Design of Multiband Band-Pass Filters Based on Novel Associated Band-Stop Resonators

Although the design of multiband band-pass filters (MBPFs) has been thoroughly studied in the literature, the synthesis of high-order and multiple pass-band filters with controllable transmission zeros (TZs) and high band-to-band isolation is hardly feasible. In this paper, we present a novel design strategy to cope with this issue. Adopting a star-like topology, the proposed design method is based on the parallel association of N - 1 band-stop stepped-impedance stubs to form an N pass-bands resonator. We show that such a simple design principle allows the accurate control of TZs positions. The principle and theory of these associated band-stop resonators (ABSRs) based filter are exposed, and their efficiency is shown through the synthesis, design, simulation, and measurement of quad-band and quint-band band-pass filters. Very good in-band filter performance and very high band-to-band isolation are achieved for both filters without the need for complex optimization process. These results make the ABSRs an attractive solution to achieve multiple band responses with advanced specifications.