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Radar Flashcards

1
Q

Discuss radar wave propagation: polarization

A

Orientation of the electrical field creaded by radar waves. Can be horizontal, vertical, sland and circular

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2
Q

Discuss radar wave propagation: power

A

Strength of the radar signal hitting the target

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3
Q

Discuss radar wave propagation: reflection

A

The process of reradiation an incident radio wave

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4
Q

Discuss radar wave propagation: refraction

A

The bend of Em energy

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5
Q

Discuss radar wave propagation: diffraction

A

Phenomenon observed when a radio wave spreads around objects whose size is comparable to its wavelength and bends aroudn the edges of larger objects

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6
Q

Discuss radar wave propagation: ducting of radar waves

A

Subrefraction decreases radar LOS by bending the radar beam upward, decreasing its range. Suberrefraction increases the radar LOS detection by bending the beam downward, increasing the radar horizon.

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7
Q

Discuss the charateristics of parabolic antennas

A

Low antenna gain, low efficiency and large sidelobes (disadvantages) Easiest and cheapest to manufacture (advantage)

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8
Q

Discuss Electronically Scanned Array ESA characteristics

A

Individual radiating elements make up the antenna array. Mounted in a fixed position. Steering is by individually controlling the phase of the radio

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9
Q

Differences in passive and active ESA

A

Passive: Operates in conjunction with the same type of central transmitter and receiver as an MSA. Beam is steered by a phase shifter placed behind radiating elements. Active: Instead of a phase shifter, a small T/R module is placed behind radiating elements

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10
Q

Discuss limitations of ESA antennas

A

Apparent size of the antenna decreases when viewed from angels off boresight. Electronically complex

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11
Q

Discuss pulsed-radar operations

A

Pulse radar transmits radio waves in short pulses and listens for echoes in periods between pulses.

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12
Q

Discuss pulsed-radar operations: PW

A

The time the radar is transmitting each pulse

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13
Q

Discuss pulsed-radar operations: PL

A

Distance between the leading and trailing edges of a pulse

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14
Q

Discuss pulsed-radar operations: range resolution

A

Radars ability to resolve multiple targets in range

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15
Q

Discuss pulsed-radar operations: range cell

A

Smallest amount of 3-D airspace in which a radar cannot distinguish between multiple targets

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16
Q

Discuss pulsed-radar operations: PRF

A

Rate at which pulses are transmitted

17
Q

Discuss pulsed-radar operations: pulse ranging

A

Radar transmits RF, RF reflects off a target, RF echos are received. Time between transmit and receive is converted to range

18
Q

Discuss pulsed-radar operations: range rate

A

computed based on the basis of change in measured range with time.

19
Q

Discuss CW/Doppler radar characteristics

A

Shift in frequency of an Em wave radiated, reflected or received by an object in motion.

20
Q

How does a CW/Doppler radar measure target velocity

A

Very accurate method to measure target velocity 1 kt = 35Hz shift 1000ft/s = 20kHz shift March 1 = 20kHz 1 kHz = 30 knots

21
Q

CW/Doppler radar canceling ground clutter

A

Target return signal compete with signals returned from the ground. Can be filtered out using Doppler processing

22
Q

Effects of mainbeam and sidelobe clutter on target detection using CW/Doppler

A

Mainbeam clutter Bad when searching for aircraft, good for ground maping. Sidelobes are lower in amlitude due to power output. Sidelobes have less doppler shift due to angular difference

23
Q

List the advantages and disadvantages of CW/Doppler radar

A

Advantages: Can filter out ground clutter, High AOP increases detection range, very accuratge velocity measurement, good agaisnt high aspect angle targets, simple Disadvantages: Two antennas required: more weight and space, No range info, Susceptible to doppler notch, degraded capes agaisnt beam and stern targets

24
Q

List the advantages and disadvantages of PD radars

A

Advantages: Only one antenna required, Filters out ground clutter, High output power, Good all aspect capes Disadvantages: Complicated electronics, susceptible to the doppler notch, Range reasurements difficult with an HPRF PD radar

25
Q

Discuss common radar acquisition and tracking techniques

A

Radar acquistion: Circular, Sector, Spiral, Raster. Tracking: Lobing (Sequential or simultanenous), Monopulse, Conical

26
Q

Define: Wavelength

A

Physical distance of one complete wave

27
Q

Define: Frequency

A

Number of cycles that the RF energy completes per second

28
Q

Define: Phase

A

One cycle

29
Q

Define: Polarization

A

Orientation of the electrical field created by radar waves: can be horizontal, vertical, slant and circular

30
Q

Define: Beam width (BW)

A

Angular measurement of the size of the mainbeam. Width in degrees between the points where the mainbeam decreases to half power

31
Q

Define: Pulse Width (PW)

A

Time the radar is transmitting each pulse

32
Q

Define: Pulse length (PL)

A

Distance between the leading and traling edges of a pulse

33
Q

Define: Pulse repetition frequency (PRF)

A

Rate at which pulses are transmitted

Radar (1 decks)

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