Super-compact stopband filter based on grounded patch resonator

A novel compact stopband microstrip filter is proposed, based on the grounded patch resonator embedded in the microstrip line. Characteristics of the proposed filter are compared with state-of-the-art stop-band filters of similar type in terms of size, performance and fabrication complexity. The fabricated fourth-order filter has overall dimensions of 0.52lg λ 0.13lg, 10 dB fractional bandwidth equal to 35% at 4.36 GHz, and insertion loss of more than 230 dB in the stopband, and it outperforms all previously published stop-band filters of that type.