Oqpsk Demod

[Eshwar varma]

Hi all ,
I implement qpsk demodulator on National instruments Fpga . Now
want to Demodulate Oqpsk signal . As the difference between qpsk an
oqpsk is only the delay of one bit period in q channel.

Q1. Can a qpsk demodulator with some changes demodulate oqpsk data ?

Q2. If it works , what changes i should make ?
flow of qpsk demodulater what i made..
1. frequency shifter (input from step 4)
2. Matched filter
3. AGC
4. coarse frequency offset estimator (Rife and broosty
algorithm).
5. Timing recovery (Gardener)
6. DDPLL
7. symbol demapping

what are the stages to be modified?

Q3. suggest me some papers ?


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[kaz]

Hi all ,
I implement qpsk demodulator on National instruments Fpga . Now i
want to Demodulate Oqpsk signal . As the difference between qpsk and
oqpsk is only the delay of one bit period in q channel.

Q1. Can a qpsk demodulator with some changes demodulate oqpsk data ?

Q2. If it works , what changes i should make ?
flow of qpsk demodulater what i made..
1. frequency shifter (input from step 4)
2. Matched filter
3. AGC
4. coarse frequency offset estimator (Rife and broostyn
algorithm).
5. Timing recovery (Gardener)
6. DDPLL
7. symbol demapping

what are the stages to be modified?

Q3. suggest me some papers ?


---------------------------------------
Posted through http://www.FPGARelated.com

For QPSK I will recover timing first then do carrier tracking.
Though I haven't done oqpsk but I don't think Gardner TED algorithm fo
either qpsk or oqpsk to be any different as it is based on sample rate o
2*symbol rate and oqpsk just means restricted symbol transtions on I
quadrants (tx transitions through origin avoided).

Once you recover timing then delay I relative to Q (opposite tx) and appl
carrier tracking as for qpsk.

Ka
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