Transmitters & Receivers Flashcards
What devices are used in the Modulator in a HPO
Pulse forming network
What device is used in the RF oscillator in a HPO
Multi cavity Magnatron
Characteristics of a HPO
Large in amplitude
Rectangular
Precise in width
Advantages of MOPA over HPO
Low power modulator
Frequency stability
Phase coherence
What is the function of a video detector
Demodulates the bi-polar pulse
Func of a Video amp
Provides sufficient gain for pulse waveform to drive display
Techniques to reduce clutter
Fast time constant
Swept gain
Logarithmic IF amps
Explain staggered tuning
By tuning each stage of the IF amp to a different frequency the bandwidth is widened without reducing voltage output
Explain operation of swept gain
Reduces Rx gain to reduce near ground clutter
Explain operation of logarithmic IF amplifiers
Small signals maximum gain
Large signals minimum gain
Noise reduction techniques that reduce noise in radar receiver
Adaptive noise reduction
Matched filter
Explain adaptive noise reduction
Automatic changes to set noise level to prevent false targets
Matched filter noise reduction
BW = 1/PW
What devices are used to produce frequency agility
FAMOPA
Spin disc magnetron
Advantages of frequency agile radar over fixed freq radar
Less interference
Less clutter
Eliminates 2nd time around echoes
Function of MO and LO in FAMOPA
MO - Runs continually - variable output
LO - runs at a constant frequency
Radar that use monopulse techniques
Terrain following radar
Ground mapping radar
Airborne interception AI
What information is obtained from monopulse ranging
Slant range
Depression angle
Explain the principle of MTI
Uses Doppler effect
Identifies moving target on the ground
Can suffer from blind speeds
Principle of pulse compression
Wide pulses are transmitted to give more energy for long range
Processed as narrow pulses
Good target discrimination
Effects minimum range
Advantages of pulse compression in primary pulsed radar systems
Some resistance to ECM jamming
Better target discrimination
Longer range
Improved s/n ratio
How could pulse compression be improved
If more frequencies were used in the transmitted pulse, this would result in a narrower pulse with a higher amplitude
What will give good target velocity info in pulsed Doppler radar
High PRF
What will give good target range information in pulsed Doppler radar
Low PRF
What is Eclipsing
Received signal coming in while still transmitting
Some of target cut off
What is blind ranges
Received signal coming in while still transmitting
All target cut off
Explain the purpose of S.A.R
Used to produce High resolution image used for ground mapping
Advantages of S.A.R over aerial photography
Operational day or night
All weather
High quality radar map produced
Explain ISAR
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
