Re: [casper] Question regarding FFT

[Nimish Sane]

Hi all:

This issue has been resolved. There was a bug in my design in a downstream
block that creates packets.

Thanks a lot for you help,

Nimish

On Mon, Mar 18, 2013 at 8:04 AM, Nimish Sane  wrote:

> @Dan:
> We apply sync pulse only once. From the memo you have mentioned, this is
> an acceptable mode. We do not apply resync pulses, and can also confirm
> that there is just one sync pulse.
>
> @Dave:
> We have never seen such behavior in simulations. I am double checking
> though.
>
> @Ryan:
> Your observations are correct, but I do not understand what you mean by
> hooking up all outputs correctly. That seems to be fine. We are using the
> block's outputs correctly.
>
> FWIW, we run the design on two different FPGA clocks (150 MHz and 200 MHz)
> and see similar behavior.
>
> Thanks,
>
> Nimish
>
>
> On Fri, Mar 15, 2013 at 2:14 PM, Ryan Monroe wrote:
>
>>  Comments:
>>
>> -The FFT is probably fine.  If it was broken, it would probably be 100%
>> broken.  At least this looks like a spectrum
>> -It appears to me as if the broken section is exactly 1/8th of the
>> spectrum.  Did you hook up all of your outputs correctly?
>> -What's up with the spikes in the spectrum?  If they were interleave
>> artifacts, I'd expect to see the one which is at channel ~1800 closer to
>> 2048.  Maybe they are some other tone though
>>
>>
>>
>> On 03/15/2013 12:14 PM, Nimish Sane wrote:
>>
>> Hi all:
>>
>>  I am attaching a plot for Power of two inputs vs frequency channels. As
>> can be seen, we have this persistent problem where some channels at the end
>> just do not make any sense. We suspect that there is something going wrong
>> in the FFT block. Has anybody seen such behavior before or can think of
>> what may be going wrong?
>>
>>  Following are some specifications that may be useful:
>> Hardware: ROACH2 with KATADC.
>> ADC Clock: 800 MHz,
>> FPGA clock: 200 MHz
>> Toolflow: XSG 11.5 with Matlab 2009b with RHEL5.8
>> Libraries: SKA
>> FFT green block: fft_wideband_real
>> FFT size: 2^13 (4096 Output channels)
>>
>>  Thanks,
>>
>>  Nimish
>> --
>>  Nimish Sane
>>
>>  Center for Solar-Terrestrial Research
>> New Jersey Institute of Technology
>> University Heights
>>
>> Newark, NJ 07102-1982 USA
>>
>> Tel: (973) 642 4958
>>
>> Fax: (973) 596 3617
>>  nimish.s...@njit.edu
>>
>>
>>
>

Re: [casper] Question regarding FFT

[Ryan Monroe]

How about this:  Send me a copy of the model and I'll do a sanity check :-)

On 03/18/2013 08:04 AM, Nimish Sane wrote:

@Dan:
We apply sync pulse only once. From the memo you have mentioned, this 
is an acceptable mode. We do not apply resync pulses, and can also 
confirm that there is just one sync pulse.


@Dave:
We have never seen such behavior in simulations. I am double checking 
though.


@Ryan:
Your observations are correct, but I do not understand what you mean 
by hooking up all outputs correctly. That seems to be fine. We are 
using the block's outputs correctly.


FWIW, we run the design on two different FPGA clocks (150 MHz and 200 
MHz) and see similar behavior.


Thanks,

Nimish


On Fri, Mar 15, 2013 at 2:14 PM, Ryan Monroe > wrote:


Comments:

-The FFT is probably fine.  If it was broken, it would probably be
100% broken.  At least this looks like a spectrum
-It appears to me as if the broken section is exactly 1/8th of the
spectrum.  Did you hook up all of your outputs correctly?
-What's up with the spikes in the spectrum?  If they were
interleave artifacts, I'd expect to see the one which is at
channel ~1800 closer to 2048.  Maybe they are some other tone though



On 03/15/2013 12:14 PM, Nimish Sane wrote:

Hi all:

I am attaching a plot for Power of two inputs vs frequency
channels. As can be seen, we have this persistent problem where
some channels at the end just do not make any sense. We suspect
that there is something going wrong in the FFT block. Has anybody
seen such behavior before or can think of what may be going wrong?

Following are some specifications that may be useful:
Hardware: ROACH2 with KATADC.
ADC Clock: 800 MHz,
FPGA clock: 200 MHz
Toolflow: XSG 11.5 with Matlab 2009b with RHEL5.8
Libraries: SKA
FFT green block: fft_wideband_real
FFT size: 2^13 (4096 Output channels)

Thanks,

Nimish
-- 
Nimish Sane


Center for Solar-Terrestrial Research
New Jersey Institute of Technology
University Heights

Newark, NJ 07102-1982 USA

Tel: (973) 642 4958 

Fax: (973) 596 3617 

nimish.s...@njit.edu 

Re: [casper] Question regarding FFT

[Nimish Sane]

@Dan:
We apply sync pulse only once. From the memo you have mentioned, this is an
acceptable mode. We do not apply resync pulses, and can also confirm that
there is just one sync pulse.

