Effects of intersymbol interference on MSK-type SAW modulators

Full and partial response signaling quadrature binary modulation techniques are being the modulation schemes of choice in direct sequence spread spectrum systems, cellular, PCs and satellite communications. SAW filters have been used as modulators in both full response and partial response signaling including QPSK, MSK, SFSK, and cosine series pulse shape modulation formats. Envelope uniformity, spectral confinement, autocorrelation function, and an intersymbol interference are important performance parameters for any given modulation format. SAW modulators implementing two cosine series pulse shapes with a center frequency of 70 MHz and a bit rate of 8 MHz were built and both time and frequency domain measurements were performed. The autocorrelation function contains processing gain information for the various pulse shape modulators. Computer simulation on the uniformity of the transmitted modulated signal is performed. A comparison of the computer simulation results and experimental measurements will be presented. The comparison includes power spectral densities, autocorrelation functions, and time domain pulse shapes.