The Micro-Doppler Effect in Radar
Answers to RF Cafe Quiz #42
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Cafe Quiz #42
This quiz is based on the information presented in Note: Some of these
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quiz is based on the information presented in "The Micro-Doppler Effect in Radar," by Victor C. Chen .
1. What is the micro-Doppler effect?
a) An oscillatory motion in
addition to a bulk motion
If the object or any structural component of the object has an oscillatory motion in
addition to the bulk motion of the object, the oscillation will induce additional frequency modulation on the
returned signal and generates its side bands about the Doppler shift frequency of the transmitted signal due to
the bulk motion. (see page 1)
2. Which of these is an image of Christian
"a" is mathematician Charles Babbage, "b" is telephone inventor Alexander Graham Bell, and "d" is spread spectrum
inventor Hedy Lamar. (see page 3)
3. What is an Euler angle?
of counterclockwise rotation about the x, y, and z axes.
The rotation angles (φ,
θ, ψ) are called Euler angles, where φ
is defined as the counterclockwise rotation about the z-axis,
is defined as the counterclockwise rotation about the y-axis, and
ψ is defined as the counterclockwise
rotation about the axis. (see page 37)
4. Which of the following are mechanisms
producing micro-Doppler shift?
In addition to those, there are the bistatic,
multistatic micro-Doppler effect
d) All the above (see pages 60, 63, 66, 71, and 77)
5. In the case of a rotating helicopter blade on a stationary aircraft, which Doppler
graph would be correct?
Because the advancing blade has a higher velocity toward the observer than does the receding blade, its Doppler
frequency is higher than that of the receding blade. The stronger amplitude signature from the receding blade is
due to the RCS difference. (see page 107)
6. In figure "a" from question 5, why
is a plateau over a range of Doppler frequencies formed
in the blade signature rather than a single
b) Blade speed varies along the span, increasing toward the tips
Although the rotational
velocity is the same along the span, the linear velocity toward the observer increases when progressing from the
hub to the tip, per v = ωr. (see page 108)
7. What is the Denavit-Hartenberg
d) A kinematic representation of human body links and joints
The D-H convention states that each link has its own coordinate system with its z-axis in the direction of the
joint axis, the x-axis aligned with the outgoing link, and the y-axis orthogonal to the x- and z-axes. (see page
8. When analyzing articulated locomotion (animal walking, bird wing flapping, etc.),
commonly assumed to describe the style of sinusoidal motion?
c) Harmonic oscillations
Harmonic oscillations are the basis of analyzing complicated motion because any motion can be decomposed into a
summation of a series of harmonic components with different amplitudes and frequencies by using the Fourier
series. (see page 195)
9. What is the difference between bipedal and quadrupedal
a) Two additional feet
biped: "animal with two feet," 1640s, from L. bipedem (nom.
from bi- "two" + pedem (nom. pes) "foot"
quadruped: from L.
quadrupes (gen. quadrupedis) "four-footed, a four-footed animal,"
from quadri- "four" (see
quadri-) + pes "foot" (see foot).
(see page 202)
10. Which parameters can be extracted from micro-Doppler
signatures of targets?
d) All the above
Feature extraction and target information based on
micro-Doppler signatures is the primary use of the technique. (see page 273)