High-Q whispering gallery mode resonator filter with photonic bandgap spurious mode suppression

We demonstrate a novel bandpass filter constructed with a dielectric resonator operating in a whispering-gallery mode and a pair of photonic bandgap structured microstrip lines. The photonic bandgap structure is used to suppress the spurious modes around an intended transmission peak. The fabricated filter has a center frequency of 13.7 GHz, a Q of 2.000, an insertion loss of 7 dB and a spurious-mode suppression of 30 dB.