Patent ID: 7587440

Claim:
A digital filter comprising: a first decimation section decimating an input signal to a signal with a first sampling frequency; and a second decimation section performing an operation on a filter coefficient according to an output signal of the first decimation section and decimating the output signal of the first decimation section to a signal with a second sampling frequency, the second decimation section comprising: a filter coefficient storage part pre-storing a filter coefficient; a shift operation part acquiring a filter coefficient from the filter coefficient part and performing a shift operation on the acquired filter coefficient; a complementary operation part acquiring a filter coefficient from the filter coefficient storage part and performing a complementary operation on the acquired filter coefficient acquired; a reset part acquiring a filter coefficient from the filter coefficient storage part and resetting the acquired filter coefficient; an adder part acquiring a filter coefficient from the filter coefficient storage part and adding the acquired filter coefficient, and a result of the shift operation; and an integrator part integrating the acquired filter coefficient, the result of the complementary operation, a result of the reset part, or a result of the addition.