Direct sequence spread spectrum differential phase shift keying SAWcorrelator on GaAs

摘要

This paper presents the design, fabrication, and experimentalnresults for a differential phase shift keying (DPSK) single SAW-basedncorrelator on GaAs for direct sequence spread spectrum applications. ThenDPSK modulation format allows for noncoherent data demodulation; the SAWndevice correlator acts as the despreader. Unlike the conventionalntechnique of using two parallel correlators and a one data bit delaynelement, this new system uses two inline correlators. When implementednon SAW devices, this in-line structure has the advantage of an inherentnone data bit delay, lower insertion loss, and less signal distortionnthan the parallel structure. The DPSK correlator is fabricated on an{100} cut GaAs substrate with SAW propagation in the ⟨110⟩ndirection, Using this cut, which is widely used in electronics, Rayleighnwaves are generated with a piezoelectric coupling coefficient of thensame order as ST-cut quartz. The piezoelectric semiconductor GaAs is ofngreat interest because it is the only substrate that can be used tonintegrate SAW devices directly with electronics on the same chip,nresulting in smaller packaging, reduction of packaging parasitics, lowerncost, and greater system integration. This paper presents experimentalnresults for SAW in-line correlator structures on GaAs along with theirndespreading system performances. Experimental measurements in both thentime and frequency domains were performed and were found to be in goodnagreement with theoretical predictions