Research On Miniaturized Microwave Filter Based On Dielectric Resonator

In recent years,the rapid development of mobile communication,the arrival of5G commercial era to promote the development of microwave devices miniaturization.As the core component of RF front-end,filter plays a very key role in signal processing.Therefore,miniaturized and high-performance filter has always been a research hotspot in the field of wireless communication.In this context,a high Dielectric constant Dielectric Resonator（DR）is an important means of realizing miniaturized filters.In this thesis,three high-performance Bandpass filters（BPF）are implemented based on the working principle of dielectric resonators and the modern comprehensive theory of filters.The details are as follows:（1）This thesis designs a miniaturized,low-loss millimeter wave band-pass filter based on TM_01δmode dielectric resonators.Cylindrical dielectric resonators use materials with high dielectric constant（typical value 35-90）to facilitate miniaturization.The resonators are arranged in a straight line inside the metal cavity to optimize the coupling coefficient between resonators at all levels.Multilevel coupling is used to achieve a wide passband.Based on the resonator structure and coupling mode,the third,fifth and seventh order bandpass filters are designed,and the seventh order dielectric filters are processed and tested.The test results show that when the center frequency of the filter is 27.0GHz and the width of the passband is6.0GHz,the return loss in the passband is better than-18.0d B.（2）Based on the embedded dielectric resonator structure,a LTCC（Low Temperature Co-fired Ceramic）band-pass filter is designed in this thesis.The filter consists of multiple layers of media and metal planes,and a cylindrical dielectric resonator with high dielectric constant is embedded in the LTCC dielectric cavity.The input/output（I/O）is coupled by the Co-Planar Wave Guide（CPW）structure through the slit to the dielectric resonator.The I/O electromagnetic coupling generates two transmission zeros in the upper and lower sideband of the filter,and the filter has a good selection characteristic.The three-dimensional integration of multilayer media and the high dielectric constant resonator make the filter size only 8.9×8.9×1.7mm3.Simulation and measurement show that the center frequency of the filter is 35.0 GHz,the relative bandwidth is about 7.0%,the insertion loss is-1.25 d B,and the return loss in the passband is-15.0 d B.Filter has the advantages of high selectivity,wide bandwidth,low profile and small size,so it has high application value in 5G communication system.（3）A dielectric resonator filter is designed by using dielectric dual-mode technology,and a dielectric disk is installed in the metal cavity with both ends grounded.A dielectric resonator working in a pair of TM11 degenerate modes is realized.The resonant frequency in this mode is 7.0 GHz by means of eigenmode analysis.The resonator is cascaded to achieve a bandwidth of 100 MHz,and the Windows are opened between the resonators and the axial metal screws are installed to achieve magnetic coupling.The optimal input/output structure size is obtained by comparing the group delay simulation curve with the metal probe excitation.Finally,a medium filter with small volume and excellent out-of-band suppression ability is realized.The center frequency of the passband is 7.0 GHz,the bandwidth is 100 MHz,and the in-band return loss is about-15.0 d B.The thesis has 68 figures,8 tables and 81 references.