| As a key device in wireless communication system,filter plays an important role in frequency selection.It is one of the key research points of the fifth generation(5G)millimeter wave communication technology.With the rapid development of wireless communication technology,there are more and more frequency bands.The filter needs to have very high out of band suppression to avoid signal interference between the target passband and other frequency bands.Therefore,high selectivity is one of the difficulties in the design of millimeter wave filter.At the same time,5G wireless communication will adopt large-scale multiple input multiple output(MIMO)system,and the demand for the number of filters by mobile terminals will increase sharply.In addition,due to the development trend of terminal equipment towards micro modularization,it has higher requirements for chip size.Therefore,miniaturization is another difficulty of millimeter wave filters.According to the application characteristics and index requirements of 5G millimeter wave wireless communication,this paper designs three high suppression miniaturized millimeter wave broadband filters.The main work and innovations are as follows:(1)The process of new glass substrate integrated passive device(IPD)and the modeling method of planar capacitance and inductance are systematically studied.A two-dimensional lumped bandpass filter with multiple transmission zeros is proposed.The generation mechanism of transmission zeros and the influence of each element on the frequency response of the filter are analyzed from the perspective of circuit.The simulation results show that the passband frequency of the two-dimensional lumped filter is 26.5GHz-29.5GHz,the in band insertion loss is less than2.6d B,the low-frequency out of band suppression is greater than-50 d B,the high-frequency out of band suppression is greater than-27 d B,and the filter size is 700um×500um。(2)In order to further realize the miniaturization and compactness of the filter,a high suppression miniaturized three-dimensional bandpass filter with a center frequency of 28 GHz designed by through glass via(TGV)technology is proposed.Through the simulation results,the influence of the technical parameters of TGV inductor on the performance of the inductor is analyzed.The simulation results show that the insertion loss in passband of the three-dimensional filter is less than 2.3d B,the flatness in 3GHz bandwidth is 0.46 d B,the low-frequency out of band suppression is greater than-55 d B,the high-frequency out of band suppression is greater than-34 d B,and the size of the filter is only 600um×400um。(3)In order to further enhance the out of band suppression performance of the filter,a high suppression broadband bandpass filter with working frequency band of 24.25GHz-27.5GHz is designed based on hairpin resonator.By adjusting the structure of the resonator,a new transmission zero is introduced to avoid the signal interference between adjacent frequency bands and increase the frequency selectivity.The bandwidth of the hairpin filter is 3.25 GHz,the insertion loss in the passband is less than 3.0d B,the return loss is more than 15 d B,and the out of band suppression of high frequency is greater than-38 d B.In this paper,a broadband IPD filter based on the glass substrate is designed.Its performance index meets the requirements of 5G millimeter wave communication for high selectivity and miniaturized broadband filter,and has certain academic research value and engineering practical significance for promoting the development of 5G millimeter wave communication technology. |
