| 摘要 |
PROBLEM TO BE SOLVED: To provide an FIR(finite impulse response) filter for limiting the frequency band of inputted analog signals by filtering without digitally converting the analog signals. SOLUTION: In this FIR filter, for instance, a distribution means A1 distributes the inputted analog signals to a pair of signals composed of a positive phase signal and an opposite phase signal, the multiplication parts B1-Bn of the same number as the number (n) of taps of filtering for inputting the pair of the signals with a time difference for one sample with each other selectively input the sample value of either one of the pair of the signals corresponding to the positive/negative of a tap coefficient and multiply the inputted sample value and the absolute value of the tap coefficient, an adder A2 totals multiplied results in the respective multiplication parts B1-Bn and thus, filtered analog signals are outputted. The respectively multiplication parts B1-Bn are constituted of a switch for selectively inputting the sample value of either one of the pair of the signals and a sample-and-hold means for holding the inputted sample value by using a capacity corresponding to the absolute value of the tap coefficient from the plural capacities.
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