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AESA Radar range calculator.

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    #21
    It is update time and various other stuff.

    What's new :
    -Antenna type added
    https://sta.sh/024qp486qzs7

    Allow range calculation for typical aircraft nose radar and linear array that might be embedded in your wing leading edge or vertical stabilizer.

    -Scan time now determined by dwell time.
    An advantages of AESA or general ESA radar is that the beam is controlled by computer and practically have no inertia, thus can be precisely controlled to achieve required dwell time/time on target.

    Dwell time is basically the time where radar beam will "stay" in a sector. It's a fraction of the total scan time (or time frame) or in fighter aircraft we know it as "scan cycle"

    This is typical fighter aircraft radar scan scheduling. As you see typical scan for fighter aircraft radar is about 1-5 seconds. Too long may cause problem in terms of update rate and tracking verification. In conventional mechanically scanned radar, this determined by the mechanical ability of the radar (actuator, hydraulics etc), which not much can be done with it.

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    In previous version user can input their scan time, which later the sheet will "allocate" it according to the scan area inputted by user. In this new version the scan time is now dependent on dwell time, which now made select-able in drop down menu by user.

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    The value in the drop down menu is based on Typical dwell time for Long range early warning radar, target acquisition and typical fighter radar found in table 1.8. ch1 from Lynch's "Introduction to RF Stealth"

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    Another additional function is atmospheric effects in shape of attenuation by atmosphere, and rain.

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    I would like to add snow, but there seems to be problem in interpolating available data, or more like it's kinda hard to do so due to nature of atmospheric absorption. However for typical radar frequency it appears to be quite satisfactory. The model used is based on simplified K.Barton's atmospheric attenuation model. There is more complete model by L.V Blake, but i decided not to use it for now to keep things simple.


    Another improvements and additions are the antenna weighting algorithm. adding new algorithms which you can try and have fun with. If anyone asks why Taylor is the default it's because Taylor weighting is the easiest to implement and quite robust.

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    Below the weightings there are new tables detailing antenna parameters for Linear and planar array. They're there to help calculating range in the next worksheet. The assumption for the linear array however is as follows :
    1.Microstrip patch, with aggressive tapering in elevation beamwidth, original beamwidth was 114 degrees. However with proper lens treatment it can be reduced to the value you see in the table.
    2.The spacing would still be half wavelength thus entire array length would be N*d where d is spacing in half wavelength. and beamwidth is Ka*(2/N) where N is number of elements and Ka is the weighting factor.

    The planar array is your typical nose radar.

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    Below the antenna table lies the dwell time selection table. This table lies the dwell time and will calculate the required scanning time based on the number of beam positions need to be scanned. In case you see changing the value of the scanning area increase the radar range, it's because the sheet will adjust the value of the scanning time to the new sector. You can edit the dwell time value to your fitting. The scan time however is off limit.

    Major change in Pre-calculated worksheet. Now most of it are automated Thus can't be edited. You can still however edit the value on green columns

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    System temperature now fully automated.
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    Loss budget, some of it are still editable, and the radar range gate and receiver columns too.

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    The fluctuation loss modeling. Now it's fully modeled. The target is assumed to be Swerling case-2 target. Suitable model for tracking radar and what radar designer want target behave to. Swerling case 1 could also be applied. However this model is more suitable for search radar, esp rotating search radar.

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    The new worksheet. The atmospheric effect, the most likely source of problem. This worksheet contain the "atmospheric model" and radar receiver noise figure "model" Based on excel trendline interpolation. The data is fortunately fits well so, the calculator is "work" However in the future i will implement better module.

    https://sta.sh/025kc3vsbsp8

    https://sta.sh/0sz0c9zanfw

    As always feedback are appreciated.







    Download Link for updated version :
    https://www.mediafire.com/file/7wrky...CalcTrial.xlsx

    Comment


      #22
      Just want to share bit of attempt in calculating "potential" range of L-band wing leading edge radar.

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      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.

      Comment


        #23
        @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.

        Comment


          #24
          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.

          Comment


            #25
            @moon_light

            They were operated as one radar. and see this :

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            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.

            Comment


              #26
              @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?
              Last edited by moon_light; 25th September 2017, 10:33.

              Comment


                #27
                @moon_light

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

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

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                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.

                Comment


                  #28
                  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/7wrky...CalcTrial.xlsx

                  -------------
                  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.

                  Comment


                    #29
                    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.

                    Comment


                      #30
                      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.

                      Comment


                        #31
                        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?

                        Comment


                          #32
                          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.

                          Comment


                            #33
                            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.
                            Last edited by moon_light; 25th September 2017, 17:34.

                            Comment


                              #34
                              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

                              Comment


                                #35
                                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.

                                Comment


                                  #36
                                  Originally posted by stealthflanker

                                  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
                                  Last edited by mig-31bm; 27th September 2017, 14:33.

                                  Comment


                                    #37
                                    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.
                                    Thanks

                                    Comment


                                      #38
                                      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.
                                      "The early bird gets the worm but the second mouse gets the cheese."

                                      Comment


                                        #39
                                        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.
                                        Last edited by haavarla; 27th September 2017, 17:08.
                                        Thanks

                                        Comment


                                          #40
                                          Originally posted by PeeD
                                          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/2753...-Radar-Systems

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

                                          https://www.scribd.com/document/2890...t-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.

                                          Originally posted by Mig31BM
                                          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.

                                          Originally posted by Haavarlaa
                                          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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