Study Of Miniaturized Bandpass Filter Based On LTCC Technology

Low Temperature co-fired Ceramic(LTCC,Low Temperature Co-fired Ceramic),as a new type of packaging technology,can be used to bury many kinds of passive circuit components in the ceramic substrate,and can achieve high integration of microwave modules with active components.Due to its high integration and high frequency characteristics,LTCC technology is widely applied in many fields such as military and mobile communications.As the indispensable frequency selection device in the wireless communication system,the performance of band-pass filter directly affects the whole communication system,the study of its miniaturization has very important significance.The study of this paper aims at the miniaturization of band-pass filter,and present some miniaturized filters design based on LTCC technology.superior performance of miniaturized bandpass filter.The main contents of the concrete work are as follows:(1)This paper introduces the research status of the miniaturization technology of microwave filter,summarizes the basic theory of microwave filter and the design method of LTCC filter,which laid the theoretical foundation for the study of new filter later.(2)Based on mixed coupling,the LTCC band pass filter with multiple transmission zeros is studied.The filter adopts two symmetrical?/4 SIR(Stepped Impedance Resonators).By introducing magnetic coupling and electric coupling between high and low impedance line of the two SIR respectively,the mixed coupling is introduced.There are many transmission zeros are produced in the stopband of the filter.This paper gives the lumped parameter model of filter,and analyzed the mechanism of transmission zeroes of mixing coupling.The final physical size of the filter is 2.4×2.6×0.8 mm~3.(3)Based on lumped parameter method of LTCC filter,the VHF band of ultra-low frequency band pass filter is studied.Due to the low frequency and large wavelength,it is difficult to realize the miniaturization of VHF bandpass filter with the traditional method.This paper present the two miniaturized bandpass filters which use high dielectric constant material with LTCC technology.One is designed by the material of dielectric constant of40,the other is designed by the material of relative dielectric constant of 96.Both of two have high frequency selectivity and widely stopband suppression characteristics.The circuit size of the filters is 5.2×3.2×1.6 mm~3 and 4.5×1.6×1.6 mm~3.