AESA Radar range calculator.

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8 years 6 months

Posts: 906

Just want to share bit of attempt in calculating "potential" range of L-band wing leading edge radar.

[ATTACH=CONFIG]255928[/ATTACH]

The assumption is Very Long dwell strategy of 0.3 seconds per beam positions making total scan time of 250 seconds. Shorter dwells of 0.1, 0.025 and 0.01 seconds are shorter ranged BUT faster update rates. The range are 54-120 km for the target. Such long dwell time is possible, however i wonder if the update rate would be acceptable.

The most difficult thing to predict is the change of target RCS. In this respect i rely on "Radar Cross Section 2nd Edition" Where it mention that object designed for low RCS in X-band will have 18dB more RCS in L-band (1250 MHz) Thus object having 0.001 sqm (-30 dB) RCS in X-band will have -12 dB or 0.06 sqm RCS in L-band.

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11 years 10 months

Posts: 999

@stealthflanker

Just want to share bit of attempt in calculating "potential" range of L-band wing leading edge radar.

You made a mistake, there are only 24 elements on 2 leading edge, 12 on each. So your T/R number is double.

Member for

11 years 10 months

Posts: 999

The assumption is Very Long dwell strategy of 0.3 seconds per beam positions making total scan time of 250 seconds

How wide is the beamwidth?. That sounds like either the beam very narrow or the search sector is very wide.

Member for

8 years 6 months

Posts: 906

@moon_light

They were operated as one radar. and see this :

[ATTACH=CONFIG]255953[/ATTACH]

Beamwidth for Horizontal is Narrow because of number of elements. Linear array beamwidth is basically 2/N Thus for array of 24 elements it is 2/24=0.08 Radian or 4.7 degrees. Vertical beamwidth would basically be the element's beamwidth which in this calculator assumed to be a patch with 114 degrees of vertical beamwidth. and no lens optimization. Beam positions need to be scanned is thereby low as the radar only scan in azimuth.

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11 years 10 months

Posts: 999

@stealthflanker

Beamwidth for Horizontal is Narrow because of number of elements. Linear array beamwidth is basically 2/N Thus for array of 24 elements it is 2/24=0.08 Radian or 4.7 degrees. Vertical beamwidth would basically be the element's beamwidth which in this calculator assumed to be a patch with 114 degrees of vertical beamwidth. and no lens optimization. Beam positions need to be scanned is thereby low as the radar only scan in azimuth.

Horizontal beam width of 4.7 degrees, if the search sector is 120 degrees then we have 25-26 beam positions. How did you get 250 seconds total scan time if dwell time is 0.3 seconds? I got approximately 7-8 seconds total scan time.
With vertical beamwidth of 114 degrees, wouldn't radar range heavily reduced by clutter?

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8 years 6 months

Posts: 906

@moon_light

You don't divide scan area with beamwidth. To get the scan time or "time frame" The methods is as follows :

[ATTACH=CONFIG]255955[/ATTACH]

Derived from original equations from Stimson's Introduction to Airborne Radar 2nd Edition

[ATTACH=CONFIG]255956[/ATTACH]

Well admittedly clutters is not in the calculator yet. However if i decide to include it you will have to input at least flight altitude and grazing angle to determine clutter patch area. Plus we may have types of clutter, is it surface (Ground patch) or volume clutter (chaff, clouds or flocks of birds) For sea clutter we may have sea states.

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8 years 6 months

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And now a quick fix for the Linear array. Since the Beam only scan in azimuth. The equation for scanning time/time frame must be adjusted that it no longer include the vertical scan for the radar.

Download Link
https://www.mediafire.com/file/7wrkyslc1p4d36r/AESACalcTrial.xlsx

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Furthermore regarding the addition of clutter and possible ECM. I would work on brand new calculator, and includes method to calculate SIR (Signal to Interference Ratio) and others like SCR (Signal to Clutter Ratio). The main problem with this is that there are no real closed form solution for calculating range. E.g the calculation would be done in iterative manner. The equation would include range as variable and the result would be Detectability factor (Dx) Which later be compared with required detectability factor.

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11 years 10 months

Posts: 999

You don't divide scan area with beamwidth

But why not? what is the difference?. I still find it weird that you got 250 seconds.

Member for

8 years 6 months

Posts: 906

Well have you looked at the equation i posted ? It's not simply like that. The beamwidth is squared.

The mistake i did however is that i still included the vertical scan part which i fixed immediately. Now you got only 57 seconds instead of 5 minutes.

Member for

11 years 10 months

Posts: 999

Well have you looked at the equation i posted ? It's not simply like that. The beamwidth is squared.

