# How to get constellation after demodulation

**URL:** <https://www.ruby-forum.com/t/how-to-get-constellation-after-demodulation/227643>\
**Category:** GNU Radio\
**Created:** [March 22, 2013, 10:54am UTC](https://www.ruby-forum.com/t/how-to-get-constellation-after-demodulation/227643 "2013-03-22T10:54:42Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Azza\_Ben\_Mosbah](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@Azza\_Ben\_Mosbah](https://www.ruby-forum.com/u/Azza_Ben_Mosbah)\
**Post date:** [March 22, 2013, 10:54am UTC](https://www.ruby-forum.com/t/how-to-get-constellation-after-demodulation/227643/1 "2013-03-22T10:54:42Z")

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Hello,

I receive data from USRP and demodulate them, then I can have the  
constellation. But, I can’t find a way to join blocks, so they can show  
a  
result. I need some help concerning the scheme I have to implement to  
get  
my constellation.  
Thanks in advance.

Best Regards,  
Azza.

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<div class="post-metadata">

**Author:** ![Azza\_Ben\_Mosbah](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@Azza\_Ben\_Mosbah](https://www.ruby-forum.com/u/Azza_Ben_Mosbah)\
**Post date:** [March 22, 2013, 5:38pm UTC](https://www.ruby-forum.com/t/how-to-get-constellation-after-demodulation/227643/2 "2013-03-22T17:38:39Z")

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I’m assuming you want to visualize the symbols after synchronization  
but before decision making. At the moment this is a pain, because the  
fine phase adjustment and the decision making are performed in the  
same block (constellation\_receiver). What you want is the fourth  
optional output of the constellation\_receiver block. Unfortunately  
this output is not available in any of the hierarchical demodulation  
blocks (because hierarchical blocks can’t have optional outputs yet).  
This means that if you want to do it in grc you won’t be able to use  
one of the straightforward demodulation blocks, rather you’ll have to  
put all the synchronization blocks in there independently.

When I want to do this, I do it in python, and hackishly connect  
directly to the ‘constellation\_receiver’ block that is inside the  
demodulation block.

i.e. tb.connect( (my\_demodulation\_block.receiver, 4),  
my\_visualization\_block)

Ben

On Fri, Mar 22, 2013 at 2:53 AM, Azza Ben Mosbah

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<div class="post-metadata">

**Author:** ![Azza\_Ben\_Mosbah](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@Azza\_Ben\_Mosbah](https://www.ruby-forum.com/u/Azza_Ben_Mosbah)\
**Post date:** [March 23, 2013, 11:51am UTC](https://www.ruby-forum.com/t/how-to-get-constellation-after-demodulation/227643/3 "2013-03-23T11:51:40Z")

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Take a look at gr-digital/python/generic\_mod\_demod.py for an example  
of the kind of signal-processing blocks that you’ll need.

On Fri, Mar 22, 2013 at 10:30 AM, Azza Ben Mosbah

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<div class="post-metadata">

**Author:** ![Azza\_Ben\_Mosbah](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@Azza\_Ben\_Mosbah](https://www.ruby-forum.com/u/Azza_Ben_Mosbah)\
**Post date:** [March 24, 2013, 10:51pm UTC](https://www.ruby-forum.com/t/how-to-get-constellation-after-demodulation/227643/4 "2013-03-24T22:51:58Z")

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dear Azza Ben

> Hello,
> 
> I am pandiyan from tirupur. how can create your link.

> what type of payment type or advance,

> Best Regards,

> pandiyan.