Research Of The Coaxial Dielectric Filter Based On The Separate Resonators

According to the development of mobile communication, demands to the device become more and more rigorous. There are almost dielectric filters in the mobile communication system nowadays. Because of the perfect performance and widely use in the future, we do some research on the transmission line dielectric filters based on the separate coaxial resonators.We introduce some survey of the dielectric ceramic material and dielectric filters, at the same time we illustrate the design theory of dielectric filter in detail. In the real process of design, we use HFSS to simulate the structure of the filter, and find the relationship between the structure and performance: the center frequency is in inverse proportion to the length of the resonator; the input resistance and the output resistance is in inverse proportion to the width of the microstrip; as the radius of the hole in the resonator increases, the thickness of the coupling capacitance increases and the length of coupling inductance decreases, the coupling among the resonators is reduced, which will lead the decrease of the bandwidth, the shift of the center frequency and the improvement of the attenuation. After the optimization by the HFSS, we use the conventional process to make dielectric resonators which are used to assemble the filter sample, and then debug the samples with Network analyzer.The performance of the final sample is: center frequency f0=1.011 GHz; 3 dB bandwidth BW=12 MHz; Insert Loss IL=3 dB; passband ripple LAr<0.5 dB; Attenuation Ls≥20 dB(f0±30 MHz). Finally we make some suggestion to improve the Insert Loss in material, structure and process, which will guide the future work.