Re: [Discuss-gnuradio] Phase shift correction in Bpsk!!

[sreeraj r]

Hi Sreenath,

In the case of BPSK the costas loop is properly locked when the quadrature component of the signal is close to zero ( ie lpf[data * cos (2*pi*f_c*t)* sin(2*pi*f_c*t)] = 0). I am not sure how you will implement this in GRC as you have to call 'advance_loop' in the plls (inherited from gri_control_loop) to correct the error in phase and frequency. You can directly use MPSK receiver block in grc which incorporates all of this. Please go through MPSK receiver block's implementation for more details.

 

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Regards
Sreeraj Rajendran
http://home.iitb.ac.in/~rsreeraj

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From: sreenath kambala <address@hidden>
To: address@hidden
Sent: Thursday, 10 May 2012 1:25 PM
Subject: [Discuss-gnuradio] Phase shift correction in Bpsk!!

Hello All,

I have designed BPSK transmitter and receiver in grc.
But Costas loop can able to correct frequency offset, not phase offset.

Here, I attached both transmitter and receiver files.



Transmitter :

1). File sink contains Bpsk symbols {-1,1}  (repeat = yes)
2). Samples per symbol : 20
3). RRC pulse lasts for 2 symbol periods

Receiver  :

1). Matched filtering
2). Costas loop & Timing recovery
3). saving samples in File sink

and final Symbols are recovered from the samples in matlab.


I'm using uhd + gnuradio + USRP1 + RFX 2400 daughter boards.

Can somebody suggest me how to deal with Phase offset ?
(especially when the gain of Rx is low phase shifts are happening
frequently)

One more Question : Is Rms value sufficient in SNR Calculation ?






Thanks & Regards
http://old.nabble.com/file/p33763663/Transmitter.grc Transmitter.grc
http://old.nabble.com/file/p33763663/Receiver.grc Receiver.grc
http://old.nabble.com/file/p33763663/Rcvd_data.png Rcvd_data.png
http://old.nabble.com/file/p33763663/Bpsk_data.dat Bpsk_data.dat
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