This paper presents a new MATLAB-based microstrip filter design tool. Stepped-impedance resonator lowpass filter, parallel-coupled bandpass filter, and end-coupled bandpass filter are included. Circuit-theory based closed-form mathematical expressions are used, instead of rigorous electromagnetic analyses. This results in significant reduction in analytical effort, without substantially affecting the accuracy. The results are verified against results obtained using commercially available Ansoft simulation tool. The agreement between the two sets of results is good enough for all practical purposes.

An accurate MATLAB-based CAD algorithm for quickly designing microstrip-based stepped-impedance resonator (SIR) low-pass filter is reported. The algorithm uses a circuit-theory approach to implement speedy computations, compared to the time-consuming computations involved in using electromagnetic theory.
The accuracy of the proposed algorithm is verified for two widely-different practical examples in the 0-4GHz frequency range, against results obtained using Ansoft/Ansys circuit simulation tool, and against results obtained using the 3D electromagnetic simulator HFSS. The agreement among the three sets of data is seen to be excellent for most cases, and is found to be practically acceptable in the worst-case.