EBG-based dual mode resonator filter

Periodic etched pattern on the ground plane underneath the ring resonator are incorporated to realize a miniaturized ring filter with stronger rejection of higher harmonic passbands. Two square microstrip ring filters, with and without periodic etched pattern on the ground plane, were designed with a bandwidth of 135 MHz centered at 2.4 GHz and 3 GHz respectively. A rejection of at least 25 dB of the second harmonic passband has been achieved for the filter with periodic etched pattern.