Analysis and Design of Stub loaded Closed Loop Microstrip Line Filter for Wi-Fi Applications

The design of a compact Band Stop Filter (BSF) operating at 2.4 GHz is discussed in this paper. Initially, a BSF is designed using insertion loss method and is validated by simulation software ANSYS Designer. The designed filter is then modified as a planar stub loaded closed loop resonator energized using microstrip line. The simulation of this filter is optimized using ANSYS HFSS. A prototype is fabricated on FR-4 epoxy having dielectric permittivity 4.4 and loss tangent 0.02. The theoretical results and simulation results are experimentally validated using Vector Network Analyzer (VNA). Empirical equations for the filter designs is also presented. The equations is able to predict the resonant frequency with less than 4 % error. All the three, theoretical results, simulation results and measured results are in good agreement.