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eecs 250 lec 1

fire control problem detect and identify localize track and classify weaponeering engagement
mechanical waves requires medium for propagation. sound => needs air or water
electromagnetic doesn't require medium, light, radio => air or water. radar => air
longitudinal waves disturbance in line with direction of porpagation
transverse waves disturbance right angles to the direction of propagation
RADAR RAdio Detection And Ranging electromagnetic wave
frequency rate at which source disturbance oscillates through one complete cycle (hertz: sec^-1)
wavelenth length period of wave
velocity EM waves travel at speed of light mechanical waves travel at speed dependent on medium
amplitude maximum displacement
period time to complete one cycle
maxwell's theory accelerating electric fied will generate a time varying magnetic field time varying magnetic field will generate a time varying electric field
spherical wave omni directional from source ripples in a pond
plan wave far from origin spreads out to appear to have same amplitude everywhere on place perpendicular of travel. entire wave moves in one directoin
phase how much a wave is shifted
propagation paths of EM waves reflection refration diffraction absorption
reflection angle of incidence = angle of reflection media boundaries with dissimilar propagation result in reflection
refraction incident passes through two transparent media in which the velocity of light differes incident wave divides into a reflected wave and a refracted wave
diffraction waves bending around an object because of different speeds of wavelet at medium interface
em signal losses spreading absorption scattering
spreading energy distributed over an increasingly larger area
absorption energy dissipated into medium
scattering energy bouncing off suspended particles
ground waves very low frequencies, vertical polarization, waves travel along earth's surface, very large wavelengths
sky waves energy refracts back towards earth's surface energy then refract back toward upper layer only useable by aircraft
space wave higher frequency, travels in straight line
#10 false
ionospheric scatter scattered reflection of VHF and up
tropospheric scatter scatters signal off troposphere.strong function of weather
radar horizon further than line of sight due to refraction R(km) = sqrt(17Ht) + sqrt(17Hr)
radar advantages can see through poor visibility longer LOS accurate range and relative motion accurate azimuth and elevation feeds info to fire control
radar disadvantages poor target resolution poor ID capabillity
radar types pulse transmission continuous wave
pulsed radars most widely used technique speed of light measures range of echo R = c*dt/2 DRAW gives range, usually altitude, susceptible to jamming
continuous wave radar DRAW continual energy transmission separate trasmit/receive antennae relies on doppler shift no range or altitude high S:N ratio more difficult to jam, easily deceived
reflector shapes basic parabolic orange peel parabolic cylinder
parabolic shape conical scan
orange peel paraboloid narrow beam => resistant to detection and jamming
parabolic cylinder wide search beam, used for long range
radar performance factors signal reception, receiver bandwidth, pulse shape, beam width, S:R, receiver sensitivity, frequency
pulse effects on radar performance pulse {shape, width, compression power}
pulse shape determines range accuracy and min and max range
pulse width the narrower the pulse, the better the range resolution
pulse compression increases frequency allows for good range resolution
pulse power the umph to get the signal out there increases range
track while scan (TWS) aegis, mk92, sps-40, an/sys-2
EW Electronic Warfare
ES electronic support, esm
EA electronic attack, ecm
EP electronic protection, eccm
Non-destructive EA confusion, deception, jamming
Destructive EA missiles{SLAM, HARM, sidewinder}, directed energy
EA-6B prowler plane with EW stuff
FLIR forward looking infrared
NVG night vision goggles
advantages of submarines passive detection concealment speed stay submerged for months
disadvantages of submarines to detect targets, subs must run deep to communicate, subs must run shallow high speed at expense of sound
advantages of surface ships more available manpower greater time on station variety of equipment ability to operate in foul weather
disadvantages of surface ships in submarine's environment relatively slow noisy
advantages of aircraft speed ability to deploy sensors over a large area
disadvantages of aircraft low time on station limited weapons limited range vulnerable to weather
Magnetic Anomaly Detection a metallic submarine disturbs the magnetic force of the earth
sonobuoy small sonar system passes info via VHF limited battery power
passive sonar equation s - n >= dt signal - noise >= detection threshold
ray propagation theory 1. the path that sound travels can be depicted as a ray 2. shell's law: rays will bend when passing between two different mediums 3. sound will always bend towards the region of slower speed
sound travel in isothermal water even straight lines everywhere
sound travel in negative gradient warm water above, cool water below, sound bends down.
sound travel in positive gradient warm water below, cool water above, sound bends up
Created by: treedog669



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