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.

Line of Sight

Radar Horizon

Any contact below the horizon will not likely be detected.

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.

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 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

Early Warning Radars

Air Search Radars

Surface Search

Fire Control Radars

• Continual energy transmission

• Separate transmit/receive antennas

• Relies on “DOPPLER SHIFT”

Continuous Wave

Doppler Effect

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

Specialized Systems

• Phased Array

• Synthetic Aperture Radar (SAR)

• Inverse synthetic Aperture Radar (ISAR)

• LIDAR