Research And Implementation Of Space-Based High Sensitivity UAT Receiver Algorithm

Limited by restricted coverage,it is difficult for land-based Automatic Dependent Surveillance-Broadcast(ADS-B)system to perform continuous monitoring and tracking on the global flights.In order to build a global ADS-B surveillance network without blind spots,the space-based ADS-B system emerges.However,new challenges are parasitized in the design of space-based ADS-B receiver system,because of the large signal attenuation and Doppler frequency offset.In this context,a signal processing algorithm,which is suited to space-based ADS-B system using Universal Access Transceiver(UAT)data link for data transmission,is studied,implemented,and tested.The specific work contents are as follows:Firstly,the sensitivity requirements of space-based UAT receiver system are derived,according to the altitude of satellites and the transmitting power of UAT transmitters stipulated in DO282-B standard of UAT data link.By comparison and analysis,it is concluded that the sensitivity of the standard UAT receiver can’t meet the requirements of UAT receiver sensitivity in the spaceborne environment.Secondly,an UAT processing algorithm suited for spaceborne environment,is studied through five aspects,including signal detection,frame synchronization,timing synchronization,carrier synchronization,and demodulation.First,the existing receiver algorithms are simulated and analyzed.Then,an improved differential correlation algorithm is proposed for frame synchronization,and a high-times oversampling correlation algorithm is improved based on differential correlation operation for timing synchronization.Finally,a set of UAT receiving algorithm is concluded.Simulation results show that when the Signal-to-Noise Rate(SNR)is 1dB for basic ADS-B messages,and 2dB for long messages,the algorithm can achieve more than 90 percent Message Success Rate(MSR),which satisfies the UAT receiver sensitivity requirements for spacebased reception scenarios.Thirdly,the space-based UAT receiving algorithm is implemented on the hardware platform with Field Programmable Gate Array(FPGA)and Digital Signal Processor(DSP),the correctness of the algorithm is verified at the board level.Finally,a space-based UAT receiver test platform is written,and a sensitivity test is performed on the space-based UAT receiver using the test platform and necessary test instruments.In the case of no external Low Noise Amplifier(LNA),the sensitivity test result of-107.4dBm is obtained for basic ADS-B messages,and-104.7dBm for long ADS-B messages,which satisfies the UAT receiver sensitivity requirements for spaceborne scenarios.