Wide-Band Bandpass Filters Simulation, Design and Diagnosis

Full wave EM modeling is used to design wide bandpass filters and extract a lumped elements equivalent circuit. Electric and magnetic couplings are represented by capacitor- and inductor-coupling elements instead of frequency-independent reactance or impedance inverters. Optimization is used to extract the filter parameters that reproduce the EM simulated response. To verify the validity of the circuit model, an 8-pole combline-like filter with a 50% bandwidth is designed. Excellent agreement between the EM simulated and the lumped elements extracted responses is obtained. Filter synthesis is also carried out by an optimization process. With the extracted and synthesized parameters, the filters can then be diagnosed and fine tuned efficiently.