A 0.12- ${\hbox {mm}}^{2}$ 2.4-GHz CMOS Inductorless High Isolation Subharmonic Mixer With Effective Current-Reuse Transconductance

In this work, the design of an inductorless, high-isolation, and high conversion gain fully differential subharmonic down-conversion mixer for 2.4-GHz wireless application is presented. A complementary current-reuse technique is adopted between the transconductance and the local oscillator (LO) switching stage to boost the conversion gain without additional power consumption in the concept of reusing the dc current of the LO switching stage. The LO switching transistors are driven by a 25% duty cycle input to further enhance the conversion gain and improve the noise-figure performance. An active balun is integrated in the design for single-balanced to differential conversion or vice-versa, along with an RC poly phase filter to generate quadrature LO signals from a differential input signal. The subharmonic mixer is fabricated in a 0.13- μm standard CMOS technology with a core chip dimension of 313 μm× 372 μm and a power consumption of 5.82 mW from a supply voltage of 1.2 V. Experimental results show a conversion gain of 13.61 dB, an input-referred third-order intercept point of -4.46 dBm, a noise figure of 20 dB, and an isolation greater than 50 dB between the LO, RF, and IF ports. The proposed inductorless subharmonic mixer has a competitive performance in size with high isolation performance and highest conversion gain in comparison to other published works.