Modeling and characterization of spiral resonators embedded in suspended microstrip line for application in low-loss diplexer

This article presents the design and realization of anovel, low-loss, compact diplexer providing high selectivity and verygood separation between very narrow spaced working channels for application in the ESEO satellite transceiver. The diplexer is based on spiral resonators (SR) embedded in the suspended microstrip line and forming band-stop filter structures. For design purpose, the equivalent-circuit model of the SR resonator embedded in microstrip line is derived, analyzed, and verified. The influence of the model parameters on S11 and S21 characteristics has been studied and discussed. The double stage filter with embedded SR resonators has been described. A novel method is proposed to precisely control the filter selectivity, bandwidth, and the position of S11 minimum. The filter has been applied in the diplexer design. The measured performance of the manufactured diplexer prototype exhibits good properties and good agreement with the simulation results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:131–135, 2014