Patent ID: 8204469

Claim:
A low-noise mixer circuit comprising: an RF input stage to receive an RF differential input signal and provide an amplification of the differential RF input signal as a first differential output signal; a switching stage to receive and mix the first output signal with a differential mixing input signal from a local oscillator LO; a first current source operatively coupled to the RF input stage to supply current thereto; a current control circuit coupled to the RF input stage, the switching stage, the first current source, and the local oscillator to reduce the noise of at least the switching stage by providing a mixer signal path modulation signal Vctl having double the frequency of the LO signal, wherein: the differential mixing input signal comprises a first and second mixing input signal; the switching stage comprises a multiplying stage including: a. a first local oscillator differential transistor pair including a first and second transistor respectively connected to the first and second mixing input; and b. a second local oscillator differential transistor pair including a third and fourth transistor respectively connected to the second and first mixing input, wherein: the RF input stage comprises a pair of transconductance amplifiers formed by a seventh and eighth transistor, the seventh transistor operatively coupled to the first and second transistor and the eighth transistor operably coupled to the third and fourth transistor; the first current source comprises a fixed DC bias current, realized by a transistor-resistor combination including a ninth transistor having a collector connected to an emitter of the seventh and the eighth transistor; and the current control circuit comprising: a. a bias coupling network including a second current source and connected to the base electrode of the ninth transistor; b. a fifth and sixth transistor respectively having a base electrode connected to the first and second mixing input, operably coupled to a common biasing line of the switching stage and to the bias coupling network.