Differential phase shift keying direct sequence spread spectrum single SAW based correlator receiver

This paper presents a SAW based correlator receiver for a Differential Phase Shift Keying Direct Sequence Spread Spectrum (DPSK/DSSS) receiver. The DPSK modulation format allows the noncoherent data demodulation while the SAW device correlator acts as the despreading operator. In a conventional DPSK receiver, the received signal is normally split into a lower and upper path. One of the paths contains a correlator, while the other path contains a one data bit delay element and another correlator. The outputs of both paths are then fed to a noncoherent data demodulator. This paper combines both the delay element and the two correlators in a single SAW device, and therefore a better temperature tracking mechanism, simplicity, as well as the elimination of the broadband SAW delay line are achieved. The SAW structure contains a broadband SAW transducer, and two serially coded Pseudo Noise (PN) DPSK filters. The SAW based correlator was built on lithium tantalate. The center frequency was set to 150 MHz, with a 63 chip PN spreading code and a data rate of 300 kbps. Experimental measurements in both the time and frequency domains were performed and were compared to computer simulation predictions