Tham khảo tài liệu 'three-dimensional integration and modeling part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | MICROSTRIP-TYPE INTEGRATED FILTERS 31 FIGURE a External quality factor Qext evaluated as a function of overlap distance Lover b Coupling coefficient k12 as a function of coupling spacing d12 between 1st resonator and 2nd resonator. Figure a shows the Qext evaluated as a function of overlap distance Lover . A larger Lover results in a stronger input output coupling and smaller Qext. Then the required kj is obtained against the variation of distance dj in Fig. a for a fixed Qext at the input output ports. Fullwave simulation was also employed to find two characteristic frequencies fp1 fp2 that represent 32 THREE-DIMENSIONAL INTEGRATION Frequency GHz FIGURE Measured and simulated S-parameters of three-pole slotted patch bandpass filter. resonant frequencies of the coupled structure when an electrical wall or a magnetic wall respectively was inserted in the symmetrical plane of the coupled structure 63 . Characteristic frequencies were associated with the coupling between resonators as follows k fp2 fp1 fp2 fl 4 . The coupling spacing d12 in Fig. a between the first and second resonators for the required k12 was determined from Fig. b . k23 and d23 are determined in the same way as k12 and d12 since the investigated filter is symmetrical around its center. Figure shows the comparison of the simulated and the measured S-parameters of the three-pole slotted patch filter. Good correlation is observed and the filter exhibits an insertion loss dB the return loss dB over passband and the 3-dB bandwidth about at center frequency GHz. The selectivity on the high side of the passband is better than the EM simulation because an inherent attenuation pole occurs at the upper side. The latter is due to the fact that the space between fabricated nonadjacent resonators might be smaller than that in simulation so that stronger cross coupling might occur. In addition the measured insertion loss is slightly higher than the theoretical .
