3-D Near-Field Passive Radar Imaging Using Multiple Illumination Sources

Abstract

Near-field (NF) passive radar imaging depends on the illumination of the imaging scene by a non-cooperative transmitter (Tx). It is demonstrated that combining imaging results obtained with Tx antennas at different positions can enhance the performance of passive radar imaging. On the one hand, multiple Tx antennas provide diverse illumination perspectives, reducing the likelihood of unilluminated regions on the targets of interest (TOIs). On the other hand, the coherent summation of imaging results obtained for different illuminations helps to suppress potential artifacts. This approach is in particular advantageous for imaging complex objects with concave structures such as dihedral arrangements, where the ghosts due to multiple reflections are highly configuration-dependent. For each illuminating configuration, a single-frequency inverse source solver is utilized to reconstruct the equivalent sources of the TOIs and the resulting single-frequency images are then superimposed coherently with corresponding phase and magnitude correction methods. The obtained multi-frequency images are finally coherently combined to enhance the imaging quality. Both simulation and measurement results are presented to validate the effectiveness of the approach.

Figures (10)

• Figure 1: Imaging configuration of the TOI with a single Tx antenna, which moves and is excited sequentially from various locations.
• Figure 2: Illustration of the simulation setup with the TOIs located around the origin. Simulations were performed separately for different positions $\mathbfit{r}'_{n}$ of the Hertzian dipole serving as the Tx source. The TOIs are a pyramid-shaped convex structure (a), and a $90^{\circ}$ dihedral corner reflector (b).
• Figure 3: Imaging results of the pyramid-shaped object with the single illumination source located at $\mathbfit{r}'_{1}=[-0.25, 0, 0.25]\,$m (a), and $\mathbfit{r}'_{2}=[0.25, 0, 0.25]\,$m (b).
• Figure 4: Imaging result of the pyramid-shaped object combining the illuminating contributions from the Tx antenna at $\mathbfit{r}'_{1}$ and $\mathbfit{r}'_{2}$.
• Figure 5: Imaging results of the dihedral corner reflector with the single illumination source located at $\mathbfit{r}'_{4}=[0,0,0.4]\,$m. (a) Incoherent summation. (b) Coherent summation using only 11 frequencies.