Thanks a bunch for your response, Matt!
> > Since you are using an interpolation is a multiple of 4, you won't see CIC > rolloff, you get a nice flat passband. > Got ya! > There are likely a couple of issues causing the spectrum to look bad. > First, successive symbols coming out of the FFT will have amplitude > discontinuities. This causes out of band emissions unless you smoothly > transition between the symbols. This is normally done with windowing. The > 802.11g spec is a good example. > I will check the spec for this, thanks for the pointer there. I will see how they do the windowing. > > Second, you may be clipping. OFDM has a very high peak to average ratio, > so you need to make sure the peaks are below clipping. > > Clipping nailed it. I get a very clean spectrum now :) Super awesome! One last question still, do you know where I am missing a factor of two here: 1) My calculation of the bandwidth of the 100 active bins, and the actual bandwidth, is off by a factor of two: (((100 MHz) / 32) / 1024) * 100 = 305.175781 kilohertz, where 32 is the interpolation rate, 1024 was the size of the IFFT, and 100 is the number of active bins. I see 610KHz, however.
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