Patent ID: 8258827

Claim:
A frequency doubler, comprising: a first transistor, having a first terminal, a second terminal and a control terminal, wherein the control terminal of the first transistor receives an in-phase oscillating signal; a second transistor, having a first terminal, a second terminal and a control terminal, wherein the control terminal of the second transistor receives an inverse oscillating signal, and the first terminal of the second transistor is the same voltage as the first terminal of the first transistor; a symmetric inductor, wherein, at a first side of the symmetric inductor there is a first connecting terminal and a second connecting terminal coupled to the second terminals of the first and second transistors, respectively, and, at a second side of the symmetric inductor there is a third connecting terminal coupled to an output terminal of the frequency doubler; and a filter coupled to the output terminal of the frequency doubler, wherein the filter comprises: an inductor, coupling a power source to the output terminal of the frequency doubler, wherein the power source powers the frequency doubler; and a capacitor, coupled between the output terminal of the frequency doubler and ground.