Differential phase shift keying direct sequence spread spectrumsingle SAW based correlator receiver

摘要

This paper presents the design and measurement of a SAW device tonbe used in a correlator receiver for a differential phase shift keyingndirect sequence spread spectrum (DPSK/DSSS) system. The DPSK modulationnformat allows noncoherent data demodulation while the SAW devicencorrelator acts as the despreading operator. In a conventional DPSKnreceiver, the received signal is normally split into a lower and uppernpath. One of the paths contains a correlator, and the other pathncontains a one data bit delay element and another correlator. Thenoutputs of both paths are then fed to a noncoherent data demodulator.nThe device presented in this paper combines both the delay element andnthe two correlators in a single SAW device; therefore, a betterntemperature tracking mechanism, simplicity, as well as the eliminationnof the broadband SAW delay line are achieved. The SAW structure containsna broadband SAW transducer, and two serially coded pseudo noise (PN)nDPSK filters. The SAW based correlator was built on lithium tantalate.nThe center frequency was set to 150 MHz, with a 63 chip PN spreadingncode and a data rate of 300 Kbps. Experimental measurements of the SAWndevice autocorrelation results are presented