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How much RF span should I set for an analog RF signal which occupies a bandwidth more than 20 MHz?

Question asked by yanjiesh on Jan 7, 2015
Latest reply on Jan 9, 2015 by rgetz

Dear all,

 

I am studying on some signals which occupy more than 20 MHz, maybe 21 MHz, e.g..

 

I was suggested setting  a RF span bandwidth around 10.5 MHz, as I was told somewhere. However I found some spectrum difference if  I set the RF span into 21 MHz than 10.5 MHz in my experiment.

 

If I set it to 21 MHz, the whole interested spectrum could be shown by voltage_0  or voltage_1, only one channel is enough.

But if I set it to 10.5MHz, the spectrum could be shown by voltage_0-voltage_1 choice, which needs two channel, and the obtained spectrums seem different.

 

What is the mystery?

 

Regards,

 

-Jie

 

2015-1-8

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