Optimization of offset for OQPSK with time limited pulses

The optimum offset for offset quaternary phase shift keying (OQPSK) in the presence of carrier phase error is determined for some time limited pulse shapes. It is shown that, for certain pulse shapes, T/2 is optimum in a minimum probability of error sense. In the case of bipolar pulse shaping it is seen that T/2 is not the optimum. It is shown that OQPSK with shaped pulses may be much more robust with respect to carrier phase errors than OQPSK with non-return-to-zero pulses.<
>