O-QPSK Demodulation
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From: langwadt on 19 Dec 2005 14:54 A.D. wrote: > Hi all, > I have to demodulate an O-QPSK signal. As usual in this kind of > modulation, symbols (chips) have an half-sine shape, and the Q channel > has a 90 degree (half simbol) offset with respect to the I channel. > The first thing I have to do (and perhaps the most difficult) is > removing the frequency offset from the received I and Q signals. I > cannot use a simple Costas loop since it doesn't work with O-QPSK > signals! > Are there dedicated loops for O-QPSK signals? Or it exists some simple > and effective way to demodultate such a signal? > > Thank you in advance for any advice! > Antonio how big do you expect the offset to be?, I believe differential chip detection can handle some offset but it will cost you a little over 3dB in sensitivity -Lasse
From: A.D. on 20 Dec 2005 04:11
<langwadt(a)ieee.org> ha scritto nel messaggio news:1135022040.250858.304390(a)g43g2000cwa.googlegroups.com... > > how big do you expect the offset to be?, I believe differential chip > detection can handle some offset but it will cost you a little over > 3dB in sensitivity I'm trying to demodulate ZigBee signals, so I have a chip rate of 1Mcps on I and Q channel and a maximum extimated offset of about 500KHz (wrost case). But data are not differentially encoded, so I think that is not possible to use a differential detection... Regards, Antonio |