J-20 5th Gen Fighter Thread VIII

[BoraTas]

I think that magnitude of range increase isn’t just from total power output but a combination of better power output, better noise floor, and better sustained operational parameters from much better thermal and voltage breakdown characteristics.

I respectfully disagree. A factor of 16x is still impossible. The circuit is still on GaN, hence you wouldn't expect a significant change in the breakdown voltage or maximum allowed temp. The required S/N and noise factor (TS on the equation) aren't fields of fast improvement. The improvement has been a few dBs over decades.

 

[LurkerZhu]

Maybe we need focus on GaO, not GaN...

 

[bsdnf]

And we need to consider the advancements in the J-20A's signal processing capabilities.

China's semiconductor industry in both software and hardware, has made remarkable progress. Half-jokingly speaking, this is also closely related to the rise of EVs and the popularization of autonomous driving. ADC/DACs, FPGAs and DSPs are becoming better, cheaper and more integrated at an astonishing pace

 

[Gloire_bb]

And we need to consider the advancements in the J-20A's signal processing capabilities.

This is probably most important and largest part.
We've a good modern example, when ancient, prehistorical AN/ALQ-167 was updated by university team with DRFM and AI to be a good redfor jammer for red flag...and darn thing started working so well, that it now flies on dedicated SEAD units to Iran.
Hardware is not even crux of the story nowadays, it's wrap.

 

[tphuang]

I respectfully disagree. A factor of 16x is still impossible. The circuit is still on GaN, hence you wouldn't expect a significant change in the breakdown voltage or maximum allowed temp. The required S/N and noise factor (TS on the equation) aren't fields of fast improvement. The improvement has been a few dBs over decades.
View attachment 170006

I don't think the difference is 16x. Higher voltage, higher efficiency, lower resistance all matter here. That's where a lot of the advancement in third generation ICs have gone toward. A previous generation of GaN-on-Si material (from late 2000s) would likely be very China first started to produce such wafers and wasn't able to do the latest material.

The improvement in SiC substrate over the past couple of years have been quite significant. You can see the resistance data on 1200V and 750V SiC modules for that. But even so, I think the power generation and cooling tech of late 2000s was also several generations behind now. You didn't have all this experience over high voltage electrical platform that China has now.

iirc, GaN-on-SiC can now reach power density of 4 W/mm2 when Chinese researchers tested out material RF applications. 1m diameter radar would have surface area of 785000 mm2. which even if we assume a significant % of surface is not used for power amplifying purposes (say only 1/4 of surface is used for that), that leaves a pretty high upper limit for theoretical peak power.

 

[bsdnf]

And let me quote from another post.

My view is that the result of countering stealth isn't that stealth becomes useless and everyone abandons it, but rather that stealth becomes a fundamental element, and those without stealth will only die faster.

Otherwise, there would be no need for the sixth-gen fighter to go through so much trouble to remove the vertical stabilizer.

Stealth doesn't mean that increasing radar power is meaningless. PLAAF will increase the power as much as they can within their capabilities; they will increase the burn-through range as much as they can.

Only incompetent fools who can't produce anything new will claim they've reached the pinnacle, that no one can crack it, no one can surpass it, that everything is in vain, and in the end, everyone can only engage in dogfights.

 

[tphuang]

Well modern RF tech means that those who have the latest and most advanced tech have such a leg up over opponent in terms of detection and counter detection.

so J20 to J20A upgrade is really big.

 

[latenlazy]

I respectfully disagree. A factor of 16x is still impossible. The circuit is still on GaN, hence you wouldn't expect a significant change in the breakdown voltage or maximum allowed temp. The required S/N and noise factor (TS on the equation) aren't fields of fast improvement. The improvement has been a few dBs over decades.
View attachment 170006

A few DB of noise reduction may not a small amount of signal gain for dim signals, and detection of long range returns are primarily dim. The scale of improvement for detection of a dim signal is the ratio of dim signal size to quantity of noise floor reduction, not total noise floor reduction.

From a detector physics standpoint range is actually decided by that relationship between dim signal and noise floor. Your range limit is essentially the limit of detection for furthest returning signals you can pick up. Higher beam power is just one of many methods to try get more separation from that dim far return signal and your noises, and scale of improvement is defined essentially by how much improvement in dim signal pickup you can achieve.

 

[Blitzo]

Some great J-20 images here.

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I'm not sure how great they are, given one of the images seems to have the front landing gear with dual wheels whereas we all know J-20s across all variants front landing gear only has a single wheel.

I'm not sure who actually made the choice to use AI for that (I can only assume they are an AI hallucination), or what the actual heck happened.

 

[A.Man]

Dose anyone know why these J-20's have double landing wheels?