| 摘要 |
PCT No. PCT/JP93/00922 Sec. 371 Date Jan. 9, 1995 Sec. 102(e) Date Jan. 9, 1995 PCT Filed Jul. 5, 1993 PCT Pub. No. WO94/01931 PCT Pub. Date Jan. 20, 1994Multiple piezoelectric ceramic filter elements have different center frequencies from each other and are cascade connected together. The piezoelectric ceramic filter elements satisfy the condition 0<|dF0|/BW3<0.8; where |dF0| is the absolute value of the frequency difference dF0 between the center frequencies, and BW3 is the band width of each piezoelectric ceramic filter element in which the amplitude loss is 3 dB or less. A low insertion loss and an improvement in the group delay characteristics are compatible at the same time.
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