AS 06 - Radar Theory 1 Flashcards
Review Questions
What is the max ramp weight for the CT-142?
34 700lbs
What components are heated electrically to guard against ice build-up?
Pilots side window Pitot tubes Prop blades Static ports Stall warning transducer Elevator horns Engine intakes Windshields
What does radar stand for, what does it do?
Stands for radio detection and ranging
Used to detect and locate objects
Describe the echo principle of radar.
A radar transmits a particular type of waveform and interprets the return signal, converting the echo return into useful information.
What types of information are provided by RADAR?
Target range
Target azimuth
Target elevation
Target speed
What are some uses for radar?
T - Traffic detection and avoidance A - Altitude G - Groundspeed and drift G - Guidance systems T - Target detection and homing M - Map reading and nav W - Weather detection and avoidance
Describe the Radio Determinization process
Strong, short bursts or radio energy are sent out (pulses)
Energy is reflected back to the receiver (echo)
Time it takes the energy to return can be converted to distance
Regarding contact detection, the strength of return is based on what factor?
The amount of scattering at the return source.
What factors affect Contact Detection?
Range - Due to spreading, the return signal may be too weak to be detected by receiving antenna
Size - Larger targets are more likely detected, smaller ones may be filtered out depending on the radar
Shape - Right angled objects are more conducive to reflecting a signal back to its receiver
Reflecting Characteristics - Some compounds reflect more readily than others
How is azimuth (direction) measured?
It is measured in relation to a specific reference point.
What are the different types of radars/ antennas used in calculating azimuth and elevation?
Parabolic, Planar Array and Phased Array
WRT Pulse RADAR Principles, why are transmissions concentrated into very short pulses, separated by sufficiently long intervals? (Think interference elimination)
To permit all echoes from targets within the operating range to be received before transmission of the next.
What does an ideal pulse look like?
Flat top, sharp leading and trailing edge (top hat)
A pulse starting abruptly, steady power then tapering off describes what pulse?
Sloped trailing edge
Describe a sloped leading edge pulse.
A sloped leading edge where the pulse builds slowly to peak power then flattens out, abrupt stop.
What does a sloped top pulse mean?
The power level varies throughout
Look more into Min/ max range pulse width, ppt doesn’t explain it great
a
Range accuracy requires what for an accurate timing start?
A sharp leading edge
What is a problem with a long pulse regarding range resolution?
If there are two targets, the leading edge from target B will reach antenna before trailing edge of the return from the first target. Results in the appearance of a single target at a distance of the nearer target.
A short pulse ensures what regarding range resolution?
No target overlap and provides two distinct returns
What are the 7 basic radar components?
A - Antenna P - Power Source R - Receiver I -Indicator S - Synchronizer M - Modulator T - Transmitter
Describe a Synchronizer, what does it generate?
Provides timing for the whole system
Generates the PRF and display range markers
Triggers modulator to release energy (its the modulators trigger)
Describe a Modulator
Stores energy between pulses
Determines the waveform of the output pulse (shape)
Releases pulses of energy when directed by the synchronizer
(Think a bullet going into a chamber as the energy)
Describe the Transmitter and the associated carrier frequency.
Provides RF energy at extremely high power in very short pulses
Carrier frequency must be extremely high to fit many cycles into the short pulse
Describe an Antenna and it’s duplexer component, which type of antenna is normally used?
Highly directional transmitting/ receiving device, usually rotated or moved back and forth between two positions
Duplexer switches from transmitting to/ from receiving.
Normally a rotating planar array which transmits and receives RF energy.
Describe a Receiver and its characteristics.
A very sensitive super-heterodyne receiver.
Accepts signals from 1 - 10 MHz
Detects and amplifies weak RF echoes
Changes echoes to video and sends the signal to the indicator
(think hearing aid and/or satellite dish)
Describe an Indicator, the type of scan depends on what?
Visually represents all necessary information to locate the target on screen
Method of representing data (type of scan) determined by the radar’s pulse
What are the different Indicator presentations?
A, B, C, J, E, PPI
What type of scan is mainly used to determine range but rough direction is also possible? Also, target returns are interpreted by vertical deflections from the transmitter pulse?
“A” Scan
What scan type is used to determine range, bearing, target size and has data presented as abscissa and ordinate?
“B” Scan
Describe a “C” Scan type
The echo appears as a bright spot with the azimuth angles as the horizontal coordinates and the elevation angle as the vertical coordinates.
Which scan type is a modification of the “A” scan, in which the spot rotates in a circle near the edge of the CRT face?
Also, how does an echo appear and what happens as the distance changes?
J scan, an echo appears as a deflection from the circle and distance is determine by the pointer rotating within a circle, similar to a aneroid barometer.
Describe a Type “E” scan, what is it normally used for?
Modification of the B scan, echo appears as a bright spot with range on the X axis and elevation on the Y axis.
Normally used for precision approach radar where AC must follow a certain angular line to reach touch-down point.
Describe PPI scan
Provides range and bearing info, most common for navigation radar and provides a map-like picture.
Go into detail about the PPI scan (slide 31)
Review Questions
If you wanted to get a very accurate ranging and target resolution, what characteristics would you ensure?
Pulse shape (sharp leading and trailing edges) and a narrow pulse width.
Review Questions
What does the synchronizer do?
Timing: determines PRF, range marks and triggers the modulator.
Is the synchronizer a stand-alone component or included within another component?
May be a separate unit or included in the transmitter.
How is power carried to the antenna from the transmitter?
Power is carried to antenna via coaxial cable or waveguide.
How does a receiver interact with weak RF echoes?
It detects and amplifies them
