Fast Design of a Multilayer Interdigital Filter Exploiting Trust Region Aggressive Space Mapping

Multilayer microstrip interdigital filter has become a research hotspot with the development of miniaturization and high integration. Many electromagnetic optimization methods have been developed with the increasing complexity and design difficulty of multilayer interdigital filters. Aggressive Space Mapping (ASM) algorithm has poor convergence and Implicit Spatial Mapping algorithm is limited to modeling structures with equivalent circuit models in ADS. Hence the improved Trust Region Aggressive Space Mapping (TRASM) algorithm is adopted to map between the coarse and fine models in this paper, where the coarse model is the coupling matrix and the fine model is the model in HFSS. Modal Vector Fitting (MVF) algorithm is used to get the coupling matrix, which enhances the uniqueness of the extraction step. This paper proposes a four-order and four-layer interdigital filter with a pass band of 8–9 GHz and an in-band return loss of 20.34 dB. The TRASM method based on MVF can complete the optimization in about 90 minutes with only two iterations, which is better than that of ASM and full- wave electromagnetic simulation. The innovative algorithm with efficient optimization proposed in this paper will be applied in electromagnetic optimization of multilayer filters extensively and improve the accuracy and simulation efficiency significantly.