Radar Theory Flashcards
Radar Polarization
The orientation of the electrical field
Frequency
The number of cycles that the RF energy completes per second
Electro Magnetic Radiation
Synchronized oscillations (sinusoidal waves) or electric and magnetic fields that propagate through a vacuum at the speed of light
Wavelength
The physical distance of one complete wave
Radar Beamwidth
The angular size of the main beam, normally expressed in degrees.
Phase Differences
The degree to which individual cycles of a wave coincide with those of a reference wave of the same frequency.
List the 7 types of electro magnetic radiation in order of decreasing wavelengths
1: Extremely low-frequency waves
2: Radio waves
3: Microwaves
4: Infrared radiation
5: Visible light
6: Ultraviolet radiation
7: X-rays & gamma rays
How is frequency measured?
Hz
A radars operating frequency impacts what performance parameters of the radar’s performance?
Atmospheric attenuation
physical size
transmitted power
doppler considerations
List characteristics of the lower frequency radar
- Long wavelength
- Large antenna
- Components able to generate high transmit power
- Low atmospheric attenuation
- Good long-range detection capability but poor precision
- Best for long-range EW radars
List characteristics of the higher frequency radar
- Shorter wavelengths
- Smaller antenna
- Smaller components for less power
- Shorter detection range
- High precision
- Atmospheric attenuation more of a problem
- Used for fire-control radars for fighters, SAMs and ADA
The strength of a radar signal hitting a target is approximately proportional to what parameter?
1/(range to the target)squared
For a fixed antenna size a radar operating at a higher frequency than another will the beamwidth be narrower or wider?
narrower
For a fixed operating frequency which radar will have a narrower beamwidth; a large antenna or a small antenna?
a large antenna
T or F: Angular (azimuth and elevation) resolution is a function of beamwidth and range to the targets.
True
An electronically scanned array atenna differs in what two fundamental ways form a mechanically scanned array radar?
- The antenna is mounted in a fixed position
- The antenna is NOT mounted in a fixed position
- The radar beam is steered by individually controlling the phase of the radio waves transmitted and received by each radiating element.
- The antenna is mounted in a fixed position
- The radar beam is steered by individually controlling the phase of the radio waves transmitted and received by each radiating element.
What are the advantages of passive and active electronically scanned array radars?
- High reliability.
- Extreme beam agility.
- Facilitate radar cross-section reduction.
Define radar range resolution
A radars ability to resolve multiple targets in range
Range resolution is based on what parameter?
Pulse width (t)
Define radar resolution cell
The smallest amount of three-dimensional air space in which a radar cannot distinguish between multiple targets
Pulse repetition frequency is?
The rate at which pulses are transmitted
Pulsed Radar (advantage or disadvantage):
Only one antenna required
Advantage
Pulsed Radar (advantage or disadvantage):
Lower average output power limits detection range
Disadvantage
Pulsed Radar (advantage or disadvantage):
Cannot filter out ground clutter without increased processing
Disadvantage
Pulsed Radar (advantage or disadvantage):
Good range accuracy
Advantage
Pulsed Radar (advantage or disadvantage):
Not very accurate in velocity measurement
Disadvantage
Pulsed Radar (advantage or disadvantage):
Simple electronics
Advantage
Continuous wave/ Doppler Radar
(advantage or disadvantage)
Simple
Advantage
Continuous wave/ Doppler Radar
(advantage or disadvantage)
No range information
Disadvantage
Continuous wave/ Doppler Radar
(advantage or disadvantage)
Good against high aspect angle targets
Advantage
Continuous wave/ Doppler Radar
(advantage or disadvantage)
Poor against beam and stern targets
Disadvantage
Continuous wave/ Doppler Radar
(advantage or disadvantage)
Very accurate velocity measurement
Advantage
Continuous wave/ Doppler Radar
(advantage or disadvantage)
Two antennas required
Disadvantage
Continuous wave/ Doppler Radar
(advantage or disadvantage)
High average output power increases detection range
Advantage
Continuous wave/ Doppler Radar
(advantage or disadvantage)
Can filter out ground clutter
Advantage
Continuous wave/ Doppler Radar
(advantage or disadvantage)
Susceptible to doppler notch
Disadvantage