topic 4 radar fundamentals enabling objectives 4.1 discuss the classifications of radars and...
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Topic 4 Radar FundamentalsTopic 4 Radar FundamentalsEnabling Objectives4.1 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 Classifications
Radar Set
Primary Radar Secondary Radar
Pulsed Radar Continuous Wave Radar
Freq. Modulated Pulse Modulated UnmodulatedModulated
Imaging Radars Non-Imaging Radars
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.
Pulsed 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:Prime factor controlling many capabilities:
RangeRange
SizeSize
AntennaAntenna
PropagationPropagationL o n g e r r a n g eL o n g e r r a n g e ss Shorter rangesShorter ranges
Hz…MHz…GHzHz…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.
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 The use for which a radar is designed determines its
scan type. Therefore, the SR and scan type are the scan type. Therefore, the SR and scan type are the
characteristics that would identify the general function characteristics that would identify the general function
of a radar.of a radar.
Scan Types
Steady Steady Conical – Fire ControlConical – Fire Control
Irregular – Search Irregular – Search Raster – Search & FCRaster – Search & FC
Circular – SearchCircular – Search Palmer – Search & FCPalmer – Search & FC
Sector Sector Helical – Search & FCHelical – Search & FC
Orthogonal – Search Orthogonal – Search Spiral – Search & FCSpiral – Search & FC
Types of Radars
CivilMilitary
Early Warning
Battlespace Mgmt
Air Traffic Control
Other
Surveillance
Missile Control
Surveillance
Navigation
Weapon Control
Missile Control
Enroute Radar
ASR
PAR
Ground Control
Weather
Weather
Speed
ND Testing
Ground Penetration
• Continual energy transmission
• Separate transmit/receive antennas
• Relies on “DOPPLER SHIFT”
Continuous Wave
Pulse Vs. Continuous Wave
Pulse Echo• Single antenna• Gives range, usually altitude
as well• Susceptible to jamming • Range determined by PW
and PRF
Continuous Wave• 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• Single antenna• Gives range, usually altitude
as well• Susceptible to jamming • Range determined by PW
and PRF
Continuous Wave• Requires 2 antennae• Range or Altitude info• High SNR• More difficult to jam but
easily deceived• Can be tuned to look for
frequencies