@Dave:
We have never seen such behavior in simulations. I am double checking
though.

@Ryan:
Your observations are correct, but I do not understand what you mean by
hooking up all outputs correctly. That seems to be fine. We are using the
block's outputs correctly.

FWIW, we run the design on two different FPGA clocks (150 MHz and 200 MHz)
and see similar behavior.

Thanks,

Nimish


On Fri, Mar 15, 2013 at 2:14 PM, Ryan Monroe wrote:

>  Comments:
>
> -The FFT is probably fine.  If it was broken, it would probably be 100%
> broken.  At least this looks like a spectrum
> -It appears to me as if the broken section is exactly 1/8th of the
> spectrum.  Did you hook up all of your outputs correctly?
> -What's up with the spikes in the spectrum?  If they were interleave
> artifacts, I'd expect to see the one which is at channel ~1800 closer to
> 2048.  Maybe they are some other tone though
>
>
>
> On 03/15/2013 12:14 PM, Nimish Sane wrote:
>
> Hi all:
>
>  I am attaching a plot for Power of two inputs vs frequency channels. As
> can be seen, we have this persistent problem where some channels at the end
> just do not make any sense. We suspect that there is something going wrong
> in the FFT block. Has anybody seen such behavior before or can think of
> what may be going wrong?
>
>  Following are some specifications that may be useful:
> Hardware: ROACH2 with KATADC.
> ADC Clock: 800 MHz,
> FPGA clock: 200 MHz
> Toolflow: XSG 11.5 with Matlab 2009b with RHEL5.8
> Libraries: SKA
> FFT green block: fft_wideband_real
> FFT size: 2^13 (4096 Output channels)
>
>  Thanks,
>
>  Nimish
> --
>  Nimish Sane
>
>  Center for Solar-Terrestrial Research
> New Jersey Institute of Technology
> University Heights
>
> Newark, NJ 07102-1982 USA
>
> Tel: (973) 642 4958
>
> Fax: (973) 596 3617
>  nimish.s...@njit.edu
>
>
>

Re: [casper] Question regarding FFT

[Ryan Monroe]

Comments:

-The FFT is probably fine.  If it was broken, it would probably be 100% 
broken.  At least this looks like a spectrum
-It appears to me as if the broken section is exactly 1/8th of the 
spectrum.  Did you hook up all of your outputs correctly?
-What's up with the spikes in the spectrum?  If they were interleave 
artifacts, I'd expect to see the one which is at channel ~1800 closer to 
2048.  Maybe they are some other tone though



On 03/15/2013 12:14 PM, Nimish Sane wrote:

Hi all:

I am attaching a plot for Power of two inputs vs frequency channels. 
As can be seen, we have this persistent problem where some channels at 
the end just do not make any sense. We suspect that there is something 
going wrong in the FFT block. Has anybody seen such behavior before or 
can think of what may be going wrong?


Following are some specifications that may be useful:
Hardware: ROACH2 with KATADC.
ADC Clock: 800 MHz,
FPGA clock: 200 MHz
Toolflow: XSG 11.5 with Matlab 2009b with RHEL5.8
Libraries: SKA
FFT green block: fft_wideband_real
FFT size: 2^13 (4096 Output channels)

Thanks,

Nimish
--
Nimish Sane

Center for Solar-Terrestrial Research
New Jersey Institute of Technology
University Heights

Newark, NJ 07102-1982 USA

Tel: (973) 642 4958

Fax: (973) 596 3617

nimish.s...@njit.edu 

Re: [casper] Question regarding FFT

[David MacMahon]

Hi, Nimish,

Does this occur in simulation as well?

Dave

On Mar 15, 2013, at 12:14 PM, Nimish Sane wrote:

> Hi all:
> 
> I am attaching a plot for Power of two inputs vs frequency channels. As can 
> be seen, we have this persistent problem where some channels at the end just 
> do not make any sense. We suspect that there is something going wrong in the 
> FFT block. Has anybody seen such behavior before or can think of what may be 
> going wrong?
> 
> Following are some specifications that may be useful:
> Hardware: ROACH2 with KATADC.
> ADC Clock: 800 MHz, 
> FPGA clock: 200 MHz
> Toolflow: XSG 11.5 with Matlab 2009b with RHEL5.8
> Libraries: SKA
> FFT green block: fft_wideband_real
> FFT size: 2^13 (4096 Output channels)
> 
> Thanks,
> 
> Nimish
> -- 
> Nimish Sane
> 
> Center for Solar-Terrestrial Research
> New Jersey Institute of Technology
> University Heights
> Newark, NJ 07102-1982 USA
> Tel: (973) 642 4958
> Fax: (973) 596 3617
> nimish.s...@njit.edu
> 

Re: [casper] Question regarding FFT

[Dan Werthimer]

hi nimish,

this could be a sync pulse problem???

