Research On The DME Interference Mitigation Based On Cyclic Wiener Filter

L-band digital aeronautical communication system 1(L-DACS1)is one of the future broadband aviation data link candidate technical solutions proposed by ICAO.It will be deployed in the radio navigation frequency band and will operate as an inlay system in the frequency gaps between adjacent distance measuring equipment(DME)channels.In addition,due to its higher transmission power,the DME signal interferes with the receiver of the L-DACS1 system.In view of this problem,the interference mitigation research is extended to the cyclic spectrum domain in this article and the DME interference signal mitigation method based on cyclic wiener filtering is carried out.The main contents are summarized as follows:(1)A DME interference mitigation method based on joint two-stage filtering and compressed sensing is proposed.Firstly,DME interference is estimated by a high-pass filter in the receiver and eliminated from the received signals in time domain.Then,the residual DME interference and noise are further filtered out by low-pass filtering.Finally,based on the sparse characteristics of DME signal in time domain,the remaining DME interference after two-stage filtering are further reconstructed and eliminated using compressed sensing algorithm.The effectiveness of the proposed method is verified by experimental simulations.(2)The basic theory of cyclic wiener filtering is investigated.Firstly,the concepts about cyclic stationary theory are described in detail,including first-order cyclic statistics,second-order cyclic statistics,and cyclic spectral density functions.Then,the working principle and adaptive algorithm of the frequency shift(FRESH)filter are given.Finally,the simulation results of AM signal cyclic spectrum and the separation of BPSK signals that have overlapped frequency spectrum are proposed as examples to verify the relevant theories.(3)A DME interference mitigation method based on FRESH filter is proposed.Firstly,the cyclic stationary characteristics of the OFDM signal are analyzed and the cyclic frequency sets are obtained.Then,the FRESH filter is designed based on the values of the cyclic frequency sets of OFDM signal and its weight vectors are optimized using the adaptive RLS algorithm.Finally,the useful OFDM signals are reconstructed and the purpose to mitigate the DME interference is achieved.The effectiveness of the proposed method is verified by experimental simulations.