PIEZOELECTRIC CERAMIC FILTER CIRCUIT AND PIEZOELECTRIC CERAMIC FILTER

摘要

MULTIPLE PIEZOELECTRIC CERAMIC FILTER ELEMENTS HAVE DIFFERENT CENTER FREQUENCIES FROM EACH OTHER AND ARE CASCADE CONNECTED TOGETHER. WHEN THE ABSOLUTE VALUE OF THE FREQUENCY DIFFERENCE DF0 BETWEEN THE CENTER FREQUENCIES IS I DF0 I AND THE BAND WIDTH WHEREIN THE AMPLITUDE LOSS IN 3DB OR LESS IS BW3, IT MAY BE REPRESENTED BY 0 < I DF0 I / BW3 < 0.8. THEREBY, A LOW INSERTION LOSS AND AN IMPROVEMENT IN THE GROUP DELAY CHARACTERISTICS CAN BE COMPATIBLE AT THE SAME TIME.(FIG. 1)