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Sidebands Generation on FM modulated signal

Hi,

 

I am generating a BFSK signal at mark frequencies 18k and space frequencies 22k then performing FM modulation on it. when i observed the same FM signal at RF 430M Center Frequency in R&S spectrum analyzer. i see some side bands generated on either side of the carrier frequency. Also I checked the IF signal at 25M, these side bands are present there also.

 

My hardware is as follows

5641r IF transceiver

5610 Rf upconverter.

 

I found that 5641R does not have band pass filters integrated on it.

 

i would like to know, how these sidebands are removed from FM signal.

 

Thanking you

 

 

 

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FM has multiple sidebands, depending on the modulation index and modulating signal amplitude. You did not specify the modulation parameters and the signal amplitudes, so we cannot tell whether this is expected or not.

 

Lynn

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HI John,

 

The modulation index defined as 1, and the signal amplitude as 2v pk-pk.

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