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Discussion in 'Navy' started by Jeff Head, Apr 6, 2015.

  1. Tam
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    Tam Senior Member
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    Rotary sweep is the best for search and detection. If the beam continuously dwells on a single target, the single target is all it sees, and you won't be able to search and acquire new targets, and give you data about the overall environment. Even fixed faced radars do a rotary sweep using a fan shaped multi-lobe pattern.

    With a rotary radar, the rate of rotation give you the rate which the track of the object is updated. So if the radar is turning at 60 rpms, then its updating targets at the rate of once per second. Radars and combat management systems also have track prediction algorithms to predict the target where its going, heading and speed while its not being updated. By the way, besides the point, do you know that online action games use track prediction on their servers? Its for a similar reason. Before the target is updated once again, there is lag and you minimize tracking errors with track prediction. Some rotary radars are back to back dual faced to increase the rate of updates by 2x.

    There is no such thing as a rotary target illuminator. Target illuminators are fixed design solely meant to follow a target. Rotary radars are mainly search radars. Another separate radar, called fire control radars, are the ones that stick to the target.

    Target illuminators are only needed for SARH or Semi Active Radar Homing missiles. These missiles don't have a radar emitter on their own. Just radar homing guidance system. Something is needed to light up the target so that missiles can home in on the target. The Standard SM-2 is a SARH missile so the Burke needs its SP-62 target illuminators. The HHQ-9 I am not sure if its SARH or ARH though I lean on the latter. ARH means the radio emitter is on the missile itself, so it can function autonomously in a fire and forget manner. If HHQ-9 is SARH, then the target illuminator is within the main panel of the Type 346 radar itself, the AESA nature of the radar allows it to use multiple beams simultaneously that can be digitally beam steered in different directions. If HHQ-9 is ARH, then there is no need for a target illuminator. An ARH missile still needs to be guided towards its long path to the target, so the ship radar still updates the missile track, and only when the missile is near the target, which is called the terminal stage or the "catch basket" the emitter on the missile lights up and the missile homes in. Because the radar emitter and receiving antenna on the missile is so small, the radar range for the missile seeker is limited, whic h is why for the journey up to near the end, it has to be command guided referred to as midphase updates. This is also true for SARH missiles.

    If targets are much closer to the ship, ARH missiles are fired in a fire and forget manner, with the ship telling the missiles to tilt toward their targets so the missiles can activate their seekers. With SARH, the illuminators are already lighting up the targets as the missiles are launched, then tilted towards the targets. There is a difference how missiles are operated in short and long range. Similar principles are also with AAMs.

    The Type 364 radar on top of the mast on the 052C/D, and also on the Type 054A in the rear mast, is mainly for searching the edge of the radar horizon for low flying or sea skimming threats. They cover a blind area the main Type 346 radars cannot.

    Rotary radars don't divide themselves that is why there are multiple radars on a ship.

    Range is determined by four factors --- frequency, power, transmit and receive gain of the antenna. Plus you must have a long pulse cycle or low PRF --- the pulse of the radar must be long enough for a long receive time to wait for the echoes to be received before it can transmit again. The longer the range, the longer is the receive time needed for the echo.

    This ship is a good example of how things work.


    Project 22350_Frigate_Admiral_Sergey_Gorshkov_Russian_Navy.jpg
     
    #411 Tam, Apr 13, 2019
    Last edited: Apr 13, 2019
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  2. Tetrach
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    Tetrach New Member
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    Okay thanks you.

    Isn't range also determined by directivity ? The main lobe's size surely affects such performances. By having more superposed signals you will result in a better receive gain.

    Also I'm quite interested in the SAMPSON. It is considered that each panel is composed of +2000 radiating elements. How is this possible, considering the Type 364 has only around 1250 elements per side for a total of +5000 T/R modules, while having bigger panels ? Considering they operate at the same frequency and as such theirs modules should have the same size, the number of T/R modules should be proportionnal to the size of a panel.
     
  3. Tam
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    Tam Senior Member
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    Yes it is, I prefer to call it transmit gain. Receive gain can also be referred to as antenna aperture.

    I forgot to mention that of course, radar cross section affects range, and also note that radar cross section changes with frequency. Something that can have a very low RCS in one frequency can be higher on another.

    Don't refer to it as Type 364, its Type 346. Type 364 is the radar encased on a globular radome on top of the mast, not the four panels. This particular radar, set on top of the mast, gets a high view of the ocean and farther radar horizon, and is used to spot and track sea skimmers and other low flying targets. It also cues the CIWS and the HQ-10 launchers towards the threat bearing.

