you can begin from the attached paper.

best regards

What is the application? Normally mm-wave antennas are used for point to point communication. The main reason is based on the free space path losses which states that the higher the frequency the smaller the antenna becomes thus the higher the losses. Furthermore, the losses in the substrate are very high (1.5 to 2 dB/cm). Most of the designs aim at high gain antennas like reflector, lens, rod etc. If you model your design take into account that you need the electrical parameters (Er and loss tangent) at mm-waves. Most of the materials are only characterized till 10 GHz. If you want to measure your design look at this link. https://www.youtube.com/watch?v=25ky8smtuGc

Good luck.

About HFSS, you follow the design guide.

For your applications from 30GHz to 300GHz, horn antennas, log periodic antennas, parabolic reflector antennas (directional and long distance), patch arrays (omni directional and long distance) and patch antennas (omni directional and short ranges) were used,  

First of all you should decide which application looking for,later think about antenna

Hello, As you mentioned about your proposed antenna, which should be worked within 30 GHz to 300 GHz, then you will have chose proper substrate material, second patch material which should not be perfect E, as assigned in normal patch antenna. After that for this frequency range, losses will be increased. so you can't handle a single structure, means single patch, you will have to designed your antenna either at MIMO technique or Array based microstrip antenna. Important thing which really should consider is epsilon and permeability. So, after doing all design, you will have to calculate epsilon and permeability versus frequency plot which decides your loss.

Thanks

Hi, I would advise you to focus more on the measurement of your real world antenna than the simulation. Simulations (CST/HFSS) do not present any problem, as long as the materials and geometries are correctly characterized.

On the other hand, real world measurement is somewhat tricky. See what kind of VNA you've got, if a CPW launcher is needed (to match to a cascaded probe), the necessary pitch to acomodarte the coaxial connector, etc. 

Dont forget that if your antenna does not have a sort of shielding (ground plane) once its laying on the measurement site it will see a large metallic area (e.g. the cascade base), which was not taken into account into the simulation. Therefore ground planes come in handy here.

I fully agree with all answers. As an additional point, you need to take in HFSS the optimal solver type and adequate meshing.