Design Of Broadband Power Divider For Digital TV Transmission System

As a widely used microwave passive device,the power divider is an important part of the power amplifier and the feeding network in the antenna array and mixer.The research topic of the thesis comes from the project "Development of Passive Devices for Digital TV Transmission System" of Liaoning Putian Digital Company limitied by shares.Based on this project,two types of power dividers are designed:one is coaxial power dividers,which have the characteristics of simple structure,low insertion loss and high power capacity;and the other is microstrip power dividers,which have small size,low cost,easy Integration and other advantages.For the design of the power divider applied to the digital TV transmission system,it is necessary to achieve good matching performance in a wide operating frequency band,and it should meet the development trend of miniaturization of microwave radio frequency devices.Therefore,it is of great significance to study the broadband and miniaturization of the power divider of the digital TV transmission system.The main works of the paper are:(1)Using the multi-section short-step Chebyshev impedance transformation theory,an eight-way short-step coaxial power divider was designed and produced for the feed network of the digital TV transmitting antenna.The circuit is simulated and then fabricated and tested on HFSS software.In the working frequency band 470?800MHz,the return loss is greater than 25dB,the insertion loss of the eight output ports is less than 11.3dB,and the isolation is greater than 15dB.The total length of the power divider is 230mm,which is reduced by 47.2%compared with the existing eight-way coaxial power splitter,achieving miniaturization.(2)Using the microstrip-slot line transition structure,a three-port broadband inverting power divider was designed and produced for the power amplifier unit of digital TV transmitters.The structure is simulated and then fabricated and tested.In the working frequency band 470?860MHz,|S11|<-23dB,|S21|>-3.5dB,|S23|<-15dB,the amplitude difference is less than 0.2dB and the phase.difference is 180°±5° between the two output ports,achieving broadband reverse phase performance.(3)Using the microstrip-slot line transition structure,a three-port broadband Gysel power divider was designed and fabricated for the power amplifier unit of digital TV transmitters.And the circuit is adjusted and tested.In the working frequency band 470?860MHz,|S11|<-25dB,|S21|>-3.4dB,|S23|<-15dB,achieving the whole frequency band of DTV.(4)A slow-wave structure is used to replace the traditional microstrip transmission line,and a miniaturized Gysel power divider is designed on the basis of(3).The circuit is simulated on HFSS and then fabricated,adjusted and tested.In the working frequency band 470?800MHz,|S11|<-25dB,|S21|>-3.5dB,|S23|<-15dB.The size of the circuit is only 0.19?g×0.125?g,achieving miniaturization.