Design And Modeling For LTCC Microwave Filter

With the development of wireless communication technology, microwave passive devices are developing toward the direction of smaller, lighter,high-performance and low-cost. Most of the traditional process technology cannot meet the demand of the miniaturization of devices, while the low-temperature co-fired ceramic(LTCC) technology makes small and high-performance microwave passive components possible, because of its stack process and the layout way of three-dimensional. Microwave filters are an essential component in microwave system. Therefore, the research on miniaturization of filters is very important.This paper introduces the huge advantage of the LTCC compared with traditional process, which is based on LTCC technology, and then it have introduced the theory of filter design and set up two kinds of the buried inductors and buried capacitors respectively. And it extracts the valid values,quality factors and self resonant frequencies of the buried inductors and capacitors. Based on the analysis of microwave filters’ basic theory, this paper designs three types of filters.Firstly, the step-impedance low pass filter with the cut-off frequency of1.7GHz is designed. The simulation results show that the insertion loss in the pass-band is less than 2d B, and the suppression in the range of 2.1GHz to 6GHz is greater than 20 d B.Secondly, lumped LC type LTCC low pass filter with the same design requirements of step-impedance low pass filter is also designed. While, the overall size of lumped LC type LTCC low pass filter is only4.8mm′2.4mm′0.72 mm.Compared with the step-impedance low pass filter, the results show that the type lumped LC type LTCC low pass filter is more able to achieve the requirements of miniaturization and high performance, embodies the advantages of LTCC technology.Thirdly, this paper designs the lumped LC type band pass filter with center frequency of 2GHz, and bandwidth of 200 MHz. The simulation results show that the insertion loss in the pass-band of it is less than 2d B, and the suppressionin the range of 2.3GHz to 3GHz is greater than 30 d B. The overall size of it is4mm′1.62mm′0.995 mm.In a word, all of the microwave filters meet the design requirements well,and the lumped LC type filters achieve the goal of the miniaturization.