07-08-2012, 04:08 PM
BENT 4343 R ADIO NAVIGATION SYSTEM
[attachment=30438]
Learning Outcomes
At the end of this subject, students should be able to :
Explain basic principles of radar radio navigation system in technical and application
Analyze structures, characteristics and working principle of radar system.
Analyze structures, characteristics and working principle of GPS.
Design basic radio navigation system that use in flights and ships communication.
Report and explain their given assignment clearly.
Radio navigation
application of radio frequencies to determine a position on the Earth.
The basic principles are measurements from/to electric beacons, especially
directions, by bearing, radio phases or interferometry
distances, ranging by measurement of travel times
velocity, by means of radio Doppler shit
Radio direction finding
By tuning in a radio station and then using a directional antenna to find the direction to the broadcasting antenna/radio sources
By using triangulation, two such measurements can be plotted on a map where their intersection is the position.
Early systems used a loop antenna that was rotated by hand to find the angle to the signal, while modern systems use a much more directional solenoid that is rotated rapidly by a motor, with electronics calculating the angle.
These later systems were also called Automatic Direction Finders, or ADF.
A more sophisticated approach to ADF was to use two loop antennas, set up at a right angle to each other, and measure the ratio of the signals from each antenna to get the angle to the beacon.
BRITISH NAVIGATION SYSTEMS: GEE (GRID)
It was the first hyperbolic navigation system to be used operationally and allowed an aircraft or ship to locate its position by timing the delays between two sets of signals.
three transmitters were used (1 Master & 2 Slave A & B) that were sited about 80 to 160 kilometers (50 to 100 miles) from each other and transmitted on wavelengths in the range of 15 to 3.5 meters (20 to 85 MHz).
The three transmitters sent out periodic radio signals in a four-part cycle, with each step of the cycle a millisecond apart:
START: Master emits a pulse.
1 ms: Slave A emits a pulse.
2 ms: Master emits a distinctive double synchronizing pulse.
3 ms: Slave B emits a pulse.
The cycle repeats every 4 milliseconds, 250 times a second.
line-of-sight system, with poor accuracy. At a distance of 400 kilometers (250 miles), Gee could target a site within an ellipse about 1.6 kilometers long and 9.6 kilometers wide
Advantages of Radar
Long range detection and tracking of targets– 1000’s of miles
All weather and day/night operation
Wide area search capability
Coherent operation enables– Simultaneous reliable target detection and rejection of unwanted “clutter” objects
Target imaging (fixed and moving)
Very fast beam movement with electronic scanning of antennas ( microseconds)
Ability to adaptively shape antenna beam to mitigate interference and jamming
“Relatively lossless, straight line propagation at microwave frequencies
Disadvantages of Radar
Long range detection requires– Large and heavy antennas
High power transmitters
Significant power usage
$$$$
Radar beams not propagate well
through the Earth, water, or heavy foliage
around obstacles
Vulnerable to jamming, and anti-radiation missiles
Target can detect that it is being illuminated
Target can locate the radar in angle-space
The echo from some targets is becoming very small
Low observable technology
[attachment=30438]
Learning Outcomes
At the end of this subject, students should be able to :
Explain basic principles of radar radio navigation system in technical and application
Analyze structures, characteristics and working principle of radar system.
Analyze structures, characteristics and working principle of GPS.
Design basic radio navigation system that use in flights and ships communication.
Report and explain their given assignment clearly.
Radio navigation
application of radio frequencies to determine a position on the Earth.
The basic principles are measurements from/to electric beacons, especially
directions, by bearing, radio phases or interferometry
distances, ranging by measurement of travel times
velocity, by means of radio Doppler shit
Radio direction finding
By tuning in a radio station and then using a directional antenna to find the direction to the broadcasting antenna/radio sources
By using triangulation, two such measurements can be plotted on a map where their intersection is the position.
Early systems used a loop antenna that was rotated by hand to find the angle to the signal, while modern systems use a much more directional solenoid that is rotated rapidly by a motor, with electronics calculating the angle.
These later systems were also called Automatic Direction Finders, or ADF.
A more sophisticated approach to ADF was to use two loop antennas, set up at a right angle to each other, and measure the ratio of the signals from each antenna to get the angle to the beacon.
BRITISH NAVIGATION SYSTEMS: GEE (GRID)
It was the first hyperbolic navigation system to be used operationally and allowed an aircraft or ship to locate its position by timing the delays between two sets of signals.
three transmitters were used (1 Master & 2 Slave A & B) that were sited about 80 to 160 kilometers (50 to 100 miles) from each other and transmitted on wavelengths in the range of 15 to 3.5 meters (20 to 85 MHz).
The three transmitters sent out periodic radio signals in a four-part cycle, with each step of the cycle a millisecond apart:
START: Master emits a pulse.
1 ms: Slave A emits a pulse.
2 ms: Master emits a distinctive double synchronizing pulse.
3 ms: Slave B emits a pulse.
The cycle repeats every 4 milliseconds, 250 times a second.
line-of-sight system, with poor accuracy. At a distance of 400 kilometers (250 miles), Gee could target a site within an ellipse about 1.6 kilometers long and 9.6 kilometers wide
Advantages of Radar
Long range detection and tracking of targets– 1000’s of miles
All weather and day/night operation
Wide area search capability
Coherent operation enables– Simultaneous reliable target detection and rejection of unwanted “clutter” objects
Target imaging (fixed and moving)
Very fast beam movement with electronic scanning of antennas ( microseconds)
Ability to adaptively shape antenna beam to mitigate interference and jamming
“Relatively lossless, straight line propagation at microwave frequencies
Disadvantages of Radar
Long range detection requires– Large and heavy antennas
High power transmitters
Significant power usage
$$$$
Radar beams not propagate well
through the Earth, water, or heavy foliage
around obstacles
Vulnerable to jamming, and anti-radiation missiles
Target can detect that it is being illuminated
Target can locate the radar in angle-space
The echo from some targets is becoming very small
Low observable technology