Re: [Discuss-gnuradio] QPSK Modulation and Demodulation Question

Hey,

Uhm looks like I didn't look at the whole flow graph. 

Now I realize the PSK Demod block.

Indeed, it doesn't make sense to use this one in this configuration as it basically contains all the other RX blocks you have in your flow graph (it is an hierarchical block).

So yes, it's best to go ahead and use the block you previously implemented which is just performing the de-mapping (if I remember correctly).

Let me know in case you have any further questions.

Cheers,

Julian

Julian Arnold, M.Sc

On 10. Aug 2018, at 21:47, 梁帆 <luckyliangfan@gmail.com> wrote:

Hi,

Thanks for your reply!

I changed my equalizer sps to 2, but the output signal still not same as the input signal. I am wondering the PSK demod problem. So I go back to learn about how to build a my qpsk block.

Best regards,

Fan

On Thu, Aug 9, 2018 at 1:29 PM, Julian Arnold <julian@elitecoding.org> wrote:

Hey,

I only have my phone available right now so I can't really check but from what I can see, you got a little problem with your decimation factors.

Your initial sps (samples per symbol) is 4 and you reduce it to 2 sps in the clock recovery process (output sps = 2). However, in you equalizer you set sps again to 4 whereas it should be 2.

Hope this helps.
Cheers,
Julian

Julian Arnold, M.Sc

> On 7. Aug 2018, at 23:08, 梁帆 <luckyliangfan@gmail.com> wrote:
>
> Hello All,
>
> I am using the Gnuradio for two weeks. I am doing the Gnuradio tutorial 7 on stage 5. There I used PSK demod to demodulate the signal. I do not know why the output signals are different than input signal. This is the screenshot of my blocks. Is that because my vector source influence the result or should I use the My_Qpsk_demod block on tutorial 4.
>
> Thanks
> Fan

> <Screenshot from 2018-08-07 15-06-50.png>
> <Screenshot from 2018-08-07 15-07-01.png>
> <Screenshot from 2018-08-07 15-07-07.png>
> <Screenshot from 2018-08-07 15-07-17.png>
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