Abstract: Aiming at the angle estimation problem of uniform linear array in multiple carrier frequencies radiation sources passive reconnaissance, the angle estimation algorithm based on maximum likelihood estimation for multiple radiation sources with different carrier frequencies was proposed. The algorithm was divided into two steps. First, by deriving the maximum likelihood function and the gradient of the multiple radiation source signals intercepted by the uniform linear array, the angles of the multiple radiation sources of different carrier frequencies were estimated simultaneously by using the steepest descent method. Second, in order to solve the problem of phase ambiguity in different carrier frequencies, the lattice algorithm was proposed to compute the nearest integer points to the fuzzy phase. The cuckoo optimization algorithm was proposed to estimate the fuzzy number corresponding to integer points. Unambiguous angles of multiple radiation sources were obtained. The simulation results show that the proposed algorithm has better performance in angle estimation and unwrapping phase ambiguity than the traditional algorithms in terms of low signal to noise ratio (SNR), low sampling number and multiple radiation sources.

Key words: passive reconnaissance, sparse array, angle estimation, unwrapping phase ambiguity