Rrc_taps filter coefficents problem in polyphase clock sync

GNU Radio
1

Hi,
I m trying to realise QPSK trasmission shown in the tutorial of Tom
Rondeau
available in this link
http://www.trondeau.com/storage/grcon12/rondeau-mpsk_tutorial.pdf
I meet problem when i try to add the vector of taps in the polyphase
clock
sync. I followed the example by creating a variable named rrc_taps and
value of firdes.root_raised_cosine to obtain directly the coefficients
but
i still have error that the polyphase clock sync taps should by a float
vertor. I think that the problem is the definition of the function
firdes.root_raised_cosine which provide filter taps. Have you any
propositions for me?
Thanks for your help
Zakaria

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2

On 02/18/2014 11:29 PM, zielalaoui wrote:

propositions for me?
Thanks for your help
Zakaria

You’ll have to post some code and the exact error messages in order for
us to help.

M

3

Hi Martin,
Thanks for your answer, actionnally I don’t have a code yet because I am
trying to run simulation from the flowgraph directly. The problem is in
the
polyphase clock sync, in this block i should define several parameters
even
the filter taps. Normally, I should add coefficients values or provide a
function able to calculate them. in the tutorial
http://www.trondeau.com/storage/grcon12/rondeau-mpsk_tutorial.pdf , Tom
used
this command firdes.root_raised… which i think that’s
firdes.root_raised_cosine and maybe I missed something, therefore it
still
red so the block cannot be functional. The question is how can i obtain
the
filter taps on my polyphase clock sync by using
firdes.root_raised_cosine?
Any proposition is appreciate
Zakaria

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4

Hi,
I am not sure I understand your problem exactly. Are you defining the
variable as

firdes.root_raised_cosine(nfilts, nfilts, 1.0/float(sps), 0.35,
11spsnfilts)

??
There is a zip file containing all these examples. I assume you already
have them.
If not, you can find them in the link below.

http://www.trondeau.com/storage/tutorial/mpsk_scripts.tar.gz

5

Hi Manu,
This is exactly what I m looking for, you solved my problem thank you so
much.
Best Regards
Zakaria

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