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Naval Weapons Systems

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Energy Fundamentals Energy Fundamentals RAdio Detection And Ranging Radar is an electromagnetic wave that acts like any other electromagnetic wave (i.e. - radio ... – PowerPoint PPT presentation

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Title: Naval Weapons Systems


1
Naval Weapons Systems
  • Energy Fundamentals

2
Energy Fundamentals
  • RAdio Detection And Ranging
  • Radar is an electromagnetic wave that acts like
    any other electromagnetic wave (i.e. - radio,
    light, etc.)
  • Characteristics of a radio wave assuming a
    frequency of 2 Hertz

Cycle
Amplitude
1 second
3
Traveling Wave Characteristics
  • Frequency
  • Period
  • Wavelength
  • Velocity
  • Amplitude
  • ...examples....

4
Maxwells Theory
  • An accelerating electric field will generate a
    time-varying magnetic field.
  • A time-varying magnetic field will generate a
    time-varying electric field.
  • ...and so on...and so on...and so on...

5
Formation of Electric and Magnetic Fields around
an Antenna
E-line
Mag field
e-
e-
e-
Electric field Magnetic Field Direction
of Propagation.
6
Electromagnetic Spectrum
7
Propagation Paths of E-M Waves
  • Reflection
  • Refraction
  • Diffraction

8
...Reflection...
Phase shift 180 degrees. Angle of incidence
Angle of reflected wave.
Reflected Wave
Incident Wave
9
...Refraction...
  • Incident wave passes through two transparent
    media in which the velocity of light differs...
  • Incident wave divides into a reflected wave and a
    refracted wave.
  • The result is that the energy ray will bend
    toward the area of higher density.

10
Snells Law
n1Sin ?1n2Sin ?2
11
...Diffraction...
...plane waves traveling in a straight path bend
around a boundary or obstruction.
detected
12
Wave Propagation Distance and Frequency
  • Ground Waves
  • Sky Waves
  • Space Waves

13
Ground Wave...
  • E-M energy travels along earths surface
  • Very low frequencies, 5-10Khz
  • Extremely wavelengths
  • Shore communications stations (HF-DF)

14
Sky Wave...
  • E-M energy refracts toward earths surface in
    upper ionosphere layer
  • E-M energy then reflects back toward upper layer
    again
  • Frequencies to 550 KHz effectively
  • Fairly long wavelengths
  • Ship and Aircraft Communications

15
Space Wave...
  • E-M energy refracts back toward earths surface
    in outer space (i.e. stratosphere)
  • Above 30 MHz, ionosphere will not refract E-M
    waves back toward earth.

16
Transmission Range Factors
  • Antenna Height
  • Target Height
  • Ducting
  • Losses
  • Spreading
  • Absorption
  • Constructive Interference
  • Destructive Interference

17
Communication Systems
18
Basic Comms Path
19
Transmitter
  • Transducers Changes energy form
  • Acoustic waves to EM waves
  • Boosts power of signal to increase distance.

20
Transmission Channel
  • Air
  • Water
  • Wire
  • Co-axial
  • Fiber Optics
  • Beer

21
Transmit/Receive Capability
  • Simplex one or the other
  • i.e. car radio
  • Half-Duplex both, but not at same time.
  • i.e. walkie-talkie
  • Full-Duplex both and at the same time
  • i.e. shipboard telecommunications systems

22
Receiver
  • Tuner allows particular frequency reception

23
Modulation
  • The process of encoding Carrier Wave
  • Carrier Wave has 3 independent parameters
  • Amplitude
  • Frequency
  • Phase

24
Noise
  • Noise is bad on a communications circuit.
  • Two types
  • Broadband Noise White Noise
  • Narrowband Noise Interference

25
Signal-to-Noise Ratio
  • Expressed as a ratio of
  • Signal power / Noise power
  • Unit of measure in Decibels
  • The more positive the number, clearer the signal.
  • Unless you want to hide it!!!

26
  • Questions?
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