OFDM Modulator

Hi Everybody...

Good Afternoon. My name is Vanessa. I�m an engineer and I�m developing a
prototype of an
OFDM Modulator. The configuration I choosed was: 2K IFFT, 64QAM and 1/16
for the cyclic 
prefix.The sampling frequency used in the IFFT was 12.5MHz. When I did the
cyclic extention, the output spectrum became filled with running spurious
tones, overlaping the correct base band signal. My question is: why did it
appeared some "spikes" in the middle of the spectrum? Did it should
happen?

I appreciate your attention and help

Best regards

Vanessa Lima