Research On Key Technologies Of Partial Porous Externally Pressurized Gas Bearing

Information return system has played an important role in battlefiled situational awareness,damage assement and subsquent wave attack.Thus,it has been a part of sapce vehicle system.Frequency hopping(FH)technology,whose transmiting frequency rapidly hops within a relatively wide frequnce range to avoid interference and interception,has strong anti-jamming capability and thus can powerfuly gurantee the safely of information return system.However,in the TT&C of space vehicle,large relative speed,acceleration and jerk is existed beteen vehicles,results in great Doppler shift,first order and high orders of frequency change rate.In addition,due to long communication distance and the presence of electronic intereferences,the signal noise ration(SNR)of the received signlas is very low,the receiver is required to accomplish the acquisition,synchronization and demodulation of the FH signals under low SNR and high dynamic conditions.The aim of the thesis is to design a effective information return system,which is able to accommodate the low SNR and high dynamic conditions.We first look for a highly effective FH signals acquisition method by the overall design of the communication system.We also investiage the symbol and carrier synchronization method which works under the conditions of low SNR and high dynamic.Moreover,we improve the bit error rate(BER)performance by high gain code design.The utilization of high gain code can alleviate the influnce Doppler shift and its change rate in the enviroment with high dynamic stress,enable the anti-jamming ablity of the receiver and help to the stable lock of carrier tracking loop and accurate demoduation of the received signals with low SNR.The algorithms of siganl acquisition,symbol timing,carrier synchronization and channel coding have been simulated in the thesis.Furthermore,we have bulit a hardware platform to verify the effectiveness of the proposed FH receiver under low SNR and high dynamic conditions.On the hardware platform we have exmined the aforementioned algorimths in the receiver,tested the overall performance of the receiver and compared with the simulation resutls.The simulation and field test resutls have shown that the FH receiver designed in the thesis can satisfy the requirement of the information return system.