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  • stealthflanker
    Rank 5 Registered User
    • Sep 2015
    • 1026

    #81
    Accuracy are always relative terms. especially if one deals with classification. But if one wish for somewhat scientifically sound method, something has to be done. Errors are meant to be corrected through discussions.

    The rest of the variables are in the "Pre-calculated variables" tab. There you can find the "working nuts and bolts" of the spreadsheet. It automatically estimates the loss budget, system noise temperatures and model some losses. The section in green can be edited but it can be left as is. I concept the sheet to be usable where the users can easily input variables they can find in the open source literature which usually very limited and let the sheet estimate rest of it.

    For the MDS it always start from estimates of the system temperatures. This part of the sheet will estimate the system temperature.



    The loss budget.


    Most part are editable but can be left as is. The value are taken from typical loss value for radar in books like Radar Technology Encyclopedia and Basic Radar Analysis.

    And this section is the important one as it consolidate and attempt to model pulse integrations. Here you can find how many pulses received and integrated.


    And then estimates of fluctuation loss.



    Other variables like weather attenuation and prediction of radar receiver noise figure can be found in the Atmospheric loss tab :



    This part of worksheet are meant to be automated, it will estimate its own variables based on interpolations and simplified K.Barton model.

    Another "automated part" is in the "Weighting algorithm" tab. Here you can find various tables regarding the antenna and supports for the drop down menus on the main sheet



    In this sheet calculations of antenna dwell time and numbers of beams are carried out.

    Comment

    • stealthflanker
      Rank 5 Registered User
      • Sep 2015
      • 1026

      #82
      Not really an update. The calculator is still on development :3 mainly i am adding more comprehensive Multipath modeling that also take account of radar antenna polarization and existence of vegetations. There is also new tool to predict your TRM's maximum emitted power based on the cooling capacity of your platform. Given the advances of technology it could be said that now only thermal barrier and thus cooling capacity of the AESA radar platform that become the main design constraint.

      At the moment. i am in process of writing sort of "user's readings" Not really a manual but it contains the spreadsheet's descriptions, equations used and why. At the moment here is 2 pages i done mainly deals with where the N^3 factor comes from. Unlike other radar equations. The one i used is a modification of active array equation found in chapter 4 or "Radar techniques using Array Antennas" Instead of usual Power and gain notation. The book use number of modules.

      Hopefully this make bit of sense :

      https://www.scribd.com/document/3942...minary-version

      Comment

      • stealthflanker
        Rank 5 Registered User
        • Sep 2015
        • 1026

        #83
        A small update. Addition of few new features and 2 new sheets.

        1.New sheet.

        A New sheet, "TR Module cooling constraint" added.

        This sheet allows estimate of limit to your AESA radar's emitted power. Based on operating wavelength, Efficiency (PAE), number of operating modules and available cooling capacity.
        Notes are provided to aid estimation. It also include 2 real world fighter radar cooling capacity. The MiG-35 and F/A-18E.

        Track and Search Spreadsheet.

        This sheet calculates the amount of targets the radar capable of tracking at the given detection range. The Equation is based on Mike Golio's book "RF and Microwaves Application and systems". The equation allow calculations of the amount of targets can be tracked by radar on thermal noise condition. Thus if one wish to calculate this part. It is advised to set the Multipath consideration column to "No"
        The user is only required to input the desired capacity at the "Fraction of time to search target". The variable is the representative of Radar time and power resources allocation. value of 50% is typical and can be assumed for modern multifunctional radar. Some other types of radar like BMD Radar may allocate more resources to search (say 50-60% or more). The other variables like tracking rates and accuracy are automatically calculated. The sheet assumes that the required accuracy would be 0.02 of 3dB beamwidth.

        Modern AESA radar however is expected to allow dynamic allocation of time-power resources. The challenge however is to weigh the frequency (as optimum frequency to search can be earth-sky difference to the one optimum to track) and timing allocations.

        The result column now include the numbers of target capable of being tracked.

        -Addition of Sanity checks
        Every calculations needs sanity check to ensure some validity. Including mine. The sheet now include simple sanity check that will check the result of the calculation and present simple comment on whether the calculations are fine or need adjustments. The sanity checks sections currently includes the following :

        1.Whether your radar have enough return pulses to work ?
        2.Is the target horizon limited ?
        3.Can your radar track more than 1 targets ?
        4.Is the target eclipsed or can be detected properly ?

