DPSK mod/demod block work well?

GNU Radio
1

I just made very simple dpsk mod/demod testing flow graph

you can see flow graph in following link:
https://picasaweb.google.com/lh/photo/76z3sTbLs9Srz1N-wJhNzw?feat=directlink

When I run it, I found strange outcome from it:
https://picasaweb.google.com/lh/photo/U0_S_71HzkL9t9RbeEBP2Q?feat=directlink

I didn’t change any parameters in mod/demod blocks.

How can I get a good signal after mod/demodulation?

2

On Thu, Mar 31, 2011 at 9:07 AM, Songsong G.
[email protected]wrote:

How can I get a good signal after mod/demodulation?

Well, the secret is that you really are getting good signals out of the
demodulator, it’s just not in the form that you think it should be.

The modulator takes in packed bits; that is, characters between 0 and
255.
You are only giving it 0’s and 1’s. The output of the demodulator is
providing you with unpacked bits, so each character represents a single
bit.
You will want to put an unpacked_to_packed block after the demod to put
them
in the same format as your input.

The reason why you are getting the zeros at the output is because a ‘1’
in
the input is really a ‘00000001’ and a ‘0’ is really ‘00000000’, which
is
what you see in your sink.

Tom

3

---------- Forwarded message ----------
From: Songsong G. [email protected]
Date: 2011/4/1
Subject: Re: [Discuss-gnuradio] DPSK mod/demod block work well?
To: Tom R. [email protected]

I have an additional problem
Here is a flow graph:
https://picasaweb.google.com/lh/photo/vwkkNZP_WFKGJQSP48MoOQ?feat=directlink
It did not change much.

And here are scope plots
https://picasaweb.google.com/lh/photo/Zx49Z_3au8uj9H7xxUmJHQ?feat=directlink

Everything is fine, but at the beginning,
There are "“3"” points which are not in the source.

Does DPSK demod block add some extra information?

Currently, I solved this problem just adding Skip 3 Head block.
However, if I change DPSK to DQPSK? or D8PSK?
I think that this value "“3"” might be also changed.

This extra 3 bits are inevitable?

2011/3/31 Songsong G. [email protected]

On Thu, Mar 31, 2011 at 9:07 AM, Songsong G. [email protected]wrote:

in the same format as your input.

The reason why you are getting the zeros at the output is because a ‘1’ in
the input is really a ‘00000001’ and a ‘0’ is really ‘00000000’, which is
what you see in your sink.

Tom

–
Seokseong Jeon (aka Songsong G.)