Optimum filling factor and performance of a transmission line at X-band perturbed by binomially distributed photonic bandgap (PBG) structure

Conventional hole patterned PBG structures yield distinct and wider stopband but it suffers from significant ripples in the passband beyond the optimized filling factor or 0.25. Binomial distribution in the amplitude of circular PBGs yields improved performance beyond this value. The optimum filling factor (FF) for binomially distributed circular PBGs at X-band namely at 9, 10.5 and 12 GHz has been reported. From the S-parameters performances of the microstrip line over circular PBGs with this distribution the frequency dependance of S-parameter performance is also investigated. It can be seen from the S-parameter performances that 0.4 may be considered as the approximate value of optimum FF and precisely 0.45, 0.47 and 0.5 may be considered as the optimum FF at 9, 10.5 and 12 GHz respectively. The performances can be seen to vary with the variation of the central stopband frequencies.