I have trouble with spectrum visualization of OFDM signal.
I implemented OFDM system on Stratix II ES180 board and convert the Q-signal to analog via on-board DAC 14bit. I got the result like the figure I attached. I wonder why the firs edge and end edge of spectrum is far away to each other? the different is large: around 20dB (in the matlab simulation, I got the same level of them)
the second is, there is a mini circuit (transformer) before the DMA output, so, the DC component should be eliminated form signal, why I still get the DC component on the spectrum analyzer (see the figure I attached) http://obrazki.elektroda.pl/6955986300_1365247637.jpg