how often do you inject a sync  pulse?
did you check the re-order block in your fft to figure out the
minimum period sync pulse that's allowed for that particular FFT?
the casper memo on sync pulse generation has info on this.

dan


On Fri, Mar 15, 2013 at 12:14 PM, Nimish Sane  wrote:

> Hi all:
>
> I am attaching a plot for Power of two inputs vs frequency channels. As
> can be seen, we have this persistent problem where some channels at the end
> just do not make any sense. We suspect that there is something going wrong
> in the FFT block. Has anybody seen such behavior before or can think of
> what may be going wrong?
>
> Following are some specifications that may be useful:
> Hardware: ROACH2 with KATADC.
> ADC Clock: 800 MHz,
> FPGA clock: 200 MHz
> Toolflow: XSG 11.5 with Matlab 2009b with RHEL5.8
> Libraries: SKA
> FFT green block: fft_wideband_real
> FFT size: 2^13 (4096 Output channels)
>
> Thanks,
>
> Nimish
> --
> Nimish Sane
>
> Center for Solar-Terrestrial Research
> New Jersey Institute of Technology
> University Heights
>
> Newark, NJ 07102-1982 USA
>
> Tel: (973) 642 4958
>
> Fax: (973) 596 3617
> nimish.s...@njit.edu
>

Re: [casper] Question regarding FFT

[Nimish Sane]

Hi Glenn,

Yes, that is the plan, but we have some issues using snap blocks
independent of this. Hence, wanted to know if someone has seen such
behavior before as we continue to probe as you have suggested.

Thanks,

Nimish

On Fri, Mar 15, 2013 at 3:22 PM, G Jones  wrote:

> Hi Nimish,
> My suggestion is to add snapshot blocks triggered on the sync pulse
> directly after the FFT and after the blocks that follow it. You can
> then look at the signal at each stage and see at which stage that
> strange behavior is occurring. You can also add a "test vector
> generator" that puts in a known sequence and see if what comes out
> matches what you expect.
>
> Glenn
>
> On Fri, Mar 15, 2013 at 3:14 PM, Nimish Sane  wrote:
> > Hi all:
> >
> > I am attaching a plot for Power of two inputs vs frequency channels. As
> can
> > be seen, we have this persistent problem where some channels at the end
> just
> > do not make any sense. We suspect that there is something going wrong in
> the
> > FFT block. Has anybody seen such behavior before or can think of what
> may be
> > going wrong?
> >
> > Following are some specifications that may be useful:
> > Hardware: ROACH2 with KATADC.
> > ADC Clock: 800 MHz,
> > FPGA clock: 200 MHz
> > Toolflow: XSG 11.5 with Matlab 2009b with RHEL5.8
> > Libraries: SKA
> > FFT green block: fft_wideband_real
> > FFT size: 2^13 (4096 Output channels)
> >
> > Thanks,
> >
> > Nimish
> > --
> > Nimish Sane
> >
> > Center for Solar-Terrestrial Research
> > New Jersey Institute of Technology
> > University Heights
> >
> > Newark, NJ 07102-1982 USA
> >
> > Tel: (973) 642 4958
> >
> > Fax: (973) 596 3617
> >
> > nimish.s...@njit.edu
>



-- 
Nimish Sane

Center for Solar-Terrestrial Research
New Jersey Institute of Technology
University Heights

Newark, NJ 07102-1982 USA

Tel: (973) 642 4958

Fax: (973) 596 3617
nimish.s...@njit.edu

Re: [casper] Question regarding FFT

[G Jones]

Hi Nimish,
My suggestion is to add snapshot blocks triggered on the sync pulse
directly after the FFT and after the blocks that follow it. You can
then look at the signal at each stage and see at which stage that
strange behavior is occurring. You can also add a "test vector
generator" that puts in a known sequence and see if what comes out
matches what you expect.

Glenn

On Fri, Mar 15, 2013 at 3:14 PM, Nimish Sane  wrote:
> Hi all:
>
> I am attaching a plot for Power of two inputs vs frequency channels. As can
> be seen, we have this persistent problem where some channels at the end just
> do not make any sense. We suspect that there is something going wrong in the
> FFT block. Has anybody seen such behavior before or can think of what may be
> going wrong?
>
> Following are some specifications that may be useful:
> Hardware: ROACH2 with KATADC.
> ADC Clock: 800 MHz,
> FPGA clock: 200 MHz
> Toolflow: XSG 11.5 with Matlab 2009b with RHEL5.8
> Libraries: SKA
> FFT green block: fft_wideband_real
> FFT size: 2^13 (4096 Output channels)
>
> Thanks,
>
> Nimish
> --
> Nimish Sane
>
> Center for Solar-Terrestrial Research
> New Jersey Institute of Technology
> University Heights
>
> Newark, NJ 07102-1982 USA
>
> Tel: (973) 642 4958
>
> Fax: (973) 596 3617
>
> nimish.s...@njit.edu