Experimental Comparative Analysis of Ultra-Wideband Microstrip Low-Pass Filters With Different Topologies and Manufacturing Methods

Abstract Microstrip filters are widely employed in radio fre-quency and microwave circuits due to their efficiency, easy fabri-cation, and compatibility with printed circuit board technologies. In this scenario, this work addresses, for the first time, to the best of our knowledge, a comprehensive study that includes the design, software simulation, and prototype fabrication of ultra-wideband low-pass filters made with microstrip lines employing different topologies. The filters were designed and constructed at 7.5 GHz with four different topologies: Minimal Stubs, Split Stubs, Radial Stubs, and Stepped Impedance. The manufacturing methods employed were the computer numeric control milling in copper and printing with silver-based conductive ink. The manu-factured filters were Chebyshev I of order 9, which ensured rapid attenuation after the cutoff frequency. The results show that the filters fabricated with the Radial Stubs topology performed better than the other topologies investigated in terms of cutoff frequency, attenuation, and insertion loss. The experimental investigations also demonstrated a slightly better performance of the filters made of copper than those made of silver, with lower insertion loss values. The simulation results and experimental measurements are in good agreement for all topologies and fabrication methods investigated. Furthermore, all fabricated filters presented relatively flat group delays.