Questions about fft megafucntion

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Hello dears,

I'll use altera's fft megafunction, and there are several question need you help:

1. The input data coming from ADC's sampling values, the sample speed is 25Mhz. However, my system clock speed is 100MHz. How to set my fft's clock speed? 25MHz or 100Mhz? Could different clock speed for fft will affect the transform result?

2. What data should be fed into sink_imag port of FFT core? i found someone connected this port to GND directly, is it right? why?

thanks in advance!

Jerry

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you do fft on your signal and not on system clock so fft has to be enabled 1:4 of system clock starting with first sample

if you don't have imaginary part of input then set it to zero

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you do fft on your signal and not on system clock so fft has to be enabled 1:4 of system clock starting with first sample

if you don't have imaginary part of input then set it to zero

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Hi kaz,

Thanks for you reply!

One more question, how to verify the result after simulation?

Hi guys,

I met issues when i use FFT iP core, one of these issues happened when i generated fft core by using Megawizard:

http://www.alteraforum.com/forum/attachment.php?attachmentid=10140&stc=1

This issue appear when i selected to generate simulation model and EDA Netlist, otherwise i can generate successfully.

Another question is that this IP seems can't support new devices,eg CIV and CV, however CII is ok:

http://www.alteraforum.com/forum/attachment.php?attachmentid=10141&stc=1

Can anybody encounter these two issues when you use FFT IP core?

1. In Quartus II 14.1, there isn't MegaWizard tool any more. However, when i double click IP file in project, i can open the Wizard for FFT core. When i create new FFT design, the tool launch from IP catalog is Qsys style:http://www.alteraforum.com/forum/attachment.php?attachmentid=10153&stc=1

I don't family with this style, and i can't generate the simulation model like old version from this tool.

2. The proposed project simulation result:http://www.alteraforum.com/forum/attachment.php?attachmentid=10154&stc=1

There are no output for Scalings, system output and complexer multipier.http://www.alteraforum.com/forum/attachment.php?attachmentid=10155&stc=1

Hi Guys,

I have resolved this simulation issue mention above post. I met this issue because i didn't load library-altera_lnsim correctly when i did simulation.

http://www.alteraforum.com/forum/attachment.php?attachmentid=10310&stc=1

Thanks