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eecs 250 lec 1
| Question | Answer |
|---|---|
| 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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