Compact lowpass filter with a sharp roll-off using patch resonators

ABSTRACT This article presents a new compact microstrip lowpass filter with sharp roll‐off and ultrawide stopband using funnel and triangular patch resonators. 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 results show 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 5.55 GHz with a roll‐off of 84 dB/GHz and its stopband extends up to 11.8 GHz. The filter has an ultra compact size of 9.4 × 8 mm2. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2534–2536, 2014