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.

Line of Sight Radar Horizon Any contact below the horizon will not likely be detected.

Radar Classifications Radar Set Primary RadarSecondary Radar Pulsed Radar Continuous Wave Radar Freq. ModulatedPulse ModulatedUnmodulatedModulated Imaging RadarsNon-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:  Range  Size  Antenna  Propagation L o n g e r r a n g e s Shorter ranges 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 r eciprocal 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 – SearchPalmer – Search & FC Sector Helical – Search & FC Orthogonal – Search Spiral – 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 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