High gain intermediate frequency input circuit with satisfactory trap characteristics

Abstract

An intermediate frequency input circuit is coupled between output nodes of a frequency mixing circuit and input nodes of an intermediate frequency amplifier circuit. The intermediate frequency input circuit includes a pair of input nodes; a pair of output nodes; and resonance circuits, which are coupled between the pair of input nodes and resonate with an intermediate frequency of a selector channel. A series circuit is coupled between one of the pair of input nodes and one of the pair of output nodes. The series circuit includes a first trap circuit for trapping an intermediate frequency component of an upper adjacent channel coupled to first resistor. The intermediate frequency input circuit further includes a second series circuit, which is coupled between the other of the pair of input nodes and the other of the pair of output nodes. The second series circuit includes a second trap circuit for trapping an intermediate frequency component of a lower adjacent channel coupled to a second resistor. A parallel circuit, which is coupled between the pair of output nodes, includes a third resistor and a capacitor.

Dependencies are inferred from the claim text.