Design And Implementation Of Filters Based On LTCC Technology For Spectrum Monitoring Device Receivers

As the electromagnetic environment changes,spectrum monitoring device has been used in more places and users have more urgent needs for small and portable devices.So the design of small passive filter which occupies large space in important component receiver is urgent.In comparison with commonly used cavity,micro-strip,LC and surface acoustic filter,LTCC(Low Temperature Co-fired Ceramic)has huge advantages in size and high levels of stability and integration.Based on above advantages,the design of this article realizes the pre-selection filter and intermediate frequency filter set of radio frequency monitoring device receiver based on LTCC technology.On the basis of combining the overall performances of radio frequency monitoring device receiver and technological characteristics of LTCC filter,getting the design objective requirements of LTCC pre-selection and intermediate frequency filters.Then getting the resonant frequency and coupling coefficient of filter resonant units through theoretical derivation with index requirements as its goal,making preliminary designs of the structure of filters through field-circuit combination method,making iterative operations of key parameters such as resonant frequency,of filter resonant units,unloaded Q value and coupling coefficient through simulation software ADS and HFSS,and finally getting the optimized filter structure.Pre-selection filters mainly use multilayer pectinate lines and straight-flanked ring structure.Through some innovative designs,such as W-shape pectinate resonator permutation,upgraded encapsulated structure and multilayer resonant ring alternate permutation,optimizing multiple parameters of filters.Intermediate frequency filters mainly use embedded LC circuit configuration in the form of lumped parameter.Researching the design method of nested embedded units and making structural innovations.On top of the above design work,making a set of PCB test fixture of LTCC filter.In the end building pre-selection filters with frequency of 3.9~4.9GHz,4.8~5.8GHz and 5.5~6.3GHz,and intermediate filters with frequency of 510~610MHz,DC~2GHz and DC~3GHz.Test results show that within pass-band range these filters can meet the design requirements in terms of insertion loss and standing-wave ratio.Generally speaking,in addition to slight differences in high-end out-of-band rejection of intermediate frequency low-pass filters,these filters show good performances and prominent advantages in terms of size.The results show the feasibility and engineering application value of design.