Microstrip Diplexer Implemented on High-Pass and Low-Pass Filters

A study is conducted on a miniature microstrip diplexer which is a planar microstrip structure containing one input and two outputs. The diplexer also contains two filters, each of which has its own operating frequency. The low-pass filter consists of a sequence of high-and low-ohm microstrip transmission line segments. The high-pass filter consists of two identical spiral resonators and two interdigital capacitors. FR-4 with dielectric permeability of 4.4 and thickness 1.5 mm is used as substrate material. The suggested structure has small dimensions and low inserted loss level within the band widths. The entire testing process was performed in special Ansoft HFSS three-dimensional electrodynamic simulation software. This software allows to design electrodynamic structures in a fast and simple manner. A diplexer prototype was manufactured using a standard PCB manufacturing method. The area of the structure is 110×100=11000 mm².