120 degree coverage longitudewise, how about latitudewise? how many degree can be form up and down. And this is true for both ship and jet AESA ?
Phase Array Radar, theory and operation
- Thread starter lilzz
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120 degree coverage longitudewise, how about latitudewise? how many degree can be form up and down. And this is true for both ship and jet AESA ?
I'm not really sure, although it should be the same theoritically longitudewise.
If PAR can't beam forming up and down, lattitudewise then it cannot track low level sea-skimmer flying couple meters above the sealevel,
or not capable of guiding the SM-3 missile during ASAT which requires the beam facing sky upward.
Dear Sirs:
Phased arrays and traditional single-line antenna arrays behave the same way. Its actually very simple and based on well-known principles of constructive and destructive wave interference.
Remember the wave tank in your high-school physics class - well, the principles of an antenna array, phased or otherwise is the same.
For example, if two wave fronts meet and the trough of one wave aligns with the crest of the other, then the waves will cancel each other out. We call that destructive interference.
If on the other hand, the crests and troughs line up together then they reinforce each other and the resultant wave has the sum of their amplitudes (it gets stronger or brighter). Thats called constructive interference.
Naturally the same thing applies to radio as well as light waves (or water waves or sound waves or any other kind of wave).
What is the behavior of an antenna array?
Let us imagine the simplest case, that of a line of identical antennas spaced exactly one-half wavelength apart.
If they are spaced at the correct interval AND they transmit simultaneously,
then:
a) the signal along the line connecting the antennas (along the array's axis) will be ZERO, as the waves will interfere destructively.
b) the signal perpendicular to that line (along the array's face) will be the sum signal of all the antennas together, as the waves will interfere constructively.
c) the signal at any angle away moving from the perpendicular towards the parallel will vary from the maximum sum signal to NULL, that is, ZERO.
Suppose now we delay the transmission time from antenna to antenna, starting at the 1st antenna at one end in sequence until we have a maximum delay at the last antenna at the opposite end.
Let us make that delay 1/4 of the transmitting wavelength.
Performing the same sum signaling across the array shows that maximum signal is obtained at a 45 degree angle to the array's perpendicular.
Please note that our null has not disappeared either, rather it has been shifted 45 degrees away also.
What we have just done is to STEER the beam away by 45 degrees, by introducing a time delay across the array.
Thats the principle of all arrays, not just the phased array. By introducing various time delays across the array's face (not just in the horizontal but in the vertical plane) the can steer the antenna by any amount we wish.
The only limitation occurs as we go past certain degrees as at a steering angle of 90 degrees the beam cancels itself out. Put simply, it varies as the cosine of the steering angle.
Thus phased arrays do not usually steer past 45 degrees as the beam has only cosine 45 degrees of intensity (0.707), at 60 degrees it is 0.5.
That process can be performed as quickly as we can switch in delays - only limited by the speed of our switches.
Furthermore the arrays' power is the sum of all individual elements of the array, the loss of a single transmission element degrades the array by only its individual contribution, making for a small loss in power and a great increase in reliability.
Hope this helps,
Best Regards,
Dusky Lim
Phased arrays and traditional single-line antenna arrays behave the same way. Its actually very simple and based on well-known principles of constructive and destructive wave interference.
Remember the wave tank in your high-school physics class - well, the principles of an antenna array, phased or otherwise is the same.
For example, if two wave fronts meet and the trough of one wave aligns with the crest of the other, then the waves will cancel each other out. We call that destructive interference.
If on the other hand, the crests and troughs line up together then they reinforce each other and the resultant wave has the sum of their amplitudes (it gets stronger or brighter). Thats called constructive interference.
Naturally the same thing applies to radio as well as light waves (or water waves or sound waves or any other kind of wave).
What is the behavior of an antenna array?
Let us imagine the simplest case, that of a line of identical antennas spaced exactly one-half wavelength apart.
If they are spaced at the correct interval AND they transmit simultaneously,
then:
a) the signal along the line connecting the antennas (along the array's axis) will be ZERO, as the waves will interfere destructively.
b) the signal perpendicular to that line (along the array's face) will be the sum signal of all the antennas together, as the waves will interfere constructively.
c) the signal at any angle away moving from the perpendicular towards the parallel will vary from the maximum sum signal to NULL, that is, ZERO.
Suppose now we delay the transmission time from antenna to antenna, starting at the 1st antenna at one end in sequence until we have a maximum delay at the last antenna at the opposite end.
Let us make that delay 1/4 of the transmitting wavelength.
Performing the same sum signaling across the array shows that maximum signal is obtained at a 45 degree angle to the array's perpendicular.
Please note that our null has not disappeared either, rather it has been shifted 45 degrees away also.
What we have just done is to STEER the beam away by 45 degrees, by introducing a time delay across the array.
Thats the principle of all arrays, not just the phased array. By introducing various time delays across the array's face (not just in the horizontal but in the vertical plane) the can steer the antenna by any amount we wish.
The only limitation occurs as we go past certain degrees as at a steering angle of 90 degrees the beam cancels itself out. Put simply, it varies as the cosine of the steering angle.
Thus phased arrays do not usually steer past 45 degrees as the beam has only cosine 45 degrees of intensity (0.707), at 60 degrees it is 0.5.
That process can be performed as quickly as we can switch in delays - only limited by the speed of our switches.
Furthermore the arrays' power is the sum of all individual elements of the array, the loss of a single transmission element degrades the array by only its individual contribution, making for a small loss in power and a great increase in reliability.
Hope this helps,
Best Regards,
Dusky Lim
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Just for academic note. Dusky what you are describing here is the timed domain beamforming. Probably the most common if not dominant phase shifting method. There is another one that uses frequency for making the phase shifts. The result is that if the beam shifts to one direction, the frequency changes, and when the beam shifts to the other direction, with the frequency changes linearly.
A good analysis on the Russian 's AESA Phazotron Zhuk AE/ASE
Judging its internal T/Module. It's using a FPGA and old process for the GaAs
It's not really cutting edge in terms of technology. I wonder What's taken so long for CHina to have its AESA to come out?
The article says because of Russia is lacking in packaging techology therefore its radar only have 50% to 70% T/R module of US design.
China 's semiconductor industry is alot more advanced and widespread than Russia. So it should be able to surpass Russia's design.
Judging its internal T/Module. It's using a FPGA and old process for the GaAs
It's not really cutting edge in terms of technology. I wonder What's taken so long for CHina to have its AESA to come out?
The article says because of Russia is lacking in packaging techology therefore its radar only have 50% to 70% T/R module of US design.
China 's semiconductor industry is alot more advanced and widespread than Russia. So it should be able to surpass Russia's design.
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FriedRiceNSpice
Captain
Wow, maybe in the future you wouldn't even need to use the radar to guide missiles.. just point the radar at a target and watch it vaporize!! Or at least deepfry the brains of its crew!!!
lol