Design and Implementation of a Novel 5G Hairpin Bandpass Filter with Defected Ground Structure

In this paper, a three-pole hairpin resonator is designed, simulated, and fabricated on the top layer of the FR4 substrate. Recent trends in miniature size and improved filter performance, particularly in terms of scattering parameters and wider bandwidth, have increased demand for such filters. This filter uses two different Defect Ground Structure (DGS) techniques utilizing the top and ground layers. The first Defect Ground Structure (DGS) technique incorporates two dumbbells and rectangular slots beneath two feed lines, resulting in a unique and modified bandpass filter design. In the second DGS, a series of grooves embedded at three hairpin resonators provide a more compact size and enhanced scattering parameters with wider bandwidth, which is considered an improvement of this design over the existing works. The simulation results use High Frequency Structure Simulator (HFSS) software. Parametric optimization has been conducted; the optimized values of three significant parameters are 4mm length of tap Lt, 0,4mm space between resonators S, and (3×9)mm2 area of rectangular slot (DGS2). The presented filter resonates at 2.5 GHz center frequency with a -3dB fractional bandwidth of 22.4%. The acquired values of insertion loss (S21) and return loss (S11) at the passband are -1.6dB and -54.19dB, respectively, with a flat group delay. The design validity has been verified using Computer Simulation Technology (CST) simulation software and a fabricated prototype. The fabrication results match the simulations excellently, making the suggested filter suitable for various fifth-generation (5G) applications.