Radar was originally developed for military purposes during World War 2 to detect ships and airplanes. Scientists later discovered that radar could also detect precipitation, making it an essential tool for weather prediction. There are two main types of radar: pulse radar which uses pulse transmission to determine range and continuous wave radar which relies on the Doppler effect. Key radar components include the transmitter, receiver, antenna, and display unit. Radar systems can be classified by their primary mission as search, tracking, or weather surveillance radars. Common examples include air search radars, long range surveillance radars, and tracking radars used in aircraft.
2. Functions of Radar
RADAR is a method of using
electromagnetic waves to remote-sense
the position, velocity and identifying
characteristics of targets.
3. History of Radar
Radar was developed for military
purposes during W. W. II.
The British and US Military used radar
to locate ships and airplanes.
5. History of Radar
During the war, radar operators found
annoying blips continually appearing on
the radar screen. Scientists had not
known that radar would be sensitive
enough to detect precipitations.
Today, radar is an essential tool for
predicting and analyzing the weather.
11. Pulse Radar Components
SynchronizerSynchronizer TransmitterTransmitter
Display UnitDisplay Unit ReceiverReceiver
PowerPower
SupplySupply
ANT.ANT.DuplexerDuplexer
RFOut
EchoIn
Antenna Control
12. Pulse Transmission
Pulse Repetition Time (PRT=1/PRF)
Pulse Width (PW)
Length or duration of a given pulse
PRT is time from beginning of one pulse to the
beginning of the next
PRF is frequency at which consecutive pulses are
transmitted.
PW can determine the radar’s minimum range
resolution.
PRF can determine the radar’s maximum detection
range.
16. Pulse Vs. Continuous Wave
Pulse Echo
Single Antenna
Gives Range & Alt.
Susceptible To
Jamming
Physical Range
Determined By PW
and PRF.
Continuous Wave
Requires 2 Antennae
No Range or Alt. Info
High SNR
More Difficult to Jam
But Easily Deceived
Amp can be tuned to
look for expected
frequencies
17. Classification by Primary Radar
Mission
Search radars and modes
• Surface search
• Air search
• Two-dimensional search radars
• Three-dimensional search radars
Tracking radars and modes
Track-while-scan
20. AN/TPS-43
The AN/TPS-43 radar
system, with a 200
mile range, was the
only Air Force
tactical ground based
long range search and
warning radar for
nearly two decades.
Most of the AN/TPS-
43 radars are being
modified to the
AN/TPS-75
configuration.
3-D Air Search Radar
24. Tracking Radar
Tracking radars dwell on individual targets
and follow their motion in azimuth,
elevation,range and Doppler.
Most tracking radars can follow only a single
target.
A few radars can track multiple targets
simultaneously. An electronically steered
array antenna is used so that beam
positions can be moved quickly from one
target to another.
29. Array Antenna
An array antenna is composed of multiple
element arrays for example, linear array, area
array or nonformal array. The element
antennas are half-wavelength dipoles,
microstrip patches and wave guide slot. The
advantages of array antenna are to enable
beam scanning without changing the looking
angle of each array antenna and to generate
an appropriate beam shaping by selective
excitation of current distribution of each
element.
31. Edgewall Slot Array-AN/APY-
2 on E-3D Aircraft
The E-3 Sentry is an airborne warning and control system (AWACS) aircraft that
provides all-weather surveillance, command, control and communications needed by
commanders of U.S. and NATO air defense forces. As proven in Desert Storm, it is
the premier air battle command and control aircraft in the world today.
32. Early Warning Radar Array
Antenna
PAWS stands for Phased Array Warning System. The radar is used primarily to detect
and track sea-launched and intercontinental ballistic missiles.
It can search over long distance(to 5000 km or more). Each system has two array faces
72.5 feet in diameter with 2677 element positions.
To provide surveillance across the horizon, the building is constructed in the shape of a
triangle. The two building faces supporting the arrays, each covering 120 degrees, will
monitor 240 degrees of azimuth.
33. Radar Performance and
Frequency Bands
Bandwidth
The bandwidth determines the range resolution and frequency agility capabilities of the radar.
Antenna
For a given gain, low frequency antennas are larger than high frequency. Low frequency are favored for long-range
search applications, because of the larger effective area associated with a given gain, allowing more effective
capture of echoes.
Transmitter
In general, more radio frequency power can be produced at low frequency than at high.
Receiver
There is no clear choice between high and low frequencies.
