max range of the an/apg81 and AESA

Cockpit, radar, helmet-mounted display, and other avionics
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SpudmanWP

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Unread post01 Oct 2016, 07:59

It's sealed in that they never "need' to remove the RAM seals. They can still do upgrades.

When the radar T&R modules get upgraded, it will happen at a depot that can do a much better job of sealing up the nose than a field tech can.
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optimist

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Unread post01 Oct 2016, 08:44

It doesn't open for array servicing, but if they got it in there, they can get it out. Even if the seat comes out first and work from that end. There would be a way in case of complete failure.
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eloise

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Unread post01 Oct 2016, 15:27

hornetfinn wrote:AESA has also the advantage of having much wider total bandwidth (frequency range) where it can operate. This makes them much more difficult to detect and much more resistant to electronic warfare. It also gives the advantage of giving much better resolution which is especially improtant in radar mapping and identification modes (like SAR/ISAR).

Why wide bandwidth give better SAR resolution?
Please correct me if iam wrong but Isn't resolution of unfocused SAR limited by this :
Image
and resolution of focused SAR is limited by this :
Image

Image
Last edited by eloise on 01 Oct 2016, 17:56, edited 2 times in total.
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bring_it_on

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Unread post01 Oct 2016, 16:10

Industry is simply waiting for AMDR-X to take GaN T/R module cost down to acceptable levels and we should see both Raytheon and Northrop Grumman offer something that upgrades the current generation of AESA's. The current JSTARS-Recap sensor could also shed some light. Raytheon has quite publicly said that it will be competing with GaN for all AESA's going forward and given that NG enjoys some advantage due to being an incumbent they may see fit to offer a GaN sensor and with them NG will most likely also offer something like that.
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popcorn

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Unread post01 Oct 2016, 21:45

Not to forget NGJ will employ GaN-based AESA.
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bring_it_on

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Unread post01 Oct 2016, 23:54

The current GaN programs completely funded by the services or industry -

- AMDR-S band (Navy)
- LRDR-S band (USAF)
- G/ATOR-S band (USMC)
- NGJ-Mid (USN)
- EPAWSS (USAF)
- AN/TPS-77s - DART - L (Export - to be delivered end of year or early next year)
- Space Fence - S
- TPY-X - L band ( under testing at Lockheed)
- TPY-2 - X band (upgraded radar contracted for in FY16)
- Raytheon Lower Tier sensor ( C band, internal testing with Raytheon)
- Lockheed Lower Tier Sensor ( S or X band under development)

3DELRR had down-selected Raytheon's C band GaN sensor but they will be going back and making a down-select again next year. All three sensors for that program use GaN.

Higher frequency components would probably be quite expensive until TPY-2 (export to Qatar and UAE) come through and AMDR-X brings in volume demand.
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hornetfinn

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Unread post03 Oct 2016, 12:42

eloise wrote:
hornetfinn wrote:AESA has also the advantage of having much wider total bandwidth (frequency range) where it can operate. This makes them much more difficult to detect and much more resistant to electronic warfare. It also gives the advantage of giving much better resolution which is especially improtant in radar mapping and identification modes (like SAR/ISAR).

Why wide bandwidth give better SAR resolution?


Please check these:
https://people.eecs.ku.edu/~callen/826/ ... cs-F15.ppt

http://www.ece.uah.edu/courses/material ... rt1_11.pdf

https://earth.esa.int/documents/10174/9 ... ciples.pdf (page 14 onwards)

http://www.geo.uzh.ch/~fpaul/sar_theory.html

This, in turn, is driven by one of the main uses of SARs: to image the ground or targets. In both cases, the radar needs to be able to resolve very closely spaced scatterers. Specifically, resolutions in the order of a few feet are needed. To realize such resolutions in the range coordinate the radar uses wide bandwidth waveforms. To realize such resolutions in cross range very long antennas are required.


