A New Synthesis and Design Approach of a Complex Termination Impedance Bandpass Filter

A new synthesis for the design of a bandpass filter (BPF) with arbitrary real and/or complex termination impedances is presented in this paper. The proposed BPF can be terminated with arbitrary complex termination impedances simply by adding series transmission lines (TLs) to the first and the last coupled resonators. For design freedom, the characteristic impedances of the additional TLs can be chosen arbitrarily. Moreover, the proposed filter can be designed in either evenor odd-ordered stages using a λ/4 stepped impedance resonator (SIR). For the validation of the proposed filter, twoand three-stage λ/4 SIR BPFs with Z
_S
= 30 + j10 Ω, Z
_L
= 50 Ω, and Z
_S
= 50 Ω, Z
_L
= 100 + j100 Ω, respectively, were designed and fabricated at the center frequency (f
₀
) of 2.6 GHz. The measured results are consistent with the simulation results.