Research And Design Of RF MEMS Coplanar Waveguide Fliter Based On SIR And Spiral Structre

With the development of communication technology, the resource of the low end frequency spectrum becomes more and more tense, but the available frequency band of the high end frequency spectrum is much abundant. At the same time, the new generation wireless communication system 5G matures gradually, the working frequency bands of the communication systems will gradually develop to millimeter wave and even higher frequency. So the communication equipment will tend to miniaturize. RF MEMS (radio frequency microelectronic mechanical systems) is involved with microelectronic, machinery, material and other disciplines and has a great advantage to achieve the kind of devices. The microwave filter, including tunable and non-tunable, is a kind of component for suppressing noise and achieving frequency selection, so it has very important applications, In this thesis, the non-tunable and the tunable band-stop filters with wide stopband are studied.In the thesis, Firstly, the characteristic impedance of microwave transmission line, especially coplanar waveguide transmission line, is studied. Then the basic design method of classical filter is introduced. On the basis of transmission line theory, the structures of CPW-SIR(Coplanar Waveguide Step Impedance Resonator), CPW-DGS (Coplanar Waveguide Defect Ground Structure) and CPW-Spiral (Coplanar Waveguide Spiral) are studied and two new structures including CPW-SIR-DGS and CPW-SIR-Spiral are proposed. Both new structures have wide stopband characteristic. Finally, a new kind of miniaturization bandstop filter with wide stopband is designed by using CPW-SIR-Spiral structure and cascade method. The filter is not only cascaded less, but also has excellent RF performance, including the maximum stop band rejection of -45dB, the band of 7.5GHz under -30dB of stop band rejection, the rectangular coefficient of 0.84. In the fourth paragraph, the electronic and mechanical characteristics of RF MEMS switch are introduced. The structures based on CPW, including single spiral, double spirals or hybrid spirals, are proposed. They have one, two and three resonator frequencies, respectively. For the hybrid spirals filter, the band is 7.54GHz under -15dB of stop band rejection and the rectangular coefficient is 0.88. Then the tunable filters are designed by using RF MEMS switches and the proposed structures. The tunable filter of the hybrid spirals filter maintains an excellent frequency selectivity. Finally,the work of the paper is summarized and the future work is forecasted.The main achievements of this thesis are as follows:1. Proposing a novel CPW-SIR-Spiral structure with multiple resonator and excellent frequency selectivity. By using the structure and cascade design method, the wide stopband filter with multi-resonance point is achieved.2. Proposing a hybrid spiral structure with wide stopband based on CPW. A tunable band-stop filter with three resonance point is designed by loading RF MEMS switches.