PESA vs AESA radar

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Vanessa1402

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What is the point of AESA radar on fighter?
- TWT of PESA don't have limitation in peak power, X band T/R modules of AESA can't go much higher than 10W
- PAE of T/R modules is only 25% with GaAs modules and at most 50% with GaN modules, so that much worse than TWT
So in term of detection range and jamming resistance then X band PESA radar is better than X band AESA radar right?
 
-Reliability, where AESA trumps over PESA. TRM last much-much longer. e.g 1000 Hr or more vs 200-300 Hr for TWT or tubes.
-Flexibility in both Transmitting and Receiving. AESA can actually use different weighting laws in receive or transmit (e.g Unweighted for transmit while for receiving it can use Taylor-40 dB for reduced sidelobe)

Jamming resistance may often have little to do with transmit power. It's yes that more transmit power generally means more burnthrough range. But one have to remember that radar is constrained by law of physics namely the 4th root law. While jammer have advantage of just square law as it only need its wave to travel one way. As a result Jammer have considerable advantage that it only need smaller amount of power vs power required by the radar to counter its jamming.

The case are even more severe for Deception jamming where power doesnt matter as the jammer attacks specific operating modes of the radar instead of brute force barrage jamming.
 
stealthflanker said:
-Flexibility in both Transmitting and Receiving. AESA can actually use different weighting laws in receive or transmit (e.g Unweighted for transmit while for receiving it can use Taylor-40 dB for reduced sidelobe)
Click to expand...
why can't PESA do the same?, and what is the benefit of using different weighting for transmit and receive?
 
Vanessa1402 said:
stealthflanker said:
-Flexibility in both Transmitting and Receiving. AESA can actually use different weighting laws in receive or transmit (e.g Unweighted for transmit while for receiving it can use Taylor-40 dB for reduced sidelobe)
Click to expand...
why can't PESA do the same?, and what is the benefit of using different weighting for transmit and receive?
Click to expand...

Because it has less control over its antenna. That the transmit path for PESA is basically as straight as possible to reduce loss from the waveguide and the feed network straight to the phase shifters. It's controlled by beam steering computer which steers the beam, but not much else.

AESA can have more control like which module can be active at any given time.

The benefit for changing the weighting scheme on transmit is you can actually have Fan beam, deliberately "defocus" your beam making it broader, therefore covering the area of interest quicker, and then you can switch back to "pencil beam" mode to focus the most energy to the area of interest if needed.

You can also have better sidelobe control, reducing the chance of your radar's sidelobe being intercepted by enemy ESM's. This usually achieved by precise manufacturing of the antenna. But with AESA, one can perhaps relax the requirement as the antenna can control its pattern.
 
Vanessa1402 said:
What is the point of AESA radar on fighter?
- TWT of PESA don't have limitation in peak power, X band T/R modules of AESA can't go much higher than 10W
- PAE of T/R modules is only 25% with GaAs modules and at most 50% with GaN modules, so that much worse than TWT
So in term of detection range and jamming resistance then X band PESA radar is better than X band AESA radar right?
Click to expand...

AESA radar has lower internal noise and can deal with clutter better than PESA
0.PNG

1.PNG
2.PNG
3.PNG
 
GARGEAN said:
Ronny said:
GARGEAN said:
Should be noted that graph above is a little bit optimistic.
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Why?
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At the very least because noise figures for AESA are extremely optimistic, best case scenario.
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The photo shows comparison between AESA and PESA. Those figure you saw are noise eliminated because certain components like phase shifter, feed ..etc are not in front of the LNA on the AESA. So if you think the number are optimistic, it would be for both PESA and AESA

GARGEAN said:
Real life models have quite a bit more modest figures.
Click to expand...
Can you give some example of real life model figures? preferably for modern AESA like APG-79 or APG-81
 
Ronny said:
So if you think the number are optimistic, it would be for both PESA and AESA
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Never said opposite) Tho can vary from case to case, for ex with hybrid PESA.
Ronny said:
Can you give some example of real life model figures? preferably for modern AESA like APG-79 or APG-81
Click to expand...
Not for those, but there are quite a few examples of TRMs with 3+ figure. 1.5 often is mentioned as quite an achievement.
 
GARGEAN said:
Ronny said:
So if you think the number are optimistic, it would be for both PESA and AESA
Click to expand...
Never said opposite) Tho can vary from case to case, for ex with hybrid PESA.
Click to expand...
What is the different in term of noise for hybrid PESA and why?

