DME Pulse Interference Characteristics Of L-DACS1

L-DACS1 is an aviation mobile space and ground communication technology for new generation air traffic management system,which is designed to meet the requirement of large capacity and high communication rate.The L-DACS1 need to be embedded in channel gap of the DME.In frequency domian,this could induce severe disturb to the receiver of L-DACS1,due to the overlap between OFDM signal,which is in L-DACS1,and DME ginal.To suppress the disturb,a detail study of DME signal is demanded.This paper mainly focus on the characteristics of DME signal in time-frequency domain,which include below content:Firstly,the L-DACS1 system is summarized,and the physical frame structure,forward link transmitter and receiver models of l-dacs1 system are introduced;And then,the working principle of the DME system and DME signal model are given,and the forward link interference budget of L-DACS1 is analyzed,which verifies that DME signal can significantly deteriorate the bit error performance of L-DACS1;Then,the time domain expression and the expression of spectrum and power spectral density of baseband DME signal,carrier offset DME signal and DME signal after low pass filtering are detailed analyzed.And get the average power relational expression between of the baseband DME signal and the DME signal after low pass filtering.And waveforms of DME signals in time domain and frequency domain are obtained by Matlab simulation.In addition to this,according to the simulation waveform of the coincidence degree between the theoretical waveforms and simulated waveforms,the correctness of the theoretical derivation is verified.In addition,it is concluded that the average power of DME signal after low-pass filtering attenuates by 33 dB compared with that before filtering;Finally,the radio frequency signal generation system is designed to build the preliminary test table of the measured signal and verify the correctness of the theoretical analysis.The vector signal generator?the oscilloscope and the spectrometer are introduced firstly.Then vector signal generator is used to generate RF DME signal and OFDM signal,and oscilloscope and spectrometer are used to observe their time domain waveform and power spectral density respectively.