| 摘要 |
PROBLEM TO BE SOLVED: To obtain a digital filter which can have a high noise eliminating ability regardless of its filter constant. SOLUTION: A dissidence detector is composed of ExOR gates G1 and G2, an AND gate G3, an OR gate G4, and a D flip-flop FF3 and is operated for detecting noise with a sample clock SCLK having a frequency higher than that of a filter clock FCLK. When the detector detects noise, the detector prevents the output of a flip-flop FF1 from being inputted to another flip-flop FF2 by switching and controlling a selector S. The flip-flops FF1 and FF2 which are cascade-connected in two stages are operated by the filter clock FCLK and, unless the dissidence detector detects noise, the flip flop FF1 holds/ outputs input signals (a) at a certain sampling time of the clock FCLK. Then the flip-flop FF2 outputs the signals (a) as post-filter input signals at the next sampling time. |
