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5 new ITU-R Recommendations (SM.1836 to SM.1840) on Radio Monitoring Receivers (by Rohde&Schwarz)

Minimum recommended specifications for analogue and digital radio monitoring receivers are described in the Spectrum Monitoring Handbook (Edition of 2002).


One of these specifications is for example the 3rd order intercept point level (IP3), a measure of the receiver’s linearity. The higher the IP3 level (usually expressed in dBm), the better the linearity of the receiver is. The full importance of this specification comes out when the receiver operates in an environment of many high level emissions in the spectra vicinity to the tuned frequency – that is a frequent scenario in a monitoring station.


L
imited linearity of a receiver is one of the reasons for the monitoring operator to get signals that do not really exist in the RF spectrum. These spurious signals are generated in the equipment itself. They make the radio monitoring task difficult and tedious and may conduct to wrong results and false reports.


When comparing the data sheets of similar receivers from different manufacturers, the IP3 levels indicated are considered by the users, among other parameters, for the purpose of receiver quality comparison. To be able to get a fair comparison between the receivers, however, they all should have been tested under the same conditions. Otherwise, Receivers from different makers showing nearly the same IP3 levels in their respective data sheets, might be of completely different linearity and performance (and therefore of different suitability as monitoring receivers) if the test procedure behind the IP3 specification is not defined in such a way that it actually describes the linearity of the receiver in an unambiguous way. A uniform measurement procedure is the way to reach this. The same is true for other receiver data, too.
 

Therefore, five new recommendations (ITU-R SM.1836 to ITU-R SM.1840) provide the definitions of test procedures for measuring IF filter properties, IP3, noise figure, scanning speed and sensitivity respectively. Hence, once the receiver data which are published by the manufacturers are measured according to these recommendations they are comparable for the one who has to determine whether a certain receiver will fulfill the necessary requirements or not. This is a large step towards more objectivity and this helps administrations as well as the industry.
 

 

 


The Rohde & Schwarz stand during WRC 07
Source: ITU / J.M. Ferré (Compulsory)
 

 

 

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