Microwave bandpass filter with quasi-lumped elements

In this paper, a new approach for microwave bandpass filters design is presented using quasi-lumped elements. The resonator is realized as a double-sided microstrip structure with two quasi-lumped elements: a square spiral inductor and a patch capacitor each printed on separate layer. Using this resonator, three bandpass filters with different types of feeder realization are designed. Furthermore, electric-circuit models are proposed instead of the three-dimensional electromagnetic (3D EM) models, which are suitable for microwave filters design. This approach is used to finally design a triple-bandpass filter.