Mixer noise reduction technique

A mixer circuit comprising:

• first and second transistors configured to receive a differential input signal, the first and second transistors coupled to a common node to receive a bias current;
• a third transistor having a bias output coupled to the common node, the third transistor coupled to receive an RF signal and generate a bias current at the bias output;
• and
• an inductor having a first terminal coupled to the common node and a second terminal coupled to a supply voltage;
• wherein the bias current comprises bias frequency components, and a frequency dependent current shunt circuit couples a first portion of the bias current frequency components within a first frequency range to the supply voltage, and couples a second portion of the bias current frequency components within a second frequency range to the supply voltage, the first portion being larger than the second portion.

A method of reducing noise in a mixer comprising:

• receiving a first signal in a gain stage;
• receiving a second signal in a bias circuit, the second signal having a first frequency;
• generating a bias current in response to the second signal, the bias current having bias current frequency components including a frequency component at the first frequency;
• shunting a first portion of the bias current frequency components within a first frequency range to a reference voltage and a second portion of the bias current frequency components within a second frequency range higher than the first frequency range to the reference voltage, the first frequency being in the second frequency range and the first portion being larger than the second portion;
• and
• coupling the bias current to the gain stage to produce a mixer output.