Design Of Filtering Power Divider Based On Substrate Integrated Suspended Line

With the development trend of multi-function and miniaturization of modern wireless communication systems,the performance requirements of passive devices are becoming more and more important.Filters and power dividers are two important devices of a wireless system,usually appearing in a cascading manner in the system circuit,which leads to large size and loss of the entire system.Therefore,the integrated circuit is designed by combining the filter and the power divider,and a filtering power divider with frequency selection and power distribution can realize the problem of loss and large volume of the circuit system.This is very important to development of the wireless communication system.At the same time,the transmission line structure used in the design of passive devices directly affects the performance of the entire device.At present,the design of the filtering power divider is mostly made by microstrip line structure,so it is necessary to introduce a new transmission line design technology to enhance its various performance parameters.Substrate Integrated Suspension Line(SISL)is a new type of transmission line based on multi-layer structure.It incorporates the advantages of high Q value and low loss of traditional suspension lines,and it solves the defects of traditional suspension line,such as large volume,difficult machining and disadvantageous to integration.and has a self-packaging structure and good shielding characteristics.Based on the new transmission line SISL design platform,this paper studies the single pass band,double pass band and wideband filtering power divider.The main contents are as follows:Firstly,based on the design theory of the filtering power divider,the quarter-wave impedance converter of traditional Wilkinson power divider is changed,and the shunt electromagnetic coupling resonator structure is introduced.The single pass band filter is realized on the basis of power divider.And the equivalent transmission line circuit is constructed,and its resonance condition is analyzed and discussed by the odd-even mode analysis method.In order to improve the frequency selectivity,the source-load coupling structure is adopted to ensure the transmission zero point on both sides of the passband.The transmission zero can be controlled by adjusting the physical parameters,and the specific influence law is analyzed and summarized.Then,a dual-band filtering power divider is designed.A pair of short-circuited section-loaded uniform impedance resonators and a pair of embedded stepped-impedance resonators are used to realize the resonant circuit with band-pass response,which is realized by the parallel passband method.Two resistors are loaded separately in input and output to ensure good isolation.At the same time,the transmission zero is introduced on both sides of the two passbands by means of source-load coupling and electromagnetic hybrid coupling,and the causes of the phenomenon are analyzed.The designed dual-band filtering power divider can adjust and control the operating frequency of another passband on the basis of a constant passband operating frequency.Finally,a wideband filtering power divider with a relative bandwidth of 40% is proposed.The structure consists of two sets of open-circuit coupling lines and a short-circuited branch.The feed is coupled and fed in a crosswise manner.The feeder part is designed as a pair of parallel coupled lines,so that multiple resonance points can be generated.Two open coupling feeders are respectively provided with an open branch at each end,which is used to increase the resonance point at a higher frequency,thereby increasing the passband bandwidth.At the same time,the equivalent circuit and resonance mode are analyzed,and the optimization achieves good broadband performance.