Thread: Radar Comparison

Came across this on another site. its a bit dated but interesting nonetheless.:

Author: Alfonso Figueroa.

"I want to add some comments to your interesting and helpful message about the current capabilities of the several European AAW frigate projects, specially taking into account their sensor suites. It's very common on
Usenet and other boards to read how such and such new-generation phased array is superior to AN/SPY-1x, "because it's active", even if some times the reasons are obscure or directly unknown to some of the readers of such boards. In my opinion, I don't really believe that using GaAs (Gallium Arsenide) modules or MMIC (Monolithic Microwave Integrated Circuits) on GaAs substrates to build a new generation active array instantly makes a better solution than the very mature passive electronically scanned fixed phased array of AN/SPY-1x. "Newer" is not always equivalent to "better". Let's see what are the supposed advantages of an active array with respect to the conventional passive one on the F-100s:

a) Adaptive beamforming to counter heavy electronic jamming. This was shown in the Sierra-band MESAR (Multifunction Electronically Scanned Adaptive Radar) prototype, from which TRISAR/SAMPSON and other
Siemens-Plessey radars evolved. Through a complex schema of sidelobe blanking beams and multiple subarray receivers a number of jammers can be cancelled (15 per array with 16 receivers). Great, but ECCM is not exclusive to active array technology, and is well known that starting from the first SPY-1B prototype the antenna design emphasized lower sidelobes and improves dramatically jamming resistance against self-screening and standoff jammers/repeaters, together with ECM analysis and burn-through processing (and SPY-1x uses very brute-force burn-through capability). So, in ECCM terms, an active array is doing what a passive array does, with a different technology. But before we ponder too much on this question, we have to ask ourselves who exactly is going to have the technical know-how and the tactical ability to get close enough to jam an AEGIS system out of service and survive the experience, because such hypothetical all-powerful threat will also jam an active array or any other radar out of the water too.

b) Progressive degradation of system functionality instead of total failure. This is the single most important characteristic of an active array. Since the array is composed by a large number of elementary radiators (almost 85-90% are T/R modules, the rest being simple phase shifters like in passive arrays), a number of them can fail or be battle-damaged, but the system could still function. On the other hand, the AN/SPY-1A/B have only two very powerful radiators, and AN/SPY-1D only one, belowdecks, so its failure is a mission kill for the ship. Great, but how can be that considered a negative aspect of an AEGIS system is something that puzzles me. We shouldn't forget that if the ship service turbo or aux generator fails, because of the sustained battle-damage, the
active array will remain as silent as a passive one. Doh! And... what if the technology on passive array like AN/SPY-1x, and specially the software of its fire control system, is more mature than the one on new-generation
barely-tested almost prototype-alike active arrays? Would that offer additional, realistic, operational reliability?

c) Performance on littoral/enclosed waters and low horizon scanning. This is due to the capability of forming narrower beams at low angles. Great, but let us not forget that this ability depends also on the frequency that
the active/passive array is using. I would like to remind that AN/SPY-1D(V) is modified for the littoral environment and for dealing with fast, sea-skimming missiles. We have to remember that a fixed array has
the capability of changing its beam scheduling/policy to hit low-elevation sectors at will, something that is not as easy in a rotator active array like the British SAMPSON, or passive one like ARABEL/EMPAR. The same can
be said to higher-elevation sector scans for ballistic missile defence (TBMD).

So, as you can see there are a number of theoretical advantages on the active arrays, but none of them is prone to revolutionize anti-air warfare any time soon. Upon a close examination, the most interesting ability is the one I mentioned in point b), and that surely is not one that can substantiate the very frequent British claim that SAMPSON is "better" than anything on earth. There are plenty of naval/ground late generations passive arrays being fielded/designed (SPY-1, TRS-22XX, RAT-31SL, EMPAR, ARABEL, Sky Watch, J/FPS-2, Type320 etc), a fact that confirms their capability is absolutely granted in their lifetime. On the other hand, a few additional comments:

