Abstract: To solve the problem of spectrum resource scarcity in aeronautical data link, L-band digital aeronautical communi－ cations system (L-DACS) will be deployed as an inlay system in the spectral gaps between channels of the distance measuring equipment (DME). Therefore, it′s unavoidable that the DME signal has a severe influence on the perfor－ mance of L-DACS system receiver. To analyze the influence of out-of-band leakage of DME/N (distance measure equipment/normal) and DME/P (distance measure equipment/precision) signal on L-DACS system receiver, the mathematical models of DME/N and DME/P signal are established, firstly. Then, the expressions of power spectral density of DME/N and DME/P signal are theoretically derived. Based on these expressions, the effect of out-ofband leakage of DME/N and DME/P signal on L-DACS receiver, which is deployed in adjacent channel, are researched. Finally, the correctness of the theoretical analysis results is verified through computer simulation. The results show that the impact of out-of-band leakage of DME signal on L-DACS system is mainly manifested in the first adjacent channel, and the leakage power of DME/P signal in the first adjacent channel is 10 dB higher than that of DME/N signal.

Key words: L-band digital aeronautical communications system, distance measure equipment, adjacent channel interfer－
ence, power spectrum, out-of-band leakage power