| 摘要 |
PURPOSE:To eliminate the noise effectively with a minimum number of constituents, by adding a signal, which is obtained by inverting a signal where a prescribed signal band is eliminated from an input signal, to the input signal when the noise exists. CONSTITUTION:When the noise does not exist, a switch SW5 is closed by the control system. Consequently, the signal path consisting of a phase inverting circuit 11 and a pass signal control circuit 12 is grounded, and a signal supplied to an input terminal IN is outputted to an output terminal OUT through a combined resistance 18. When the noise is mixed with the coming signal, the switch SW5 is opened. The output of an LPF10 has the phase inverted by the circuit 11 and has a prescribed signal band such as a main signal frequency band stopped by the circuit 12 and is supplied to the combined resistance 18. Consequently, the output of the LPF10 and a signal, which is obtained by eliminating a prescribed signal band of the main signal from the output of the LPF10 and inverting the phase, are synthesized by the resistance 18. Thus, the noise mixed outside the prescribed signal band is cancelled and eliminated. |