        More to be added in the future. Along with hopefully better multipath model.

        Wish you all have a nice day

        DOWNLOAD SECTION :
        https://www.mediafire.com/file/fdmzs...7wpjUua-yFJzQg




        Comment

        • garryA
          Rank 5 Registered User
          • Dec 2015
          • 1120

          #84
          stealthflanker
          Thank you, i will check it out, your is the most detail calculator we can find on the public sector
          P/s: with all due respect, i think there is something seriously wrong with the multipath model, I tested the calculator with several RCS values and found that
          1) The detection range is far shorter vs a target with RCS = 12 m2 than a target with RCS =10m2

          Click image for larger version  Name:	1.PNG Views:	1 Size:	65.8 KB ID:	3847341
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          ​​​​​​​
          And target with RCS = 0.4 m2 is detected at much shorter distance than target with RCS =0.001 m2
          ​​​​​​​
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          Last edited by garryA; 18th January 2019, 04:44.

          Comment

          • stealthflanker
            Rank 5 Registered User
            • Sep 2015
            • 1026

            #85
            garryA

            The only downside of the path propagation factor model that i used is that it's assume flat smooth earth. Which could be representative for sea than land. However The model works just as fine and yes it will show non-linear result and yes it might be surprising given how non-linear it is. It is because the F4 (path propagation factor) is a function of range-altitude. If we plot path propagation factor for your altitude value, we will have the following graph.




            As you see The path propagation factor is not linear, which reflect the environment where reflection from radar may travel different path and interact in various manner. As indication you may see the "Target Effective RCS" Which the target RCS is corrected with the calculated path propagation factor. That is what your radar actually see instead of academic "free space" RCS which you inputted. Thus an object with RCS of 12 Sqm at some point can look alike it's 0.01 sqm thanks to the local path propagation factor. If you follow my previous post addressing your concern regarding RCS value in VHF. You will find i also address path propagation factor there, which explain why different detection range just based on antenna height.

            As for calculation method, given that the F4 factor is not linear. I am using the suggested method by "Handbook of Simulation in Radio engineering, Communications and Radar" by S.A Leonov and A.I Leonov.
            In the book the way to calculate the radar range in presence of environment factor is to first calculate the "free space range" or "radar range in Vacuum" Then use the range value from there to compute the Path propagation factor and then re-use it for the refined calculation of the radar range.
            Last edited by stealthflanker; 23rd January 2019, 09:43.

            Comment

            • garryA
              Rank 5 Registered User
              • Dec 2015
              • 1120

              #86
              Originally posted by stealthflanker
              It is because the F4 (path propagation factor) is a function of range-altitude.
              As you see The path propagation factor is not linear, which reflect the environment where reflection from radar may travel different path and interact in various manner. As indication you may see the "Target Effective RCS" Which the target RCS is corrected with the calculated path propagation factor. That is what your radar actually see instead of academic "free space" RCS which you inputted. Thus an object with RCS of 12 Sqm at some point can look alike it's 0.01 sqm thanks to the local path propagation factor.
              I think i got your point, so at some point, a target with RCS of 12 m2 can look like it is 0.001m2 thanks to destructive interference from path propagation factor , yet, on the other hand a target with rcs of 1 m2 may not benefit from that, since its reflection is too weak to abuse the scattering/reflecting effect of the surface?

              Comment

              • stealthflanker
                Rank 5 Registered User
                • Sep 2015
                • 1026

                #87
                Yes. You can also plot the target RCS fluctuations the same way and yielded with following plot.

                The "free space" target RCS is 0.1 sqm. As you see it fluctuates from very small value (but not zero) to 1.6 sqm.

                It could explain why it's hard to detect and maintain proper contact with low flying target and the reason why Israel use of Delilah Cruise missiles were of high effectiveness.

                Comment

                • halloweene
                  Rank 5 Registered User
                  • Jan 2012
                  • 4351

                  #88
                  Forgot to tell you all that the model presented here was more or less validated by the "dad" of RBE2AESA. Greetings!

