Re: [Discuss-gnuradio] BPSK Demod

[Julian Arnold]

Hey Kacie,

I don't have time to try you example right now but one thing to watch
out for is unpacked to packed conversion.
I think the Constellation Modulator expects packed bytes at the input.
However, you are sending unpacked bytes from you vector source.
Look at [1] for a block that can help to convert from unpacked to packed.

Hope that helps.

[1]
http://gnuradio.org/doc/doxygen/classgr_1_1blocks_1_1unpacked__to__packed__bb.html

Cheers,
Julian

On 04/13/2017 12:40 AM, Kacie O'Neil wrote:
>
> I'm having trouble with a BPSK Modulation/Demodulation flowgraph I
> built (picture attached). I am using a Vector Source and a
> Constellation Modulator block with a BPSK default constellation
> object. I'm using a vector source because I want to verify that I can
> modulate and correctly demodulate/decode data, not just a random
> source. I'm trying to start with something simple.
>
> For the demod, I'm following the PSK Demodulation Tutorial from the
> gnuradio wiki
> (https://wiki.gnuradio.org/index.php/Guided_Tutorial_PSK_Demodulation)
> so I have a Polyphase Clock Sync, CMA Equalizer and Costas Loop
> followed by a Constellation Decode block (using the same bpsk object
> as the constellation modulator) which I send into a file sink.
>
> Part of my problem is that what I end up with in my File Sink is not
> what I'm expecting, so I have no way to know if the data I'm
> attempting to send is being modulated and demodulated correctly. I'm
> wondering if maybe I'm not sending data in the right format to the
> file sink (or any other block really), or if the fact that I didn't
> include a channel model or used a UHD device is creating a different
> result. If anyone has any suggestions or comments, they would be
> greatly appreciated!
>
> Thanks!
>
>
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-- 
Julian Arnold, M.Sc.

Institute for Networked Systems
RWTH Aachen University

Kackertstrasse 9
52072 Aachen
Germany