Study Of Wide-band Spread Spectrum Signal Capturing And Tracking Unit

With the rapid development of the unmanned aircraft, rapid communication and secret communication between UVA and the ground station is becoming more and more important. What’s more, with the enrichment of unmanned aerial vehicle (uav) transmit data types, communications bandwidth demand is also growing. Spread spectrum communication was first used in military communication security. Spread spectrum communication because of its excellent reliability, anti-jamming and multiple access performance has been widely adopted by civilian areas and satellite. In broadband wireless communication,because of the spread spectrum communication problems such as faster rate,difficult to capture, track easily lost lock, moving target doppler frequency shift, so it is urgently needed to study a reliable fast tracking capture and engineering implementtation method. This study is the hotspot in the field.This article is based on FPGA hardware platform design a kind of high speed large bandwidth signal transmission, including a quickly capture tracking system of up and down link. System by capturing tracking wide-band spread spectrum signal, in complete fine synchronization implement expansion demodulation solution at the same time, it is concluded that the original data symbols. And then put those original data symbols into the subsequent decoding module processing. In this paper, main work is as follows:1.Put forward a king of scheme which is based on TDD between arcraft and ground station including up and down link broadband hybrid spread spectrum communication system implementation. TDD system up and down link adopts different ways of spread spectrum and modulation mode. System requires airborne end complete soft spread spectrum of direct sequence spread spectrum signal capture trace and enlarge demodulation task, and Ground station complete airborne end a mixture of spread spectrum and frequency hopping spread spectrum signal tracking capture and solution of demodulation task.2.Through the analysis and comparison of spread spectrum signal capture tracking algorith, to complete the uplink direct sequence spread spectrum system tracking capture and expansion of demodulation scheme design.3.According to different requirements of spread spectrum gain of the whole system, this paper designs a gain switch down link tracking capture of hybrid spread spectrum system and expansion of demodulation scheme.4.The system come ture by Xilinx company’s latest Kintex-7 series xc7k325tffg676-2 the FPGA chip as the system hardware platform and cooperating with the latest development platform Vivado.Through the actual test system can complete 250 MHZ clock speed,50 McHips two-way link of different modes of spread spectrum communication mode tracking capture and expansion of demodulation solution, and tracking capture success rate of above 97%, can meet the expected targets system.