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[Discuss-gnuradio] DBPSK and Carrier Suppressed or Not?

From: w w
Subject: [Discuss-gnuradio] DBPSK and Carrier Suppressed or Not?
Date: Wed, 18 Mar 2009 14:55:41 -0400

I'm putting together a DBPSK Tx and Rx and running into problems when the modulated signal hits the USRP.   When I receive the signal on the USRP there's  a very pronouced carrier....I've confirmed with a spectrum analyser that the signal on the FFT is the one that I'm recieving.   It seems to me that the sidebands should be close to the highest amplitute and the carrier should be suppressed.....is this correct?  Shouldn't the output of the DPSK modulator FFT plot look very similar to the FFT plot on the RX side of the usrp?   I'm modeling the block connections after the benchmark samples in the digital example section.   I put a channel filter inline with the usrp and the dpsk demod block just like the example.....do I need to put more filtering in place to suppress the carrier?  If so, do you have any examples?  
 If I take the output of the modulator and go directly to the demod thru the channel filter, data flows just fine(bypassing the usrp).  
I'm only using one usrp and taking the output of the TX via coax and going into the RX side...that shouldn't make a difference should it?
Any thoughts?

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