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Aircraft Systems > AS 06 - Radar Theory 1 > Flashcards

AS 06 - Radar Theory 1 Flashcards

1
Q

Review Questions

What is the max ramp weight for the CT-142?

A

34 700lbs

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2
Q

What components are heated electrically to guard against ice build-up?

A 
Pilots side window
Pitot tubes
Prop blades
Static ports
Stall warning transducer
Elevator horns
Engine intakes
Windshields
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3
Q

What does radar stand for, what does it do?

A

Stands for radio detection and ranging

Used to detect and locate objects

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4
Q

Describe the echo principle of radar.

A

A radar transmits a particular type of waveform and interprets the return signal, converting the echo return into useful information.

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5
Q

What types of information are provided by RADAR?

A

Target range
Target azimuth
Target elevation
Target speed

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6
Q

What are some uses for radar?

A 
T - Traffic detection and avoidance
A - Altitude
G - Groundspeed and drift
G - Guidance systems 
T - Target detection and homing
M - Map reading and nav
W - Weather detection and avoidance
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7
Q

Describe the Radio Determinization process

A

Strong, short bursts or radio energy are sent out (pulses)
Energy is reflected back to the receiver (echo)
Time it takes the energy to return can be converted to distance

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8
Q

Regarding contact detection, the strength of return is based on what factor?

A

The amount of scattering at the return source.

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9
Q

What factors affect Contact Detection?

A

Range - Due to spreading, the return signal may be too weak to be detected by receiving antenna

Size - Larger targets are more likely detected, smaller ones may be filtered out depending on the radar

Shape - Right angled objects are more conducive to reflecting a signal back to its receiver

Reflecting Characteristics - Some compounds reflect more readily than others

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10
Q

How is azimuth (direction) measured?

A

It is measured in relation to a specific reference point.

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11
Q

What are the different types of radars/ antennas used in calculating azimuth and elevation?

A

Parabolic, Planar Array and Phased Array

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12
Q

WRT Pulse RADAR Principles, why are transmissions concentrated into very short pulses, separated by sufficiently long intervals? (Think interference elimination)

A

To permit all echoes from targets within the operating range to be received before transmission of the next.

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13
Q

What does an ideal pulse look like?

A

Flat top, sharp leading and trailing edge (top hat)

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14
Q

A pulse starting abruptly, steady power then tapering off describes what pulse?

A

Sloped trailing edge

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15
Q

Describe a sloped leading edge pulse.

A

A sloped leading edge where the pulse builds slowly to peak power then flattens out, abrupt stop.

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16
Q

What does a sloped top pulse mean?

A

The power level varies throughout

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17
Q

Look more into Min/ max range pulse width, ppt doesn’t explain it great

A

a

18
Q

Range accuracy requires what for an accurate timing start?

A

A sharp leading edge

19
Q

What is a problem with a long pulse regarding range resolution?

A

If there are two targets, the leading edge from target B will reach antenna before trailing edge of the return from the first target. Results in the appearance of a single target at a distance of the nearer target.

20
Q

A short pulse ensures what regarding range resolution?

A

No target overlap and provides two distinct returns

21
Q

What are the 7 basic radar components?

A 
A - Antenna
P - Power Source
R - Receiver
I -Indicator
S - Synchronizer
M - Modulator
T - Transmitter
22
Q

Describe a Synchronizer, what does it generate?

A

Provides timing for the whole system
Generates the PRF and display range markers
Triggers modulator to release energy (its the modulators trigger)

23
Q

Describe a Modulator

A

Stores energy between pulses
Determines the waveform of the output pulse (shape)
Releases pulses of energy when directed by the synchronizer

(Think a bullet going into a chamber as the energy)

24
Q

Describe the Transmitter and the associated carrier frequency.

A

Provides RF energy at extremely high power in very short pulses
Carrier frequency must be extremely high to fit many cycles into the short pulse

25
Q

Describe an Antenna and it’s duplexer component, which type of antenna is normally used?

A

Highly directional transmitting/ receiving device, usually rotated or moved back and forth between two positions

Duplexer switches from transmitting to/ from receiving.

Normally a rotating planar array which transmits and receives RF energy.

26
Q

Describe a Receiver and its characteristics.

A

A very sensitive super-heterodyne receiver.
Accepts signals from 1 - 10 MHz
Detects and amplifies weak RF echoes
Changes echoes to video and sends the signal to the indicator

(think hearing aid and/or satellite dish)

27
Q

Describe an Indicator, the type of scan depends on what?

A

Visually represents all necessary information to locate the target on screen

Method of representing data (type of scan) determined by the radar’s pulse

28
Q

What are the different Indicator presentations?

A

A, B, C, J, E, PPI

29
Q

What type of scan is mainly used to determine range but rough direction is also possible? Also, target returns are interpreted by vertical deflections from the transmitter pulse?

A

“A” Scan

30
Q

What scan type is used to determine range, bearing, target size and has data presented as abscissa and ordinate?

A

“B” Scan

31
Q

Describe a “C” Scan type

A

The echo appears as a bright spot with the azimuth angles as the horizontal coordinates and the elevation angle as the vertical coordinates.

32
Q

Which scan type is a modification of the “A” scan, in which the spot rotates in a circle near the edge of the CRT face?
Also, how does an echo appear and what happens as the distance changes?

A

J scan, an echo appears as a deflection from the circle and distance is determine by the pointer rotating within a circle, similar to a aneroid barometer.

33
Q

Describe a Type “E” scan, what is it normally used for?

A

Modification of the B scan, echo appears as a bright spot with range on the X axis and elevation on the Y axis.
Normally used for precision approach radar where AC must follow a certain angular line to reach touch-down point.

34
Q

Describe PPI scan

A

Provides range and bearing info, most common for navigation radar and provides a map-like picture.

35
Q

Go into detail about the PPI scan (slide 31)

A
36
Q

Review Questions

If you wanted to get a very accurate ranging and target resolution, what characteristics would you ensure?

A

Pulse shape (sharp leading and trailing edges) and a narrow pulse width.

37
Q

Review Questions

What does the synchronizer do?

A

Timing: determines PRF, range marks and triggers the modulator.

38
Q

Is the synchronizer a stand-alone component or included within another component?

A

May be a separate unit or included in the transmitter.

39
Q

How is power carried to the antenna from the transmitter?

A

Power is carried to antenna via coaxial cable or waveguide.

40
Q

How does a receiver interact with weak RF echoes?

A

It detects and amplifies them

Aircraft Systems (19 decks)

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