# Localization of GNSS Spoofing Interference Source Based on a Moving Array Antenna
## 3 Proposed Methods
### The Method Processing Flow  
Figure 7 illustrates the data processing flow description of the GNSS spoofing interference source localization method based on a moving array antenna. The steps of the method are as follows:  
1. We conduct real-time monitoring of the satellite identification code tracked by each tracking channel and determine whether there are two different channels tracking the same satellite. If the above conditions exist, it is judged spoofing interference is detected, and output the corresponding tracking channel vector \(\mathbf{Cha}=[Cha1,\)\(Cha1^{\prime},\cdots\)\(Chaj,Chaj^{\prime},\cdots,ChaK,ChaK^{\prime}]\), where \(Chaj\) and \(Chaj^{\prime}\) are channel numbers tracking the same satellite. 2. Take any pair of tracking channels \(Chaj\) and \(Chaj^{\prime}\) that track the same satellite signal, take any antenna array element \(i\), and calculate the carrier phase double-difference between the other channels in \(\mathbf{Cha}\) and the selected channel to obtain the carrier phase double-difference observation vectors \(\Delta\mathbf{\Phi_{i}^{Chaj}}=[\Delta\varphi_{i}^{Cha1^{\prime},Chaj},\cdots\Delta \varphi_{i}^{Chaj^{\prime}-1,Chaj},\cdots,\)\(\Delta\varphi_{i}^{ChaK^{\prime},Chaj}]\) and \(\Delta\mathbf{\Phi_{i}^{Chaj^{\prime}}}=[\Delta\varphi_{i}^{Cha1,Chaj^{\prime}}, \cdots\Delta\varphi_{i}^{Chaj-1,Chaj^{\prime}},\cdots,\Delta\varphi_{i}^{ChaK,Chaj ^{\prime}}]\), where the expression of double-differenced carrier phase \(\Delta\varphi_{i}^{Chaj^{\prime}-1,Chaj}\) is the same as that of Equation (5). 3. After obtaining the carrier phase double-difference, use the method in Section 3.1 to extract and confirm the spoofing interference signals and output the tracking channel vector \(\mathbf{Cha}^{\prime}=[Cha1^{\prime},\cdots\)\(Chaj^{\prime}\cdots,ChaK^{\prime}]\) corresponding to the deception satellite signals. 4. Compare the carrier-to-noise ratio (C/N0) of the tracking signals of each channel in vector \(\mathbf{Cha}^{\prime}\), and take the deception satellite signal \(\mathbf{Chamax}^{\prime}\) with the highest C/N0 among them. 5. Collect carrier phase single-difference data of the deception signal \(\mathbf{Chamax}^{\prime}\) along the spoofing location path and obtain the observation vector \(\mathbf{\varphi}^{\mathbf{Chamax}^{\prime}}=[\varphi_{1,1}{}^{\mathbf{Chamax}^{\prime}}, \varphi_{1,2}{}^{\mathbf{Chamax}^{\prime}},\cdots,\varphi_{j,i}{}^{\mathbf{Chamax}^{ \prime}},\cdots,\varphi_{M,6}{}^{\mathbf{Chamax}^{\prime}}]^{T}\), where the expression of carrier phase single-difference \(\varphi_{j,i}{}^{\mathbf{Chamax}^{\prime}}\) is the same as that of Equation (6). 6. After acquiring the carrier phase single difference data, employ the methodology elucidated in Section 3.2 to directly ascertain the precise location of the spoofing interference and yield the spatial coordinates of its source \(\mathbf{p_{t}}\). We would like to give the following explanation for the practical application of the method:* The double-differenced carrier phase-based spoofing interference extraction method enables an efficient separation between the real satellite signals and the spoofing signals, thereby facilitating the use of authentic satellite signals for determining the position of the array antenna itself. * After implementing spoofing interference extraction, in principle, any satellite signal of the spoofing interference can be utilized to construct equation system (9). With increased signal strength, the accuracy of carrier phase measurement also improves, thus enhancing the effectiveness of the method; we select the satellite signal with the highest C/N0 for establishing the equation. * The method presented in this paper is also applicable to multiple spoofing interference source localization scenarios; however, the applicable scenario requires that the located interfering source emits two or more spurious satellite signals. For multiple spoofing interference sources, the method in Section 3.1 of this paper can be used multiple times to extract multiple spoofing source signals.