Synthesis Techniques on Multiband Impedance Matching Networks for Frequency-Dependent Complex Loads

In this paper, broad multiband impedance matching networks (MBIMNs) are synthesized for frequency-dependent complex loads. The MBIMNs are derived from a multiband bandpass topology that is obtained by conducting multiple low-pass-bandpass transformations and by sharing one topology for all matching bands. The concept of a frequency-dependent voltage transformer is then used for generating a frequency-dependent load conductance, while the load susceptance is borrowed from the nearest susceptance unit of the topology. The resulted MBIMN contains several multimode resonators that are practically realized by parallel connections of series LCs and series connections of parallel LCs, and iterative methods are used for extracting the circuit parameters. Three dual-band examples and one triband example are designed and simulated, and two of them are fabricated and measured, with compared results sufficiently demonstrating the feasibility of the topologies and theories. Broad bandwidths referring to low reflection coefficients are observed. The topologies and methods can also be expected to realize more than three matching bands provided with enough convenience in circuit implementation. Multiband bandpass filtering is another important function of the matching networks.