Power Spectrum Of Distance Measure Equipment Signal And Its Out-of-band Leakage Power

Distance Measure Equipment(DME)is a radio pulse ranging system,which is used to measure the distance between aircraft and DME ground station.L-DACS1 is a new generation of broadband aviation data link system of civil aviation.According to the plan of ICAO,L-DACS1 will be deployed in the spectral gaps between two adjacent channels used by the DME.Due to the spectrum of DME signal partial overlaps with that of L-DACS1 receiver signal,it’s unavoidable that the DME signal has a severe influence on the performance of L-DACS1 receiver.In order to study the influence of the out-of-band leakage power of DME signal on the L-DACS1 receiver,the following two aspects are carried out in this paper:1)Firstly,the influence of DME signal on L-DACS1 is analyzed.The operation principle of DME and L-DACS1 is introduced,and then the problem of DME signal interfering with the receiver of L-DACS1 is analyzed from four aspects: the time domain,the frequency domain,the constellation diagram and the BER of the system performance of the received signal.The simulation results show that DME interference signal significantly deteriorates the link transmission reliability of L-DACS1.2)The influence of DME/N,DME/P,DME/STP and DME/SCP signal on L-DACS1 receiver are analyzed respectively.The expressions of power spectral density of DME/N and DME/P signal are theoretically derived.Based on these expressions,the effect of out-of-band leakage of four DME signals on L-DACS1 receiver,which is deployed in adjacent channel,are presented quantitatively.3)Finally,the computer simulation results are provided to demonstrate the correctness of the theoretical analysis.The research results show that the DME signal has a severe influence on the performance of L-DACS1 which is deployed in the first adjacent channel and the leakage power of DME/STP signal in the first adjacent channel is the highest,which is 14 d B higher than that of the DME/N signal.