FPGA Intellectual Property
PCI Express*, Networking and Connectivity, Memory Interfaces, DSP IP, and Video IP
Announcements
Intel Support hours are Monday-Fridays, 8am-5pm PST, except Holidays. Thanks to our community members who provide support during our down time or before we get to your questions. We appreciate you!

Need Forum Guidance? Click here
Search our FPGA Knowledge Articles here.

frequency spectrum

Altera_Forum
Honored Contributor I
872 Views

Hallo, 

I worked with the Altera FFT Megafunction.At the output i have an imaginery and a real part. but the output (sourcereal and sourceim)in the simulator is time-dependent. How can i get the frequency-spectrum for the signal? and how can i analyse the output, if its right or wrong?
0 Kudos
2 Replies
Altera_Forum
Honored Contributor I
62 Views

The I/Q of fft is the frequency domain. 

so just plot the absolute value of output.  

 

IQ = I + jQ; 

power = 20* log10(abs(IQ)); %dB 

f = linspace(-.5*Fs,.5*Fs,fft_points) % if centered on dc else 

%f = linspace(0,1*Fs,fft_points); 

 

%Fs = fft clock frequency 

plot(f,power)
Altera_Forum
Honored Contributor I
62 Views

So If i have a 1024 fft i take the last 1024 values of the real and imaginery part and set them as an array in i and q? What means "centered on dc"?

Reply