Research On Low Noise Block For K Band Satellite Communication

With the development of economy and the progress of society,the traditional band(C and Ku)bandwidth is limited,which can not meet the growing market demand.Compared with the traditional band,K band frequency not only has a wide range of available bandwidth,but also has higher gain.Therefore,under the premise that the antenna gain value is invariable,the K band satellite antenna can be made more compact and portable,which is convenient for disassembly and carrying.Therefore,the K band satellite communication technology has become the focus of research and development in the industry.In this paper,the K band transceiver,which is an important RF(Radio Frequency)unit in the satellite communication system,plays an irreplaceable role in the satellite communication system.The wireless transceiver can send and receive duplex,including the frequency up converter and power amplifier part(BUC),low noise amplification and frequency down conversion part(LNB),The research object of this thesis is LNB,which located in the K band wireless transceiver and applied for low noise down converter.Firstly,this paper introduces the basic principle and design parameters under low noise down converter.Secondly,the design of active and passive circuits in low noise frequency conversion is introduced,the design of the passive circuit including waveguide to microstrip structure,band-pass filter(requirements of image rejection is greater than 35 d Bc)and the mixer;the active part includes the low noise amplifier(single tube amplifier requires a gain of more than 11 d B),dielectric oscillator(18.25GHz),and DC bias circuit.After that,in this paper,the design principles,parameters and design methods of each part are discussed in detail.And with the help of Ansys software and Keysight software,the radio frequency parameters of each part are simulated and analyzed by HFSS software and ADS software.After assembling the whole machine,the noise figure and gain of low noise down converter are measured by vector network analyzer N5247 A.The results show that the noise figure of the converter is lower than 1.6d B,and the gain is higher than 56 d B,which has reached the design requirements of the relevant products.