Transcript Topic 4 Radar Fundamentals inst ppt 14Jul08

Topic 4 Radar Fundamentals
Enabling Objectives
4.1 DISCUSS the classifications of radars and specific radar systems employed by military
and civilian users.
4.2 DISCUSS the primary differences between pulsed and continuous wave radars.
4.3 DEFINE key parameters to include RF, PRF, PRI, PD and Scan Rate.
4.4 DISCUSS operating characteristics and key features associated with early warning, air
and surface search, weapons control, and other radars.
Radar Horizon
Any contact below the
horizon will not likely be
detected.
Radar Classifications
Radar Set
Imaging Radars
Non-Imaging Radars
Primary Radar
Pulsed Radar
Freq. Modulated
Pulse Modulated
Secondary Radar
Continuous Wave Radar
Modulated
Unmodulated
Pulsed Radar
A PULSED radar is the most common radar in use
today. It provides range information and uses a single
antenna for transmission and reception of RF energy.
The basic receiver for a pulsed radar can be enhanced to provide velocity
as well as the range info - then the radar is called a Pulsed Doppler radar.
Measurable Parameters
•Radio Frequency (RF)
• Pulse Repetition Frequency (PRF)
• Pulse Repetition Interval (PRI)
• Pulse Duration (PD)
• Scan Period (SP)
Radio Frequency (RF)
Prime factor controlling many capabilities:
 Range
 Size
 Antenna
 Propagation
Shorter ranges
Longer range s
Hz…MHz…GHz
PRF and PRI
• PRF - Number of pulses generated in ONE second
(PPS).
- Min & max PRF’s depend on radar’s tactical use.
• PRI - The reciprocal of the PRF.
- Time between the start of one pulse to the start
of the next pulse.
- Length of time including transmit and receive time
of a radar.
PRI
Pulse Duration (PD)
Time required by the radar to transmit a burst of energy
 “On-time” for the transmitter.
 One of the least reliable parameters (bandwidth).
 PD is the width and shape of the RF pulse.
 Influences min range, range accuracy, and max range.
Scan Rate (SR)/Scan Period (SP)
SR - Angular rate that the antenna beam is moved
through a scan volume while performing various
functions. (Hz or RPM)
SP - Time for one complete scan cycle. Reciprocal of
SR. (SPS)
The use for which a radar is designed determines its
scan type. Therefore, the SR and scan type are the
characteristics that would identify the general function
of a radar.
Scan Types
Steady
Conical – Fire Control
Irregular – Search
Raster – Search & FC
Circular – Search
Palmer – Search & FC
Sector
Helical – Search & FC
Orthogonal – Search
Spiral – Search & FC
Types of Radars
Military
Early
Warning
Battlespace
Mgmt
Civil
Air Traffic
Control
Surveillance
Surveillance
Enroute Radar
Missile Control
Navigation
ASR
Weapon Control
PAR
Missile Control
Ground Control
Weather
Other
Weather
Speed
ND Testing
Ground
Penetration
Early Warning Radars
Air Search Radars
Surface Search
Fire Control Radars
Continuous Wave
• Continual energy transmission
• Separate transmit/receive antennas
• Relies on “DOPPLER SHIFT”
Doppler Effect
Pulse Vs. Continuous Wave
Pulse Echo
Continuous Wave
• Single antenna
• Gives range, usually
altitude as well
• Susceptible to jamming
• Range determined by PW
and PRF
•
•
•
•
Requires 2 antennae
Range or Altitude info
High SNR
More difficult to jam but
easily deceived
• Can be tuned to look for
frequencies
Pulse Vs. Continuous Wave
Pulse Echo
Continuous Wave
• Single antenna
• Gives range, usually
altitude as well
• Susceptible to jamming
• Range determined by PW
and PRF
•
•
•
•
Requires 2 antennae
Range or Altitude info
High SNR
More difficult to jam but
easily deceived
• Can be tuned to look for
frequencies
Specialized Systems
•
•
•
•
Phased Array
Synthetic Aperture Radar (SAR)
Inverse synthetic Aperture Radar (ISAR)
LIDAR