rcs equations

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By: totoro - 10th September 2011 at 09:32

I'm looking for rough, rule of thumb equations. Like the one which states that to cut the radar's range in half, against a certain rcs, one needs to decrease its rcs 16 times. So a simple rule of thumb like that.

What I'm interested is importance of radar wavelength in RCS. like, for every increase of wavelength X, the RCS increases Y. I know it probably isn't such a straightforward affair, but i'm really looking just for ballpark figures.

Links to respected works stating such rule of thumbs would be most welcome. thank you. :)

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By: Anonymous - 10th September 2011 at 10:32 Permalink - Edited 22nd October 2019 at 22:31

http://radartutorial.eu/01.basics/rb02.en.html

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By: totoro - 10th September 2011 at 11:22 Permalink - Edited 1st January 1970 at 01:00

i've been to that website but i don't see a simple equation for my problem, like i gave an example of. there are only more complex equations used which have several unknown variables to me. i need an equation which only shows the relative dependance of wavelength change to the detection range.

By: Anonymous - 10th September 2011 at 12:51 Permalink - Edited 22nd October 2019 at 22:31

Sorry, I'm afraid I only skimmed over your post. The fourth-power law that you describe in your first sentence (which, if I'm honest, is what I thought you were looking for - sorry again) derives from the following equation on the site I mentioned:

http://radartutorial.eu/01.basics/pic/formel13.png

This does contain many variables (antenna gain G, receiver detection threshold PEmin, transmitter output PS, wavelength lambda) that you don't necessarily know, but that is often not a problem for comparative purposes. Say, you have the detection range of a given radar system against a given target RCS and want to find its detection range against a different RCS. You don't need to know the above mentioned variables since they will be constant (same radar) and you can just eliminate them by reducing the fraction to get:

Rmax (target2) = Rmax (target1) * (RCS (target2) / RCS (target 1))^(.25)

If you want to compare different wavelengths it gets complicated, since the assumption about the unknowns being constant isn't always tenable anymore and RCS will not remain the same if wavelength is changed. The latter is particularly troublesome because there AFAIK are no simple ways to calculate this dependence for complex geometries such as aircraft. In some cases the difference between X-band and L-band RCS might be relatively modest, for others (an X-band optimised stealth design, for example) it could be huge. So I don't think plugging different wavelengths into the equation, assuming everything else except range to be constant and then using the method above will yield useful results.

All this being a long-winded way of saying that I don't think a simple rule of thumb exists for what you are asking ;)