Expedited microwave optimization using variable-fidelity EM analysis and convergence/quality-driven model adjustment

Abstract

Electromagnetic (EM)-based optimization is imperative for most microwave circuits. This is because designs produced by circuit theory methods require further adjustments to ensure satisfactory performance. Unfortunately, repetitive EM simulations incurred by optimization procedures are associated with considerable expenses. Expediting the process is essential to reduce the time span of design cycles and time-to-market in the case of industrial products. One possibility is utilization of variable-resolution EM simulations; however, available frameworks typically employ two discrete levels of fidelity (coarse/fine) combined with often sophisticated model correction methods. This paper proposes an alternative approach to accelerated microwave component tuning. Our methodology involves a continuous spectrum of EM simulation resolutions, which are controlled using the convergence and design quality indicators of the underlying optimization routine. A management scheme adjusting the model resolution is developed to utilize the lowest usable resolution at the search process onset, which is continuously increased as the algorithm approaches convergence and the objective function reaches satisfactory levels. The final stages are carried out with high-fidelity resolution to ensure accuracy. Verification experiments conducted using three microstrip circuits demonstrate over sixty percent of average savings over the reference (single-resolution) gradient-based routine, and noticeable and consistent acceleration regarding several state-of-the-art expedited versions. Selected designs are experimentally validated.