Rf Active Quadrature Mixer Design

Riding the rapid technological advancement, RFIC using CMOS technology has been increasingly popular. Among the various building blocks of an RF system, the mixer is certainly one of the most important, with its performance having a huge impact on the system performance. In a receiver, the noise figure of a mixer is crucial to the sensitivity of the overall system. This research addresses the noise issue in an active mixer design.In this paper, a general description of an RF system with various building blocks, including the mixer, is given first, followed by the TSMC 0.18um RF CMOS models used in this paper and then a summary of noise. Next is a general introduction to mixer and Gilbert Cell active mixer, which is widely used in RF system is presented. Some further study about the physical mechanism noise appear in the active mixer is described. Moreover, some analysis of the nonlinearity in local oscillator (LO) switch is present. After an expensive research work on the noise figure (NF) improvement methods in recent years, a new quadrature mixer with an inductor which is used to cancel out the effect of parasitic capacitance on noise figure is presented. Finally, some simulation results in cadence Spectre RF using TSMC 0.18um RF CMOS models are given. The simulations show that the NF of the new quadrature mixer achieved 2.4dBbetter than conventional quadrature mixer at LO and intermediate frequency (IF) are 5.51GHz and 10MHz respectively.