I did, but to be honest, I don't reall understand why it can't be calculated my way. Can you explain in layman terms?

Member for

8 years 6 months

Posts: 906

Well the beamwidth is squared to take account of its cross sectional area. The number of beam positions equation basically states the area of the search sector divided by the cross sectional area of the beamwidth.

So you can't just divide the horizontal sector with beamwidth and later multiply it with dwell time to get scanning time.

Member for

11 years 10 months

Posts: 999

The number of beam positions equation basically states the area of the search sector divided by the cross sectional area of the beamwidth.

To summary, the number of beam positions equivalent to the area of search sector (in degrees) /area of beamwidth (in degrees). Correct?. It's like filling a rectangle with small squares.
So if the radar can't scan vertically, wouldn't it make sense to only consider the horizontal length?. Vertical length is irrelevant because radar can't scan up and down.

Member for

8 years 6 months

Posts: 906

The vertical length of the search sector might be irrelevant. But, radar beamwidth still have 2 dimensional nature, thus you can't simply discard it as the target may arrive at the vertical part of the beamwidth. Therefore the squared value

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20 years 3 months

Posts: 114

Very insightful, thanks.

I have some general questions:

- How applicable is the use of the spreadsheet for PESA? Can we take the peakpower, divide it by amount of phaseshifters and put it in a T/R modules? Would the result be representative or are there some effects for AESA that are considered and hence this would deliver false results?

- How would the parameters of a hypothetical AESA 92N6 S-400 engagement radar look like? Since just a single array is used, we can exclude a continuous wave operation (although many sources for some reason state that the SA-6 with its single engagement antenna is a CW system)? So how would the parameters (PRF, pulsewidth) for a pulsed illumination look like approximately?

- A general question on AESAs for illumination role I always had is, whether a part of the array could use transmit-only elements with higher peak power per element, and the other part normal T/R modules. I see much higher power levels for transmit-only modules which may could compensate the lower number of receive-capable modules. Even if there would be no benefit for the range performance due to the lower receive modules; in SARH (bi-static) operation, the missile seeker would receive higher RF energy.

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10 years 5 months

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https://forum.keypublishing.com/attachment.php?attachmentid=255953&d=1438210247
Linear array beamwidth is basically 2/N Thus for array of 24 elements it is 2/24=0.08 Radian or 4.7 degrees

Does that formula take into account elements spacing?. Elements seem very close together, your example wavelength is 24 cm, 24/2= 12, i doubt that woman wrist can be 12 cm wide. Even 6 cm wide wrist seem very rare

Member for

15 years 3 months

Posts: 6,441

Guys.. i hope you don'T mean to debate the L-band IFF transmitter as a magical Russian AESA.

And likewise ppl whom state that the L-band is ineffective as a radar to detecting Stealth or whatever. Both are dead wrong!

The Key point is wave lenght. As it is an IFF system, it is not required to constantly hit a Radar Contact with Radio waves. One small return is enough for the N035 complex to catorize the target as Friendly, unknown or Bandit. The onboard computer will memorize the rest of any contacts.

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15 years 2 months

Posts: 5,197

One small return is enough for the N035 complex

IIRC, That is not how IFF works.

It's basically an AESA radio. It's sends out a coded pulse. If the targeted aircraft recognizes the pulse it then sends a coded pulse in reply. It's not a radar that is listening for a reflected return of it's own pulse.

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15 years 3 months

Posts: 6,441

My knowhow on Radars are not that Great. But that i knew, spud. Its traditionally called a radar transponder, it contains cryptic ID on your own jet and other jets Allies or own airforce. Remember what happend when the Mig-25 pilot defected. Every military Radar transponder had to be re coded in USSR.

Anyway my point was you do not have to constantly T/r on the IFF to keep contacts Identified. Idealy Its a one deal ordeal.

If not you loose a contact over some given time and then re-acq it.. there are limitations.
Today the Radar transponder is part(integrated and software driven) of the radar complex itself.

Just don't think of it as a AESA Radar in the traditional way.

My 2cent is that the Su-35S transpond IFF in X- band from main Array as well(only logical). For N035 it is advs that it is less prone to Jamming. Guess T/r IFF in L-band has its merrits.

Member for

8 years 6 months

Posts: 906


Very insightful, thanks.

I have some general questions:

- How applicable is the use of the spreadsheet for PESA? Can we take the peakpower, divide it by amount of phaseshifters and put it in a T/R modules? Would the result be representative or are there some effects for AESA that are considered and hence this would deliver false results?