Propagation
The attenuation at high frequency is dramatic. A given raindrop has over three orders of magnitude more scattering
cross-section at X-band(10 GHz) than at L-band(1.3 GHz), producing far more clutter and signal at the higher
frequency.
Targets
If the wavelength is long compared to the target extent, targets are Rayleigh scatterers, and have small, non-fluctuating
RCS.
Summary
In general, the longer the range at which the radar must detect targets, the lower the frequency of the
radar.
1. Make copies of graphic and distribute to class.
2. Synchronizer:
a. Coordinates the entire system
b. Determines the timing of the transmitted pulse
c. Includes timers, modulator and central control.
3. Transmitter:
a. Generate the pulses at the proper RF (radio frequency) for the radar.
4. Antenna:
a. Receives energy from the transmitter, radiates it in the form of a
highly directional beam and receives the echoes.
5. Duplexer:
a. Allows one antenna to be used to transmit and receive.
b. Prevents transmitted RF energy from going directly to the receiver.
c. Tells the antenna to radiate or receive.
6. Receiver: receives incoming echoes from antenna, detects and amplifies
the signal, and sends them to the display.
7. Display: Displays the received video to the operator.
8. Power Supply: Provides power to all the components of the system.
9. Discuss the antenna Bearing loop back to the display and its function.
Second major type of radar.
Produces a constant stream of energy.
Can’t distinguish distances (range) because no interval between pulses.
Can distinguish between moving and non-moving targets by using Doppler frequency shifts.
a. Frequency expansion is the lowering of the echo frequency caused
by an opening target (target moving away). DOWN DOPPLER
b. Frequency compression is the raising of the echo frequency caused
by the closing target (target moving closer). UP DOPPLER
c. The moving of the transmitter can also cause frequency shifts (it’s
relative motion that produces the effect).
d. The faster the relative motion change the more the frequency shift.
1. Transmit/Receive Antennas. Since must operate simultaneously, must be located separately so receiving antenna doesn’t pick up transmitted signal.
2. Oscillator or Power Amplifier. Sends out signal to transmit antenna. Also sends sample signal to Mixer. (used as a reference)
3. Mixer.
a. A weak sample of the transmitted RF energy is combined with the received echo signal.
b. The two signal will differ because of the Doppler shift.
c. The output of the mixer is a function of the difference in frequencies.
4. Amplifier. Increases strength of signal before sending it to the indicator.
5. Discriminator.
a. Selects desired frequency bands for Doppler shifts.
b. The unit will only allow certain frequency bands so won’t process stray
signals.
6. Indicator. Displays data. Measures radial velocity or the component inbound or directly outbound. Range is not measured.
7. Filters. Used to reduce noise, used in amp to reduce sea return, land clutter, and other non-desirable targets.
There are many different radar missions, types of radars and radar modes. This is one of radar groupings.
It’s 2-D search radar. I guess it for azimuth search since it has a narrow azimuth beam and wide elevation beam.
The Radar Set AN/SPS-49 is an L-band, long-range, two-dimensional, air-search radar system that provides automatic detection and reporting of targets within its surveillance volume.
The AN/SPS-49(V) radar operates in the frequency range of 850 - 942 MHZ.
It shows the elevation coverage of a typical air search radar.
http://www.fas.org/man/dod-101/sys/ac/equip/an-tps-43.htm
It resolves in elevation as well as azimuth. It uses multiple feeds and switches between feeds for different elevation angles. It has six stacked beams.
The AN/APG-66 is a pulse-doppler radar designed specifically for the F-16 Fighting Falcon fighter aircraft. APG-66 uses a slotted planar-array antenna located in the aircraft's nose and has four operating frequencies within the I/J band.
The system has ten operating modes, which are divided into air-to-air, air-to-surface display, and sub-modes.
In the search mode APG-66 performs uplook and downlook scanning. Once a target is located via the search mode, the engagement sub-mode can be used.
There are two main manual acquisition modes, single-target track and situation awareness. The situation awareness mode performs Track-While-Scan (TWS), allowing the pilot to continue observing search targets while tracking a specific target. While in this mode, the search area does not need to include the tracked target's sector.
http://www.tpub.com/neets/book11/46a.htm
Y: surveillance and control, multi-target tracking, fire control, and air control
PAVE is an Air Force program name, that, contrary to some reports, does not have an expansion, while PAWS stands for Phased Array Warning System.