| Summary: | 碩士 === 國立彰化師範大學 === 電子工程學系 === 98 === In this thesis, balanced bandpass filters (BPFs) design using ring resonators were studied. The operating characteristics of ring resonators and the whole balanced BPFs were analyzed, which would serve as the mathematical and theoretical bases of this research.
The first balanced BPF examined in this thesis is a single-band one that uses two uniform ring resonators as its key resonant elements. To obtain the required differential-mode (DM) operation and common-mode (CM) suppression, the two ring resonators are designed to have the same odd-mode but different even-mode resonant frequencies. The separation of the even-mode resonant frequencies of the two resonators in CM operation results from loading at the center of one of the ring resonators a T-shape open stub.
In the second balanced filter design, a second-order dualband BPF using two stepped-impedance ring resonators (SIRRs) is proposed. For practical application consideration, the two passbands are designed at the WLAN 2.45-GHz and 5.25-GHz bands. Similarly, the two SSIRs are designed to have the same odd-mode but different even-mode resonant frequencies to obtain the designated DM operation and to reject CM signals. Separation of the even-mode resonant frequencies of the two SIRRs in CM operation can also be achieved by loading at the center of one of the SIRR an open stub to make the electric length longer.
Prototype circuits of the proposed balanced BPFs are fabricated and measured. Good performances were observed and the simulated and measured results are seen to agree very well with each other. Results show that the minimum insertion loss is less than 2 dB in the passband(s) when operated differentially and 22 dB for CM operation within 1 - 8 GHz frequency range for both of the proposed single-band and dualband balanced BPFs.
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