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The Micro-Doppler Effect in Radar
Answers to RF Cafe Quiz #42
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RF Engineering Quizzes - RF CafeAll RF Cafe Quizzes make great fodder for employment interviews for technicians or engineers - particularly those who are fresh out of school or are relatively new to the work world. Come to think of it, they would make equally excellent study material for the same persons who are going to be interviewed for a job. Bonne chance, Viel Glück, がんばろう, buena suerte, удачи, in bocca al lupo, 행운을 빕니다, ádh mór, בהצלחה, lykke til, 祝你好運. Well, you know what I mean: Good luck!

Click here for the complete list of RF Cafe Quizzes.

Note: Some material based on books have quoted passages.

Return to RF Cafe Quiz #42

This quiz is based on the information presented in  Note: Some of these books are available as prizes in the monthly RF Cafe Giveaway.

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)

Quizzes from vintage electronics magazines such as Popular Electronics, Electronics-World, QST, Radio-Electronics, and Radio News were published over the years - some really simple and others not so simple. Robert P. Balin created most of the quizzes for Popular Electronics. This is a listing of all I have posted thus far.

RF Cafe Quizzes

Vintage Electronics Magazine Quizzes

Vintage Electronics Magazine Quizzes
PCB Directory Manufacturer Directory Database - RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2026
Webmaster: Kirt Blattenberger
   BSEE - KB3UON - AMA92498
   USAF Radar Technician

About RF Cafe

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a lady's voice announced "You've Got Mail" when a new message arrived...

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