SURFACE ACOUSTIC WAVE FILTER

摘要

PURPOSE:To improve the degree of freedom of electrode design and mounting circuit design by keeping parameters such as a resultant susceptance between the irradiation susceptance of the entire intermediate electrode group and the susceptance of the circuit side and an irradiation conductance of the entire intermediate electrode to a prescribed relation. CONSTITUTION:An LiNbO3 single crystal of 128 deg. rotation Y axis cut is used as a piezoelectric substrate and the propagating direction of a surface acoustic wave is taken as the X axis. The center frequency is 402.8MHz, the input reed screen electrode group 15 is 15 pairs of normal electrodes, and the output reed screen electrodes 16 are 60 pairs weighted electrodes. A matching inductance for output side is constant as 5nH. A load conductance 18 is connected in parallel with the inductance 17. A direct wave preventing electrode 20 is provided between the input and output reed screen electrodes in order to eliminate an electromagnetic wave due to electromagnetic coupling. A sound absorbing material 19 is coated on the end face of the substrate to suppress a reflected wave from the end face.