Sea target detection using the GNSS reflection signals

Global navigation satellite system (GNSS) reflection signal to form a passive radar system for sea target detection has attracted attention in recent years. Low signal power on the earth’s surface is the main bottleneck of this passive radar system. Prolonging the integration time is an effective way to improve the radar detection ability. However, the range cell migration (RCM) and Doppler frequency migration (DFM) induced by the target motion during the long integration time cause integration gain loss and degrade the detection ability. A long-time hybrid coherent and noncoherent integration method is proposed to overcome such issues. This method uses the keystone transform and the matched filtering function H ₁ to remove the linear RCM and quadratic RCM, respectively. Then, the long-time integration time is segmented into multiple frames with the same duration. Another matched filtering function H ₂ is designed to eliminate the DFM. Finally, coherent integration and noncoherent integration operations are implemented inside and among the frames to improve the signal-to-noise ratio of the target-reflected GNSS signal available for detection. A maritime measurement campaign is conducted and confirms the effectiveness of the proposed method for sea target detection. Monte Carlos trials and computational cost analysis show that the detection capability of the proposed method outperforms that of the existing methods, but the computational cost is in the same order as O(N³log N) .