Research On Split-ring Resonator For Filter And Antenna Applications

With ever-increasing demands for microwave communication systems, the wireless communicationdevices and ends with low loss, sharp transition, strong anti-interference capabilities and compact sizeare highly desired. The components including filter and antenna plays an important role in the part ofRF front end. It’s a always goal for researchers to improve these functions of microwave apparatus.The split-ring resonator (SRR) has attracted extensive attention of researchers for its novel properties.Utilizing these properties, various exotic circuits have been presented and improved. In thisdissertation, the SRR provides a particular interest, specifically for its resonant behaviors. Since theSRR can be considered as an electronically small resonator with very high Q-value, it is a very usefulstructure in constructing microwave apparatus with compact size. In this work, several kinds of theresonators based on SRR and coupling structure are presented, and different apparatus with improvedproperties are designed from the application of these resonators.The main innovations of this dissertation are as follows:1. A high selectivity quadruple-mode broadband bandpass filter (BPF) with source-load coupling isproposed using two different sizes short stub loaded stepped-impedance resonators (SIR). Two SIRscan generate four operating modes, which can be approximately adjusted individually. Owing to thespecial designs of the filter, the coupling of two resonators is weak. In each resonator, the even-modefrequency can be flexibly controlled by changing the length of the short stub in central plane, whereasthe odd-mode one remains stationary. Due to the source-load coupling, two transmission zeros areclose to the cut-off frequencies of the passband, which leads to high selectivity.2. A novel miniaturized split ring resonator (SRR) structure is introduced in designing highfrequency selectivity and stopband expanded BPF with four transmission zeros. Such fundamentalresonators consist of a pair of half-wavelength hairpin-shaped ring resonators nested in each other,which improved SRR structure. Compared with conventional SRR, this stepped impedance split ringresonator (SISRR) has better performance on miniaturization. To verify good characteristics of thenovel structure, a new resonator-embedded cross-coupled filter which is constructed by a pair of newresonators, is proposed.This novel filter is very compact and has high frequency selectivity.3. In order to provide sufficient degrees of freedom for achieving wideband of the couping filter, anovel SRR loaded interdigitail capacitor is proposed. Some coupling filters with good characteristics are designed using these resonators. Furthermore，a novel planar diplexer is developed based onsplit-ring resonators (SRRs). The proposed diplexer is comprised of three SRR, which have differentcouping style. This diplexer shows advantages in terms of the compact size, low loss, easy fabricationand integration with other circuits.4. A miniaturized CSR2is presented to improve the effect of the notch frequency for the proposedantenna and filter. Compared with CSRR, the CSR2can excite a lower central frequency resonance,when they have the same dimensions. Due to this miniaturized characteristic, the antenna can loadmultiple CSR2unit cells which generate multiple corresponding resonant modes to control the notchbandwidth and improve high frequency selectivity at the rejection frequency. Moreover, it is veryconvenient to etch SR2s slot in UWB device for band-notched. What’more, a miniaturized substrateintegrated waveguide (SIW) filter is proposed using a complementary spiral resonator (CSR). CSRtechnique can be applied to the design of miniaturized filter by increasing electrical length. Todemonstrate the idea, the miniaturized SIW filter is designed with CSR2and CSR3, respectively. Themeasured central resonant frequencies are3.25GHz and2.23GHz, which are lower than the SIW filterwith CSRR occurs at5.17GHz.5. A novel dual-band circularly-polarized microstrip antenna is proposed. The designs are based onthe complementary two turns spiral resonator (CSR2). They are the counterparts of two turns spiralresonators (SR2s), which were introduced in2004by some of the authors. CSR2s technique can beapplied to the design of miniaturized antenna by increasing electrical length. To demonstrate the idea,the proposed circularly-polarized antenna is designed to work at658MHz and2.74GHz. The gaporientation asymmetric or symmetric to the current propagating direction will render the antenna toradiate circular polarization (CP) waves with the CSR2etched on the antenna. Details of theexperimental results compared with the simulated results are presented and discussed.