Design of stepped-impedance low pass filters with impedance matching by the particle swarm optimization and conjugate gradient method

In This paper, the method of least square is used for the design and optimization of stepped-impedance low pass filters, which also incorporates impedance matching of source and load impedances. The minimization of the error function is performed by the combination of particle swarm optimization (PSO) and conjugate gradient method (CG). The dispersion relations and step discontinuity equivalent circuits are incorporated in the design procedure. The achieved frequency response of designed filters match those obtained by HFSS simulator software and are much better than those obtained by the classical methods, such as Butterworth, Chebyshev and elliptic filters.