| 摘要 |
PURPOSE:To effectively suppress interference waves with the minimum power consumption by successively selecting the minimum number of cascade connections within a range where detected interference amount does not exceed a prescribed value and inhibiting the supply of electric power to unused unit filters. CONSTITUTION:In the constitution of a band-pass filter, changeover switches 220-22n are provided between and both the ends of respective unit filters 211-21n. A switching control circuit 23 decides the number of the cascade connections of the unit filters 211-21n by a control signal from an interference amount detector and outputs a switching control signal (a) for switching the corresponding switch to the unit filter side. Further, a voltage control signal (b) is outputted to supply the operating electric power only to the unit filters to be cascade connected. Thus, the unit filters 211 and 212 are cascade connected when selectively obtained by the unit filters of two steps from the interference amount detected at the interference detector is sufficient. Consequently, the power consumption at the unit filters 213-21n can be saved and the power consumption of the entire band-pass filter can be suppressed at the irreducible minimum. |
