Large-Scale Monolithic SAW Convolver/Correlator on Silicon

Convolver and correlator devices are key components for spread-spectrum communication systems. These devices are employed most effectively as matched filter elements to improve the signal-to-noise ratio in spread-spectrum communication systems. The basic design, fabrication, and operaling parameters of a monolithic SAW convolver/ correlator on a silicon semiconductor substrate are described. Both passive convolvers, such as metal-zinc oxide semiconductor structures, and active convolvers, such as PI-FET will be included. By use of a zinc oxide (ZnO) piezoelectric thin film material, both acoustoeleclric SAW and semiconductor electronic device components may be fabricated on the same monolithic substrate. The development of such monolithic signal processors is expected to result in very large time-bandwidth devices monolithically integrated on a single substrate compatible with low cost batch fabrication techniques. The device characterization is mainly performed by using an HP-8505 automatic network analyzer system controlled by an HP-9845 computer. Using this ystem, the transduction properties of ZnO/Si structures were evaluated. State-ofthe-art SAW monolithic technology is discussed for devices as long as 1.6 in and acoustic delays of 10 p , which are successfully fabricated on 3-in Si wafers. These large-scale devices are operating at 340 MHz and demonstrate insertion loss better than 35 dB at a feedthrough level of 90 dB, resulting in a dynamic range of better than 55 dB.