Bridging the Gap between Physical and Circuit Analysis for Variability-Aware Microwave Design: Power Amplifier Design

Process Induced Variability (PIV) stemming from fabrication tolerance can impact the performance of integrated circuits. This issue is particularly significant at high frequencies, since Monolithic Microwave Integrated Circuits (MMICs) rely on advanced semiconductor technologies exploiting device sizes at the nanoscale in conjunction with complex passive structures, featuring both distributed elements (transmission lines) and lumped components. Black-box (behavioral) models extracted from accurate physical simulations can be profitably exploited to incorporate PIV into circuit-level MMIC analysis. In this paper, these models are applied to the statistical analysis of a single and of a combined MMIC power amplifier designed in GaAs technology for X-band applications. The relative impact of the active device variability towards the passive matching networks one is evaluated, demonstrating the relevance of PIV. The significant spread found, with only two variable parameters, confirms the importance of a PIV-aware PA design approach, with suitable margins and careful network optimization.