Abstract
Passive localization is an important part of intelligent surveillance in security and emergency applications. Nowadays, Global Navigation Satellite Systems (GNSSs) have been widely deployed. As a result, the satellite signal receiver may receive multiple GPS signals simultaneously, incurring echo signal detection failure. Therefore, in this paper, a passive method leveraging signals from multiple GPS satellites is proposed for moving aerial target detection. In passive detection, the first challenge is the interference caused by multiple GPS signals transmitted upon the same spectrum resources. To address this issue, successive interference cancellation (SIC) is utilized to separate and reconstruct multiple GPS signals on the reference channel. Moreover, on the monitoring channel, direct wave and multi-path interference are eliminated by extensive cancellation algorithm (ECA). After interference from multiple GPS signals is suppressed, the cycle cross ambiguity function (CCAF) of the signal on the monitoring channel is calculated and coordinate transformation method is adopted to map multiple groups of different time delay-Doppler spectrum into the distance–velocity spectrum. The detection statistics are calculated by the superposition of multiple groups of distance-velocity spectrum. Finally, the echo signal is detected based on a properly defined adaptive detection threshold. Simulation results demonstrate the effectiveness of our proposed method. They show that the detection probability of our proposed method can reach 99%, when the echo signal signal-to-noise ratio (SNR) is only −64 dB. Moreover, our proposed method can achieve 5 dB improvement over the detection method using a single GPS satellite.
Highlights
With the development of space technologies, Global Navigation Satellite Systems (GNSSs) have been widely applied in various applications and have been playing an extremely important role in many fields [1,2,3]
The system model of the echo signal detection and reception system based on data fusion of multiple Global Positioning System (GPS) satellites is shown in Figure 1, where Rt is the distance from the satellite to a target, L is the distance from a satellite to a receiver, θ is the arrival angle of the echo, φ is the arrival angle of the direct wave, and Rr is the distance from a target to a receiver
I=1 i=1 where Qm(·, ·) is the Marcum Q function. It can be seen from Equation (42) that the theoretical detection probability of the GPS weak echo signal detection method based on multi-star data fusion is related to the parameters, such as the monitoring channel noise, the number of sampling points N, the number of satellites, and the false alarm probability
Summary
With the development of space technologies, Global Navigation Satellite Systems (GNSSs) have been widely applied in various applications and have been playing an extremely important role in many fields [1,2,3]. Instead of relying on only a single GPS satellite radiation source, effective weak echo signal detection methods using multiple GPS satellite radiation sources need to be studied. Due to the benefits of global coverage, 24-h operation, and easy-to-access signal sources, GPS navigation satellite signals will be employed as third-party illumination sources to study GPS-based external radiation source target detection methods in this paper. Firstly, the proposed method separates and reconstructs multiple GPS reference signals on the reference channel, based on which the Extensive Cancellation Algorithm (ECA) is used to monitor and suppress DPI and MPI. To address the problem of the weak target reflection echo, which is very difficult to be detected, a coordinate conversion algorithm is applied to fuse detection statistics of multiple GPS satellites and obtain a final detection statistic.
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