Sub-Harmonic Mixer Linearity Characteristics Improvement by Injecting Second Harmonic of Fundamental Signal, From Two Auxiliary Paths Toward The Basic Circuit (Design and Analysis using Volterra expansion)

The importance of linearity and noise arises a lot of challenges in mixer design. A new technique is presented in this paper in order to improve mixer linearity, which tries to make the circuit more linear by means of displacing switching and transconductance stages and producing second harmonic of the fundamental signal using a frequency doubler and then injecting it to the basic circuit from two auxiliary paths. In this topology, quadrature oscillator is used for appropriate operation of the switching stage. Because of using frequency doublers, the problem of local oscillator signal leakage and DC offset in direct-conversion and heterodyne receivers is reduced, and also, this doublers make the design procedure of this topology easier. Obtained results from simulations in ADS software using TSMC 0.18 um technology, show that linearity characteristics (IIP3 and IIP2) are improved in this topology compared to conventional gilbert cell topologies.