Research On Critical Technologies Of Triplexer With Continuous Channels

In order to improve the utilization rate of frequency resources,reduce the broadband performance requirements of other microwave devices and achieve the"dilution" function of signal,channelized filtering of wideband spectrum signals is usually adopted.The continuous-channel multiplexer,which is widely used in the communication system,is the key device to realize the process and one of the significant components of the broadband digital receiver.Its main principle is to use multiple adjacent channel filters to form a filter group to separate multiple independent sub-band signals from the broadband signal for further processing.Generally,the number of the channel filters in the multiplexer demands the name of a multiplexer.The traditional continuous-channel multiplexer is usually constructed by microwave devices with three-dimensional structures,such as cavity filters and circulators.Although the insertion loss of this kind of multiplexer is relatively good,and channel isolation is relatively high,the device size is large,and the structure is complex,which is detrimental to system integration.Therefore,aiming at the planar structure,some crucial technologies of continuous-channel multiplexer are studied in this paper.Because the matching circuit structure of planar multiplexers is monotonous and not easy to realize the matching of more than three channels,the planar continuous-channel triplexers with star junction matching circuit are the focus of this paper.Firstly,the fast construction method of the initial values of the planar continuous-channel triplexers is investigated.The direct design method and the 1/4 wavelength T-junction matching method are mainly used.The design idea is that the first and second channel filters are constructed into a duplexer firstly,and then the duplexer as a whole continues to connect the third channel filter with using the same matching approache,and finally the design of the continuous-channel triplexer is completed.During the process of design,in order to find the key factors that affect the matching and make appropriate corrections to them,the circuit models of duplexer and triplexer are analyzed by ADS simulation software.Subsequently,in order to avoid using high-order configuration to improve the selectivities of the channel filters,three methods of introducing transmission zeros are applied to design the continuous-channel triplexers.Because the Q value of the resonator structure in the channel filters is low,the insertion losses of the continuous-channel triplexer realized by the traditional cross-coupling method are relatively large.In order to solve this problem,based on the open ring resonator with larger Q value,two continuous-channel triplexers are designed respectively by using the electric and magnetic mixed coupling method and the loading extraction-pole unit(EPU)method.And loading two EPUs can directly introduce two pairs of transmission zeros in the case of low insertion loss.Finally,the measured insertion losses of the continuous-channel triplexers based on cross-coupling and electric and magnetic mixed coupling technologies are 8.9dB and 2.5dB respectively,the isolation degree 45dB and 3 8dB respectively.The insertion loss of the continuous-channel triplexer based on loading EPU technology is 3.4dB,and the isolation degree is 45dB.Finally,the implementation technology of planar broadband continuous-channel triplexer is researched.It is found that cascading high-and low-pass filters with suspended stripline structure could realize the broadband triplexer.Based on this,a 4?7GHz continuous-channel triplexer is developed.The measured results show that the insertion losses of three channels are about 1.2dB,the return losses around 13dB,and the isolation between the channels is better than 53dB.The planar continuous-channel multiplexers with more channels,high temperature superconducting(HTS)triplexer with continuous channels and the broadband matching techniques for microstrip structure would be studied in the following plans.