Analysis of higher order Microstrip Filter to Reduce Out-of-Band Emissions

Abstract

In this paper a fifth order wide-band Chebyshev micro-strip filter is designed at 5.2 GHz frequency, where the spectrum contains white spaces. The fifth order is extended to 7th, 9th, 11th, and 13th order and simulated using HFSS EM simulator. Simulation results show that compared to 5th order, the higher order filters provide more and more reduction in out-of-band emissions in increasing order from 5th to 13th order filter. A 13th order filter is fabricated and tested for more reduction in the OOBE by using dumbbell shaped slots as defected ground plane structure. Five such slots are made in the ground plane for better results to reduce more OOBE. This 13th order filer with slots is fabricated and tested. The substrate chosen is FR4 with height 1.6 mm. Here we have given a mathematical treatment for emission mask for OOBE according to ITU recommendations. The designed filter’s transmission characteristics from port 1 to port 2 give good agreement with the recommendations.