Theoretical Study And Optimal Design On Rf Mems Filter Based On Cpw Defect Structures

Because the features of RF MEMS filter, such as the highly integrated, low loss, small size, excellent linearity and frequency adjustment, RF MEMS filter become the research focus in the world. The paper studied the basic knowledge and design methods of shunt capacitive RF MEMS switch first, including symmetry load and asymmetry load structures of MEMS switch model. It designed three kinds of "no pull-down" MEMS switch, achieved the extraction of MEMS capacitance using the micro-strip characteristic impedance method, and proposed a MEMS structure model with high isolation and low drive voltage. The coplanar waveguide transmission line was widely used in RF MEMS filter to reduce the parasitic effect of parameters, since the signal line and ground in a planar. The paper studied the equivalent capacitance and characteristic impedance of CPW defect structures based on conformal transformation, including the defect structure in CPW ground and CPW signal line. It designed three kinds structure model of band-stop filter, proposed a design method of band-stop filter based on characteristic impedance of defect CPW structure, studied the equivalent circuit of the filter, on this basis, It designed the tunable band-stop MEMS filter model using defect ground in CPW structure, analyzed frequency feature and MEMS switch structure of filter unit, studied the equivalent circuit and adjustable principle of MEMS switch in the tunable filter, and then analyzed the fabrication, test and test error of MEMS switch, proposed the method of error correction and so on.The paper studied the MEMS filter using defect structure in signal line of CPW, including tunable band-pass filter, tunable band-stop filter and tunable low-pass filter. The paper also analyzed the single MEMS switch for achieving two stage tunable filter model, the equivalent circuit and adjustable method of symmetry load MEMS switch in the filter was analyzed and studied. It achieved the adjustment of filter band, center frequency and the conversion with pass and band-stop filter by revising the slots in signal line. It used the signal line slot and MEMS switch to design the tunable low-pass filter. The slot structure of this kind filter was studied, and the filter equivalent circuit was extracted by using conformal transformation.The fabrication and test of filter in this paper were analyzed and studied, including non-tunable filter and tunable MEMS filter. It analyzed the process of fabrication, designed the filter MASKs, and complete the filter test. The paper also analyzed the fall of MEMS switch, and proposed the related solution.The main innovation in this paper:1. Design three kinds "no-pull down" MEMS switch and a kind High isolation low drive voltage MEMS switch. It used micro-strip characteristic impedance method to achieve the equivalent capacitance extraction of the MEMS switch and applied a double integral to obtain the elasticity coefficient extraction of asymmetric loading MEMS switch. Proposed the calculate method of capacitance and characteristic impedance of defect CPW structure, achieved the method support of designing the filter using such characteristic impedance.(Chapter two and three)2. Proposed a method to design band-stop filter using defect CPW ground based on the CPW characteristic impedance. The method achieve the conversion of band-stop filters from lumped parameter to the distributed CPW band-stop filter, which provide away to design the CPW filter.(Chapter four)3. Design a hybrid resonator based on defect CPW ground and MEMS switch, the resonator can usefully reduce the unit volume. It also establish the mathematical model of the nonlinear relationship between the height variation of MEMS switches and the resonant frequency, which is used to analyze the relationship among the drive voltage, height, and resonator frequency of MEMS switch.(Chapter four)4. Design the band pass tunable filter structure model based on a single MEMS switch, which can reduce the filter size, the stability and synchronous, adjustable range of up to30%.(Chapter five)...