Investigation Of DME/TACAN Interference On GNSS

GlobalPositioning System(GPS)is currently one of the most important Global Navigation Satellite Systems(GNSS).The new thirdgeneration civil signal GPS L5 which has a center frequency of 1176.45 MHz and a bandwidth of 24 MHz,is covered by the working frequency band of Global Aeronautical Radio Navigation Service(ARNS).Therefore,GPS L5 has to share the spectrum of this band with Distance Measure Equipment(DME),Tactical Air Navigation System(TACAN)and other radio systems in ARNS band.Due to the worldwide distribution of DME/TACAN ground stations,pulsed signals from DME/TACAN ground stations and airborne equipment will reduce the signal-to-noise ratio of GPS L5,make the receiver tracking loop unable to converge,and therefore make the decoding process difficult.As a result,pulsed signals from DME/TACAN become one of the major sources of interference for GPS L5,especially at a high altitude.In order to investigate the impact of DME/TACAN pulsed signals on GNSS signals,based on the real flight data up to 1.5T which was collected by EUROCONTROL for around 3.5 hours over Europe in 2016,a detection algorithm is designed for DME/TACAN pulsed signals.Combined with the correlation assessment method,the task of detecting DME/TACAN pulse pairs in all flight data is completed.Besides,the pulse pair repeat frequency and average power of interference signals are also analyzed and calculated;According to the analysis of DME/TACAN impact on GNSS signal,the evaluation model for DME/TACAN interference on GPS L5 is mainly investigated.The calculation methods of interference signal duty cycle,power density ratio,signal to noise ratio and other evaluation parameters are also given in this paper.Based on theflight data up to 1.5T,the trends of these evaluation parameters during 3.5 hours are given;The International Telecommunication Union(ITU)standard simulation experiment is also designed and completed,and the worst case impact on GNSS signals caused by DME/TACAN interference is evaluated and compared with the real measurement results.In this paper,the results of the research are compared with the report from European Control Center of Radio Communication(C.C.R.M.)published in 2016.The results are highly consistent.Finally,based on the analysis of DME/TACAN interference suppression methods,three interference suppression algorithms are programmed and achieved.The timedomain blanking method is applied to the acquisition and tracking process of GPS L5 signal.The experimental results verify the DME/TACAN impact on acquisition and tracking performance of GPS L5 signal.And the acquisition and tracking performanceof GPS L5 signalis improved significantly after interference suppression.