New High-performance Miniaturized Filter Design

With the rapid development of modern wireless communication and people's need for multiple kinds of communication modes, the design of filters with high performance, low cost, compact size, and design flexibility has drawn much attention. In this dissertation, the planar coupled-scheme using the stepped impedance resonator (SIR) is employed to design the single- and dual-band bandpass filters. Besides, the broadside-coupled microstrip/CPW structure is introduced to implement ultra-wideband (UWB) bandpass filter. These filters have the merits of high performance and compact size. The research fields of this dissertation are listed as follow:First, the characteristics of the half wavelength (λ/2) SIR are investigated in detail, including the resonant condition, the relationship between spurious frequency and the impedance radio, and the relationship between the normalized SIR length and electrical length of the high impedance.Secondly, the combination of coupled structure using the SIR and uniform impedance resonator (UIR) is investigated for bandpass filter design with wide stopband, compact size, low cost, and design flexibility.Thirdly, a novel coupling scheme is introduced to suppress stopband spurious in hexagonal SIR filter design. With proper coupled scheme using the proposed resonators, a narrow-band bandpass filter is achieved with good stopband spurious suppression and compact size.Fourthly, a dual-mode resonator based on SIR with open stub is investigated. The transmission line model of the dual-mode resonator is discussed in detail. Meanwhile, the effect of the tap position on external quality of the resonator is investigated. The two passbands of the bandpass filter based on the dual-mode resonator can be relatively independent adjusted. The proposed filter has the merits of strong passband selectivity, miniaturized size, and good stopband rejection level.Fifthly, an ultra-wideband (UWB) bandpass filter using broad-band coupled microstrip/coplanar waveguide (CPW) structure is introduced. The proposed filter has compact size and good passband/stopband response. Finally, a conclusion for the dissertation is given and the further research work is prospected.