In response to the increasing threat of terrorism, standoff security screening of person-borne concealed weapons or contraband in public areas, such as airports and railway stations, is an urgent requirement; however, current solutions suffer from the limited field of view and the problem of security screening with interfering with the passenger flow. This paper proposes an imaging method that exploits the angular diversity of distributed multistatic terahertz (THz) radar network in combination with inverse synthetic aperture radar (ISAR) technique to realize high-resolution penetration imaging at a standoff range. The radar network is based on multistatic ISAR systems, and the multistatic ISAR system’s equivalent monostatic model is derived. According to the equivalent monostatic model, we develop the image formation algorithm and give the analytical expression of the cross-range resolution. Compared with conventional monostatic ISAR configuration, the analytical expression shows that the multistatic ISAR configuration can enhance the image’s cross-range resolution and the maximum enhanced factor is approximately equal to the number of radars in the multistatic system. Numerical simulations and experimental results agree well with the theoretical derivation. The proposed imaging approach offers a low-cost and flexible alternative to the present systems not only for security screening but also for noncooperative target imaging.
The high-resolution inverse synthetic aperture radar (ISAR) imaging of the maneuvering target with small-angle measurements is expected, which can be achieved by using the radar operating at a higher central frequency. However, because the defocus induced by the spatially variant phase error becomes significant with the resolution improvement and the central frequency increasing, the global phase correction is invalid. Moreover, due to the scattering characteristics of aspect-dependent scatterers and small-angle measurements, we can rarely obtain the rough outline of the maneuvering target. To deal with these difficulties, we propose an ISAR imaging method for the maneuvering target with distributed high resolution radars. To mitigate the spatially variant phase error, we correct phase errors in patches based on the weighted least-squares algorithm, which makes the image well-focused. Then, the ISAR imaging method with distributed radars is presented to obtain the fusion image, with the object to capture enough scatterers to represent the maneuvering target. The fusion image could provide more details. Real data have verified the effectiveness of the proposed method.
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