 Naval Weapons Systems Energy Fundamentals Learning Objectives  Comprehend basic communication theory, electromagnetic (EM) wave theory  Comprehend.

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Naval Weapons Systems Energy Fundamentals

Learning Objectives  Comprehend basic communication theory, electromagnetic (EM) wave theory  Comprehend radar and radio wave parameters including frequency, period, wavelength, velocity, and amplitude  Know Maxwell’s theory, relationship between wave parameters  Comprehend concepts of time and distance (wave phase angle) and interference

Learning Objectives (cont)  Know EM wave propagation principles such as reflection, refraction, diffraction, and ducting  Know the definition of sky, space, and ground waves

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

Traveling Wave Characteristics  Frequency  Period  Wavelength  Velocity  Amplitude

Maxwell’s 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... Electric FieldMagnetic FieldElectric Field

Formation of Electric and Magnetic Fields around an Antenna e- E-line Mag field Electric field | Magnetic Field | Direction of Propagation.

Electromagnetic Spectrum

Propagation Paths of E-M Waves  Reflection  Refraction  Diffraction

...Reflection... Incident Wave Reflected Wave Phase shift = 180 degrees. Angle of incidence = Angle of reflected wave.

-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....Refraction...

Snell’s Law n 1 * Sin θ 1 = n 2 * Sin θ 2

...Diffraction... island not detected detected...plane waves traveling in a straight path bend around a boundary or obstruction.

Wave Propagation – Distance and Frequency  Ground Waves  Sky Waves  Space Waves

Ground Wave...  E-M energy travels along earth’s surface  Very low frequencies, 5-10Khz  Extremely long wavelengths  Shore communications stations (HF-DF)

Sky Wave...  E-M energy refracts toward earth’s 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

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

Transmission Range Factors  Antenna Height  Target Height  Ducting  Losses –Spreading –Absorption –Constructive Interference –Destructive Interference

Modulation  The process of encoding “Carrier Wave”  “Carrier Wave” has 3 independent parameters –Amplitude –Frequency –Phase

WHEW!

Questions?

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