The Su-35 gets its 20kw power from employing 2 TWT (as say the ASG-18 on the YF-12, oh so many years ago) which also gives wider channel coverage and greater ECCM options but only insofar as 'half of each' they are stepped between lower and upper X band (H/I Band) with an overlap in the middle.
My understanding is that this causes coherency and frequency lock issues which effects S/Nr at the PSP which in turn denies the use of a high end radar dataprocessor.
In any case, the VKS has lost a couple Su-35s over Ukraine under circumstances where the likelihood of techint recovery was almost certain. Putting No-35 Irbis tech into the Zaslon is thus kind've a yeah but...no deal at this point. The No-36 Byelka of the Su-57 would be a better option or one of the Type 1245/1248 series (Chinese) AESA if the russians cannot do the tech development.
The SBI-16 Zaslon gains it's power by virtue of being FMICW.
Meaning it operates at high PRF equivalent, all the time. At 2,600kg, it weighs almost twice as much as the AWG-9 and there is a good chance that that is at least partially a PAO cooling loop for a radar that operates at scaled outputs approaching 30kw (you can't measure FMICW by duty cycle).
This is why it has such an enormous range. This is why it can track TBM targets of .1m2 and guide missiles on them with closures above Mach 7.
This is why Zaslon was built to track and kill .3-.5m2 TLAM-N and .25m2 AGM-86B (mod 1) ALCM. And later was adapted to track the .01m2 AGM-129.
Even equipped with the older R-33 missile, it was never intended solely as a 'bomber/tanker/C4ISR killer' but rather to kill small, agile, targets over heavy terrain clutter, after handoff from central Russian EWR, acting as part of the Russian national air defense system in a nuclear environment.
In this, it is necessary to understand that FMICW radars work to a nominally 'older' style of LDSD capability. Where Pulse Doppler is based on eliminating anything that isn't generating frequency compression by movement, leaving a 'blank screen' effect.
FMICW takes an alternative, additive, approach of measuring real beam flashback from the immediate terrain under illumination and then looking harder at anything which is higher than the average db of that averaged return. This was standard as a means of locking up targets below the jet in the F-4 era and the machine-tracking was actually quite good at it, though the WSO/RIO needed effectively a video trick to adjust target display contrasts in seeing the initial bright-blip (which the filter also automated).
This is actually innately superior to PD tracking, provided you have an EPAR which can rapidly refresh and frequency surf the given illumination zone while having a large enough framing buffer that you can average out aspect shifts and chaff blooms etc. by a maneuvering target. A PD system is simply too vulnerable to beaming and the null speed doppler filter. Whereas a FMICW system will always see additive differences between base clutter and target multiplier, even if the latter is negative as a function of shadowing (due to multipath).
FMICW always has issues with range finding and ECCM inserts as it depends on specific waveform encoding to split targets into range gated filter stacks. But, conversely, it's never bothered by hi/lo interleave in determining range uncertainty, simply because it has such fast scanning.
The original Zaslon, which Adolf Tolkachev compromised to the West, being a product of the 1970s, was almost certainly an analogue system which was limited in it's tracking capabilities (numbers and active scan waveforms). But the later Zaslon A introduced a digital Argonne 5/7/11/15 and then the Baget radar dataprocessor which are actually pretty good.
Over Ukraine, one of the key commonalities of the rash of R-37 kills which has all but denuded the ZPU of fighter inventory (after 30 days of 6 missiles fired per day, even at .25 SSPK, we're talking ~45 downings with one Foxhound pilot claiming 9 kills...) has been the lack of hard track warning.
Back in the day (1980s) a lot of 'new' RWR like the ALR-56 did not pick up the signal or at least did not treat it as AI. This led to scenarios like the 36th TFW out of Bitburg being constantly bushwacked in their new-hotness F-15As by older-and-cunninger F-4Es of the Wolfhounds 'Royal Squadron' because the Phantom WSOs would unplug the APQ-120 breaker and perform the lock-on (from a zoom climb) with the TISEO. Then flip on the CW for Sparrow illumination and zap the Rodans without a hard pulse track since the APQ-120 was linked to the optics boresight and performing angle off calculations which the CW floods sent to the missile.
