Phase–frequency transfer model of analogue and mixed-signal front-end architectures for system-level design

Abstract

A framework to model the behaviour of front-end architectures is presented. To make the model useful for systematic architectural exploration during front-end system design, a wide range of architectures are represented. Compared to other models, it emphasises the information flow throughout the architecture and also enables incremental modelling to represent the system at lower levels of abstraction. All signals in the architecture are represented as polyphase harmonic signals which are transformed by the building blocks of the architectures in the phase-frequency space. Their linear transformation behaviour is modelled by a multiplication of a polyphase harmonic transfer matrix with the input signal. It is shown that this representation for a polyphase mixer can be easily derived from the harmonic transfer matrices for the individual mixers. Extensions to weakly nonlinear behaviour are realised by adding distortion tensors to the model which take both intermodulation and harmonic distortion into account. The nonlinear mapping operation is represented by a repeated calculation of inner products of the distortion tensor and the input signal. As an example, the model has been applied to a downconversion architecture. It is shown that the non-ideal behaviour of the architecture is the result of parasitic transfers between phases and frequencies within the phase-frequency space. This allows a clear identification of the causes of performance degradation and gives suggestions to improve the performance.