A Design of a Compact Microwave Diplexer in Microstrip Technology Based on Bandpass Filters Using Stepped Impedance Resonator

Abstract This paper describes the design of a compact microstrip microwave diplexer based on bandpass filters and a stepped impedance resonator for 4G applications. The diplexer is composed of two band-pass filters (BPF) that operate at 1.8 and 2.5 GHz. Both bandpass filters for the receiver at 1.705-1.895 GHZ and the transmitter at 2.41-2.6 GHZ have a -3dB fractional bandwidth of 10.5 % and 7.6 % respectively. These BPF, suitable for 4G telecommunications, are examined, evaluated, developed, and simulated, yielding theoretically consistent results. With a dielectric permittivity of 4.4 and a thickness of 1.6 mm, FR-4 is employed as a substrate material. The theoretical design and simulation are used to calculate the size and position of the SIR and feed lines. The diplexer has a low insertion loss and a high isolation, and its efficiency is quantitatively analyzed using the HFSS software. This application allows us to swiftly and simply create electrodynamic structures. A diplexer prototype was developed using a typical method of fabricating PCBs, with a structural area of (47.4020x247.063=11711.28 mm2). The obtained simulation results of the proposed circuit are in good agreement with the measurements.