Something similar may be going on with the Zaslon/Axehead pairing in that the latter missile _does_ use PD as a range:rate lead steering mechanism and, with the parent radar offering radio correction updates and the VLRAAM using it's incredibly high cruise speed, the missile may actually be engaging in a form of track via missile as the datalink is confirmed to be two-way. TVM flies an inertial flight path for part of the trip, sees the SARH reflection and begins homing (for the R-37M) around 18nm and then says: "Okay, is _this the guy_" which the radar's long range angle tracking with the Zaslon confirms as the missile again uses it's spectacular (Mach 6.7) kinematics to always positive-lead steer to a high RCS aspect. And then, as LOS-R goes to zero, activates a separate, Ka band, active seeker which snaps the missile back to collision lead and scores the hit.
Again, this corresponds with what Ukrainian pilots have said it the 'bolt from blue' effect of sudden kills with no passive threat warning as the SARH becomes ARH.
Finally, the Russians have long used idiomatic scientific expressions which have rather different meanings in English or German (the two engineering languages) to strongly imply that the Zaslon is capable of not just datalink shared tracking but true _cooperative sensing_ which is to say that Foxhounds up to 200km apart can link scans and tick / tock \ derive common triangulated reads of target bearing from enhanced/multi-aspect illumination.
Again, if true, with such powerful baseline systems operating in a mode similar to the USNs CEC mode, flinging dual mode, dual band, hypervelocity VLRAAM; it would go a long ways towards explaining why the Russians are both confident in their ability to track stealth and able to achieve long range intercepts of 217km or more against fastjets, low in the clutter.
The Russians always admired the F-14, it fits in with their 'artillery rocket' mindset. When Belenko defected in the Foxbat, we gave him a fam ride in one and he said: 'How do you even get close...?'.
The MiG-31 is the answer to that question and, over multiple upgrades, now has an SBI-16AM radar weapons system specifically optimized to the delivery of the R-37M in three modes:
Anti-fighter, in which the missiles fly a direct trajectory and shift immediately to ARH in what we would call Fire And Forget or Skating.
Radio-corrected inertial, which is the primary long range mode for SARH-TVM.
And 'Reprogrammable' which has alternately been asserted to mean the ability to set a homing point (airfield baselane) where target activity is expected to be. Or/and a method of seconding illumination authority to another aircraft.
When the original K-37 (AA-X-13 Arrow) program achieved it's 308km, 1994, hit, the distance was so great that an intermediate Su-30 was used (as was the No-11 Bars-M antenna frontend in the MiG-31BM upgrade) to provide the midcourse update as the launching Foxhound was literally firing beyond its baseline tracking range.
While at least two of the operational R-37M kills are known to have been attributed to the Su-57 Felon. Of course the Axehead itself is a third of a meter shorter than the testbed missile. But the engagement circumstances and supposed LPI/LPD capability of the No-36 radar do highlight a possible 'feature not workaround' intentional operation mode which simply maximizes the missile kinematic capabilities while perhaps compensating for any residual Su-57 signature issues as well.
The point here is that the Russians are always methodical and careful with their planned mission increment changes in capabilities, rather than simply the 'More range, speed, or ECCM?' 'Yes!' approach of pushing boundaries for its own sake, in the West. They have to carefully weigh capabilities improvements and so have time to bring things all together.
Given the K-37 program nominally ended in 1998, yet incremental development continued until a 2016-18 service debut of the R-37M; it would not be at all impossible for the Zaslon to be what it (now) is because the Axehead is what the Russians deemed necessary as an ultimate counter to the AMRAAM evolutionary potential. All the way back in 1988 when development first started.
The very notion that Zaslon could grow that far is a hallmark of how capable the system, itself an artifact of a 1970s, pre-digital, era really may be. As a multi-role set, the No-35 is likely too compromised to be as good, in the pure air defense mission.
