A novel photonic bandgap structure for low-pass filter of wide stopband

In this letter, a novel photonic bandgap (PBG) structure is proposed for in creasing the stopband of a low-pass biter without the increasing circit siz e for applications in microstrip circuits. The proposed structure is connec ted in parallel two periodic structures which have different center frequen cy of the stopband. The wide stopband is achieved by two periodic structure s of two different stopbands. We also show the performance improvement of m icrostrip patch antenna by etching of the proposed structure in ground plan e.