Design of Balanced Dual-Band Bandpass Filter with parallel Coupled lines

• Main Authors: I-Chin Wang, 王怡今
• Other Authors: Ching-Her Lee
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/02698318548046803750

碩士 === 國立彰化師範大學 === 電信工程研究所 === 97 === In this thesis, balanced dual-band bandpass filters (BPFs) designed using coupled stepped-impedance resonators (SIRs) are studied. Two balanced dual-band BPFs with suppressed common-mode (CM) transmission are proposed. The first balanced dual-band BPF consists of four coupled bi-section half-wavelength (λ/2) SIRs. To obtain the required differential-mode (DM) operation with a high CM rejection level, these SIRs should have the same odd-mode, but different even-mode, resonant frequencies. For that purpose, the two inner SIRs are loaded at the center with T-shaped open stubs of different dimensions so that their even-mode resonant frequencies are shifted away form those of the outer SIRs. The second balanced BPF proposed in this thesis is a simple fourth-order balanced dual-band BPF having a high CM rejection level. It consists of six conventional equal-electric-length (EEL) bi-section SIRs. These SIRs can very easily be designed using analytic formulas. The inner SIRs are designed to resonate only at the odd-mode resonant frequencies of the outer. Results obtained in this research can be applied to commercially practical WLAN systems. The techniques presented in this research are expected to serve as a useful reference for microwave filter designers in this and related research fields.