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A new hybrid method for solving inverse scattering problems in time domain is proposed. In this method, a two-step optimization-based routine is used in which direct and so called expansion methods are utilized simultaneously to obtain more precise and rapid reconstruction. In the first step, a coarse solution is achieved with the help of truncated cosine Fourier series expansion method. Then, with this solution as an initial guess for the second step, direct optimization is used to obtain a much more accurate solution of the problem. In both steps, finite difference time domain and particle swarm optimization are used as an appropriate electromagnetic solver and global optimization routine, respectively. The most important advantage of this method is that because of a suitable initial answer in direct optimization routine, sensitivity of the algorithm to the regularization parameter is decreased and convergence of the results is completely guaranteed. Performance of the proposed method is demonstrated and compared with expansion and conventional direct optimization methods for several 1-D permittivity and conductivity profile reconstruction cases.