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NS212 Exam_1_Guide

# NS212 Exam_1_Guide - James Wilker Exam 1 19FEB2014 Lecture...

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James Wilker Exam 1 19FEB2014 Lecture 2 Weapon system requirements o Reliability o Flexibility o Safety o Simplicity of Operation o Maintainability o Specific Military Requirements Three Naval Warfare Areas o Anti-Air Warfare (AAW) o Anti-Submarine Warfare (ASW/USW) o Anti-Surface Warfare (ASUW/ASU) Basic characteristics of a wave o Frequency Rate at which expand/collapse Cycles per sec f = 1/T f=frequency (Hz) T=period(time)(sec) o Period The time required to complete one cycle T = 1/f f=frequency (Hz) T=period(time)(sec) o Wavelength Distance between two identical points on the wave Wavelength (m) = wave propagation (m/s) / frequency (Hz) o Amplitude Maximum displacement of any point on the wave from a constant reference value (measure the level of energy) Reflection / Refraction / Diffraction

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o o Reflection theta 1 = theta 1 o Refraction theta 1 ≠ theta 2 but theta 1 = theta 1 Snell’s Law n1sin(theta1) = n2sin(theta2) o Diffraction Lecture 3 Diploe antenna radiation pattern o Dipole antenna radiates its energy in all directions perpendicular to its axis o Nothing comes out the ends EM wave – electric field vs. magnetic field (orientation) o Beamforming o Desirable to concentrate the radiated electromagnetic energy into a directional beam o Radiates out like a doughnut Reflectors Capitalize on reflectivity of waves, increasing directivity Arrays
Arranges half-wave antennas such that their fields add together in a specific direction and cancel in others Wave propagation o Ground Low frequency o Sky Middle frequency o Space Waves High frequency o Know that frequencies go from low (ground waves) to high (space waves) o LOS Radar is a space wave Radar LOS horizon Max allowable separation between transmitter and receiver Lecture 4 “Radar” is an acronym for _________ o RADAR RA dio D etection A nd R anging Pulse Transmission radar o basic concept Transmits energy in a series of short pulses separated by non-transmission intervals or rest times During the “on” period the radar transmits short burst (pulse) of energy Pulse strikes an object, part of reflected energy returns to receiver o PW + RT = PRT Pulse width + rest time = pulse repetition time o Pulse Repetition Frequency (PRF) Number of pulses transmitted per second (Hz) o Why is PW important

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Determines the minimum range at which a target can be detected o basic schematic of Pulse Transmission system Radar cross section o Defined as the area intercepting that amount of power which, when scattered equally in all directions, produces an echo at the radar o Generally, the larger the object, the larger the cross section o Determined by target size, shape, skin material, aspect angle, polarization, radar carrier frequency Lecture 5 Concept of beamwidth o Early warning radar used to search wide area, wide beam pattern —accuracy is sacrificed for max detection probability o
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