Compact microstrip lowpass filter with sharp roll-off and wide stopband by cascading multiple resonators

This paper presents a new compact microstrip lowpass filter with sharp roll-off and wide stopband by cascading multiple polygonal patch resonators using high impedance transmission line. The patch resonators are placed symmetrically about a high impedance central microstrip line. The filter has been designed and fabricated using a very low cost material. The experimental result shows a good agreement with the simulated results and demonstrate that, the sharp roll-off and good stopband performance is obtained by the proposed filter. The 3 dB cutoff frequency of the proposed filter is at 2.21 GHz with a roll-off of 94 dB/GHz and has a wide stopband from 2.38 GHz to 6.7 GHz. The filter has a compact size of 17.4 mm × 12.2 mm.