A frequency separation macromodel for system-level simulation of RF circuits

In this paper, we propose a frequency-separation methodology to generate system-level macromodels for analog and RF circuits. The proposed macromodels are similar in form to those based on Volterra kernel calculations, but are much simpler in terms of characterization and overall model complexity, and can be derived from existing device models. This simplicity is realized by applying some basic assumptions on the form of the input excitations, and via separation of the nonlinearities from the dynamic behavior. In addition, by further separating the ideal model functionality, this macromodel is applicable to strongly nonlinear components such as mixers. While time-varying Volterra series models have been proposed for mixers with a fixed local oscillation (LO) signal, the proposed frequency separation model is completely general and can capture the variations of the LO input during a system-level simulation. The proposed macromodels are demonstrated in a system-level simulation tool based on Simulink for efficient evaluation of the entire RF system and associated components. A GSM receiver system in 0.25 μm CMOS process is used to demonstrate the efficacy of these macromodels in our system-level simulation environment.