Hi folks,

I have implemented a multi sub-carriers AM transmitter and here I still

have a strange problem: I plotted the FFT of the modulated signal at

baseband (as attached) and the number of the bins (spikes) I have on the

plot was exactly the same as the number of the sub-carriers as I set in

the program. This is correct so far as I know. But after the signal was

tuned to 2.45GHz by USRP, the number of the bins(spikes) on my spectrum

analyzer was not the same, which is only 4 or 6. While I have 20

sub-carriers at different frequencies and it seems that I lost most of

them after the signal was tuned to RF. Is there anybody who knows the

reason behind that? I have been stuck at here for a long time. Any helps

or suggestions will be greatly appreciated.

Thanks,

Milo