Basic Radar Theory

Question 1

RADAR stands for

Answer 1

Radio Detection and ranging

Question 2

Principles of radar system

Answer 2

Sends pulses at speed of light which hit an object and pulse reflected in the form of an echo

Time taken for pulse to return used to calculate range.

Question 3

Primary Radar Gives

Answer 3

Bearing and distance of targets

Question 4

Primary ground radar is used to detect

Answer 4

Aircraft not equipped with secondary radar transponder

Question 5

Echo returns depend on

Answer 5

Corners = more echoes
Size/shape big/sharp = more returns
Water = more echoes
Ice crystal = less echoes

Question 6

Transmit/receive switch

Answer 6

Protect receiver from high powered pulses

Ensures receiver is switched off when transmitting and ensures transmitter is off when receiver is on

Question 7

Operations of a radar

Answer 7

Antenna transmits a big pulse of energy from the amplifier

Receiver receives the returning signal at a lower energy

Received signal is amplified

Processor calculate the range by comparing time and displays on screen

Question 8

Waiting period

Answer 8

Duration in the receive phase waiting to receive returns
Must be twice max design range

Question 9

Pulse length

Answer 9

Duration of the pulse measured in microseconds
Transmit phase

Question 10

Pulse recurrence interval

Answer 10

Time from the transmission of one pulse to the next pulse

Question 11

Pulse repetition frequency

Answer 11

Number of pulses occurring in a second

1 ———    PRI

Question 12

Beam width

Answer 12

Narrow beam ideal/more information on target
Bigger dish = narrower beam width

Question 13

Shorter the range the higher the

Answer 13

Frequency

Question 14

Larger the range the lower the

Answer 14

Frequency

Question 15

Radar range depends on

Answer 15

Frequency
Height of antenna
Height of aircraft
Pulse repetition frequency
Pulse length
Power of the pulse

Question 16

Aerodrome surface movement radar

Answer 16

SHF 10-20GHZ

+ faster rotating antenna
+ higher frequency - shorter wavelength/narrower beam
+ shorter range = shorter pulse = greater resolution in depth

Question 17

Maximum unambiguous range is effected by

Answer 17

Pulse repetition frequency

Question 18

Minimum range of radar is affected by

Answer 18

Pulse width

Question 19

Max unambiguous range formula

Answer 19

Speed of light
—————————————-
2 x Pulse repetition frequency

Range (in km) = 300,000/ (PRF x 2)

Question 20

Range formula with transmitter power

Answer 20

4 x square root of transmitter power

Question 21

Minimum pulse range formula

Answer 21

Speed of light x pulse width
—————————————-
2

Question 22

Terminal Radar (PRF and Range)

Answer 22

High Pulse repetition frequency
Short range
Short time between pulses

Question 23

Area radar (PRF) (Range)

Answer 23

Low pulse repetition frequency
Relatively long range
Long time between pulses

Question 24

Equation to determine distance of a radar return

Answer 24

Time between sending pulse/receiving echo x speed of light
———————————————————————————-
2

Question 25

PSR - range and bearing is acquired

Answer 25

At the same time

Question 26

Max and minimum range of primary radar

Answer 26

Max range = c/(2xPRF) (remember km) Min Range = (c x pulse width)/2

Question 27

MTI

Answer 27

Moving target indicator used to indicate moving targets and eliminate objects on the ground

Question 28

To double the range of PSR the power output required

Answer 28

Increases by 16

Question 29

Propagation delay

Answer 29

Time taken for the pulse to travel from the radar to the target and back to the radar

Question 30

Formula for PRF frequency

Answer 30

Rearranging the range formula PRF = 300,000/ (range km x 2)

Question 31

Pulse Recurrence Rate

Answer 31

Rate at which pulses are emitted - Same as pulse repetition frequency Amount of pulses transmitted per second

Question 32

Minimum and maximum is limited by

Answer 32

Minimum - Pulse Length Maximum - Pulse repetition frequency

Question 33

ASMR

Answer 33

Aerodrome surface movement radar Provides high quality display of all aircraft and vehicles and taxiways