Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

- Community Forums
- :
- Forums
- :
- Hardware Development
- :
- AI Engine, DSP IP and Tools
- :
- FFT Simulation Results Problem: Incorrect Imaginar...

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page

yasirmahmoodqureshi

Observer

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

09-09-2009 10:24 AM

11,193 Views

Registered:
09-03-2009

I am usinf FFT IP core V6.0. When I took the FFT of following data points

1.1 2.2 3.3 4.4 1.1 2.2 3.3 4.4

in floating point format using the transform length of eight, i get the following Result

22 0 -4.4000 - 4.4000i 0 -4.4000 0 -4.4000 + 4.4000i 0

whereas MATLAB gives the following Result

22 0 -4.4000 + 4.4000i 0 -4.4000 0 -4.4000 - 4.4000i 0

The problem is that the signs of imaginary part is inverted. I have check it in both fixed point and floating formats, but problem remains the same, the signs of the imaginary parts are inverted, when we compare the results of MATLAB with that of FFT core.

Regards

Yaasir

1 Solution

Accepted Solutions

yasirmahmoodqureshi

Observer

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

09-28-2009 05:56 AM

12,658 Views

Registered:
09-03-2009

thanks everyone, got it right

actually there was some mistake with my initializations

thanks again

Regards

Yasir

9 Replies

ywu

Xilinx Employee

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

09-11-2009 01:20 PM

11,171 Views

Registered:
11-28-2007

Can you attach your model or testbench?

Cheers,

Jim

Cheers,

Jim

Jim

oliviert

Xilinx Employee

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

09-22-2009 02:39 AM

11,120 Views

Registered:
01-09-2008

Hi,

I think you've done an IFFT instead of an FFT.

Check the 'fwd_inv' input; it must be set to 0 for inverse transform and 1 forforward transform

Olivier

==================================

**Olivier Trémois**

XILINX SW Marketing AI Engine Tools

*Don't forget to reply, give kudos, and accept as solution.*

XILINX SW Marketing AI Engine Tools

vytautas

Explorer

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

09-28-2009 05:09 AM

11,082 Views

Registered:
10-01-2007

Hello.

FFT datasheet includes waveforms how initialization should be done. This is the first step. Second, you need to add 3 clocks delay between every input. How do you read output?

Best Regards,

Vytautas

Vytautas

yasirmahmoodqureshi

Observer

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

09-28-2009 05:56 AM

12,659 Views

Registered:
09-03-2009

thanks everyone, got it right

actually there was some mistake with my initializations

thanks again

Regards

Yasir

mofa77

Newbie

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

10-17-2011 06:20 PM

8,975 Views

Registered:
10-17-2011

i use the fft ipcore to compute fft and ifft

but both the result are fft data

i have set the fwd_inv both 0 and 1

the result is fft result

can you tell me some reason

thank you

technovlsi

Explorer

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

11-20-2011 10:52 AM

8,956 Views

Registered:
01-30-2011

vinodlk123

Observer

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

01-30-2012 02:59 AM

8,903 Views

Registered:
01-27-2012

hello sir,

when im simulating fft core 7.1, im getting unexpected results....

i am not able to understand where i'v done wrong ...

i'v added some simulation results...

if u can plz provide the correct code or help me to get correct output...

thank you...

bwiec

Xilinx Employee

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

02-12-2012 05:33 PM

8,879 Views

Registered:
08-02-2011

For completeness, refer to this thread:

www.xilinx.com

879229666@qq.com

Newbie

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

04-27-2015 11:26 PM

4,615 Views

Registered:
04-27-2015

I got the same problem

I wanna know what is the mistake with your initializations

thank you