Re: [Discuss-gnuradio] DQPSK Transmitter and Receiver

[Tom Rondeau]

On Mon, Apr 26, 2010 at 1:30 AM, devin kelly <address@hidden> wrote:
> Hello Everyone,
> I've made a basic DBPSK transmitter and receiver.  I can receive ASCII
> strings fine and the spectrum looks exactly as it should.
> However, if I swap the DBPSK modulator/demodulator for the DQPSK
> modulator/demodulator, my system breaks.   I can no longer receive the same
> strings and the spectrum looks very strange.  It's much wider and triangular
> shaped.
> Same goes for the D8PSK system and the D16PSK system I recently was asking
> about.
> I believe marcin_w asked a similar question a few days ago and I haven't
> seen a reply yet (am I wrong?)  My question is, should I be doing something
> different?  Do I need to add in some extra block when I switch from DBPSK to
> DQPSK?  While searching old posts, I found some people talking about DQPSK
> not working correctly, but that was about a year ago.
> Any help would be greatly appreciated.
> Devin


Well, you haven't really told us what you are doing (code-wise), so
it's hard to tell...

Have you compared your code to the dbpsk/dbpsk2 and dqpsk/dqpsk2
blocks in the source code? That might give you a hint.

My best (blind) guess is that you are feeding the modulator the wrong
number of bits per sample. You have to send a dbspk a chunk size of 1
bit / byte while the dqpsk takes 2 bits/byte chunks.

Tom