FILTER

摘要

PROBLEM TO BE SOLVED: To provide a filter using SCFs (switched capacitor filters) that reduces noise produced from the SCFs. SOLUTION: A BPF 10 includes: the SCF 11 with a cut-off frequency fc11 for eliminating a high frequency component from an object signal finto provide an output of an output signal S11; the SCF 12 with a cut-off frequency fc12 (>fc1) for eliminating the high frequency component from the object signal finto provide an output of an output signal S12; and a subtraction section 13 for subtracting the output signals S11, S12with each other and outputting a signal of a band with frequencies of about the fc1 to fc2 in the object signal fin. The noises sn11, sn12produced from the SCFs are superimposed on passing signals being the output signals S11, S12resulting from eliminating the high frequency component from the object signal fin. The SCFs 11, 12 are configured in such a way that the passing signals are in phase to each other and the noises sn11, sn12are in phase to each other, and the subtraction section 13 subtracts the output signals S11, S12with the result that the noises sn11, sn12are canceled each other. COPYRIGHT: (C)2006,JPO&NCIPI