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The Micro-Doppler Effect in Radar
Answers to RF Cafe Quiz #42

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Return to RF Cafe Quiz #42

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The Micro-Doppler Effect in Radar - RF Cafe Quiz #42This 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 Doppler?

c)  Christian Doppler - RF Cafe

"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?

b)  Angles 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, θ 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 for

     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 frequency

     graph would be correct?

a)  The Micro-Doppler Effect in Radar, Helicopter Blade Doppler Signature - RF Cafe Quiz #42

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 frequency?

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-H convention)?

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 162)

8.  When analyzing articulated locomotion (animal walking, bird wing flapping, etc.), what is

     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 locomotion?

a)  Two additional feet

       biped:  "animal with two feet," 1640s, from L. bipedem (nom. bipes) "two-footed,"

                     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)

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