054B/new generation frigate
- Thread starter Blitzo
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All depends on set of inbound targets that the radar is supposed to counter.
4 face radar provides better search and acqui for saturated attacks from multiple angles simultaneously.
If your target set is controlling 200+ km radius of airspace, then 4 face is better.
If it is a radius of 100+ km which is relevant to a frigate class, then 2 face rotating radar + x band tracker equivalent to a destroyer class is quite a good cost/capability proposition.
Phase arrays have some transmission loss when the beam is steered off directly boresight from its plane, with more losses the more the beam is steered off center. Likewise, its also loses receive gain. When you have a fixed four set, the strength of the radar signal is not even, and there is going to be four weaker zones around the corners of each face. Rotary antenna gives an even signal around a 360 degree field. In fact the beam need not be steered electronically, it can be steered around horizontally with its mechanical rotation.
But that's not the main reason why the rotary is used. The main reason is cost. One face is cheaper than two and two is cheaper than four. Each module in an AESA can cost as much as a small car, and there can be thousands in a single face. If your cost and thermal budget is say, 4000 elements, you have greater range if you put all of them in one single face of 4,000 elements than divide them into four faces of 1000 elements each. Dual face with 2,000 elements each would be between.
The one face or dual face is also lighter, which enables you to put the radar up higher which gives you a longer radar horizon, which makes more advanced warning of low flying sea skimming antiship missiles possible. You can also put a four face up high too, but the total set would need to be light, resulting in smaller faces, so you're back comparing a single face with 4,000 elements vs. dual face with 2,000 elements each, vs. 4 faces with 1,000 elements each.
Of course, the four face has 360 degrees coverage simultaneously, the one face has to turn around for the 360 degrees and the rate of rotation is important. The dual face doubles the rate of rotating updates, sitting between the two.
One disadvantage of the rotary set is mechanical wear and tear, the radar has to be periodically taken down for overhaul. We see this happen on the Type 054A, where the top radar is removed for overhaul.
Another disadvantage is that if the radar has to be put on top of a mast, there is a weight and thermal budget that goes along. The radar cannot be very large, it cannot be very heavy for obvious reasons. The space is limited which limits how much heat it is allowed to generate internally, which curbs its power, and therefore its range.
One advantage which applies to fixed AESAs only is that superstructure and mast mounted fixed AESAs allow backside access for the crew to replace defective modules during the sea. After this, the radar can be recalibrated while on sea --- which can explain the calibration booms you see on the 052C and 052D --- although this system can, should and was replaced with an internal system later. If the AESA is mounted on a rotary, there is no access to it and repairs can only be done on port.
Rotary AESA can deal with supersonic ASM, or at least that is what the advertising for such radars will tell you.
It doesn't need to spin very fast constantly. It can slow down, so the face is allowed to dwell on the target longer. If the radar is turning in one direction, the tracking beam can contra rotate, which also allows a longer dwell time on the target. Remember the array allows an X and Y scan, compared to search radars that only electronically scan vertically, and need to be mechanically turned around for horizontal scan, like the Type 382.
So the explanation makes sense for the future PLAN FFG to adopt a 2 face radar if the displacement is roughly 5000 tons. This is especially true if the fitment is more for ASW than AAW (if sailing in a group with 052X and 055, doesn't make sense to also have FFG also geared for AAW).
On smaller ships employing 4 faced radars (Future FFG-X Korea and the Poliment on Admiral Gorshkov, or even the the export model from the 054A thread), it would almost seem like a suboptimal arrangement with all the extra cooling required to support the multiple arrays.
You have to remember that efficiency, as in cost-optimal, isn't the same as redundancy. I don't know about the future Korean FFG-X, but the Russians tend to emphasize more on redundancy. For example, in a European radar design like Thales STIR, you have a fire control radar all in one that handles gunnery, antiship and missile target illumination. For the Russians they would put this into three separate radar sets, each dedicated to one function, e.g. MR123 Kite Screech, Mineral ME, MR90 Orekh. Sure it costs more, weighs more, uses more power, but if one breaks, the other still works and won't take down your entire functionality, not to mention redundancy also means they are able to multitask more.
