Patent ID: 8121579

Claim:
An active mixer circuit, comprising: a voltage-to-current converter; a multiplier; and a transformer that is connected between the voltage-to-current converter and the multiplier, wherein the voltage-to-current converter is configured of one transistor or a plurality of transistors connected in parallel, wherein the transformer includes primary winding and secondary winding, wherein the voltage-to-current converter is connected in series between a pair of terminals of a reference voltage that supply the supply voltage to the transformer via the primary winding of the transformer, wherein a capacitor is disposed between an input terminal of the primary winding of the transformer and a ground terminal which is one of the pair of terminals of the reference voltage, wherein an output terminal of the secondary winding of the transformer is connected to the multiplier, wherein the primary winding and the secondary winding of the transformer are separated from each other with respect to direct current inside the transformer, and wherein a self-inductance value between the input terminal and the ground terminal, and a capacitance value of the capacitor, are both controlled to set a resonant frequency corresponding with a frequency of an input signal.