SURFACE ACOUSTIC WAVE MATCHED FILTER

摘要

PROBLEM TO BE SOLVED: To prevent the decline of the correlation peak of output demodulation signals, to improve the S/N of output signals and to reduce the power consumption of a system as well by providing the tap interval of an output side electrode with a value designed based on the group velocity of surface acoustic waves. SOLUTION: On the surface of a piezoelectric substrate 11, an input side electrode 12 for receiving spread spectrum signals from an input terminal 14 and converting them into the surface acoustic waves and the output side electrode 13 for generating the output demodulation signals for indicating correlation with the spread spectrum signals to an output terminal 15 are provided. The substrate 11 is formed by depositing a thin film composed of aluminum nitride on a sapphire base body. The tap interval L of the output side electrode 13 is designed based on the group velocity Vg of the surface acoustic waves. At the time of defining a chip rate as f1, it is preferable to turn the interval L between taps to Vg/f1×0.97<=L<=Vg/f1×1.02.