carrier recovery in software using PLL
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From: Vladimir Vassilevsky on 14 Jan 2008 09:10 "mizer03" <belet_mes(a)hotmail.com> wrote in message news:7ZednZAi0aHpZBfanZ2dnUVZ_qSonZ2d(a)giganews.com... > > > >> I want to implement QPSK modulation in software. But i know that QPSK > >> signals can only be detected coherently. i.e knowledge of the carrier > >> frequency and phase is mandatory for correct detection. > > > >If you can tolerate the loss of 2...3dB, the QPSK can be demodulated > >incoherently. > > > >> How is possible to > >> recover the carrier synchronization in software? Is it possible to > >> implement PLL for carrier recovery and synchronization using software? > > > >Everything is possible. > > > >Thanks for your reply, But my question was: > 1. How is possible to recover the carrier using software? Either a 4th power loop or decision directed. If the data is sufficiently random, Costas loop would do, too. > 2. Is there a code in c++/C# to implement PLL for carrier recovery, > especially for QPSK detection? It certainly is. But not for free. Vladimir Vassilevsky DSP and Mixed Signal Consultant www.abvolt.com
From: glen herrmannsfeldt on 16 Jan 2008 23:40 Someone wrote: >I want to implement QPSK modulation in software. But i know that QPSK >signals can only be detected coherently. i.e knowledge of the carrier >frequency and phase is mandatory for correct detection. The method I have seen described squares the signal which generates peaks at the transitions. One can then run a PLL on the squared signal and lock onto the frequency and phase. A scrambler is usually used to generate a high level of phase transitions. Decoding phase difference instead of absolute phase also makes it easier. -- glen
From: tony kirke on 17 Jan 2008 13:56
On Jan 14, 6:10 am, "Vladimir Vassilevsky" <antispam_bo...(a)hotmail.com> wrote: > "mizer03" <belet_...(a)hotmail.com> wrote in message > > news:7ZednZAi0aHpZBfanZ2dnUVZ_qSonZ2d(a)giganews.com... > > > > > > > >> I want to implement QPSK modulation in software. But i know that QPSK > > >> signals can only be detected coherently. i.e knowledge of the carrier > > >> frequency and phase is mandatory for correct detection. > > > >If you can tolerate the loss of 2...3dB, the QPSK can be demodulated > > >incoherently. > > > >> How is possible to > > >> recover the carrier synchronization in software? Is it possible to > > >> implement PLL for carrier recovery and synchronization using software? > > > >Everything is possible. > > > >Thanks for your reply, But my question was: > > 1. How is possible to recover the carrier using software? > > Either a 4th power loop or decision directed. If the data is sufficiently > random, Costas loop would do, too. > > > 2. Is there a code in c++/C# to implement PLL for carrier recovery, > > especially for QPSK detection? > > It certainly is. But not for free. > > Vladimir Vassilevsky > DSP and Mixed Signal Consultantwww.abvolt.com Did you look at SPUC on sourceforge? |