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Noise measurement: needed shielded room??

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wccheng

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used shielded room

Dear all,

In the industrial, will they measure their RF circuit in the shielded room in order to get all the figure of merits ( 1-dB, IIP3, power gain, NF etc.)? Or, just use shielded room to measure all the Noise parameters? Or, just measure all parameters under the normal environment wihtout any shielding? Could any people suggest to me how do the industrial do it?

thanks

wccheng
 

When I measure noise in general I am using a shielded room only if there are external noise in the band where I am doing the measurement. For example if you are doing noise figure of an LNA for cellular bands, is possible to have some external Base Stations that are transmitting near by in that band, and you need a shielded room. Some microwave applications also requires shielded room for Noise Figure measurements. In this case have to be sure that room frequency response covers that bands.
For two-tone test you don’t need a shielded room, assuming that you checked before the spectrum to don’t have an interferer in top of your signals.
 

I had a shielded room the past. I've used shielded room two times only. practically there is no need.
Lots are EMI/RFI that disturb noise measurement, many are coming from far, many are generate locally, all are described into Agilent AN 57-1.
Nowadays, many people use wireless devices such mobile phone, wireless LAN, bluetooth etc. In this context, the inner side of a shielded room act as cavity, an inside RFI generate by a cell-phone will be enlarged.

Anechoic chambers are better.
 

just use an agilent instrument with noise feature
 

I think don't need ,only some instruments
 

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