In this paper we present a new compact microstrip lowpass filter using a П-H-П-DGS resonator etched in the ground plane and two patches compensated capacitors placed on the top layer. Two DGS shapes are electromagnetically coupled. The proposed lowpass filter has shown improvement by adding a square microstrip to the single DGS resonator. The design procedure is validated using the commercial full-wave EM MoM simulator Microwave Office. Simulated as well as measured results exhibit sharp roll-off (ξ) of 34 dB/GHz and create a transmission zero at around 4 GHz with attenuation level -34 dB near the passband. On the other hand, the proposed LPF has shown wide stopband bandwidth with rejection better than -20 dB from 3.5 GHz up to 11.5 GHz, while the size of the whole structure is smaller (20 mm x 20 mm). Finally, the proposed filter structure was fabricated and measured. The measurements are in a good agreement with the simulated results.
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