Detection of DSSS/UQPSK signal based on fourth-order cumulant algorithm

For the problem of Direct Sequence spread spectrum unbalance Quadrature Phase Shift Keying (DSSS/UQPSK) signal can´t be detected easily, the method of the fourth-order cumulant detection is proposed in this paper. On the basis of the fourth-order cumulant of the Gaussian White Noise is equal to zero, Firstly, the paper analyzes the theory knowledge of direct sequence unbalance QPSK signal and the feasibility of estimating carrier-frequency based on fourth-order statistic slice. Then, proposes a detecting method of the DSSS/UQPSK signal with the fourth-order cumulant c_4x (0,0,0), c_4x (0,0,τ), c_4x (0, τ, τ) and c_4x (τ, τ, τ). Finally, the performance of the fourth-order cumulant different slices will be acquired by doing some effectively simulations, and the DSSS/UQPSK signal´ carrier-frequency will be estimated based on the slices´ frequency spectrum. Experimental results show that the detection performance of c_4x (0, τ, τ) is the best, while the fourth-order cumulant c_4x (τ,τ,τ) can estimate the carrier-frequency effectively at low signal-to-noise ratio. The proposed method is of high feasibility and has practical application value.