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FFT + IFFT processing

Altera_Forum
Honored Contributor I
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Hello! I use FFT + IFFT pair, my adc is 12 bit and Vp 3,3 Volts, input signal is sin Amp 400mv DC offset 800mv, i have right amplitude spectrum after FFT (the square root of the sum of squares х 2, exactly DC component) .  

Now i add IFFT to my project, connect source_fft to sink ifft directly and make sum scalling after ifft.  

 

assign EXP_SUM = ((~SOURCE_EXP1 + 1'b1) + (~SOURCE_EXP2 + 1'b1) - 4'd8); assign REAL_EXP = ~EXP_SUM + 1'b1;  

 

The output IFFT - sin with right frequency, but amplitude peak values is wrong, something about 2000 - 6000(the square root of the sum of squares). I'm expect values of 12 bit ADC, it's right? please help me calculate output voltage or tell what i doing wrong.  

 

mmm...if this values divide by 4 and calculate voltage (0.0008 V - 1 bit), it's will be right)))) but why?)
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