                  Comment

                  • garryA
                    Rank 5 Registered User
                    • Dec 2015
                    • 1120

                    #89
                    Originally posted by stealthflanker
                    Yes. You can also plot the target RCS fluctuations the same way and yielded with following plot. The "free space" target RCS is 0.1 sqm. As you see it fluctuates from very small value (but not zero) to 1.6 sqm. It could explain why it's hard to detect and maintain proper contact with low flying target and the reason why Israel use of Delilah Cruise missiles were of high effectiveness.
                    Alright if that is the case, i think there are 2 issues: 1) The detection range should be displayed with a chart instead of a single number , because if i understand correctly, your model will show the radar detect something, then totally lost it , then detect it again, then lost it again, and so on, we will have something like a "skip area" and "anti low VLO area" 2) If the target's free space RCS affects the path propargation the way i described above, then clearly the amount of "reflection" which comming toward the ground surface matter which mean the shape of the object matter, because 2 objects can have the same RCS, yet have different distribution of radar scattering sector, to put it simple, one object can reflect 60% radar wave toward the sky and 40% toward the surface, while another with the same RCS can reflect 20% radar wave toward the sky and 80% toward the surface.

                    Comment

                    • garryA
                      Rank 5 Registered User
                      • Dec 2015
                      • 1120

                      #90
                      To make it easier to understand, imagine for example, if your radar looking at an aircraft at the same altitude as you, the free space RCS is a fixed number, if you flipped that aircraft upside down, the free space RCS is the same, but the path propagation RCS should change, this can't be intergrated in the current model i think, i guess it might be too complex for us to use excel

                      Comment

                      • stealthflanker
                        Rank 5 Registered User
                        • Sep 2015
                        • 1026

                        #91
                        garryA Thanks for the suggestions. The thing is that it would make the calculator more difficult to use. The basic equations will also change closer to the one in K.Barton's book which may require user to actually input designated range for plotting. For most generic use the single value is adequate.

                        And regarding the path propagation model, it assume point target, so the target is assumed to be pointlike (basically having same RCS in all sides)

                        Comment

                        • RALL
                          Rank 5 Registered User
                          • Aug 2017
                          • 215

                          #92
                          Code:
                          Yes. You can also plot the target RCS fluctuations the same way and yielded with following plot.
                          
                          The "free space" target RCS is 0.1 sqm. As you see it fluctuates from very small value (but not zero) to 1.6 sqm.
                          
                          It could explain why it's hard to detect and maintain proper contact with low flying target and the reason why Israel use of Delilah Cruise missiles were of high effectiveness.
                          
                          
                          
                          1 Photo
                          11 kms heigh of the antenna....you are talking about a Awacs antenna?

                          Comment

                          • stealthflanker
                            Rank 5 Registered User
                            • Sep 2015
                            • 1026

                            #93
                            yes RALL I'm using AEW as example for the graph.

                            Comment

                            • RALL
                              Rank 5 Registered User
                              • Aug 2017
                              • 215

                              #94
                              Originally posted by stealthflanker View Post
                              yes RALL I'm using AEW as example for the graph.
                              Thanks.

                              I am reading last page and i am litle confuse about sometimes is is possible have better rcs in L band than X band....really i thought always will be worst rcs for stelth fighters in L or UHF bands. Of course bombers as B-2 is different.

                              Comment

                              • stealthflanker
                                Rank 5 Registered User
                                • Sep 2015
                                • 1026

                                #95
                                Not really an update. but as part of development i added a "result sheet" where one can review its radar specifications, and it has a graphical comparison with some known radars.

                                The idea is to create a "standarized" sheet one can simply block, copy-paste to paint then put it online or elsewhere to show its Radar.

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                                Since this calculator is basically for fighter aircraft radar. It is of course at the moment the available comparison "database" would be based on fighter radars too. All values of the comparison database has been "mercilessly" normalized to R90 or Detection range where the probability of target detection is 90%. So don't freak out on why Irbis-E only have 223 Km of range vs 3m sqm. I assume the 350-400 Km range is 50% detection probability. Same goes for other radars.

                                In the future i would try working a way that can compare the radar in more "reasonable" value. As its clear that one cannot really compare AEW Radar with Fighter radar nor comparing X-band to VHF band at least directly. The system i am thinking of is to use Frequency as means of comparison. So when you input say X-band the sheet will display X-band Radars and maybe up to C-band. if you input S-Band it will display comparable radar system that works in similar band and so on. If one wish to compare S-band with VHF. Then i need to think a way to make a representative conversion factor for RCS.

