Tham khảo tài liệu 'three-dimensional integration and modeling part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CAVITY-TYPE INTEGRATED PASSIVES 61 FIGURE External quality factor Qext evaluated as a function of external slot length El- Transmission Zero. In this section the dual-mode filter realization with transmission zeros for high selectivity will be discussed. The equivalent circuit model of the proposed dual-mode cavity filter is shown in Fig. a . The filter consists of major four sections 1 a pair of LC resonators that represent each of the degenerate dual modes in the cavity resonator 2 mutual internal electric coupling M between a pair of parallel LC resonators 3 external magnetic coupling Lext from each of the I O external slots and 4 magnetic cross coupling Lc representing the parasitic source to load coupling associated with the perturbed electric fields in the cavity 84 . A pair of transmission zeros at the upper and lower sides of the passband can be created when Lc has a 180 phase difference with respect to M with similar magnitudes. This sign reversal is attributed to a destructive interference between two modes therefore resulting in the construction of transmission zeros at two frequencies. The fundamental cross coupling technique is well explained in 85 by using multipath coupling diagrams to illustrate the relative phase shifts of multiple single paths. In 85 Brian adopted the S21 phase shift 21 of each lumped element in the equivalent circuits of a resonator and calculated the total phase shift at the input or output of the resonator to predict the behavior of transmission zeros. Since transmission zeros appear away from the passband the off-resonance behavior of each lumped component is of concern. Based on Brian s theory the equivalent circuit for a dual-mode cavity filter can be represented by a multipath diagram as described in Fig. b . The shunt capacitor inductor pairs of the equivalent circuit have been replaced by the black circles and M 62 THREE-DIMENSIONAL INTEGRATION Lc port 1 Lext b port 2 Lext M FIGURE .
