A binomially distributed photonic bandgap structure (PBGS) and its application to bandpass filter

Conventional hole-patterned photonic bandgap structures (PBGSs) yield distinct and wide stopband, but suffer from a significant ripples in the passband beyond the optimized filling factor (FF) of 0.25. Binomial distribution in PBGSs can yield improved performance beyond this value. The optimum FF of binomially distributed PBGSs has been ivestigated at multifrequencies in the X-band, namely, at 9, 10.5, and 12 GHz. It can be seen that 0.4 may be considered as the optimum FF for binomially distributed PBGSs at different frequencies within X-band operations. Finally, binomially PBGSs with this optimium FF are applied in a bandpass filter (BPF) for suppresing the intrinsic spurious harmonics of a BPF. The various experimental investigations reveal that the variation in number of PBG elements and their locations affect the performance of harmonic suppression. Binomially distributed PBGSs are found to be potential candidate to suppress the harmonic signal and to improve the return- and insertion-loss bandwidths.