The harmonic of transmitter in the wifi system

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Jameslu

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Hi all

why the 2nd/3rd harmonic of DSSS modulation is highest than QAM modulation in the same channel?

i think that is cause to different modulation, Is it correct or not?

many thanks
 

What exactly is the type of modulation in the DSSS?

the amount of "power" contained in a broad bandwith can "appear" to be different when viewed on a spectrum analyzer set to a narrow resolution bandwidth. For instance, FSK is a contant envelope signal and can appear to be bigger than QAM if captured in a small resolution bandwith. therefore the 2nd/3rd harmonic will also appear to be bigger than that caused by QAM.

Also, the 2nd harmonic is at twice the frequency, so its power/hz will drop by 3 dB, and more so with the 3rd harmonic.
 
thank your reply and remind to me

as your mentioned, if i will test the harmonic for DSSS and QAM of modulation, the spectrum analyzer need to set the same conditions (resolution bandwidth or video bandwidth..etc) and get the similar results.

thanks
 

if I am measuring harmonics in a modulated system, I crank up the RBW as big as it can get. Even then it might not be big enough.
 
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