Direction of arrival estimation of wideband LFM signals in multipath environment

A novel direction of arrival (DOA) estimation method is proposed when uncorrelated and coherent wideband linear frequency modulated (LFM) signals coexist in multipath environment. By using the concentration property of signals, the wideband LFM signals are first transformed into fractional Fourier (FRF) domain to construct the array model, in which the time-variant steering vector is changed into time-invariant one. Afterwards, the DOAs of uncorrelated wideband LFM signals are estimated by the total least square estimation of signal parameters via rotation invariance technique (TLS-ESPRIT). Then, a spatial difference matrix is constructed to eliminate uncorrelated wideband LFM signals, and the coherent wideband LFM signals are resolved by performing a forward spatial smoothing technique. The proposed method can resolve more accute DOAs of uncorrelated and coherent wideband LFM signals in multipath environment with no a priori knowledge of the initial frequency and chirp rate of wideband LFM signals simultaneously. Simulation results demonstrate the effectiveness of the proposed method.