Research Of Key Technology Of Ka/Ku Airborne Communication Transmitter

As one of the important communication methods in the field of wireless communication,satellite communication plays an increasingly important role in military and civilian fields with its unique technical advantages.In recent years,more and more researches and applications of satellite communication system have been made.Based on a crossing research project of the laboratory,this project developed a Ka/Ku dual-channel airborne communication transmitting system with excellent performance.The Ka-band transmission frequency is 29-30 GHz with transmission power up to 20 W,and the Ku-band transmission frequency is 13.75-14.5 GHz with transmission power up to 40 W.Besides,the transmitter gain,spur suppression,phase noise and other performance of this work have advantages in similar products.This paper mainly introduces the design and development process of the transmitter front end in the system,which is also the main work that I participated in.The main work of this paper is:1.Analyze system indicators and develop system scheme;2.Distribute indicators to each module,then design and test the intermediate frequency preprocessing module,frequency source and Ku frequency conversion and amplification module,Ka upconversion module and Ka drive amplification module.Besides,give test results and analyze existing problems and solutions..3.First,cascade the modules of the Ku transmission channel and the Ka transmission channel respectively.Besides,test gain,drive power,gain flatness,phase noise,spur suppression and other indicators as well as channel switching,reference detection,lock indication and gain adjustment.Then cascade the power amplifier to test the gain and saturation output power of the whole system.Finally,test the gain fluctuation of the whole system in high and low temperature environment.4.Propose an improvement plan for the problems existing in this thesis.According to the test results,the system functions such as channel switching,reference detection,lock indication and gain adjustment of the Ka/Ku transmission system are normal.The Ku transmission channel has higher then 55 dB gain,better than 3dB gain flatness,higher than 29 dBm drive power and 55 dBc spur reduction.The phase noise of Ku transmission chanel also meets the requirements of the index,the whole system gain is about 80 dB,and the saturated output power is higher than 40 W.Besides,gain fluctuation is less than 3dB in the test environment of-40~+70°C.The Ka transmission channel also has higher then 55 dB gain,better than 3dB gain flatness,higher than 31 dBm drive power and 50 dBc spur reduction.But the far end phase noise is slightly worse.However,it also basically meets the requirements of the index.The gain of the whole system is about 77 dB,and the saturated output power is higher than 20 W.Besides,the gain fluctuation is less than 3dB in the test environment of-40~+70°C.