Differential phase shift keying SAW correlator on GaAs

The present Differential Phase Shift Keying (DPSK) modulation format allows noncoherent data demodulation while the SAW device correlator acts as a despreading operator. Compared to the conventional technique of using two correlators and a one data bit delay element, the combination of two in-line correlators has the advantage of an inherent one data bit delay, less insertion loss and minor signal distortion due to usage of a single SAW device. The DPSK correlator is fabricated on a (100) cut GaAs substrate with SAW propagation in the ⟨110⟩ direction. Using this cut, Rayleigh waves have been generated with a piezoelectric coupling coefficient of the same order as ST-quartz. The piezoelectric semiconductor GaAs is very interesting in terms of monolithic integration of very fast electronic devices and surface acoustic wave modules on the same substrate. Results of first experiments towards integration of the DPSK correlator receiver as part of a signal processor, in both the time and frequency domains, are presented and compared to computer predictions