TIME VARIANT FILTER

PURPOSE:To minimize the S/N against white noise by adding input noises at an adder circuit B after they are processed by both main and sub time variant filter circuits in a time other than the peaking time. CONSTITUTION:An input signal and an input noise are processed by a main time variant filter circuit I only at the peaking time tauq+taur when the signal is inputted until the signal is measured and the input noises are processed by both the main and sub time variant filter circuits I, II at a time other than the peaking time tauq+taur and then added by the adder circuit B. Thus, a nearly linear waiting function 3 as shown in solid lines is obtained as the sum between a waiting function 1 shown in alternate long and short dash line and a waiting function 2 shown in alternate long and two short dashes line and then the wait ing function minimizing the S/N against the white noise is obtained.