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Tam

Brigadier
Registered Member
Okay, thanks you very much Tam and Iron man !



Is it actually possible to subdivide a single radar panel into different surfaces to multiple the number of tasks executed at the same time ?



So the size of a T/R module depends of its frequency ?


Yes and yes.

For the second question, it should be with one of the dimensions of the module facing the array itself connected to an antenna (dipole, monopole, plate, notch, gate slot, etc,.)

Do note there are things like DTRMs and QTRMs, which means Dual T/R Module and Quad T/R module. In which case, the spacing between the T/Rs themselves must be half of the wavelength. DTRMs and QTRMs are meant to reduce AESA costs. For a QTRM you have one LNA for four transmitters, instead of one LNA per transmitter on a TRM.

For example this is a QTRM. The distance between each T/R in this module should be half the wavelength and should give you an idea what spectrum this operates on.

images (3).jpeg
 
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AlyxMS

Junior Member
Registered Member
Why is part of Type 054A painted black? I’m not seeing the same thing on 052s.

Why does the radar-panel-looking-thingy that hangs on top of 054A’s mast sit at an angle?
 

gelgoog

Brigadier
Registered Member
I suspect its some kind of fire or heat proof resistant paint. The engine exhaust is right below the black painted areas.
 

Tam

Brigadier
Registered Member
Not easy to explain briefly why the radars must be angled. There is also the context of these types of radars and how they function, and in this case, the particular history of these radars. There are several points that need to be made.

1. These radars electronically scan in the vertical for elevation, and is mechanically rotated for horizontal for azimuth or bearing information on the target. By using a serial time delay on the on each of the linear transmitters, the frequency shifts across the face and the interaction of these varying frequencies causes the beams to steer in a vertical pattern. This is why they are called Frequency Scan or FRESCAN radars. Radars that use this principle are commonly used as volume air search radars both on land and sea.

2. Almost all of these radars are single faced and don't angle, with the notable exception of the Type 382 radar, which is not just used on the Type 054A, but also on the Liaoning and Carrier 002, with the carrier variants having a bit of a variation. The Type 382 in turn, copied this configuration from the Russian Top Plate radar, also known as Fregat, and these were imported with the Sovremenny destroyers, and ordered also for the Type 052B and Type 051C destroyers. The Type 381, which operates on the frequency scanning principle and is the predecessor to the Type 382, only has a single face and doesn't angle. This radar is featured on the Type 051B before the ship was refitted.

Type_381_1.jpg

a. The main difference between Type 382 and the Russian Fregat M2EM is that the Russian radar has an IFF array on top and the Type 382 has none. The carrier version of the Type 382 has a circular disk on top, reasons not clear. Another difference is that the Type 382 works is dual band, works on the S and C band, while the Fregat M2EM is only on the S-band. To accomplish this dual band, one face of the radar has to be on the S-band, which is the larger face, and the C-band is on the smaller face, which has smaller and finer elements.

382-radar.jpg


3. This is the Fregat M2EM. You can see the IFF bar on top. While the frequency scanning principle is common, and not invented by the Russians ---- you can trace this even earlier to US radars, like the SPS-48 used in US carriers --- the dual faced, with angled offset is unique to the Fregat. Hence why when this configuration appeared on the Type 382, the Russians have a good reason to complain about Chinese copying.



One face is at 55 degrees and the other is at 45 degrees. The Russians have never fully explained the reason for that, but my guess is that the results between the two faces are compared to better precisely obtain both azimuth and elevation information on the target. If its really only about increasing update rate by going dual faces, the dual faces would be identical. The imposed differences between the two faces are deliberate for the purposes of signal comparison.

4. Fregat/Top Plate is not the only Russian radars that are dual faced with each face being different. Take a look at the Top Steer and Top Sail radars, on the Slava and Kirov class cruisers. I think why the faces of one side and another are different is for signal comparison.


MarshalUstinov1989radar.jpg
 
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Deino

Lieutenant General
Staff member
Super Moderator
Registered Member
And with the Type 002 carrier close to hand-over, there seems to be something different in preparation at Dalian shipyard.
Time to guess? ;)

PLN Type 002 carrier + news maybe in empty dry dock at Dalian - 20190405 part+.jpg PLN Type 002 carrier + news maybe in empty dry dock at Dalian - 20190405.jpg
 

Deino

Lieutenant General
Staff member
Super Moderator
Registered Member
Reminds a bit to this one ... start of construction of the 002 carrier in March 2015.
But surely could be any other large vessel too.

PLN Type 002 carrier at Dalian sat image 20150310.jpg
 

Tam

Brigadier
Registered Member
I won't be surprised if they started building a fourth aircraft carrier there. But it can just be another large container ship.
 

KIENCHIN

Junior Member
Registered Member
I won't be surprised if they started building a fourth aircraft carrier there. But it can just be another large container ship.
Wasn’t there a rumour the second CATOBAR carrier would be build in Dalian? Hope this is it but then this could just be another container ship as you said.
 

Tetrach

Junior Member
Registered Member
Hello it's me again. I'm wondering a few more questions;

-Why does the Burke class embark a target illuminator for its missiles while the Type 52C/D doesn't ?

-What is the actual objective of the type364 ?

- What is the point of a rotary target illuminator radar as it won't be able to continuously track the enemy aircraft ?

-How can a rotary radar "divide itself" if it is moving 40 rpm ?

-The range of a radar is one thing, and how far it can effectively detect a potential target is an another concept. As such how can you optimise the effective range of a radar ? bigger front lobe? frequency ? etc

A lot of (probably) stupid questions, I know. I'm just very interested in how radars work and I feel I will only learn but putting my thoughts and problems here !
 

Tam

Brigadier
Registered Member
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
 
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