Signal Direction Estimation Method for Wideband Aeronautical Data Link System Based on Signal Characteristics

‍ ‍L-band digital aeronautical communication system （L-DACS） is the future air-ground data link for the route stage. The working frequency band of L-DACS is planned to be deployed in the aviation radio navigation band， and the spectrum of L-DACS is partially overlapped with the spectrum of distance measuring equipment （DME）， which is vulnerable to the interference of high power DME signal.In order to make full use of the gain of the array antenna while suppressing the interference， it is necessary to estimate the direction of arrival of the L-DACS signal in advance.According to the characteristics of aviation channel and considering the Doppler frequency shift caused by the high-speed motion of airborne platform， the L-DACS signal is modeled as a wide-sense generalized almost-cyclostationary signal（GACS）， and the direction estimation method of L-DACS signal based on the wide-sense generalized almost-cyclostationary feature is proposed. Simulation results show that this method can estimate the direction of OFDM signal in the scene of high-speed movement of airborne platform and interference of DME signal， and has high estimation accuracy and good adaptability to low signal-to-noise ratio.