Patent ID: 8687124

Claim:
A signal processing device that outputs an output signal in which noise components mixed in an input signal have been reduced, comprising: a plurality of noise reduction units, cascade-connected to each other, the input signal being supplied to a most upstream side of the plurality of noise reduction units, each of the plurality of noise reduction units including: a signal selection device arranged to (i) sample, from a received signal, (a) a target signal to be subjected to a noise reduction and (b) a plurality of signals which are away from the target signal by given intervals and (ii) select a representative value from sampled signals; a voltage determination device arranged to determine which of a determined representative value and a voltage of the target signal is larger; and a signal output device arranged to (i) reduce the voltage of the target signal by a given voltage and outputting, as the output signal, the target signal thus reduced, in a case where the voltage of the target signal is determined to be larger than the representative value, (ii) increase the voltage of the target signal by a given value and outputting, as the output signal, the target signal thus increased, in a case where the voltage of the target signal is determined to be smaller than the representative value, or (iii) output, as the output signal, the target signal as it is, in a case where the voltage of the target signal is equal to the representative value, a combination of intervals between a target signal and a plurality of signal excluding the target signal to vary from noise reduction unit to noise reduction unit, a first noise reduction unit, which is located on a more upstream side of the plurality of noise reduction units, carries out processing in a lower frequency range and a second noise reduction unit, which is located on a more downstream side of the plurality of noise reduction units, carries out processing in a high frequency range; and each time the input signal is passed through one of the plurality of noise reduction units, which are cascade-connected to each other, noise components mixed in the input signal are gradually reduced in a lower frequency range and gradually increased in a higher frequency range, causing noise components mixed in a signal outputted from the most downstream side of the plurality of noise reduction units to be concentrated in a higher frequency range.