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energy & radar elements Flashcards

1
Q

electromagnetic wave applications

A

communications, radar, missile guidance, GPS

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2
Q

WAVE

A

a disturbance which travels thru a medium, transverse (EM energy, water) and longitudinal (sound, spring compressions)

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3
Q

amplitude

A

max displacement of any point on the wave from the wave’s axis

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4
Q

wavelength

A

distance covered by a wave during one complete cycle (meters)

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5
Q

period

A

time for one complete cycle of a wave (seconds)

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6
Q

frequency

A

the number of cycles per second (hertz)

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7
Q

Velocity

A

EM waves travel at the speed of light in a perfect vacuum

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8
Q

constructive interference

A

wave strength increases

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9
Q

destructive interference

A

wave strength decreases

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10
Q

radar beam forming

A

illuminates a specific location with a more intense radar beam

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11
Q

phased arrays

A

create and move radar beams by adjusting transmitter phases. NOT physical antenna rotation

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12
Q

relection

A

incident and ___ waves travel in directions that make equal angle perpendicular to the _____ surface

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13
Q

refraction

A

waves are bent while passing thru different mediums. due to change in wave speed

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14
Q

diffraction

A

waves traveling in a straight path bend around a boundary or obstruction

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15
Q

pulse transmission

A

RADAR transmits a series of pulses separated by non-transmission intervals during which the radar “listens” for a return

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16
Q

continuous wave

A

constantly emitting radar, relative motion of either the radar or the target is required to indicate target position, frequency shift

17
Q

range determination

A

pulse transmission measures distance with time. EM waves travel at a constant velocity of about 3x10^8 m/s. Range determined by the 2 way energy transmission. Radar measures total time for reflected pulse to return from target and calculates distance. Direction determined from bearing of radar return

18
Q

pulse width (PW)

A

length of duration of a given pulse

19
Q

pulse repetition time (PRT)

A

time from beginning of one pule to beginning of next

20
Q

pulse repetition frequency (PRF)

A

frequency at which consecutive pulses are transmitted PRT = 1/PRF

21
Q

LONGER PULSE

A

longer detection ranges

22
Q

shorter pulse

A

better range resolution & short range detection

23
Q

long pulse adv vs disadv

A

Advantage: transmits farther, can detect further contacts. Disadvantage: overlooks close contacts, pulse returns while transmitting, receiver cannot process return

24
Q

long pulse close contact

A

echo is received during transmit time, NOT detected

25
Q

short pulse adv vs disadv

A

ADV: clearer return, processes return quicker, detect close contact. DISADV: doesn’t transmit as far

26
Q

range resolution

A

ability to differentiate between two closely spaced contacts

27
Q

radar cross section

A

measures the reflective properties of a contact, function of size, shape, material and angle

28
Q

doppler shift

A

Difference between reference signal and received signal due to target’s motion. A target moving away will reflect a lower frequency return. A target closing in will reflect a higher frequency return

29
Q

transmitter antenna

A

sends out continuous EM wave, provides reference signal to receiving antenna

30
Q

receiver antenna

A

picks up returned signals, compares it to the reference signal

31
Q

phased array/ SPY-1D

A

search, track, beam steering, weapon guidance

32
Q

phased array operation

A

EM energy received from two or more closely spaced radiating elements is maximized when energy from each radiating element arrives at the point in phase. employs constructive and destructive interference. Path lengths from the elements from point P equalize as P approaches infinity

33
Q

beam steering

A

radiate the antenna elements out of phase with one another

34
Q

mechanical scanning

A

requires large amounts of power, processing multiple high-speed targets. antenna inertia, slower reaction times due to stable beam positioning

35
Q

electronic scanning

A

increased data rates, faster reaction time, less mechanical failures, multi-mode operation, automatic multi-target tracking, missile guidance

36
Q

electronic scanning USAGE

A

TICONDEROGA’s CG’s, ARLEIGH BURKE DDG’s, AN/SPS -48 Air search, FORD CVN’s

ocs (20 decks)

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