Optimization of lowpass filters using the coupling matrix approach

This paper presents a novel approach for designing lowpass filters using the coupling matrix technique. First, a relationship is established between the coupling coefficients and a surrogate model consisting of lumped elements. Applying a coupling matrix extraction to simulated or measured data, such a surrogate model approximating the characteristics of a planar filter geometry can be created. Comparing the surrogate model with the desired filter prototype, adjusting the filter geometry can be done in a purposive manner. The feasibility of this method is demonstrated by the design, fabrication, and testing of lowpass filters, realized on a multilayer printed circuit board.