Design of distributed-element RF filters via reflectance data modeling

A reflectance-based modeling method is presented, to obtain the distributed-element counterpart of a lumped-element network, which is described by measured or computed reflectance data at a set of frequencies. Numerical generation of the scattering parameters forms the basis of this modeling tool. It is not necessary to select a circuit topology for the distributed-element model, which is the natural consequence of the modeling process. Our approach supplements the known interpolation methods by a simple technique that does not involve complicated cascaded circuit topologies and whose numerical convergence is proven. To illustrate the utilization of the proposed method, a lumped-element low-pass Chebyshev filter is transformed to its distributed-element counterpart. The filter, designed for a frequency band around 1 GHz, was fabricated and experimentally characterized. We find excellent agreement between measured and simulated transducer power gain over the entire frequency band.