Design of Low Pass Filter using Microstrip Line - A Comparative Study

In this article, a three-stage Butterworth low-pass passive filter having a 0.5dB equal ripple response for L-band applications is designed. This work is designed using lumped components and distributed components with RT/Duroid-6010 substrate with ε
r
= 10.8, Loss tangent = 0.002 and h = 1.27mm along with a microstrip with t = 0.035mm using the T-network. The three-Stage stepped impedance microstrip low-pass filter is compared with the three-stage microstrip stubbed low-pass filter on the basis of design approach and an additional comparison has been made by changing the substrate to FR-4 with ε
r
= 4.3, Loss tangent = 0.025 and h = 1.27mm along with copper (annealed) as a microstrip with t = 0.035mm. The simulation is worked out on the CST-Design Environment where the schematics are used to design the filter and the responses are plotted for the same designs. The originality of this work would be to show the change in sharpness, group delay along with the change in parameters upon changing the materials.