                                As the calculator develops i might also try incorporating some signal processing element, and yes better multipath plus clutter. It will however have weaknesses and may rely on deep approximation and simplification of cases. However it should be good to know if say Pulse doppler is better than MTI in certain situation or vice versa. The main output of the process if i could implement it would be Improvement factor in dB which can later be used along with plot of SCR (Signal to Clutter Ratio) to determine if the processing managed to clear the clutter or not. The range however can no longer be directly computed. It has to be plotted and then range is found through skimming the graph when the signal energy exceeds clutter energy.

                                The sheet however will first compute free space range, then using that range as the "edge" of the plot and baseline for signal processing calculation.

                                Comment

                                • RALL
                                  Rank 5 Registered User
                                  • Aug 2017
                                  • 215

                                  #96
                                  Originally posted by stealthflanker View Post
                                  garryA

                                  The only downside of the path propagation factor model that i used is that it's assume flat smooth earth. Which could be representative for sea than land. However The model works just as fine and yes it will show non-linear result and yes it might be surprising given how non-linear it is. It is because the F4 (path propagation factor) is a function of range-altitude. If we plot path propagation factor for your altitude value, we will have the following graph.




                                  As you see The path propagation factor is not linear, which reflect the environment where reflection from radar may travel different path and interact in various manner. As indication you may see the "Target Effective RCS" Which the target RCS is corrected with the calculated path propagation factor. That is what your radar actually see instead of academic "free space" RCS which you inputted. Thus an object with RCS of 12 Sqm at some point can look alike it's 0.01 sqm thanks to the local path propagation factor. If you follow my previous post addressing your concern regarding RCS value in VHF. You will find i also address path propagation factor there, which explain why different detection range just based on antenna height.

                                  As for calculation method, given that the F4 factor is not linear. I am using the suggested method by "Handbook of Simulation in Radio engineering, Communications and Radar" by S.A Leonov and A.I Leonov.
                                  In the book the way to calculate the radar range in presence of environment factor is to first calculate the "free space range" or "radar range in Vacuum" Then use the range value from there to compute the Path propagation factor and then re-use it for the refined calculation of the radar range.
                                  But propagation path is changing in very moment, because geography change. How is possible to take a propagation path factor for all enviroments? each enviroment is diferent, so each enviroment have a unique propagaqtion path factor...is it not?

                                  Comment

                                  • stealthflanker
                                    Rank 5 Registered User
                                    • Sep 2015
                                    • 1026

                                    #97
                                    Originally posted by RALL View Post

                                    But propagation path is changing in very moment, because geography change. How is possible to take a propagation path factor for all enviroments? each enviroment is diferent, so each enviroment have a unique propagaqtion path factor...is it not?
                                    It is. Sea, ground have different electrical properties including the presence of vegetation and this have effects on propagation.

                                    Exact solution however is not available. But approximate and estimates are available, which i am thinking to implement. You can see methods and calculations involved in determining path propagation factor in "Handbook of Computer Simulation, in Radio Engineering, Radar and Communications"

                                    The main weaknesses in the method however is that it assumes uniform distribution of the environment. e.g "jungle all the way" There is no real method yet as far as i know that allows for multiple environment (say 100 km of sea then 10 Km land to radar station).

                                    Comment

                                    • RALL
                                      Rank 5 Registered User
                                      • Aug 2017
                                      • 215

                                      #98
                                      Thanks stealthflanker. I understand it..

                                      Comment

                                      • moon_light
                                        Rank 5 Registered User
                                        • May 2012
                                        • 1033

                                        #99
                                        stealthflanker
                                        are these formula incorrect?

                                        ​​​​ Click image for larger version  Name:	self protection.PNG Views:	0 Size:	79.8 KB ID:	3851943

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                                        Last edited by moon_light; 20th February 2019, 03:11.

                                        Comment

                                        • stealthflanker
                                          Rank 5 Registered User
                                          • Sep 2015
                                          • 1026

                                          Originally posted by moon_light View Post
                                          stealthflanker
                                          are these formula incorrect?

                                          ​​​​ Click image for larger version Name:	self protection.PNG Views:	0 Size:	79.8 KB ID:	3851943

                                          Click image for larger version Name:	standoff jamming.PNG Views:	0 Size:	70.6 KB ID:	3851944


                                          Should be correct. although i wonder why it has different arrangement to the one in the possible source material, David Adamy's EW-101 book. This is the equation look like in the book.

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