A Different Approach Design for Higher-Order Highly Selective Wideband Bandpass Filters Using Cascaded Building Blocks

This paper presents a novel design approach for creating higher-order wideband bandpass filters (BPFs). The technique builds on a conventional filter topology, featuring shunt short-circuited stubs connected by transmission lines. In this method, the traditional λ{{g/4 interconnecting lines and λ{{g/4 short-circuited stubs are replaced by a building block comprising λ{{g/8 lines separated by λ{{g/8 short-circuited coupled-line sections. To enhance selectivity, )vee {g/2 open-and short-circuited coupled-line segments are used at the filter's input and output. The paper provides design guidelines and formulas through ABCD analysis for practical filter implementations. Additionally, a design example is demonstrated, along with its practical validation through the manufacturing and testing of a fifth-order microstrip-type BPF.