- German/Ducth F-124/LCF Side. We are not sure that APAR-STIR/SMART-L is inferior to AN/SPY-1D, but it doesn't look superior either. For a start, one of the most important functions of the ship (long range volume search) is assigned to the Delta-band rotator SMART-L. A rotator is prone to mechanical failure and it's sensible to special kinds of countermeasures (more of its sidelobes are exposed on every rotation). So two of the advantages of the active APAR system (reliability through progressive degradation and ECCM) could be moot points if balanced with the disadvantage of SMART-L. Second, a rotator will never be as efficient in littoral areas or in TBMD (where long range volume search is vital) as a fixed array with beam scheduling. Third, SMART-L is forcing you to have a bigger radar cross section (RCS) than with a single fixed array that combine search and mid-course guidance. Fourth, APAR is very nice, but is working in a higher frequency (India-band) than SPY-1D, since it's basically a fire control radar. That means shorter range, worse weather penetration and clutter rejection, which implies that your backup volume-search in case of SMART-L mechanical failure is compromised. Having APAR/SMART-L could look like a nice redundancy feature, until close examination: if you loose APAR you are mission-kill due to FCS loss, but if you loose SMART-L, you have your early warning detection and volume search on an India-band fire control radar! Uh-oh, looks like a mission kill to me. Fifth, if your want to integrate SM-2IVA and CEC you have to pay for its development. None of that applies to the F-100's AN/SPY-1D. (It could be argued that the AN/SPG-62 of the Mk.99 AEGIS FCS can also suffer mechanical failures, but remember that such end-game India-band CW illuminator is not subject to same mechanical stress as a constant long-range search rotator).

- French/Italian ARABEL/EMPAR side. With due respect, though nice and modern radars, their overall capability is not even in the same league as AN/SPY-1D (though it must be said that EMPAR looks better than ARABEL, at least on paper). For a start both ARABEL/EMPAR are passive phased array mechanical rotators. That implies bigger RCS, bigger still due to the use of a second rotator S1850M (SMART-L/MARTELLO coctel), for long-range volume search. It also implies worser data rate than a fixed array like APAR or AN/SPY-1x. The same problems described in the previous paragraph regarding the rotator SMART-L can be applied to these systems, with increased manning costs to maintain two mechanical radar systems instead of a single reliable fixed one like SPY-1x. In addition, both of them are higher frequency (specially ARABEL, since EMPAR is Golf-band, but still a mere 80Km range or 150Km with dedicated surveillance and decreased data
rate), and that implies shorter range, worser clutter rejection etc. ARABEL/EMPAR are not even a multibeam radar like SPY-1x, though they can change the beam from pulse to pulse. (No mention goes to the use of Sylver and the need to get rid of the 5" gun to make space for the missiles!)

- British SAMPSON side. Again, a much vaunted active array evolved from MESAR/TRISAR/TRIXAR, with all its theoretical advantages, which are a lot bigger on paper than on practice. But... an active phased array on a
rotator? Again, in order to reduce cost your get worse data-rate, even if you use a back-to-back configuration and sophisticated beam steering. Again, it needs a second radar for PAAMS volume search, with all the implications previously described. Additional maintenance. Bigger RCS, etc. But the most important thing is, we have AN/SPY-1x today. We know it works. Where is SAMPSON and its associated FCS? How can be the advantages
of something that doesn't exist be analyzed?

Cutting long stories short, I agree that APAR looks very nice, and we only got out of it because there were some initial problems and doubts. Also, SAMPSON looks good on paper, but it will take many years to reach full operational reliability. The most important thing that Iñigo wants to say is that the AEGIS combat system is very mature and proven technology, with a minimum technological risk and development cost for Spain and with
a very promising future through CEC and TBMD. Software is an extremely complex beast, and I wouln't change the stability of an AEGIS tried and tested WCS for a newer generation bells-and-whistle one if the decision was in my hands. The Armada has chosen the best possible solution for Spain. Taking aside national, political, industrial and darker interests, the F-100 and its technology could have been the best solution for Italy,
France and the UK. They won't admit it, but they know it, and they suffer in silence....."