Mixer topology selection for a 1.8 - 2.5 GHz multi-standard front-end in 0.18 μm CMOS

In this paper the selection of a mixer topology for a multi-standard, non-concurrent front-end is presented. The front-end is designed for Digital Enhanced Cordless Telephone (DECT) systems and systems for wireless communications, which operate in the 2.4 GHz Industrial Scientific Medical (ISM) band (like Bluetooth or DECT alike systems at 2.4 GHz). Three mixer topologies are presented and evaluated. In order to choose the most promising one, a figure of merit for mixers is defined. A novel, folded switching mixer topology utilizing a current reuse technique achieves the best performance. With this topology the following simulation results are achieved: noise figure (NF) 11 dB, voltage gain 17 dB, linearity (IIP₃) 1 dBm with a power consumption of 5 mW at an operating frequency of 2.5 GHz. Given the fast migration of the CMOS technologies towards the deep submicron processes, mixer operation at low supply voltages is considered. The operation at a supply voltage of 1 V providing moderate NF, gain and linearity for two mixer topologies is shown, which is not reported in the literature so far.