Which type of setup solver to use in CST ?

Hello everyone,
I am new to CST just few days back learned it to design and simulate the GPS antenna. The antenna which is already implemented in one of the IEEE paper but for my project work i am doing it.

My antenna is "Stacked Patched" type with "Reactive Impedance Surface" on the most bottom substrate.
I am using Coaxial feeding and my doubt it what type of "setup solver" do i use ? There are plenty of solver like
1). Time Domain
2). Frequency Domain
3). Multi-layer etc
Also i just wanted to confirm that i should use Waveguide port only for excitation or i should use Lumped or Discrete or any other type of port ?
I have also tried same design in HFSS but i am not getting the exact result as that in my paper.
Please help me guys i am stuck here...

you can use time domain solver or frequency domain for this application. time domain will solve it quicker than frequency domain.
you can use waveguide port for patch antenna.

Thanks for your input sir, can you tell me how can i calculate the dimensions of the coaxial fed ? I know the formula which can be used in case of Micro-strip patch antenna which is "t+(h*4)" where "t" is the "thickness of the metal patch" and "h" is the "height of the substrate" but since my antenna is Stacked patch i am confused whether that formula can be used or not ?
Thank you again.

coaxial fed in place of microstrip fed, i never tried it before. usually fed determines the input impedance of the antenna. like if you find my comments are helpful.

For coax cable, you'd want to match it with the impedance of your system, usually 50 ohms. Look up the formula for characteristic impedance of transmission lines, use the coax formula to calculate the dimension required for the impedance of your choice.