Basically to get high range resolution with radar you need to have very wide bandwidth. To get high resolution in azimuth (also known as cross-range resolution), a very long antenna is needed (which is done synthetically with SAR). I was talking about range resolution, where bandwidth is inversely proportional to resolution. Your formulas and pictures are about azimuth resolution. Basically the wider the bandwidth, the finer details can be resolved from the return signals in range given that there is enough processing power to do so. The links I provided tell much more about the issue.
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hornetfinn

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Unread post03 Oct 2016, 13:16

Dragon029 wrote:GaN will almost certainly make its way into the F-35 (unless an even better tech comes out / becomes mass produceable in the next decade or so). Increased output power may not seem ideal for a stealth aircraft, but it'll help with self-defensive EW and stand-off EW, and it might also allow the F-35 to boost the range of its MADL even further.


Actually increased output power can be very beneficial even for stealth aircraft if some thought is put into designing radar and other systems. Putting out more power does not directly mean the radar is more detectable. GaN technology gives many potential advantages that make it potentially much better than GaAs.

- Significantly higher output power of individual TR modules mean that it can create many more simultaneous beams or individual beams have higher power. There is no need to always blast at full power and modules can be run at low output power when high power is not needed. A lot of power is also good when a lot of power is needed. If enemy has VLO aircraft, having more radar power is better for detecting them and for jamming their radar.

- GaN allows much wider bandwidth which means it's much harder to detect and track. Current GaN systems can have 5-10 times the bandwidth of current GaAs systems. This means it can use 5-10 times more power and remain as tough to detect as GaAs system.

- GaN allows higher average power with the same peak power meaning that it will have better range performance while enemy ESM system performance stays the same as against GaAs system if all else remains equal.

Of course GaN also has other advantages like better efficiency. lower noise levels, smaller size and better reliability. Overall the improvement in performance can be as large as going from MSA or PESA radar to GaAs AESA. I'm sure F-35 will be the first mass produced fighter aircraft to adopt GaN radar system as that's where the development money really is and others are playing with pennies in comparison.
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sferrin

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Unread post03 Oct 2016, 13:42

I always think these, "what's the max range of radar X" questions are dumb. What's the max range of a flashlight? It's infinite. The photons will travel forever until they hit something. Without setting conditions the question is useless.
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Unread post03 Oct 2016, 18:09

sferrin wrote:I always think these, "what's the max range of radar X" questions are dumb. What's the max range of a flashlight? It's infinite. The photons will travel forever until they hit something. Without setting conditions the question is useless.

I agree. I tend to think of the "standard" as a 1m^2 RCS target with positive closure in a "look-up" and ECM-free environment while using a normal volume search technique. Adjust accordingly from there.
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vanshilar

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Unread post03 Oct 2016, 19:02

sferrin wrote:I always think these, "what's the max range of radar X" questions are dumb. What's the max range of a flashlight? It's infinite. The photons will travel forever until they hit something. Without setting conditions the question is useless.


I feel the same way about when people quote supposed IR or IRST ranges. "No problem tracking the F-22 from 90 km away!" because of unstated assumptions sort of thing. It's like, yeah, even with our naked eyes we can detect stars from thousands of light years away, it really depends on what your assumptions and conditions are.
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Unread post04 Oct 2016, 11:13

sprstdlyscottsmn wrote:
sferrin wrote:I always think these, "what's the max range of radar X" questions are dumb. What's the max range of a flashlight? It's infinite. The photons will travel forever until they hit something. Without setting conditions the question is useless.

I agree. I tend to think of the "standard" as a 1m^2 RCS target with positive closure in a "look-up" and ECM-free environment while using a normal volume search technique. Adjust accordingly from there.


