Through-Wall-Imaging (TWI) radar offers considerable advantages for applications that require safety and security, such as disaster survivor rescue and tracking terrorist activities. In such situations, the use of an impulse UWB radar system is constantly increasing due to its ability to provide precise images of hidden targets in a short period of time. This paper presents a new radar system for through-wall imaging using an impulse-radio ultra-wideband (IR-UWB) signal. The radar system is built using a field-programmable gate array (FPGA) board, an oscilloscope, and Vivaldi antennas. The radar system transmits impulse signals, which have a monocycle shape with a 400-picosecond duration and a 4.6 GHz bandwidth. The FPGA board is used to produce impulse signals that have a short time duration in the sub-nanosecond range in order to expand the bandwidth of the generated signal and make the developed radar capable of providing high-resolution images. The FPGA-based implementation of the IR-UWB generator offers the flexibility to modify the spectrum characteristics of the generated signal. The receiver side of the radar system collects the echoes using the principle of synthetic aperture radar (SAR), and then the time-domain back-projection algorithm is applied to the radar echo to form 2D images. An indoor imaging experiment was carried out with two human targets to investigate the imaging capability of the designed IR-UWB radar. The obtained experimental results demonstrate that this radar has the potential to deliver high-resolution images of multiple human targets and identify their locations.
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