Design Of Multilayer Chip LC Bandpass Filter Based On LTCC Technology

With the development of modern communication technology and the pressing demandfor miniaturization, modularization of RF and microwave divices, design of LTCC filterhas been one of the research hotspots in recent years. The main work of this paper is theresearch into multilayer chip LC bandpass filter based on LTCC technology.Firstly, LTCC embedded inductors and capacitors are designed by a full-waveelectromagnetic simulation tool （High Frequency Structure Simulator, HFSS）. Then somevaluable conclusions are obtained which contributes to design of the LTCC filter, after theplanar spiral inductor, helical inductor and vertically interdigitated capacitor （VIC） aresimulated and analyzed respectively by HFSS. Finally, this paper elaborates design,modeling and analysis of a modified LTCC multilayer LC bandpass filter with threecontrollable transmission zeros by utilizing a feedback capacitor and a grounded inductor.The two-dimensional （2-D） circuit model of the filter and three-dimensional （3-D） layout ofeach layer are disclosed as well. Effects of some key parameters on characteristics of thefilter are investigated. Influences of parasitic effects of vias, filled with metallic paste in themultilayer structure, upon the equivalent circuit are analyzed. The corresponding circuitmodel of the3-D multilayer structure is revealed. And that leads to the design of partlyasymmetrical layout for the filter.The overall size of the LTCC filter is4×2.5×0.653mm³, based on the selection ofFerro A6M-E material system. The center frequency is located at2.45GHz, and threetransmission zeros are at the frequencies of1.9,2.7, and3.86GHz, respectively. Theinsertion loss of the passband between2.285-2.615GHz （the true application is2.4-2.483GHz） is less than2dB, and the return loss is greater than20dB. The properties of the filtere.g. insertion loss, return loss, the slopes of the passband skirt, stop-band attenuation areimproved, which can meet the practical requirements better, compared with the mentionedsecond-order LC bandpass filter in many papers. Good agreement between the expectedand simulation results is observed. This proves that the detailed analysis of the circuitmodel and the parasitic effects in3-D configuration is indispensable and valid, and that the3-D configuration of the filter including the asymmetrical design of Lrand Lr₁is effective.