Miniaturization of planar microwave filters with irregular geometries

Traditional planar microwave filter designs are limited to regular shapes so that the results may not be optimal. In this paper, we present a novel design approach of planar microwave filters with irregular shapes, which leads to more freedom and possibly better designs, including considerable reduction of filter size. This approach is based on the flexible finite element method (FEM) as the 3-D field simulator and the powerful particle swarm optimization (PSO) as the optimization engine. Using this design approach, new filter structures may be invented automatically with extraordinary performance.