Pseudoelliptic bandpass filter realized using coupled stepped-impedance resonators with tapped I/O

A tapped combline bandpass filter composed of two coupled stepped-impedance resonators (SIRs) and with tapped lines fed in/out is modeled. The admittance matrix for the entire circuit has been derived from the four-port coupled-line impedance and admittance matrices. The obtained admittance matrix is suitable for the design of a stepped-impedance combline filter, in which the coupled-line length, as opposed to the previous work, is not restricted. The most effective miniaturization for the filter is achieved by setting the critical condition (θ₁ = θ₂+θ₃) for the cases of K>1. Without using the cross-coupling resonator structure, the simulation result and the manipulation reveal the potential of this configuration to realize a pseudoelliptic bandpass filtering response.