Patent ID: 8406357

Claim:
A filter circuit comprising: first and second real filters of a zero-IF scheme which are provided for receiving an I component and a Q component separated from a reception signal, respectively; and a switch section for producing a complex filter by switchably connecting the first and second real filters through interconnection elements when receiving a switching signal for switching from the zero-IF scheme to a low-IF scheme, wherein the complex filter outputs a mixing of I and Q components from the two real filters, and wherein each of the first and second real filters includes at least one operational amplifier, and an input of the operational amplifier in the first filter is coupled to an output of the operational amplifier in the second filter based on the switching signal in the low-IF scheme, and wherein an output of the operational amplifier in the first filter is coupled to an input of the operational amplifier in the second filter based on the switching signal in the low-IF scheme.