055 DDG Large Destroyer Thread

Status
Not open for further replies.
T

Tam

Brigadier
Registered Member
Stealthflanker said:
So, have anyone make a range estimate for those big phased arrays ? Particularly the 346B.


think i can try make one, with some assumptions tho.

wikipedia states that earlier Type 346 have 4x4 meter antenna and S-band. Assuming array fill factor of say 90%. the 4x4 m array can contain about 4522 TRM assuming operational frequency of 3 GHz. The range of this early types is stated to be at least 400 Km.

The type 346B for Type-055 is stated to have 40% larger array. This corrensponds to area of about 17.59 sqm. Assuming same fill factor, the array would contain 6332 TRM. This is about 1.4 Times.

There is simple 4th root rules of thumb one can follow to calculate range based on the module numbers alone.


aesamodule-vs-range-jpg.666105


The deriviation of above can be read from book "Radar Technique using Array Antenna" by Dietrich Wulfer. and the way it is possible to do with such simplicity can be read in Richard G Curry's "Radar System Performance Modeling".

Now with reference range of 400 Km. Assuming same module architecture and same cooling the 346B with that assumption will have increased range with factor of (1.4^3)^(1/4) = 1.28 Times or 514 km.

Now with change of cooling system, what kind of range we can get ? This requires deeper look in cooling capacity. But for sake of simplicity let's assume the designers were able to provide 3 times more power compared to the earlier design with new liquid cooling system. The equations can then be adjusted by adding the power factor in it. Thus :

((1.4^3)*(3))^(1/4) = 1.693 or 1.7 times or 680 Km.

To make deeper insight however more have to be assumed e.g Target RCS and probability of detection which requires target model (e.g Swerling 1 or 2). Then SNR can be determined and used as a basis to estimate sensitivity (using loop gain method) and accuracy( range, doppler and monopulse) of the radar.
Click to expand...

An article written by one of the designers of the array, now retired and living in Canada, states around 4700 elements for what is to be the Type 346 array on the 052C. So you are close.

Range estimation is more nuanced than that. For example, in the West, radars are often stated by Instrumented Range. This is based on the length of the longest pulse duty cycle that allows for a return to allow for computing unambiguous range. When the Russians mention range, its even more nuanced because there is an RCS context to it. 300km for a 2m2 RCS object is not the same performance as 300km for a 10m2 RCS, its superior.
 
S

Stealthflanker

Senior Member
Registered Member
Tam said:
An article written by one of the designers of the array, now retired and living in Canada, states around 4700 elements for what is to be the Type 346 array on the 052C. So you are close.

Range estimation is more nuanced than that. For example, in the West, radars are often stated by Instrumented Range. This is based on the length of the longest pulse duty cycle that allows for a return to allow for computing unambiguous range. When the Russians mention range, its even more nuanced because there is an RCS context to it. 300km for a 2m2 RCS object is not the same performance as 300km for a 10m2 RCS, its superior.
Click to expand...

Well one can assume RCS too. All you need to do is to plug the assumed RCS. Thus making the whole equations as follows :

Reference ranges.png

This is the "whole" reference range equations for Active Array Radar. the value with "ref" is the reference which obtained from available informations. while the one without "ref" is the assumed value. They work as long as the units are consistent (metric or imperial).

What i described was only the first 2 variables as they are the currently available one. One can of course assumes more. e.g
Target RCS of 2 sqm as usually quoted for surveillance radar. The rest of the variables are kinda hard to find but can be assumed.
ToT or Dwell time of say 0.025 seconds, this value is typical for Fighter aircraft radar, 0.1 to 0.3 seconds might be more typical for surveillance radar.

SNR which determine the detection threshold this requires target model (can be assumed to be Swerling-1) With probability of Detection of say 90% for "tracking range". There usually two values of these one for 90% and another is 50% where 90% indicates "high degree of confidence of your contacts" while 50% is "it can be real or it's an angel echo". For Swerling 1 the required SNR or D (Detectability Factor) can be found with simple equation D=(Ln Pfa)/(Ln Pd) Where Pfa is probability of False Alarm while PD is the required Probability of Detection. the D here assumes single pulse detection. There are procedure to derive required SNR from integration of multiple pulses but

The typical "textbook" value for Pfa is 10^-6 while PD can be either 90% or 50%

Thus there can be two range estimates one is for "track" or your lock-on range for say missile engagement while another is for "volume search". The thing is of course, what value i could use for "deeper" estimates.

I'm kinda curious about the "instrumented range" part. Your description seems to indicate that the instrumented range are defined from the Lowest PRF (that PRF which gives long unambiguous range). Now if the radar is multifunctional which may feature all three kinds of PRF (High, Low and Medium PRF) How one will define the instrumented range ? Especially for High PRF mode where pulse delay ranging is not possible unlike in Medium or low PRF.


From what i understand from K.Barton's "Radar Analysis and Modelling" 2005 Edition. It's pretty much from what i see how "western radar maker" describe instrumented range. The instrumented range is some form of "safety net" where the radar is designed with "excess" range so that the target can be detected when it actually reach the Rm or Maximum required detection range. So when one require maximum range of 400 km, the design will have an instrumented range of 40% beyond that or 560 km.

Below is the excerpt from the book regarding Instrumented range.

Medium duty cycle.png
 
T

Tam

Brigadier
Registered Member
Here's the little data I have.

Please, Log in or Register to view URLs content!
Please, Log in or Register to view URLs content!

Note that this is the genesis to the prototype.

"The solid-state active phased array scheme adopted in 14 is that each antenna unit corresponds to a T/R component, and 4768 antenna units in each array correspond to 4768 T/R components."

You have 4m x 4m size array with 4763 elements.

The guy who did the wiki entry has additional information.

Please, Log in or Register to view URLs content!

"Based on this progress, Star of the Sea APAR went through yet another redesign in March 1996 by increasing transceivers in each face from 4768 to more than five thousands.
Please, Log in or Register to view URLs content!
Please, Log in or Register to view URLs content!
As a result, the maximum range was increased a further seven percent to more than four hundred kilometers."
"
Says the elements increased to over 5000 in the production version and now has over 450 km range.

Now this is for the Type 346 as it is on the Type 052C which is air cooled.

The Type 346A on the 052D is bigger than that.
  • Type 346A: Development of Type 346 with increased number of T/R module and increased range, utilizing liquid cooling system and identifiable by the flat surface of the cover of the radar array. Installed onboard
    Please, Log in or Register to view URLs content!
    and
    Please, Log in or Register to view URLs content!
    aircraft carrier.
    Please, Log in or Register to view URLs content!
...according to wiki page.

Visually, the 346A radars do look bigger than on the 346.

The Type 346B on the 055 is bigger than on the 052D. 40% bigger according to Jane's article which sources from CCTV media report which you also pointed out in the post.

Please, Log in or Register to view URLs content!
 
Status
Not open for further replies.
Top