Microstrip low-pass filter using modified log periodic radial stub

This paper presents a novel compact microstrip lowpass filter (LPF) configuration employing modified log periodic radial stubs. The proposed LPF includes three radial stubs of different dimensions to generate three different resonating frequencies at the desired location over the specified band to attain ultra-wide stopband. The operating mechanism of the proposed filter is investigated based on equivalent circuit model and the S-parameter characteristics of the proposed filter are obtained using the simulation tools. A prototype model of the proposed filter is developed and measured. Measurement and simulation results show good agreement. The size of the proposed LPF is only 20.33 × 10.38 mm².