| 摘要 |
PROBLEM TO BE SOLVED: To provide a capacitance switching type filter having a little switching noise at switching of its resonant frequency. SOLUTION: The capacitance switching type filter uses a high speed frequency variable resonator 100 which quickly changes the resonant frequency according to the value of a capacitance connected to a resonator 70. A frequency data input unit 10, a data converter 20 and a decoder 30 cooperate to decode a designated frequency data to output a plurality of bit data. Buffers 41, 42,..., 4n, drivers 51, 52,..., 5n and switches 61, 62,..., 6n disposed corresponding to the outputted plurality of bit data cooperate to switch over to a specific capacitance, and connect it to the resonator while a timing setting means involved in the decoder 30 sets a timing for connecting the specific capacitance to the resonator in correspondence to each bit of the plurality of bit data so that the set timing is different every bit.
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