Patent ID: 8249537

Claim:
A noise cancellation circuit for a mixer device comprising: a first signal terminal, coupled to a first output terminal of an RF input stage of the mixer device; a second signal terminal, coupled to a second output terminal of the RF input stage of the mixer device; a first variable current source comprising a first end coupled to the first signal terminal, a second end coupled to the second signal terminal, and a third end coupled to a first voltage source, for adjusting current between the first end to the third end according to signals of the second end; a second variable current source comprising a first end coupled to the second signal terminal, a second end, and a third end coupled to the first voltage source, for adjusting current between the first end to the third end according to signals of the second end; and a phase shift device coupled between the first signal terminal and the second end of the second variable current source, for transforming a first signal into a second signal, and outputting the second signal to the second end of the second variable current source.