Primary and Secondary Radar
Reflected energy is called an _______ or "Target"
"Echo"
Linear Polarization (LP)
-A normal radar transmission that will cause an echo from anything that has mass. -The normal radar receiver is called Linear Polarization (LP). -Linear Polarization presents ALL reflected signals, either moving or stationary.
There are two types of radar jamming:
-Active jamming -Passive jamming
Airborne Secondary Radar Components
-Aircraft transponder -Aircraft transponder antenna
Advantages of ATCRBS
-Allows for rapid target identification -Allows for transmission of altitude and other data
Circular Polarization (CP)
-Altered radar pulses filter out returns from precipitation -Clutter is reduced by Circular Polarization
Anomalous Propagation
-Caused by density or moisture. -During AP, the radar beam does NOT travel in a straight line. -Beams are bent either horizontally or vertically. -Beams are bent in the direction of dry dense air. -Possible range or azimuth errors are due to the bending of radar beams.
Electronic Radar Interference
-Cross channeling (other channel - same system) -Maintenance testing on other channel -Other radar systems operating on a similar frequency
Duplexer
-Disconnects the Receiver during transmission, and the Transmitter during reception of reflected energy -Makes it possible to transmit and receive through the same waveguide and antenna.
False MTI Targets
-False MTI targets create a strong echo whose distance is greater than the radar range. -It has a strobe-like appearance and often travels at tremendous speeds and changes direction.
Air Traffic Control Radar Beacon System (ATCRBS) is also referred to as Secondary Surveillance Radar. Comprised of(3):
-Ground-based interrogator -Airborne transponder -Ground based decoder for deciphering the coded replies from the transponder.
Ground-Based Secondary Radar Components(3):
-Interrogator/Receiver (IR) Unit -Antenna -Defruiter
There are two types of resolution:
-Range -Azimuth
Timer (Synchronizer)
-Starts and controls the sequence of operations that make up a complete cycle. -Starts with the beginning of a transmitted pulse and ends with the beginning of the next transmitted pulse.
Factors Affecting Operation(3)
-Target fade -False targets -Fruit
basic components of primary radar(7)
-Timer (Synchronizer) -Modulator -Transmitter -Duplexer -Antenna -Receiver -Indicator
Interrogator/Receiver (IR) Unit (Ground-Based Secondary Radar Component)
-Transmitter/receiver -Transmits a radio signal repetitiously which requests all transponders on the mode being used to reply and then receives those signals.
AP/INVERSION INTERFERENCE
-caused by temperature inversion. -May cause interference similar to ground clutter -May cause false targets -Affects primary radar
Radar Jamming
-disrupting the radar display or radio reception by means of electronic or mechanical interference.
MTI Blind Speed
-essentially a dead spot caused by the a/c speed
FAA radar systems include: Airport Surveillance Radar (ASR) - range up to ____ nautical miles Air Route Surveillance Radar (ARSR) - range up to ____ nautical miles
60, 250
_______________ is caused by jammers that generate radar energy
Active jamming
Receiver
Amplifies and converts the reflected RF energy into video.
Moving Target Indicator (MTI)
An electronic device which will permit radar scope presentation only from targets which are in motion, but reduces target strength and loses the target on tangential or circumferential course
Target fades (fringe areas)
Area of NO coverage will occur over the antenna and below the coverage pattern
________________ is caused by parasitic radiators such as chaff.
Passive jamming
Indicator
Presents radar information in a usable manner.
Antenna (Ground-Based Secondary Radar Component)
Shapes transmitted Radio Frequency (RF)
Antenna
Shapes transmitted Radio Frequency (RF) energy into the desired pattern.
Modulator
Turns the transmitter on and off for predetermined intervals.
Defruiter (Ground-Based Secondary Radar Component)
When a transponder is activated by more than one interrogator in the same vicinity, interference or fruit may be displayed. Defruiters remove the interference/fruit.
Transmitter
When it is on, the pulse is sent out, when the it is off, the receiver is in operation.
The beam width determines the ________________________
azimuth resolution
The __________ is the device in the secondary radar system used in the video circuitry between the receiver and the radar indicator to decipher signals received from ATCRBS and aircraft transponders.
decoder
Azimuth
is the direction to the object.
Range
is the distance to the object based on slant range.
non-discrete transponder code
last two digits are ALWAYS zeroes
MTI Blind Speed is reduced or eliminated by _______________________________ stagger
pulse repetition frequency
Primary radar is based on the _________ principle.
radar pulse
Primary radar information is obtained by _________ and __________.
range, azimuth.
Aircraft Transponder
replies to only those interrogations being received on the mode to which it is adjusted.
Resolution
the minimum separation between two targets which can exist and still make it possible to distinguish between the two targets on the indicator.
Pulse Repetition Frequency (PRF)
the number of times the transmitter fires in 1 second.
radar mile
the time it takes for a radar signal to travel one nautical mile out to the object and one nautical mile back to the antenna.
discrete transponder code
when the last two digits are other than zero
Beacon targets exceeding __ mile displacement are not usable.
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