Transmitters & Receivers

Question 1

What devices are used in the Modulator in a HPO

Answer 1

Pulse forming network

Question 2

What device is used in the RF oscillator in a HPO

Answer 2

Multi cavity Magnatron

Question 3

Characteristics of a HPO

Answer 3

Large in amplitude
Rectangular
Precise in width

Question 4

Advantages of MOPA over HPO

Answer 4

Low power modulator
Frequency stability
Phase coherence

Question 5

What is the function of a video detector

Answer 5

Demodulates the bi-polar pulse

Question 6

Func of a Video amp

Answer 6

Provides sufficient gain for pulse waveform to drive display

Question 7

Techniques to reduce clutter

Answer 7

Fast time constant
Swept gain
Logarithmic IF amps

Question 8

Explain staggered tuning

Answer 8

By tuning each stage of the IF amp to a different frequency the bandwidth is widened without reducing voltage output

Question 9

Explain operation of swept gain

Answer 9

Reduces Rx gain to reduce near ground clutter

Question 10

Explain operation of logarithmic IF amplifiers

Answer 10

Small signals maximum gain
Large signals minimum gain

Question 11

Noise reduction techniques that reduce noise in radar receiver

Answer 11

Adaptive noise reduction
Matched filter

Question 12

Explain adaptive noise reduction

Answer 12

Automatic changes to set noise level to prevent false targets

Question 13

Matched filter noise reduction

Answer 13

BW = 1/PW

Question 14

What devices are used to produce frequency agility

Answer 14

FAMOPA
Spin disc magnetron

Question 15

Advantages of frequency agile radar over fixed freq radar

Answer 15

Less interference
Less clutter
Eliminates 2nd time around echoes

Question 16

Function of MO and LO in FAMOPA

Answer 16

MO - Runs continually - variable output
LO - runs at a constant frequency

Question 17

Radar that use monopulse techniques

Answer 17

Terrain following radar
Ground mapping radar
Airborne interception AI

Question 18

What information is obtained from monopulse ranging

Answer 18

Slant range
Depression angle

Question 19

Explain the principle of MTI

Answer 19

Uses Doppler effect
Identifies moving target on the ground
Can suffer from blind speeds

Question 20

Principle of pulse compression

Answer 20

Wide pulses are transmitted to give more energy for long range

Processed as narrow pulses

Good target discrimination

Effects minimum range

Question 21

Advantages of pulse compression in primary pulsed radar systems

Answer 21

Some resistance to ECM jamming
Better target discrimination
Longer range
Improved s/n ratio

Question 22

How could pulse compression be improved

Answer 22

If more frequencies were used in the transmitted pulse, this would result in a narrower pulse with a higher amplitude

Question 23

What will give good target velocity info in pulsed Doppler radar

Answer 23

High PRF

Question 24

What will give good target range information in pulsed Doppler radar

Answer 24

Low PRF

Question 25

What is Eclipsing

Answer 25

Received signal coming in while still transmitting
Some of target cut off

Question 26

What is blind ranges

Answer 26

Received signal coming in while still transmitting
All target cut off

Question 27

Explain the purpose of S.A.R

Answer 27

Used to produce High resolution image used for ground mapping

Question 28

Advantages of S.A.R over aerial photography

Answer 28

Operational day or night
All weather
High quality radar map produced

Question 29

Explain ISAR

Answer 29

Generates a 2D high res image

The image allows the operator to detect missiles and aircraft

Used in shop surveillance as the movement of sea improves the image