| Summary: | 博士 === 國立成功大學 === 微電子工程研究所碩博士班 === 100 === The dissertation is divided into three sections, comprising: (a) design and implementation of dual-band bandpass filter (BPF) by using ring-like stepped-impedance resonator (SIR); (b) design and implementation of ultra-wide-band (UWB) and tri-band bandpass filter (BPF) by using asymmetric SIR and (c) design and implementation of tri-band and quad-band BPFs by using stub-loaded SIR.
Firstly, the basic transmission line theory and the introduction of three kinds of SIRs are proposed. The analyses of the resonant behaviors of these three SIRs are well investigated.
Secondly, the ring-like SIR consists of a section with the impedance of Z1 and a ring section with the impedance of Z2 is proposed, where the Z2 is higher than Z1. The ring section of the proposed ring-like SIR can be interpreted as two open stubs, which have input impedances of Zin2’ and Zin2”, the electrical lengths of θ2’ and θ2”, respectively. As compared with the conventional SIR, the Zin2’ and Zin2” of these two stubs, seen from the parallel terminal, are equal to the section with impedance of Z2 (Z2 = Zin2’// Zin2”), and the summation of electrical lengths of θ2’ and θ2” are equal to the electrical length of the section with impedance of Z2 of (θ2=θ2’+θ2”) while in parallel. Therefore, a dual-band BPF are design by using the ring-like SIR and embedded coupled open stubs for application to a wireless local area network (WLAN), 2.4 GHz and 5.2 GHz. The center frequencies of the dual-passbands are created by optimally selecting the impedance ratio (K) and the length ratio (u) in the resonant behavior of a conventional SIR. Without increasing the circuit size, the performance of the second passband can be enhanced by adding the coupled open stubs in the ring-like SIR. Experimental results show good agreement with the simulated results.
Thirdly, the asymmetric SIR with only one discontinuity as compared with the conventional SIR which has two discontinuity in construction is further proposed, that is, it composed by a high-impedance section (Z1, θ1) and a low-impedance (Z2, θ2), By properly selecting the length ratio (u), defined as u= θ2/(θ1+θ2), and the impedance ratio (R), defined as R=Z2/Z1, of the asymmetric SIRs, the resonant behaviors of the asymmetric SIRs can be determined. The resonant behaviors provide a design guideline for the multi-band BPFs design. Therefore, there are a UWB BPF and two tri-band BPFs proposed in this section. First, we propose a simple method and structure to design a high selectivity and wide stopband UWB filter by only one asymmetric SIR with split-end. The transmission poles for the generation of passband and the transmission zeros for the suppressing of spurious are well investigated. Second, a tri-band BPF located at 1.8 / 3.5 / 5.2 GHz for applications of Global System for Mobile Communications (GSM), Worldwide Interoperability for Microwave Access (WiMAX) and WLAN. The tri-band BPF comprises a pair of split-end asymmetric SIRs and a pair of impedance transformers as the tapped feedline structure. Moreover, in order to verify the asymmetric SIR can be applied to various communication standards, a tri-band BPF with two narrow passbands and UWB responses are proposed. The tri-band comprises two pairs of coupled asymmetric SIRs and a direct coupled feedline structure. The three passbands are designed for GSM and WiMAX and a wide passband at UWB system from 3.3 GHz to 4.8 GHz. The measured results of abovementioned three tri-band filters are all with good agreement with the simulations.
Finally, the stub-loaded SIR, composed of a convention SIR with two discontinuities and a stub-loaded section located on the symmetric plane of the convention SIR, is proposed. The impedance and electrical length of the stub-loaded section are expressed as Zs and θs, respectively. By properly selecting the length ratio (α), defined as α= 2θ2/2(θ1+θ2), and the length ratio (r), defined as r=θS/(θ1+θ2), the resonant behavior of the stub-loaded SIR can be determined. Therefore, a tri-band BPF designed at 1.575 GHz, 2.4 GHz and 3.5 GHz and a quad-band BPF designed at 1.7 GHz, 1.9 GHz 3.5 GHz and 5.5 GHz, are proposed. The tri-band BPF comprises a pair of coupled stub-loaded SIR and a 0o feedline structure which results in high selectivity of the passbands. The quad-band BPF comprises a pair of interdigital coupled stub-loaded SIR and tapped coupling, which provides seven transmission zeros aside the passband. Experimental results show good agreement with the simulated results.
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