| 摘要 |
PURPOSE:To increase the tolerance of dispersion of a duty factor of a grating reflector formed with grooves and to improve the yield, by setting the duty factor in 20%-30% range, forming the grating reflectors and increasing the tolerance in the dispersion of the duty factor. CONSTITUTION:In a surface acoustic wave comb type filter, an LiTaO3 substrate 1 is used as a piezoelectric substrate and input and output electrodes 2, 3 are formed from an A thin film on the said substrate by using a photoetching technology. The grating reflector 4 is formed by forming grooves on the substrate with an ion etching method by taking a photoresist as a mask member. In the surface acoustic wave filter, the filter having two frequency bands of 150-162MHz and 230-276MHz are formed on one substrate. Low-frequency side reflector 4-1 and high frequency side reflector 4-2 are formed by suppressing the comb 149, 228, and 229 MHz for >=12dB. |
