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Modern radars can pick up target motions other than just the principle target Doppler; they pick out the
small micro-Doppler variations as well. These can be used to visually identify both the target type as well
as the target activity. We model and measure some of the micro-Doppler motions that are amenable to
polarimetric measurement.
Understanding the capabilities and limitations of radar systems that utilize micro-Doppler to measure
human characteristics is important for improving the effectiveness of these systems at securing areas. In
security applications one would like to observe humans unobtrusively and without privacy issues, which
make radar an effective approach. In this paper we focus on the characteristics of radar systems designed
for the estimation of human motion for the determination of whether someone is loaded.
Radar can be used to measure the direction, distance, and radial velocity of a walking person as a function
of time. Detailed radar processing can reveal more characteristics of the walking human. The parts of the
human body do not move with constant radial velocity; the small micro-Doppler signatures are timevarying
and therefore analysis techniques can be used to obtain more characteristics. Looking for
modulations of the radar return from arms, legs, and even body sway are being assessed by researchers. We
analyze these techniques and focus on the improved performance that fully polarimetric radar techniques
can add. We perform simulations and fully polarimetric measurements of the varying micro-Doppler
signatures of humans as a function of elevation angle and azimuthal angle in order to try to optimize this
type of system for the detection of arm motion, especially for the determination of whether someone is
carrying something in their arms. The arm is often bent at the elbow, providing a surface similar to a
dihedral. This is distinct from the more planar surfaces of the body and allows us to separate the signals
from the arm (and knee) motion from the rest of the body. The double-bounce can be measured in
polarimetric radar data by measuring the phase difference between HH and VV. Additionally, the cross-pol
and co-pol Doppler signatures are analyzed, showing that the HH polarization may perform better on
dismounts in open grass.
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