| 摘要 |
PROBLEM TO BE SOLVED: To provide a ladder type filter capable of establishing a compatibility between a wide bandwidth and a high selectivity. SOLUTION: This device is provided with a first ladder type filer 4 having a center frequency of f1 and a 3dB passing band width of bw1, and a second ladder type filter 5 connected to the latter stage of the filter 4 and having a center frequency of f2 and a 3dB passing band width of bw2. The first and second ladder type filters are configured so as to satisfy formulas (1) and (2) 0<|f1-f2|<bw1/2. COPYRIGHT: (C)2004,JPO
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