Mixed-Signal Modeling and Analysis for a Digital RF Direct Sampling Mixer

This paper presents a mixed-signal model of a digital RF direct sampling mixer using Verilog-A language and circuit-based macro models in SpectreRF. The model proposed avoids "hidden state" problem in order to use RF simulation algorithms. The analysis of the charge sampling, filtering and charge sharing of the mixer is addressed in the paper. The model is validated through the simulation in SpectreRF using transient analysis and periodic analysis. The simulation results also verify the theory analysis for the transfer functions and charge sharing problem. In the design of the direct sampling mixer, fully charge sharing between capacitors should be guaranteed by using small capacitors.