Intermodulation antiinterference device for superheterodyne receiver

摘要

An intermodulation antiinterference circuit for a superheterodyne receiver having a receiving antenna comprising a first high frequency amplifying circuit responsive to the receiving antenna; a local oscillating circuit; a first frequency conversion circuit responsive to the first high frequency amplifying circuit and the local oscillating circuit; a variable attenuation circuit disposed between the receiving antenna and the first frequency conversion circuit; a nonlinear circuit responsive to the receiving antenna having less linearity than the first high frequency amplifying circuit; a second frequency conversion circuit responsive to the local oscillating circuit and the nonlinear circuit; a comparison circuit responsive to the first and second frequency conversion circuits for generating an output when the output of the second frequency conversion circuit is greater than the output of the first frequency conversion circuit; and means for changing the attenuation of the attenuating circuit.