| 摘要 |
PURPOSE:To obtain a digital filter having a proper time constant easily at low cost by making variable the time constant of a primary delay element according to the amplitude of an input signal. CONSTITUTION:An input signal SI is sampled and held by a sample and hold circuit 1 then converted by an A/D converter 2 into a digital signal, which is supplied to an amplitude detector 3 and the primary delay element 5. The amplitude detector 3 detects the amplitude of the input signal SI during the past time TA, i.e. difference A between a maximum and a minimum. Further, the difference A is compared with the amplitude AO of a signal SI having no superposed noise in a period TA to evaluate the level of a noise in the input signal. The output of this detector 3 is converted to a time constant by a function generator 4 according to a predetermined function. The primary delay element 5 performs prescribed arithmetic corresponding to the primary delay element on the basis of the time constant and input signal SI. |
