Re: [Discuss-gnuradio] (no subject)

[Martin Braun]

Hi,

the Costas-Loop makes sure the phase is corrected -- within possible ambiguity -- for the slicer. For QPSK, this means that the constellation points are mapped to the four points (on the corners of a square) as you would expect, but there are 4 possible rotations how to achieve this. Look up "phase synchronisation" for more details.

Have a look at the costas_loop_cc source code, in gr-digital.

M

On Thu, Feb 26, 2015 at 8:42 AM, Martin Braun <address@hidden> wrote:

Hi,

the Costas-Loop makes sure the phase is corrected -- within possible ambiguity -- for the slicer. For QPSK, this means that the constellation points are mapped to the four points (on the corners of a square) as you would expect, but there are 4 possible rotations how to achieve this. Look up "phase synchronisation" for more details.

Have a look at the costas_loop_cc source code, in gr-digital.

M

On Thu, Feb 26, 2015 at 8:28 AM, Vishwanatha H G <address@hidden> wrote:

sir, what is the importance of the COSTOS loop in the QPSK mod/demod? This block is working fine for 4-qpsk, 8-qpsk. But it does not works for QAM modulation techniques. Is it needs to modify the cc code? if it is, where I have to modify? plz mail me.

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