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ISTAR foundation > Radar > Flashcards

Radar Flashcards

1
Q

What are the four factors affecting an aircrafts detection on radar?

A

Material

Shape

Size

Distance

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2
Q

What does Radar mean?

A

Radio detection and ranging

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3
Q

What is the usual length of an aerial in relation to wavelength?

A

The aerial length is 1/2 the wavelength

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4
Q

What general frequencies do radars operate on?

A

UHF, SHF, EHF

1-300 GHz

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5
Q

Would a high frequencies have a shorter or longer aerial?

A

Shorter aerial due to shorter wavelength

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6
Q

When a radar is metric, it……

A

Operates on a wavelength of one metre or More

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7
Q

What is a centimetric radar?

A

Operates on a wavelength of 1 centimetre or more

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8
Q

A radar operating on a wavelength of 1 millimetre or more is….

A

Millimetric

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9
Q

What three ways can radar systems be described as? (Wavelength they operate on)

A

Metric - 1m or more

Centimetric - 1cm or more

Millimetric - 1mm or more

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10
Q

What is the speed of EM waves?

A

3 x 10^8 metres per second

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11
Q

How many milliseconds is 1 mile?

A

10.75

Or

1.075 x 10^-5 seconds

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12
Q

How does frequency affect wavelength and aerial length?

A

High frequency = shorter wavelength = shorter aerial

Low frequency = longer wavelength = longer aerial

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13
Q

Describe primary radar

A

A radar that transmits energy, and receives that same energy back (known as echos or returns) after being reflected by a target.

It is used to track both hostile and friendly targets.

Primary radar acts independently from an aircraft.

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14
Q

Describe secondary radar

A

A radar system transmits energy to an aircraft, known as interrogation.

This energy triggers a transponder in the aircraft being interrogated,which sends a coded reply to the interrogator.

This acts with an aircraft or target and has a greater range than most primary radars.

Usually SSRs are used with primary radars

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15
Q

What band would 3 GHz, 10cm wavelength belong to?

A

E or F band

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16
Q

What band would a 3cm wavelength, 10GHz belong to ?

A

I to J band

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17
Q

What effect does frequency have on range and antenna size?

A

High freq = lower range due to greater attenuation
= small antenna

Low freq = higher range = large antenna

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18
Q

What is PRF and what is it’s main element?

A

Pulse repetition frequency, how many pulses in a second.

Higher prf = more pulses = larger data rate

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19
Q

What is the importance of pulse width?

A

Large pulse width = more power = further

But

Large pulse width = less accurate/defined

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20
Q

What is ARP?

A

Aerial rotation period

21
Q

What is SSR and IFF?

A

Secondary surveillance radar - civil

Identification friend or foe - mil

22
Q

What frequencies do secondary radars interrogate and reply on?

A

1030 MHz - interrogate

1090 MHz - replies

23
Q

What are the four main parts of secondary radars?

A

Transponder

Controller

Aerials

Interrogator (ground)

24
Q

What are the common civilian modes on aircraft (SSR)?

A

Mode A

Mode B

Mode C

Mode S

25
Q

What is mode 5?

A

Encrypted data link

Includes mode 1,2 and 3 information as well.

26
Q

What is mode 3/A?

A

This is mode emits an identification code

Mode 3 is the military equivalent.

27
Q

What does mode C do?

A

It gives altitude information, helpful for controllers.

28
Q

What is mode S ?

A

A selective interrogation from controllers.

Is used in T-CAS

29
Q

What does squawk ident mean?

A

Ident is a button that can be pressed in the aircraft, that will allow identification of your position.

It will cause a flashing image on the Controllers screen.

30
Q

What is T-CAS?

A

Traffic collision and avoidance system

Uses mode C and S to build a 3D picture of surrounding traffic

It is autonomous.

31
Q

What two types of settings are on T-CAS systems?

A

Traffic advisory (3.3nm - 850ft) - provides traffic advise on surrounding traffic

Resolution advisory (2.1nm - 600ft) - 
mandatory, you must listen to the instructions given
32
Q

What are the VHF frequency ranges?

A

118 - 137 MHz

8.33 KHz spacings

33
Q

What is the useable UHF range?

A

25.0 to 399.95 MHz

25KHz spacings

34
Q

What are the main types of primary radars?

A

Continuous wave

Moving target indicator (MTI)

Synthetic aperture

35
Q

What are the three types of continuous wave radars, and describe how they work

A

Pure CW - uses Doppler shift to determine the relative velocity of a target.

Frequency modulated continuous wave radar-
Used to measure target range, and can be used to measure down to zero range

36
Q

What are some issues with cw radar

A

Problems with CW:
2 aerials needed

Difficult to isolate the receiver from direct transmission from the receiver

37
Q

What is MTI radar?

A

Moving target indicator

This uses Doppler shift to remove clutter.

It then determines a speed threshold for low and high moving targets

38
Q

What are the two types of radar display?

A

Type A (horizontal display with vertical displacement) - displays range

PPI (plan position indicator) - displays a range and a bearing. A circular display where target bright up.
Also displays clutter.

39
Q

How can range be measured with radars?

A

Using a rotating radar aerial with a fan shaped beam in azimuth.
This movement is then synchronised with PPI display allowing bearing and range.

40
Q

How can height and elevation be measured using radars?

A

Nodding a radar aerial beam in elevation.

Vertically, thin
Horizontally, wide

41
Q

What is SAR?

A

Synthetic aperture radars

A fixed antenna on an aircraft, scanning is achieved through movement of the aircraft

42
Q

What is strip/swath SAR?

A

Using synthetic aperture radars to send multiple pulses and processing the returns

The returning signal is similar to that of radars with aerials 100s of feet long.

43
Q

What is spot SAR?

A

Through movement of the aircraft, a beam can be focused to a point of interest, allowing a high definition picture.

44
Q

What is inverse synthetic aperture radar? (ISAR)

A

Target movement and Doppler is used.

Returns from moving targets allow an image of the target.

45
Q

What are the types of radars and their designations?

A

Circular = A

Sectoring = B

Complex = J

46
Q

What is PRF?

A

Pulse repetition frequency

Number of pulses per second

47
Q

What is PRI?

A

Pulse repetition interval/period

Time from start of one pulse to the start of the next

48
Q

What is ARP?

A

Aerial rotation period

Time taken to complete one rotation

ISTAR foundation (7 decks)

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