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Altera_Forum
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13 years ago

FFT Megafunction problem - strange spikes

Hi, I use FFT IP Core (Quartus 9.1 SP2 / Quartus 11.1 SP2). I send sine-signal to sink pins and get fft-signal from source pins of core. Then I plot ABS, real and imag of my fft-signal in Matlab. ...
Altera_Forum's avatar
Altera_Forum
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13 years ago

It is likely to be harmonics of your tone. A harmonic occurs if your tone correlates with sampling frequency(integer relation). It is basically quantisation noise concentrated in certain frequencies. As such it is normal but you need to see how far in dBs are they down from signal level