Human detection and tracking are
a topic of recent interest because
of the increased concerns regarding security and surveillance. Detection and
localization of moving human subjects in line-of-sight or through-wall
environment can be applied in disaster search-and-rescue operation, physical security, law enforcement, and border
patrol. To detect human subjects, various sensor technologies have been
developed. They include the use of computer vision, seismic sensor, infrared detectors,
lidar, and radar. Among them, radar offers a number of unique advantages compared
with the other technologies because it can penetrate obstacles such as walls
and can detect targets under various weather conditions. Here, a method for detecting a
human subject using Doppler radar by investigating the physical characteristics
of targets is analysed. To classify a target from the Doppler signal, several
features related to the physical characteristics of a target are extracted. The
features include the frequency of the limb motion, stride, bandwidth of the
Doppler signal, and distribution of the signal strength.
Owing to the different lengths of legs
and kinematic signatures of the target species, a human subject occupies a
unique space in the terms of the stride and the frequency of limb motion. To
verify the proposed method, the motions of humans, dogs, bicycles, and vehicles
are observed using the developed continuous-wave Doppler radar. The use
of the Doppler radar is a natural choice for human detection. A method for
identifying a human subject against other targets using the physical
characteristics of a target extracted from the Doppler signals is implemented
in this. Human detection has a number
of applications in security, surveillance, and search-and-rescue operations.
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