Agree totally with both of you. I'd like to add that range depends a lot also from probability of detection and false alarm rate. If we drop the pD to 0.01 percent and have high false alarm rate, a radar can have far better max range than another radar which has the pD of 90 percent and low false alarm rate. Only problem is that the first one would be totally useless as it would see thousands or millions of false targets along with the real target but range would be very long. There would be no way of knowing which target was false and which was real and thus the system would have zero usefullness. The latter would see very low number of false targets and would see the real target at significantly shorter range but confidence would be high that it is a real target. Of course the latter one would be useful as an actual radar system. Without knowing these two values along the things you listed, the comparison between two radar systems could be totally misleading.
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eloise

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Unread post06 Oct 2016, 04:43

hornetfinn wrote:
Please check these:
https://people.eecs.ku.edu/~callen/826/ ... cs-F15.ppt

http://www.ece.uah.edu/courses/material ... rt1_11.pdf

https://earth.esa.int/documents/10174/9 ... ciples.pdf (page 14 onwards)

http://www.geo.uzh.ch/~fpaul/sar_theory.html

This, in turn, is driven by one of the main uses of SARs: to image the ground or targets. In both cases, the radar needs to be able to resolve very closely spaced scatterers. Specifically, resolutions in the order of a few feet are needed. To realize such resolutions in the range coordinate the radar uses wide bandwidth waveforms. To realize such resolutions in cross range very long antennas are required.


Basically to get high range resolution with radar you need to have very wide bandwidth. To get high resolution in azimuth (also known as cross-range resolution), a very long antenna is needed (which is done synthetically with SAR). I was talking about range resolution, where bandwidth is inversely proportional to resolution. Your formulas and pictures are about azimuth resolution. Basically the wider the bandwidth, the finer details can be resolved from the return signals in range given that there is enough processing power to do so. The links I provided tell much more about the issue.

Thank hornet , very informative post
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Unread post07 Oct 2016, 20:03

hornetfinn wrote:
eloise wrote:
hornetfinn wrote:AESA has also the advantage of having much wider total bandwidth (frequency range) where it can operate. This makes them much more difficult to detect and much more resistant to electronic warfare. It also gives the advantage of giving much better resolution which is especially improtant in radar mapping and identification modes (like SAR/ISAR).

Why wide bandwidth give better SAR resolution?


Please check these:
https://people.eecs.ku.edu/~callen/826/ ... cs-F15.ppt

http://www.ece.uah.edu/courses/material ... rt1_11.pdf

https://earth.esa.int/documents/10174/9 ... ciples.pdf (page 14 onwards)

http://www.geo.uzh.ch/~fpaul/sar_theory.html

This, in turn, is driven by one of the main uses of SARs: to image the ground or targets. In both cases, the radar needs to be able to resolve very closely spaced scatterers. Specifically, resolutions in the order of a few feet are needed. To realize such resolutions in the range coordinate the radar uses wide bandwidth waveforms. To realize such resolutions in cross range very long antennas are required.


Basically to get high range resolution with radar you need to have very wide bandwidth. To get high resolution in azimuth (also known as cross-range resolution), a very long antenna is needed (which is done synthetically with SAR). I was talking about range resolution, where bandwidth is inversely proportional to resolution. Your formulas and pictures are about azimuth resolution. Basically the wider the bandwidth, the finer details can be resolved from the return signals in range given that there is enough processing power to do so. The links I provided tell much more about the issue.


So, what's the problem with Russian AESAs being so crappy in SAR both in resolution and range, do you think? Range of bandwidth or processing? Or both?
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Unread post10 Oct 2016, 14:29

arian wrote:So, what's the problem with Russian AESAs being so crappy in SAR both in resolution and range, do you think? Range of bandwidth or processing? Or both?


Probably both. Russian T/R module specs and general construction seems to be much like what Western T/R modules and fighter AESA prototypes were 25-30 years ago. This is what typical Western T/R modules looked like almost 30 years ago:

http://techdigest.jhuapl.edu/views/pdfs ... _Abita.pdf

Those performance figures are not that far away from figure for current Russian T/R modules. Processing power has been rather low in all Russian radars to this day.
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