Design Of Dual-Band Filter And Balanced Bandpass Filter Based On SISL Structure

Modern communication has developed rapidly,and people's communication needs have continued to increase,with the consequent higher requirements of RF transceiver systems.In the entire communication system,the filter is at the front end of the transceiver system,so that the performance of the filter directly affects the quality of the entire communication system.Therefore,we urgently need to research and develop higher performance,stronger anti-interference performance,and convenient cascading with other devices.And integrated filter structure.The balanced filter has an important position in modern communication systems because of its good ability to suppress environmental noise and its small influence on electromagnetic interference.In addition,the balanced filter can be directly cascaded with the active components of the balanced structure,thereby reducing the system size and facilitating the on-chip integration of the entire system.Therefore,it has attracted the attention of many scholars and research teams.In addition to the development of the device structure,the performance of the transmission line is one of the important factors determining the performance of the device.At present,most existing balanced filters use planar structure transmission lines,so new high-performance transmission lines are required to improve the performance of microwave devices.In this paper,a new type of transmission line,dielectric integrated suspension line(SISL),is used to study the dual-passband filter,balanced band-pass filter,and dual-passband balanced filter.First,a dual-passband filter based on the SISL structure is proposed.The electromagnetic bypass coupling resonator is used to design the passband of the circuit.Through the source and load coupling and the coupling between the resonators,the two passbands have four transmission zeros.Model the equivalent circuit of the filter structure and analyze the equivalent circuit.The transmission zeros on both sides of the passband are analyzed and controlled separately,and specific influence laws are given.The method of adjusting the frequency of the filter is also given so that it can be applied to different frequency requirements.Secondly,a balanced band-pass filter based on SISL structure is proposed.A resonator is used to achieve the passband response under differential mode excitation,and a good common-mode rejection in the passband of the differential mode response is achieved by introducing a coupling structure.Compared with a common mode stopband resonator that is directly coupled to the corresponding differential mode passband by loading branches,the method can effectively reduce the circuit size and realize the miniaturization design of the circuit on the basis of meeting the requirements of the circuit passband.Based on the equivalent analysis of the circuit,the influencing factors affecting the three transmission zeros in the differential mode passband are given and the specific influencing laws are given.Finally,a double-passband balanced filter based on SISL structure is proposed.The dual-passband response of the differential-mode excitation is achieved using the SIR structure.The two passbands contain three transmission zeros.T-type resonators with asymmetric open stubs and SIR structures loaded on the symmetry plane are used to suppress the response under common-mode excitation signals.By analyzing the performance of the two-section and three-section SIR structures and the open stubs,the design and the final results are obtained within two passbands corresponding to the differential mode response and within the frequency range between the two passbands.Common mode rejection.The comparative diagram of the influence of loading different resonator structures on the common mode response is analyzed and given.Finally,the optimal resonator loading method on the symmetry plane is given.