aesa radar

[svizomang]

aesa radar uses transmiter/receivers cells. Each cell is capable of transmiting a radio signal and receiving the echo. Each cell has it's own little angle range so in case such a radar is mounted into the fighter nose cone there's no need to mechanical steer the radar anttena.
And here is my question. If there is no need to mechanicaly steer the antenna why is there scanning time when radar scanns from left to right (horizontaly) and from 1st to 4th bar (verticaly). If radar is electronicaly scanned shouldn't this scann be done is a fraction of a second, much like a ccd camera scanns across all pixels in a ccd element?

even if there is a problem of signal interferance and we can only have one cell active at present time this still doesn't explain the F18s full scanning time of more than 10 sec. Radio signal is fast and even if we shoot at 100 km distante target we get the echo instantly or in about half a milisecond. So even if there's a 1000 cells ia a radar array and if we get a window of 1 milisec for each cell we would scann acros the entire ray in 1 second.

 

[thebard3]

I think you are correct in most of your statements, but you surely are mistaken that any military radar takes more than a few milliseconds to complete a scan across the entire array. I don't know anything about the F-18 radar set you refer, but it can't possibly have such a slow interval.

Brad Waybright

It's all okay as long as it's okay.

 

[VEBill]

An Active Electronically-Scanned Array radar uses the multiple sources (and receivers) as a phased array, working in concert. They don't "have [only] one cell active at [a] time".

Detection of small, distant, or stealthy targets could require a slower scan, to put more energy on the target. The radar equation and related waveform and signal processing considerations adds great complexity.

One could imagine that modern systems might grow their capabilities with software updates.

 

[IRstuff]

AESA often performs RWR functions, which means that emitters must be scanned for AoA, frequency, and waveform, which consumes quite a bit of time, particularly since AoA needs to be extremely precise, and waveform identification and yield critical information about the emitter's platform.

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[svizomang]

https://www.youtube.com/watch?v=Byqt8AJD4WE

this is yt tutorial on F18 radar. I believe F18 uses AESA radar, so no mechanicaly steering.
You can see that scaning horizontaly from left to right takes quite a bit of time. It only scans one bar verticaly of a total 6 bars it has.
So full 180 degree horizontaly scan for whole 6 bars verticaly scann takes more than 10 sec.

then if aesa is electronicaly scanned and if uses multiple moduls at the same time, this should be way faster.

 

[rb1957]

I wonder if USAF would allow yt videos to show accurate scanning rates, which I imagine is a very important number if trying to detect (or evade) the plane behind the radar ?

another day in paradise, or is paradise one day closer ?

 

[IRstuff]

F/A-18 is a USN aircraft, so USAF would only be peripherally concerned ;-)

As for the OP, I'm not going to say more except to point out that the F-18 shown in the YT video is specifically an F/A-18C.

As for time, all I'm going to say is so what? Ignoring stealth aircraft, this radar with a maximum range of 150 km would have at least 72 seconds before the AIM-120 could even contemplate engagement against a Mach 2 opponent.

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[thebard3]

Assuming the youtube video you reference is actually like the real system, I believe the trace moving back and forth across the display has nothing to do with the scanning of the array. In the old analog days that little bit of RF energy reflected from the target excited the receiver circuitry that amplified it to drive another circuit and so on until it ended up as a voltage bias on the electron gun grid, therefore creating the video 'blip', and the revolving trace to line up with the antenna angle at which it was received. The original phased array elevation scanning radars worked much the same way, with a separate display to discern the height and size of the object being detected. None of that happens today with the digital technology in use, but sometimes the old analog type presentation is deemed to be appropriate because it best suits our eyes, ears and other tactile sensors. I expect the actual frequency scan takes place in no more than a few milliseconds but I have no professional knowledge of this particular system to support that. The heart of the original Aegis system, SPY-1 radar is about 40 years old and functions much the same way. Frequency, pulse width, PRF and the like are all classified so it couldn't likewise be presented here but that radar frequency scans much, much faster than you suggest the AESA does.

Brad Waybright

It's all okay as long as it's okay.

 

[IRstuff]

The bar indicator cycles about every 8.7 seconds.

I wouldn't necessarily be surprised with a 2.2-s cycle per bar. The scan rate is going to be tied to the MTI functionality, as well as the RWR functionality. The MTI functionality will be dictated by the spatial resolution desired at max range of the radar, which dictates the angular resolution, and hence, the scan rate. The same scan rate is also driven by the time required to scan all frequencies of OPFOR radars long enough to acquire the waveforms so that the radar can be identified.

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