Design Flexibility of SIR Coaxial Resonators for UHF Filters

This paper focus on one particularity of a filtering coaxial architecture, allowing to satisfy the same requirements in terms of central frequency and bandwidth with various dimensions. The filtering architecture is based on miniature two-section Stepped Impedance Resonators (SIR) built from air-filled coaxial structures fitted inside one another. The SIR effect is a freedom degree allowing to adjust on demand, the global size of the resonators and thus of the filters. In order to illustrate the concept, two UHF 2
^nd
-order bandpass filters, with a strong contrast of dimensions are designed, fabricated, measured and compared.