Miniaturized Microstrip Diplexer Based on FR4 Substrate for Wireless Communications

In this paper, the miniaturized microstrip diplexer has been designed for dual channels based on FR4 substrate material. It consists of two bandpass filters (BPFs) functioning under dissimilar frequency bands coupled with a unified junction. Every BPF has been created by a meandered line resonator, step impedance resonator, uniform impedance resonator, and input/output feed lines. The AWR electromagnetic simulator has been used for characterizing the frequency responses of the projected diplexer. Noble scattering parameter results with narrow band responses and negative group delay values are obtained for the proposed diplexer. The microstrip diplexer has an interesting band isolation between the two filters around 31 dB. The device has been successfully fabricated and verified with the simulations.