GARGEAN said:
Ronny said:
Can you give some example of real life model figures? preferably for modern AESA like APG-79 or APG-81
Click to expand...
Not for those, but there are quite a few examples of TRMs with 3+ figure. 1.5 often is mentioned as quite an achievement.
Click to expand...
Can you post them here? when was they made and what frequency they operate in
Also, since the reduction of noise from PESA to AESA is literally due to the fact that these stuffs like Phase shifter, feeds..etc are in front of the LNA on a PESA and behind the LNA on an AESA. So let say if the noise figure of AESA is 3+ then on a PESA of similar technology level the noise figure will become something like 6 dB. Because you basically the reason PESA has more internal noise is just because it got more lossy components in front of the amplifier
 
Ronny said:
What is the different in term of noise for hybrid PESA and why?
Click to expand...
Mostly in multiple receivers placed within antenna and not buried deep like in common PESA.

Ronny said:
Can you post them here?
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Just a couple.
20210408_072148.jpg

Common one
Screenshot_20210625-004409.jpg
Study roughty from times of F-22 creation.
unknown.png
"Nice" one.


And please, be a little bit less defensive. That's not looking honorable.
 
GARGEAN said:
Ronny said:
What is the different in term of noise for hybrid PESA and why?
Click to expand...
Mostly in multiple receivers placed within antenna and not buried deep like in common PESA.
Click to expand...
So it suffered the 3 dB additional loss in transmit compared to AESA, but not in receive path then

GARGEAN said:
Ronny said:
Can you post them here?
Click to expand...
Just a couple.
View attachment 662439
Common one
Study roughty from times of F-22 creation.
"Nice" one.
And please, be a little bit less defensive. That's not looking honorable.
Click to expand...
So the theoretical Duplexer loss + Low power receiver protection loss is 0.25 dB, the real world loss from these component following your example is 3.5 dB or 14 times higher than in theory. Maybe these component are just a lot more lossy
However, a PESA also has a duplexer and a receiver protection just like AESA, and since it is central duplexer and central receiver protection, so there is even more loss compared to the duplexer and low power receiver protection on AESA. At minimum, you will also lose 3.5 dB from these two parts alone. If we keep the same ratio then you lose 10.5 dB from these component. But then in front of the LNA of PESA, you also have the feed, waveguide, phase shifter , which accounted for another 2.3 dB. So if AESA noise is 3.5 dB, then a PESA with similar technology level will have noise level of 12.6 dB. That is just in 1 path- transmit or receive, account for both transmit and receive path then you double the number. Regardless, AESA still has much lower internal noise.
1.PNG
 
It was said about many advantages of AESA over PESA. Personally I found some multi beam possibility (of whole array) as nice; possibility to work at the same time as radar jammer, communication; better frequency agility and output power management those lead into better LPi;
Etc.
But it was missed that AESA tends to have better power aperture product than PESA. It is easier to increase power of individual transistors than stress TWT waveguids, I/O switch etc.
Least say that APG_79 from F-18E is estimated to be much more powerful (in terms of power-aperture product) than AWG-9 despite having smaller array.
Using GaN will increase this benefits...
As reference link... to some old post page, in next post
 
LukaszK said:
It is easier to increase power of individual transistors than stress TWT waveguids, I/O switch etc.
Click to expand...
Is it tho? N035 got 2.5 times increase in transmitting power over N011M with roughty same array size and without substantial change in hardware. Meanwhile 50% increase in AESA TRMs emission is a very big and hard to achieve deal without big tech leaps like GaAs>GaN
 
Yeah, naturally the waveguide, phase shifters, those components in conventional or PESA antenna can be easily sized to handle very high power level.
 
The "True Time Delay" beamsteering is apparently still a future technology. to my knowledge no AESA radar today using such technology.
The bandwidth advantage is thus limited similarly to PESA's. Which roughly equivalent to beamwidth. Thus a phased array radar having beamwidth of 4 degrees will have 4% bandwidth.

Implementation of True time delay is problematic due to the needs of actually provide the physical delay line to the module. This was to be achieved with optic fiber. Thus term "Photonic True Time Delay" was born.

Waveguide eliminations can be achieved by use of Space feed array. Unlike Russia/FSU Development however, US almost entirely abandon the development of space feed array since 1969. With only Patriot MPQ-53/65, Multipurpose Missile Tracking Radar and Safeguard ABM Target tracking radar ever reached production.
 

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