    052d-17.png


    Actually, Type 346 has over 5,000 elements per panel, but also note that its using a QTRM, which means there are four T/Rs per module. Go back to one of my previous post. So there are 1250 modules, each module a QTRM, so about 5,000 T/Rs. QTRMs is a great way to save money on AESAs. Given the size of each panel, about 5,000 or over S-band T/R elements is about right. The whole ship should have about 20,000+ T/R elements, and this is going to be very expensive if each element has its own LNA (low noise amp). So in a QTRM, four T/R elements share the same LNA and A/D converter as a single module. So over 20,000 T/R elements, 5000 modules.

    Aside from the poor English, this statement describes a QTRM, by someone who is writing this in Chinese and having it poorly translated in Bing or Google Translate then cleaned up with editing.

    https://en.wikipedia.org/wiki/Type_346_Radar

    "Instead, the design team took an approach similar to that of British MESAR and Israeli EL/M-2075 APARs by group four transceivers into a transmitting/receiving (T/R) module with 100W peak power,"

    "Type 346 inherits the design feature of the prototype of grouping four transceivers into a 100W peak power T/R module with its own power source.[4][10]"

    Here is an example of an X-band QTRM.

    aesa-activeantennaarrayvidthumbnail.jpg

    India's Uttams AESA radar uses QTRMs with radiator shaped antennas on the elements.

    uttam side view.JPG
     
    #413 Tam, Apr 14, 2019
    Last edited: Apr 14, 2019
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  4. Lethe
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    Lethe Senior Member

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    I don't follow the construction process of new warships in nearly as much detail as some posters here do, but if the numbers from Chinese Wikipedia are to be believed (26 052Ds and 8 055s identified) then, given that all those units should be commissioned by 2025, they suggest a fleet size in 2025 of 40 to 52 destroyers. The lower bound requires everything pre-052C to have been decommissioned by 2025, which seems unlikely, while the upper requires the final pair of 051s (and everything newer) to remain in service. While it is possible that the pace of retirements could accelerate considerably going forward, I do think that the upper end of the range is more likely than the lower, with a midrange estimate of perhaps 48 destroyers in 2025, consisting of the 055s and 052Ds, 052Cs, Sovs/052Bs, 051Cs and perhaps the 051B.

    Of course this is just regurgitating publicly available information, but I found it rather interesting when one considers that it was only a few years ago that mainstream projections of China's future naval strength were far more modest, with destroyer numbers in the 30s commonly cited. How quickly things can change, even when one is vaguely paying attention.
     
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  5. Bhurki
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    Bhurki Junior Member
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    Destroyer production currently stands at about 4 per annum (2.5 for 052d and 1.5 for 055). Considering a average hull life of 30 years, that means PLAN can field more than 100 destoyers even after accounting for decommissioning of older combatants.
    Its obviously in the spurt phase now and may not continue at the same speed in the future, but starting 2030, PLAN would be able to field a force of atleast 60+ modern destroyers ( under 25 years of hull age) on a sustainable basis even after including MLU in the loop.
     
  6. Deino
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    Deino Brigadier
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    Just a strange question ... what do you think about this post??




    PLN Type 003 carrier at Dalian maybe - 20190427.jpg




    Pardon, but I cannot see a certain part that could fit to a 003/004 carrier? .... even if I don't know what these strange long structures are, I don't remember similar ones already to be seen.

    Or did I miss a certain part?
     
    #416 Deino, Apr 28, 2019
    Last edited: Apr 28, 2019
  7. Higgle
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    Higgle Junior Member
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    I think it's too early to say.

    The OP's explanation is that the support struts you see in the middle of the picture are the same struts that were used to support the flight deck overhang of 002, before it was welded onto the main hull component. Given that Dalian will likely not employ large module construction (different from Jiangnan), this is a plausible theory.

    But this explanation is still rather weak. We will probably hear something more concrete in a few months time.
     
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  8. Xsizor
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    Xsizor Junior Member
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    https://thediplomat.com/2019/05/china-has-constructed-six-ballistic-missile-submarines/

    Is there some kind of informal agreement between the world powers in limiting the number of nuclear delivery platforms like SSBNs? I've noticed that the French and British limit themselves at the 4+4 or 4+6 SSBN and SSN. I know that Russia and US might have a formal "understanding" . Both seems to limit it at 12 to 14. US can choose to build more.

    My doubt is whether China is limited by such agreements or understandings. How much SSBN China can build? What if China tries to match US ? Any backstage dealings regarding the current buildup? Has all this got anything to do with the trade relationship between the two countries?
     
  9. Lethe
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    Lethe Senior Member

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    There are no formal or informal understandings regarding SSBN numbers.
     
  10. Biscuits
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    Biscuits Junior Member
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    Not really. Historically, China focused it's nuclear budget on making ways for the population and not just the missiles to survive in an exchange. The SSBNs are more for keeping the technologies alive than as a decisive arm of the nuclear force, unlike in UK and France where they are THE nuclear arm.
     
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