If a bearing breaks in your rotating two face, the whole set ceases to work and the ship will have to cancel its mission. That's not going to happen with a fixed four set, and you have the additional bonus of having the set being able to be repaired at sea by accessing the panel at the back. This one is not the Admiral Gorshkov but Project 20385 Gremyaschy. Shows you the radars that are integrated to the mast with back access from the inside. Note that even with two sets of fixed face radars, they still have to add a rotating search radar on the top. On the Gorshkov, you not only have the four faces of the Poliments radar around the mast, but you have the rotating search radar Furke on top. The Gremyaschy's Zaslon set is an evolution to the set you have on the Gorshkov.
The integrated mast on 20385 has S-band rotating single-face Furke for volume search of surface/air targets on the top, fixed four-face X-band Zaslon (derived from MiG-31 fighter radar) for SAM/artillery fire control in the middle and the lowest set of four faces is passive/active ESM (S, C, X, Ku band)/ECM (X, Ku band) set also used for OTH of AShM.
That's the smaller version of Furke from the one on the Gorshkov. I think there are three different versions.
The Zaslon here only shares one thing with the Zaslon on the MiG-31 and that is the name. The MiG-31 Zaslon is a PESA, with a very circular array.
This one here has a modular block like face, with the radar divided into subarrays, as you can see from the image, and this points to be a much more advanced AESA.
The lower set of faces is also an AESA, not ESM. You can see the face divided into four sections, that's a monopulse radar.
It may work in a passive mode, but there is definitely an active mode which is straight out radar targeting. And it needs it, since the ship needs a gunnery fire control radar for the AK-630s and the main gun, as the Puma FCR used on the Gorshkov class is omitted in this ship.
Directional finding and signal collection ESM is the pair you see on twin arms on the upper part of the mast, and the three panels of different sizes behind the radars are the ECM. These are all a brand new set not seen in the Gorshkov class or in any previous Russian ship.
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Yes, it is the smaller version Furke-2, 22350 has Furke-4.
No, Zaslon on 20385 also is PESA, Russians prefer to call it quasi-AESA, but that doesn't make it real AESA. It has inherited quite a lot from Zaslon-AM of later MiG-31s.
The lower 4 arrays are for ESM/ECM. Actually, not only the 4 larger faces, but the set of 3 smaller arrays as well. It makes no difference for their function if they use PESA or AESA. If you prefer to disbelieve what the Russians provide in booklets and videos at the exhibitions, it's your choice.
Artillery fire control is one of the functions of Zaslon MFRLS (Multifunctional Radiolocation System).
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Illustration given is not consistent to a PESA since it would require a large analog transmitter on the back of the array that is connected to the array with line feeds of equal length. Equal length linefeed to every element is essential to prevent frequency steer. The illustration on the back of the array looks more like a cabinet where the TRMs are housed and can be pulled out for servicing or replacement. See Thales integrated mast below.
You cannot do artillery fire control just by pure ESM as in directional finding passive radar alone. That's unheard of. What if your target isn't emitting radar? Common sense will tell you what you have on the ship is obviously a fire control radar. The array would have to be multi-modal, switching between active FCR and passive (ESM) modes. FCRs are monopulse by the way.
The two units on the two arms on the higher mast are also ESM, though their primary purpose is to passive detect and directional find incoming sea skimmer threats, but the question is whether they can do DF of OTH targets, similar to Mineral ME2 which is also set like two small units on a pair of arms.
3 smaller arrays on each side are definitely ECM. Similar to RAMSES, each panel is meant for jamming at a different frequency. Future Canadian surface combatant has a similar arrangement where they have four dimple shaped arrays of different sizes at each side. You set ECM on the side because that's where you expect the antiship missile to be heading to the side of the ship, giving the jammers the best possible arc at the attacking missile. ECM is dependent on a separate ESM unit to collate threat signals for analysis, determination and directional finding, and that has to fall to those two units you see on the mast arms.
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Once again, Artillery control is managed by the middle set of four, the same which provides for Redut missile guidance. Bottom four are ESM/ECM. This is the third time I am writing this. There are four frequency bands monitored and two can be actively jammed.
"llustration given is not consistent to a PESA since it would require a large analog transmitter on the back of the array that is connected to the array with line feeds of equal length. Equal length linefeed to every element is essential to prevent frequency steer."
Ever heard of digital antenna arrays?
"llustration given is not consistent to a PESA since it would require a large analog transmitter on the back of the array that is connected to the array with line feeds of equal length. Equal length linefeed to every element is essential to prevent frequency steer."
Ever heard of digital antenna arrays?