The Research Of Miniaturized Filter Based On Space Mapping

With the rapid development of wireless communication system,as the key component of the RF front-end,the filter is constantly improving to the direction of high-performance,low-cost and miniaturization.However the traditional Printed Circuit Board(PCB)can't meet the high frequency band(GHz)filter performance and miniaturization requirements.Low Temperature Co-fired Ceramic(LTCC)technology becomes the first choice for miniaturized filter design because of its miniaturization,high frequency and high Q characteristics.Aiming at the problems that the optimization direction is not clear and time consuming in the design process of LTCC filter,the space mapping algorithm provides a new optimization idea and design scheme,which can greatly reduce the quantity of the electromagnetic simulation calculation without affecting the accuracy,save design time,improve design efficiency.In this paper,during the design and optimization of LTCC filter,using the existing LTCC filter design method to design filters,while optimizing the space mapping algorithm to improve the efficiency of the algorithm,combined with different filters design and optimization to save a huge time and computing cost.Then the improved space mapping algorithm is used to optimize the designed LTCC filters,and finally the effectiveness of the algorithm is verified by the filter results.Firstly,the concepts and mathematical representations of space mapping algorithm are expatiated,and the explicit and implicit space mapping algorithms are introduced respectively according to the mapping relations between Coarse Model and Fine Model.Depending on the design requirements of LTCC filters,using the implicit space mapping algorithm is more appropriate.Then focusing on introducing the implicit space mapping algorithm,and using the implicit space mapping algorithm to optimize microstrip parallel coupled filter as example.In the design of LTCC multi-layer capacitor,the MIM(Metal-Insulator-Metal)capacitor structure and the VIC(Vertically-Interdigitated-Capacitor)capacitor structure are analyzed.The fine and coarse model of VIC capacitor are established in Advanced Design System(ADS)software and High Frequency Structure Simulator(HFSS)software,and the implicit space mapping algorithm is used to optimize the design.In the analysis of LTCC multi-layer inductor,the U-shaped three-dimensional spiral inductor fine model and coarse model are established,and the space mapping algorithm is used to optimize the design.In the filter design,the LTCC filter structures are established by previously capacitor and inductor model,then using the separate model in ADS software multi-layer circuit component library to establish the coarse model of LTCC filters and optimizing the designs with the space mapping algorithm.For the low pass filter with very low cut-off frequency,it is necessary to design a large equivalent inductor model,which is not conducive to miniaturization,and cannot be modeled in ADS(Advanced Design system)software to optimize with space mapping algorithm.In this paper,the innovative dielectric ceramic-ferrite ceramic-dielectric ceramic sandwich composite structure is used,the design of the equivalent inductance model in ferrite ceramic,while keeping the inductance unchanged,greatly reduce the size of the model to achieve the purpose of miniaturization.The inductors that cannot be modeled in the coarse model are simulated directly in the HFSS software.Combined with the capacitors designed by space mapping algorithm,designed two low pass filters with low cut-off frequency.For the next design of the low pass,bandpass and high pass three filters,the coarse models of the whole filters are modeled in the ADS software.Applying implicit space mapping algorithm to optimize the filters and improving the algorithm.Compared with the standard implicit space mapping algorithm,this paper improves the application of the algorithm such as the number of pre-selected parameters,parameter extraction,allowable maximum error and optimization weight,it can effectively reduce the false convergence in the traditional iterative optimization process.Reducing the number of iterations and getting results more efficient.Finally,five miniaturized LTCC filters are designed to verify the feasibility and effectiveness of the improved space mapping algorithm.