Efficient Design of Compact and Wideband Microstrip Filters Using Space Mapping and Surrogate-Based Modeling Techniques

This article describes a systematic design approach, based on the use of surrogate models in a low-accuracy space, to achieve smaller footprints and wider bandwidths for direct-coupled microstrip filter topologies. To reduce the computational cost of the design procedure, the frequency response of each resonant structure is matched (individually) to that of its equivalent circuit model, thus avoiding extensive optimization at electromagnetic (EM) level. The designed filter can then be translated into a high-accuracy space using the Aggressive Space Mapping (ASM) technique. In addition, an equivalent circuit based on a combination of inductive, capacitive and distributed elements is firstly synthesized. Results for the new filter topology are fully validated, through full-wave EM simulations from two commercial codes, and successfully compared (in terms of size and performance) with those of traditional coupled-line filters.