Oqpsk Demod

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).

  1. Timing recovery (Gardener) 6. DDPLL 7. symbol demapping what are the stages to be modified?

Q3. suggest me some papers ?

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Eshwar varma
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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 for either qpsk or oqpsk to be any different as it is based on sample rate of

2*symbol rate and oqpsk just means restricted symbol transtions on IQ quadrants (tx transitions through origin avoided).

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

Kaz

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kaz

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