| About the domain of communication satellite,in recent years,as the satellite toward higher component integration,greater transmission power and higher receiver sensitivity direction,furthermore,the communication antenna for the sharing of work mode,or two of the antenna distance is very close to the reasons,the passive device nonlinearity caused by the source of interference becomes very serious.This kind of jamming signal is passive inter-modulation(passive system-modulation,PIM),in the case of without control can cause communication system communication transmission ability or channel congestion,resulting in abnormal satellite work,failure,etc.Ku-band antenna feed systems have been used widely in communication satellites in our country,having high transmitting frequencies,high power capability(up to hundreds of watts).As a result of transmitting channel band spreading and deviating,but no change in receive bands,the orders of PIM such as ninth and seventh order will be turned into third order.And at the same time with influences under high/low temperature environment,From product design to PIM test system require ments have become higher and more stringent.This paper is aiming at the above problems,with some sat ellite type 3 order PIM test Ku-band antenna feed as the main object of study.It introduces the principle of passive inter-modulation Ku-band,the characteristics of the test,test methods,the testing system of high and low temperature building and testing steps in detail,and the testing system of key indicators and matters needing attention in the process of testing.In addition to this,the key indicators of the test system and the precautions during the test are described.The existing test system is verified in advance,and then the problems in the current system are found out.Based on the mechanisms of PIM production and taking no account of influence of material and contact nonlinearity,process technology and surface treatments are analyzed sufficiently.Meanwhile,the design of key test system accessories is improved,and a large number of the system link integration processing work and designs are completed to reduce the thermal test cycle.Finally,the test verification is completed.In this paper,the principles of testing system,specific improvement methods of the system and test steps are described in detail.The PIM test of 3.5 cycles has been carried out from-65? to +145? under the condition of high and low temperature.The third order test result of PIM is-140dBm@2*132W,much better than-130dBm@2*110W of the project target,reaching the international advanced level and Meeting the requirements of product testing.At last,Ensure that the star-borne antenna feed can work well in the extreme temperature variation of space.The research results of this project sufficiently verify t he correctness of the theoretical analysis in the early stage.Reliable theoretical and experimental supports are provided for the improvement of other band PIM systems in the future,and the development of low PIM test verification technology for high power feed products is improved.The research will lay the foundation for the PIM test of the Ku-band high power antenna feed products in our country. |
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