A +7.6 dBm IIP3 2.4-GHz Double-Balanced Mixer With 10.5 dB NF in 65-nm CMOS

In this brief, an enhanced derivative superposition (DS) method is proposed to increase the third-order input intercept point (IIP3) of double-balanced CMOS active mixers. In the proposed mixer, an auxiliary common-gate transconductor biased in the moderate inversion region with a source inductive degeneration is used in the feedforward AC-coupled path to the main transconductor to generate the third-order intermodulation distortion (IMD3) current. Hence, the overall IMD3 current of the transconductance stage is minimized while optimizing the conversion gain (CG). This auxiliary transconductor also improves the overall NF of the mixer by partially cancelling the output noise voltage. In addition, the current reuse and current bleeding techniques are utilized to further improve the overall performance. As a proof-of-concept, a 2.4-GHz down-conversion mixer with an output bandwidth of 10 MHz is implemented in a 65-nm CMOS process. Measurement results show that the mixer achieves a peak CG of 12.5 dB, a double-sideband (DSB) noise figure (NF) of 10.5 dB, and IIP3 of +7.6 dBm. The circuit consumes 1.2 mW from a 1-V supply and excluding the pads, it occupies a silicon area of 0.2208 mm2.