Chinese Radar Developments - KLJ series and others

Brumby said:

That may be the case but in regards to that particular example posted, a T/R count of 832 appears to be highly overkill for an air-air AESA seeker although the choice of Ku band seems to suggest otherwise. A rather strange combination. Do you have any idea the number of T/R used on the AAM-4B?

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Have no idea. The only thing I can say is that the missile diameter is 203mm so the radar diameter is less then 180 mm but it has GaN chips installed.
The reason why JSDF adopted AESA radars for the AAM-4B is to counter ECM. Although OT JSDF had done live field test against GQM-163 Coyote hitting it 10 out of 10 in 2005.

SamuraiBlue said:

Have no idea. The only thing I can say is that the missile diameter is 203mm so the radar diameter is less then 180 mm but it has GaN chips installed.

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Normally based on the diameter and some assumptions, a reasonable guess can be established on the T/R count. However with the AAM-4B, I would speculate its targeted frequency is either in Ku or Ka band. There is practically no technical literature out there in packing density of T/R modules on such bands unlike with X band. As T/R packaging technology is limited by the 1/2 wavelength rule, such bands will likely introduce additional miniaturization hurdles not seen with X band.
Btw, what is your reference source that it uses GaN rather than GaAs? It seems less plausible to me given state of airborne AESA development.

SamuraiBlue said:

The reason why JSDF adopted AESA radars for the AAM-4B is to counter ECM. Although OT JSDF had done live field test against GQM-163 Coyote hitting it 10 out of 10 in 2005.

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Going to AESA radar on the AAM alone is not necessarily effective against the other side if it also has AESA radar to barrage jam the missile. The reason I suspect that AAM-4B is at least in KU band is because airborne AESA in X band cannot barrage jam something that is outside its frequency bandwidth. It makes perfect sense for an AAM to go up the frequency tree because it offers higher angular resolution and reduction in antenna size requirement by giving up tracking range as after all the engagement envelope is terminal phase.

Also back to the original subject concerning the Chinese AESA, given the diameter and choice of KU band, I believe it is most likely some kind of AESA radar research targeted for anti ship missile.

Brumby said:

Normally based on the diameter and some assumptions, a reasonable guess can be established on the T/R count. However with the AAM-4B, I would speculate its targeted frequency is either in Ku or Ka band. There is practically no technical literature out there in packing density of T/R modules on such bands unlike with X band. As T/R packaging technology is limited by the 1/2 wavelength rule, such bands will likely introduce additional miniaturization hurdles not seen with X band.
Btw, what is your reference source that it uses GaN rather than GaAs? It seems less plausible to me given state of airborne AESA development.

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I concur with your thinking that it utilizes Ku band since it doesn't require the range for X band. As for the chips it's GaN. To reduce cost Mitsubishi Electronics are using massive amount of off the self civilian technology to develop this missile. As a result the AAM-4 costs less then the license built AIM-7.

Brumby said:

Also back to the original subject concerning the Chinese AESA, given the diameter and choice of KU band, I believe it is most likely some kind of AESA radar research targeted for anti ship missile.

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Now, IIRC, that AESA has 12 "sections", so in theory, they could take 4 of those sections for an AAM, assuming that you can scale it properly.

SamuraiBlue said:

I concur with your thinking that it utilizes Ku band since it doesn't require the range for X band. As for the chips it's GaN. To reduce cost Mitsubishi Electronics are using massive amount of off the self civilian technology to develop this missile. As a result the AAM-4 costs less then the license built AIM-7.

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In this particular example, cost effectiveness to implement was not a consideration. My basic knowledge on AESA and antenna propagation tells me that the inter element spacing on the arrays would be reduced by 50 % in the AAM-4B which would give rise immediately to added mutual coupling issues besides cooling management aggravated by use of GaN. I am curious how Japan managed to overcome these technical hurdles as this development had been rather off the radar considering the significance of it.

Skywatcher said:

Now, IIRC, that AESA has 12 "sections", so in theory, they could take 4 of those sections for an AAM, assuming that you can scale it properly.

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In AESA technology almost all the problems are connected in some way to scaling. In other words, assuming it away doesn't make the problem any less.

tidalwave said:

据国内雷达科研单位资料透露，歼-20得益于充足的头部空间，AESA雷达的TR组件高达2000到2200个之多，发射功率在24KW，全球最大！完全能保证在F22战斗机探测范围外首先发现其踪迹，相信美国人现在很后悔当初不把F22造的大一点，虽然F22为分布式合成孔径系统留下了余地，但是想换大雷达，可得使劲折腾一番，我国后发优势的体现就在于吸取对方的教训走自己的路，

They said J20 AESA has the largest power therefore longest detecting range , more than F22.

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Unless it's more inefficient

latenlazy said:

Unless it's more inefficient

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Can't you just say "less efficient"?

tidalwave said:

据国内雷达科研单位资料透露，歼-20得益于充足的头部空间，AESA雷达的TR组件高达2000到2200个之多，发射功率在24KW，全球最大！完全能保证在F22战斗机探测范围外首先发现其踪迹，相信美国人现在很后悔当初不把F22造的大一点，虽然F22为分布式合成孔径系统留下了余地，但是想换大雷达，可得使劲折腾一番，我国后发优势的体现就在于吸取对方的教训走自己的路，

They said J20 AESA has the largest power therefore longest detecting range , more than F22.

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Assuming the source is reliable, a peak output of 24KW would place the T/R peak power output between 11-12w. That would probably be consistent with where China is in terms of technological development with T/R and consistent with 2nd generation Western T/R's that became available in the 90's. I have not seen any open source information on the power output of the T/R's used in APG-77 (F-22) but 3rd generation T/R's with power output of 15/16w became available approx. 15 years ago. Currently 4th generation output at 25w is starting to be available. It is more than likely that APG-81 (F-35) would be using 3rd generation T/R's and that would give it an output of 27kW although that would be a guess.

You're still limited by heat dissipation issues. The APG-77's reported kW is around 20kW, the APG-81's reputed at 17 kw. Going by the same logic, you could assume the J-20 runs GaN or some other high-power AESA and is capable of 80 kW. In either case, simply the fact that the J-20's radar is larger gives it a significant advantage.

Inst said:

You're still limited by heat dissipation issues. The APG-77's reported kW is around 20kW, the APG-81's reputed at 17 kw. Going by the same logic, you could assume the J-20 runs GaN or some other high-power AESA and is capable of 80 kW. In either case, simply the fact that the J-20's radar is larger gives it a significant advantage.

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As a start I have assumed non are GaN based because the technology is not ready for prime time on a fighter. I said I was making a guess as I have not seen any official figures on the F-35. Do you have a source that you can quote on the reported 17kW? At that output level it would placed the T/R output at 10w which would be rather low even considering heat dissipation as a technological limiter given the T/R's were being specially built for the APG-81.