Patent ID: 7650123

Claim:
A receiver for receiving a radio frequency signal, comprising: an attenuator for attenuating a disturbance signal which causes disturbance to a received frequency of the radio frequency signal, on a basis of set information of the received frequency; said attenuator comprising a trap circuit for producing a resonance frequency according to the set information; said trap circuit being connected on a supply line for the radio frequency signal to suppress the disturbance signal by the resonance frequency, wherein said trap circuit is supplied with a control voltage based on the set information; said trap circuit comprising an inductor and a variable capacitance diode, said variable capacitance diode having a capacitance determined by the control voltage supplied, said trap circuit producing the resonance frequency according to an inductor value of said inductor and said capacitance, wherein said attenuator comprises a switch circuit for selecting any of a plurality of different frequency bands on a basis of the set information; and said trap circuit produces a resonance frequency according to the frequency band selected by said switch circuit, wherein a plurality of inductor values are determined so that the plurality of different frequency bands are obtained, on the basis of a predetermined range of the control voltage which is predicted beforehand; said attenuator comprising a plurality of inductors each of which has different one of the plurality of inductor values; said switch circuit selecting any of said plurality of inductors on the basis of the set information; and said trap circuit being formed by the inductor selected by said switch circuit and said variable capacitance diode.