Analysis and compact behavioral modeling of nonlinear distortion in analog communication circuits

The design of analog front-ends of digital telecommunication transceivers requires mixed-signal simulations at the architectural level. The nonlinear nature of the analog front-end blocks is a complication for their modeling at the architectural level, especially when the nonlinear behavior is frequency dependent. This paper describes an analysis and modeling method based on Volterra theory. The method derives bottom-up models of nonlinear analog continuous-time circuits. These behavioral models predict the dominant nonlinear effects using a composition of linear transfer functions and multiplications. This makes it possible to accurately model frequency dependencies and to gain insight into the dominant nonlinear sources of the circuit. The basic models are afterwards described using its multicarrier complex low-pass representation to enable their efficient cosimulation with the digital circuits in a dataflow simulation environment. The multicarrier representation is a direct extension of the classically used complex low-pass equivalent models, which considers the modulation of a single carrier only. The accuracy of the multicarrier representation is higher than classical complex low-pass equivalent models since out-of-band nonlinear distortion is taken into account. The main advantage of the proposed technique is that it yields both insight in the nonlinear behavior at the circuit level and that it provides an important gain in simulation efficiency of RF integrated circuits at the system level. Both aspects are demonstrated on a 5-GHz WLAN design.