Understanding radiation pattern

Generally speaking, side lobes are a bad thing, so the ideal value for them is 0. But there are exceptions to that.

As for the main lobe, the gain (and hence 3 dB beamwidth) depend very much on the application.

What (if any) other sources of information have you looked at for this information?

So, in CST software, when I simulate the antenna, what is the important value need to look up?

I don't know how to use CST Microwave Studio (or any other of their products). But what is the application?

Your question is a bit like "what is the important property of a vehicle?" For use in a battleground, resiliance to gunfire and other explosive devices is probably important. For use on water, the ability to float is probably important. For moving quickly from one side of the Atlantic to the other, the ability to fly will be important.

Are you a student, or a practising engineer with a specific application in mind?

Hi friends
Main lobe is very big, and side lobe small. when u using antenna, u always care about value of main lobe, beacause it help u have lots of length cover distance.
http://www.google.com.vn/imgres?num=...81&tx=48&ty=84
I hope useful for u

But if the main lobe is too narrow (too much gain), then you will not be able to transmit or receive signals over a sufficiently wide range of angles. To "cover lots of distance" as you call it, will require high gain, but that is not always a good thing. Sometimes you need to "cover lots of directions".

it depends on the application , in GSM , the first upper side lobe level should be at least 15 and preferably greater than 18 dB below the peak of beam , i have seen values better than this provided be some vendors .