The Research Of Band-pass Filters With Narrow Bandwidth Based On LTCC Technology

The main research content of this thesis is about the filter which is one of key passive microwave components. A low-pass filter and two narrow bandwidth band-pass filters with different 3D structures based on the multi-layer structure of LTCC technology are presented in this thesis.The characteristics of material and the typical manufacturing process in LTCC technology are described in this thesis. The 3D structure of the basic circuit components including inductance and capacitance based on LTCC technology, the parameters extraction from the different circuit models and the comparison after full-wave electromagnetic (EM) simulation and circuit simulation are described later in the thesis. A low-pass filter whose cutoff frequency is 3.4GHz is designed using the basic inductances and capacitances mode. Simulation results show that the minimum return loss is 15dB and the maximum insertion loss is to 0.67dB in the pass band. And its size is only 3.2mm×1.6mm×1mmTwo different kinds of narrow bandwidth band-pass filters whose centre frequencies are 3.4GHz and 2.4 GHz are presented by the methods of insertion and the equivalent transformation. The filters'performance has improved by taking advantage of the coupling effect between the components. Among them, the band-pass filter whose center frequency is 3.4GHz and relative bandwidth is 5.9%, the return loss is 28.79dB and the insertion loss is 1.23dB in the center frequency of 3.4GHz, the insertion loss is more than 30dB out of the passband at 2.8GHz and 4.0GHz. And the size of the filter is only 3.8mm×2.8mm×0.8mm; the other filter whose center frequency is 2.4GHz band-pass and the relative bandwidth is 10.4%, the insertion loss is 1.45dB and the return loss the 23dB in the center frequency of 2.4GHz, and the insertion loss is 35dB and 40dB out of the passband at 2.0 GHz and 2.8GHz respectively. And the size of the filter is only 3mm×2mm×1mm.The characteristics of filters which are designed in this thesis are small size, high performance and meet the requirements of practical applications.