1 meeting, a number of Recommendations and Reports were adopted. The unwanted emission 'family' of Recommendations now consists of:
| ITU-R Rec. SM.[OOB]* | Unwanted emissions in the OUT-OF-BAND domain |
| ITU-R Rec. SM.329 | Spurious emissions |
| ITU-R Rec. SM.[Boundary]* | Variation of the boundary between the out-of-band and spurious domains required for the application of recommendations ITU-R SM.329 and ITU-R SM.[OOB] |
| ITU-R Rec. SM.[OAB]* |
Unwanted emissions in the out-of-band domain falling into adjacent allocated bands |
These are supplemented by recommendations dealing with effects of unwanted emissions on passive and safety services:
| Rec. ITU-R SM.[PS]* | The protection of passive services from unwanted emissions |
| Rec. ITU-R SM.[SAF]* | The protection of safety services from unwanted emissions |
(* These new recommendations will be numbered once they have completed approval by correspondence)
The following Reports were adopted:
ITU-R Report on the Monte Carlo methodology:
This Report describes the methodology that has been derived from the work in CEPT on the Spectrum Engineering Advanced Monte Carlo Analysis Tool (SEAMCAT) compatibility analysis software and ERC Report 68. The completion of the ITU-R report is a significant milestone which will improve the possibility to submit studies to ITU-R groups using SEAMCAT
TG1/5 Report on Definitions:
This Report provides a useful guide to the definitions appearing in the various Recommendations and Reports
- new Task Group established A number of tasks remain in preparation for WRC-2003. Agenda Item 1.8.1, dealing with the boundary between spurious and out-of-band emissions, will be progressed by a correspondence group. For Agenda Item 1.8.2, dealing with regulatory measures for the protection of the passive services, a new Task Group (TG 1/7) has been established.
The UK will participate in both groups and the initial contact point for the UK preparations for both CEPT (WGSE) and ITU (SG1) studies is: steve.bond@ra.gsi.gov.uk
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