Low PIM Triplexer Design And Realization

RF filter is an indispensable component in the wireless communication system and the performance of the RF filter directly affects the quality of the whole communication system.This thesis takes the example of Triplexer of the AT&T operator in the USA as the design targets(the pass frequency band Insertion Loss better than-0.45 dB,Return Loss better than-18 dB and Residual Passive Intermodulation better than-115dBm),using the advantage of the Chebyshev coaxial cavity filters to realize the smaller and lighter triplexer design in order to meet the demand of smaller and lighter communication system.In this way,the whole design can satisfy the modern communication system requirements.The electromagnetic properties of coaxial cavity resonator is analyzed in this thesis(resonant frequency,coupling structure and external Q factor)and the contents and steps of the cavity filter design.Firstly layout the circuit mode of the single filter by using Geneys to simulate and optimize mode to get the number of resonators,Q factor,the number of transmission zero and topological structure that follows the specification;Secondly layout circuit diagram of triplexer based on previous the single filter parameters by adopting Geneys to simulate and optimize each component in order to get all the parameters of the triplexer in the specification;Thirdly It utilizes HFSS(High Frequency Structure Simulator)software to design the structure of the resonator(the coupling of the resonator input and output port,the coupling window between each resonator and the crossing coupling between each resonator);Finally,according to the results of HFSS simulation,the thesis analyses how to realize the design of all resonators and the cavity layout.Ultimately,the paper illustrates an engineering design of the triplexer and the comparison data between the circuit simulation and sample measurement.All the measurement data totally meet the demand of the designing targets.The measurement result of the triplexer is the pass band insertion loss better than-0.41 dB,return loss better than-18.6dB and residual passive intermodulation better than-119 dBm.