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Sensors Final > Sensors 1 > Flashcards

Sensors 1 Flashcards

1
Q

Electromagnetic (EM) Waves definition

A

Forms of radiant energy such as radio waves, infrared radiation, light waves, X rays, gamma rays, and cosmic rays.

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2
Q

Describe EM Spectrum. Which band are used for voice comms?

A

BAND FREQ λ BANDWIDTH
ELF 3-30 HZ 100 000-10 000 KM 27 HZ
SLF 30-300 HZ 10 000-1000 KM 270 HZ
ULF 300-3000 HZ 1000-100KM 2700 HZ
VLF 3-30 KHZ 100-10 KM 27 KHZ
LF 30-300 KHZ 10-1 KM 270 KHZ
MF (VOICE COMMS) 300-3000 KHZ 1000-100 M 2700 KHZ
HF (VOICE COMMS) 3-30 MHZ 100-10 M 27 MHZ
VHF (VOICE COMMS) 30-300 MHZ 10-1 M 270 MHZ
UHF (VOICE COMMS) 300-3000 MHZ 100-10 CM 2700 MHZ
SHF 3-30 GHZ 10-1 CM 27 GHZ
EHF 30-300 GHZ 10-1 MM 270 GHZ

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3
Q

Which NATO Designator is related to military?

A

I (India)

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4
Q

Characteristics of EM Waves? (7)

A

a. Amplitude
b. Cycle
c. Phase
d. Speed of propagation
e. Frequency
f. Period
g. Wavelength

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5
Q

Propagation Effects (6)

A
  1. Doppler Shift
  2. Interference
  3. Attenuation
  4. Diffraction
  5. Refraction
  6. Reflection
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6
Q

Describe Doppler shift (propagation effect)

A

Change in frequency and wavelength, due to the relative motion of the EM wave source in relation to the observer.

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7
Q

Describe Interference (propagation effect)

A

Occurs when 2 waves of the same frequency arrive at the same point via different paths. Constructive interf. = same phase & Destructive interference = out of phase.

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8
Q

Describe Attenuation (propagation effect)

A

Combined effects of Spreading, Absorption and Scattering.

Spreading: Power density loss is proportional to square of distance travelled.

Absorption: Reduction of energy due to energy being absorbed in full or part by surrounding particles in his path. Frequency dependant.

Scattering: A change in direction of EM energy due to collision with particles.

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9
Q

Describe diffraction (propagation effect)

A

Bending of an EM wave around objects or barriers.

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10
Q

Describe Refraction (propagation effect)

A

Change in direction due to its change in velocity when passing into a medium of a differing density.

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11
Q

Describe Reflection (propagation effect)

A

Bouncing of EM energy off an object that has a density different than that of the propagating medium.

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12
Q

What are the EM propagation Modes? (3)

A
  1. Surface Waves (Diffraction, 30 to 300 KHz)
  2. Sky Waves (Refraction with Ionosphere, 300 KHz to 30 MHz)
  3. Space Waves (Very high Freq., more than 30 MHz)
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13
Q

Comms Goal?

A

To provide friendly forces with the intended information while denying that information to the enemy.

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14
Q

DEFENSIVE + OFFENSIVE DESIRED CHARACTERISTICS?

A 
Security	        Timeliness
Survivability	Completeness
Availability 	Reliability
Affordability	Fidelity
Accuracy	         Interoperability
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15
Q

The basic comms system consist of what?

A

Transmitter………MEDIUM………Receiver

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16
Q

Comms Modes?

A
  1. Simplex (oneway) i.e. TV
  2. Half Duplex (Morse Code & Push to talk)
  3. Full Duplex (Telephone)
17
Q

Energy Types?

A
  1. Electrical Energy: for short-distance metallic wires only

2. Electromagnetic Energy: For all other links…Long-distance metallic wires, Optical fibres, wireless transmissions.

18
Q

Comms Methods?

A
  1. Bounded vs. Wireless
  2. Analogue vs. Digital
  3. Voice vs. Data
19
Q

Communication Signals (Types)?

A
  1. Signal Form (Analogue vs Digital)
  2. Carrier Signal (Baseband vs. Modulated)
  3. Frequency Coverage (Narrow vs. Wideband)
20
Q

Signal Representations?

A
  1. Time Domain

2. Frequency Domain

21
Q

Medium?

A
  1. Telephone wires
  2. TV coaxial cables
  3. Computer network connections
  4. Waveguides
  5. Optical fibres
  6. The atmosphere
22
Q

Signal Source Examples?

A

a. Analogue (Voice, Images, Video)

b. Digital (1’s and 0’s or conversion from analogue)

23
Q

Comms Constraints: PICK 2!!

A
  1. Lots of DATA
  2. Small Bandwidth **
  3. Short Transmission
24
Q

What is the Biggest limitation on the volume of communications that can be transmitted by an operator?

A

Bandwidth

25
Q

Comms Obstacles?

A
  1. Noise (Cooling your system)
  2. Distortion (Using high quality equipment)
  3. Attenuation (measured in Decibel) (Going Digital & better shape antenna to be as close as possible as a parabola)
  4. Interference (Changing frequencies)
  5. Multi-Path Fading (GPS en ville, le signal rebondi sur les buildings)…reduced the fading possibilities.

Sensors Final (12 decks)

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