The Design Of Active Multiplexer

Multiplexer is an important device in modern communication system.It can make multiple communication stations and systems to share common antennas,reducing the mutual interference between signals and the complexity of space electromagnetic environment.The traditional multiplexer usually uses multiple filters to achieve the function of multiplexer by matching to reach the common antenna.However,when the multiplexer's requirements are more stringent,it will lead to its complex structure,and its volume and weight will be sharp increasing.It is not conducive to miniaturization of the system.Using active devices or combining active devices with passive devices to design active multiplexers can take full advantage of the small size,light weight,and ease of integration of active devices,miniaturizing the multiplexer,which is also the case research direction.Based on the background and practical requirements of the multiplexer,this thesis discusses the research significance of the active multiplexer and introduces its current development status through extensive literature research.It is mainly the development of active(quasi)circulators and active multiplexers based on distributed power amplifiers.Then introduced some basic theoretical knowledge of the multiplexer,including the main implementation program of the multiplexer.The key is to use the active quasi-circulator to implement the active multiplexer method,and the implementation of the active quasicirculator.And finally,the design of active multiplexer based on distributed power amplifier is introduced.The third chapter is the core of the thesis,and briefly describes the technical solution of the active multiplexer,that is,using the circulator coupling method to design the active multiplexer,the core of which is the design of the active quasi-circulator.In the structure,some improvements have been made.Using the unequal-split Wilkinson power divider,the input power of the first port of the active quasi-circulator is transmitted to the second port as much as possible,and the 50 Ohm resistor balanced with the second port is removed.This method increases power utilization and the utilization of phase cancellation techniques isolate the first and third port.The parts of the active quasi-circulator were simulated and analyzed by commercial advanced simulation software ADS.Firstly,the power amplifier is designed according to the design steps of the power amplifier by using the transistor ATF33143.Then the unequal-split Wilkinson power divider with a power ratio of 2:1 is simulated.Finally,the power synthesis section of the active quasi-circulator is designed based on the power amplifier.The circuit,at this time,should use the random algorithm and the gradient optimization algorithm to optimize the size of each microstrip line so that the S-parameters meet the requirements of the active quasi-circulator.In the fourth chapter,the design principle and method of the parallel-coupled band-pass filter are introduced firstly.Then three channel filters are designed.Second,the active quasicirculator described in the third chapter is used to design the active multiplexer.And the advantages and disadvantages of the simulation results compared with the traditional multiplexer are analyzed.