- How would the parameters of a hypothetical AESA 92N6 S-400 engagement radar look like? Since just a single array is used, we can exclude a continuous wave operation (although many sources for some reason state that the SA-6 with its single engagement antenna is a CW system)? So how would the parameters (PRF, pulsewidth) for a pulsed illumination look like approximately?

- A general question on AESAs for illumination role I always had is, whether a part of the array could use transmit-only elements with higher peak power per element, and the other part normal T/R modules. I see much higher power levels for transmit-only modules which may could compensate the lower number of receive-capable modules. Even if there would be no benefit for the range performance due to the lower receive modules; in SARH (bi-static) operation, the missile seeker would receive higher RF energy.

1. I will not recommend it for PESA. As it need to be treated differently. Especially for the space feed array. Russian research on Space feed array appears to be ahead of US. To the point where they can realize advanced feed with low sidelobe. As described below :

https://www.scribd.com/document/275319467/Recent-Developments-in-Russian-Radar-Systems

Some technical informations regarding the design of array in S-300 and S-300V

https://www.scribd.com/document/289047418/Survey-of-Russian-Low-Cost-Phased-Array

2.Hypothetical AESA for 92N6 would be massive. 2.5 sqm array of 92N6 will contain about 12000 TRM assuming it wish to retain same beamwidth as original 30N6/92N6. The maximum attainable peak transmit power with current state of the art technology (1.5 Watt/mm for GaAs) would be 22 Watt multiply it with 12000 it would be 264 Kilowatt for peak transmit power using GaAs. GaN would be even more powerful with 7 Watt/mm power density. X-band module with half wavelength width would attain 105 watt. and the transmit power would be 1.26 MW for 12000 elements. Range figure with GaN would roughly be about 68% higher than GaAs.

The 5N63 family and her siblings, 30N6 and 92N6 is a pulse doppler design with 100 KHz of PRF. The pulsewidth would be around 1-2 microseconds. There is no info though on how much pulse compression factor involved. Unfortunately so if you desire to calculate, you will have to consult on the table of waveform i provided. In previous page. There also be another factor which i haven't implemented in the sheet which is F4 or Pattern propagation Factor. This would affect ground based radar more than the one airborne. The design duty cycle however could be assumed to be 25% maximum for avoiding/reducing eclipsing issues.

Regarding Illumination role. Some AESA's do behave similar way as you describe, which is SMART-L where some elements with wide beamwidth will "flood" the area with radar energy while the receive party scans the skies for target return. However it's the transmit module that are less in number than receive as transmit does not need such large beamwidth. Receive module would be more in numbers due to need for narrow beamwidth resolution.


Does that formula take into account elements spacing?. Elements seem very close together, your example wavelength is 24 cm, 24/2= 12, i doubt that woman wrist can be 12 cm wide. Even 6 cm wide wrist seem very rare

Yes, my formulas automatically assume that it's a half wavelength spacing. If there is any less like in the image, the only explanation would be that the array isn't exactly 1250 Mhz but rather lower wavelength. It could operate in 1250 Mhz but with limited scanning angle. Otherwise it might not be in L-band at all but something higher maybe S or C band.


Guys.. i hope you don'T mean to debate the L-band IFF transmitter as a magical Russian AESA.

Well given the controversial nature of the device, one or two debates would occur sooner or later. and naturally i am also interested to see its potential as real Primary radar. The reason is similar as given by Carlo Kopp. Why putting the antenna there ?.

Traditionally IFF is always in L-band. Implementation however usually embedded together with main nose array Thus the radar can interrogate while also doing scanning. If it placed anywhere else, naturally one would question why. I would love to see other people brewing their own calculations too.

I really not bought into theory "the beamwidth is too wide" etc as the radar have narrow beamwidth just for 1 side (horizontal) and that's about enough for scanning. The elevation beamwidth is indeed very broad But, treatment with dielectric lens can mitigate it into somewhat acceptable (still wide tho 20-80 degrees) Heightfinding cannot be done in the way usual radar does BUT can use the same way as how E-2 determine altitude via multipath heightfinding.

E-2 Hawkeye's radar antenna is also a linear array consist of several YAGI elements. The differences is that it scans mechanically while this NIIP array scans electronically. The APY-9 for new E-2D would scan electronically and conceptually similar as one in NIIP.

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19 years 9 months

Posts: 12,109

2.Hypothetical AESA for 92N6 would be massive. 2.5 sqm array of 92N6 will contain about 12000 TRM assuming it wish to retain same beamwidth as original 30N6/92N6.

Do you mean 2.5 sqm or 2.5 m side?