hfss sweep type

I am working on microstrip antenna design in HFSS 9.0. I learned more about it by the help of traning (A friend gives me) but I don't understand some functions' physical meaning in this program. In sweep type, three options possible: Fast, discrete and interpollating.
If anyone explains their difference and how to use them efficiently for the type of design, I am grateful to him.
Thanks

Fast sweep solves over a frequency range. Usually, when the bandwidth is narrow, fast sweep is used. When the bandwidth is broad, fast sweep can also be used but it will consume a lot of computational time. In this case, it is better to use the interpolating type. It is, however, less accurate but OK. Especially, when you want to play with time domain, you need a very broad bandwidth to cover all the information you need. The discrete one is when you are interested in particular frequencies.

As a guideline if the rang of frequencies is 1 to 5 (for example between 1 and 5 Ghz - or between 4 to 20 Ghz) using Fast Sweep will be faster.
Interpolating sweep will be faster for broad band (although in some cases three fast sweeps covering a different freq range could be faster than interpolating).

However - and this is important to understand - all methods will give you exactly the same result. The interpolating sweep has also a convergence factor that you specify. After the simulation ends, I recommend to check the profile of the simulation and see if the message "interpolating sweep converged" appears. If it does not you will need to increase the number of interpolating points and continue the simulation.

my supplementary comments: using fast solution type to simulate wide frequency range, most of the time the simulated result is not accurate enough, especially high Q structure, you can find the positive S value, passive device works as amplifier. lolz
Best Regards.