Planar Diplexer Design Using an Energetic Coupling Approach

This paper presents a simple procedure to design planar diplexers making use of an energetic coupling approach. The targeted diplexer uses a stepped impedance resonator (SIR) to generate two resonant frequencies at the desired pass bands. The energetic coupling theory is employed to obtain appropriate coupling factors between the SIR and the diplexer outputs. In order to validate the proposed design method two diplexers satisfying the GSM and WLAN application frequencies have been fabricated and characterized. One prototype has been implemented in microstrip technology, while for the fabrication of the other one a low-cost 3D printing multilayer process has been used. In both cases measurements are in good agreement with simulated responses.