Research And Implementation Of Automatic Dependent Surveillance-broadcast (ADS-B) Receiving System

Automatic Dependent Surveillance–Broadcast(ADS-B)is a kind of emerging aircraft surveillance technology that has been widely regarded as the core of the next generation of surveillance technology.Many countries in Europe,America,and Australia have developed mature systems for ADS-B technology,and China is also actively promoting the application of ADS-B technology in recent years.In the beginning,this article describes the research background and the significance of this subject,then introduces the history of ADS-B technology and the current research status.Several ADS-B data links are introduced,among which the most widely used is the 1090 ES signal mode.Therefore,this article carried out research on the design of the ADS-B signal receiving system of S mode 1090 ES.In this project,my work focused on the design of the baseband signal processing algorithm in the ADS-B system.The baseband signal process mainly includes ADS-B preamble detection,PPM decoding,CRC verification and error correction,and separation of the overlapped signal.For ADS-B preamble detection,this article proposes an algorithm,which is optimized based on the cross-correlation detection method.Before cross-correlation detection,extraction of potential signal sequences process is added,and amplitude confirmation of the preamble is performed after the process above.Also,simulation and analysis are carried out to prove the algorithm.Next,this article introduces two PPM demodulation algorithms.One is to simply add the amplitudes of the sampling points in the first and second half of a bit,and then compare the two accumulated sums to obtain the value of the bit.Another method is to assign weights to different sampling points according to the confidence degree of the signal and corrects the amplitude of the points with abnormal amplitudes,then calculates the weighted sum and performs the bit judgment.Cyclic Redundancy Check is required to be performed on the decoding result.This paper introduces basic check methods and several common error correction methods and introduces an algorithm which achieves the judgment of long message and short message on the base of CRC.In the actual communication process,it is a common occasion that overlapping appears among different ADS-B signals,so we continue to make a study on overlapped signal processing algorithm.After introducing two currently available algorithms for the overlapped signal separation,the algorithm adopted in this paper is introduced in detail.Firstly,the amplitude detection method was used to preliminarily determine the existence of overlapping,and then the overlapped signal segment was roughly extracted by the rising edge detection method.Finally,the overlapped signal is separated into two signals by the K-Means algorithm and signal reconstruction process,and the simulation of the overlapped signal processing algorithm is carried out and successfully completes the separation of the overlapped signal.To make further verification of the algorithm in this article,we obtained several groups of signals that were collected at Nanjing Lukou Airport.We decoded the actual signals using algorithms in this article,the test results verified that the baseband processing scheme designed in this article is feasible and has practical significance for engineering application.In the end,to achieve the ADS-B signal receiving system,this article adopts RF Agile Transceiver AD9361 and Zedboard as hardware.Then made an experiment to transmit an ADSB signal and receive the signal transmitted by itself,finally,it completed the self-loop process,which means the preliminary debugging of the hardware has been implemented successfully.