A low-power K-band CMOS current-mode up-conversion mixer is proposed. The proposed mixer is realized using four analog current-squaring circuits. This current-mode up-conversion mixer is fabricated in 0.13-µm 1P8M triple-well CMOS process, and has the measured power conversion gain of -5dB. The fabricated CMOS up-conversion mixer dissipates only 3.1mW from a 1-V supply voltage. The VCO can be tuned from 20.8GHz to 22.7GHz. Its phase noise is -108dBc/Hz at 10-MHz offset frequency. It is shown that the proposed mixer has great potential for low-voltage and low-power CMOS transmitter front-ends in advanced nano-CMOS technologies.