Design of a Microstrip Bandpass Filter Using Advanced Numerical Models

Advanced numerical linear circuit models for parallel microstrip coupled line sections have been developed by Applied Wave Research (AWR) for use with their Microwave Office simulation program. The linear elements incorporate closedform solution techniques that may be evaluated with a linear circuit simulator. The response of the elements provides a high degree of accuracy with respect to electromagnetic simulation, but retain the computation speed of linear simulation. The elements can be used as an alternative to conventional coupled line circuit and electromagnetic models This article describes how the models were used to design a fifth-order hairpin microstrip band pass filter. A yield analysis was performed to verify measured data results. The transmission line characteristic impedance was determined using TDR (time domain reflectometry) techniques, to accurately determine the relative dielectric constant of the substrate material, which is necessary in order to verify measured and simulated data.