A Cell-Based Coherent Signal Fusion in Range-Doppler Domain for Networked Radars

Signal-to-noise ratio (SNR) gain of coherent signal fusions can be higher than noncoherent fusions for networked radars. However, the difficulty of coherent fusion is that echoes from multiple radars are required to be accumulated with the same phase. The phase differences to be compensated are different for signals in different range-Doppler cells. Therefore, a cell-based coherent signal fusion in range-Doppler domain is proposed for networked radars, which is different from the existing fusions in echo domain. Before fusion, the range and Doppler compensation is made to keep the same target in the same range-Doppler cell for different radars. Then, we need to calculate the weight for each cell separately because of the different phase differences. An objective function is established to estimate the fusion weight for each range-Doppler cell using linearly constrained minimum power fusion. The weight maintains the signal power of the range-Doppler cell in which the target appears fixed after fusion and minimizes the power of all cells. The range and velocity of the target in each cell are detected by cell averaging constant false alarm rate (CA-CFAR) detection on the signal fused by the corresponding weight. Simulation results show that the SNRs after fusion using the proposed algorithm are improved and the targets can be detected via CA-CFAR when a monostatic radar cannot detect the targets due to low SNRs. To verify the effectiveness of the proposed algorithm, a hardware test is carried out, and the result is consistent with the simulation result.