A COMPARATIVE STUDY OF DIFFERENT TYPES OF MIXER TOPOLOGIES

Abstract

In this paper, a comparative study of different types of mixer topologies is presented. Gilbert cell is widely used as core of the mixer because it provides high conversion gain, good port-to-port isolation and low even-order distortion. It is found that the linearity of mixer is very good for Multi-Tanh technique by incorporating multiple differential trans-conductance stage but it reaches to very low conversion gain whereas, use of current bleeding technique increase linearity and conversion gain of the mixer by adding current source to increase the bias current at the expense of power consumption. A very low value of noise figure can be achieved with the switched biasing technique by replacing current source with parallel connected nMOS transistors but due to use of the transistor in place of tail current source, linearity is degraded and more power is consumed. Folded Cascode Technique is used to reduce DC supply voltage by folding the LO switching stage with pMOS transistors in switching stage but it degrades the noise figure. Bulk-driven technique can be employed to lower down the power consumption by providing the switching action via the gate of LO (RF) and amplification by the bulk of LO (RF) transistors, however it reduces the linearity. High linearity is obtained by using CCPD (Cross coupled post distortion) technique by cancelling of third order derivatives but it decreases the conversion gain and consume more power due to increase in the number of auxiliary transistors. MGTR enables to achieve high linearity by incorporating auxiliary transistor but it decreases the overall conversion gain and increases noise figure of the mixer. So it is observed that there is a trade-off among the performance metrics, i.e., conversion gain, noise figure linearity, and power consumption of the mixer.