CST manual shows a very simple method for the waveguide port setup in Microwave studios. Generally the width of the port is 5*times width of the Microstrip line, while the length doesn't effect the overall settings (as per my experience).

In HFSS wave port height is between 6h to 10h whilst, the width is 10w (w>=h) or 5w (w

thank you dears. your answers are usefull. i try them

It is better to use HFSS from the point of waveport dimension. For example, to apply waveport at the end of SMA connector, the dimension is same as found for SMA connector in HFSS whereas, in CST, we have to take10-15% larger dimensions. Why? I do not know. Therefore, use HFSS. Now, come to the point of the dimension of waveport. Draw your structure using SMA connector as will be fabricated in practice. Define waveport at the end of SMA connector using same dimension (SMA connector). There will be no confusion and you will get error free results at your first attempt.

@Sudipta

dear sudipta, thank you to your answer, you know i have to simulate the antenna in cst, because i place an extra layer above the antenna and hfss results about gain is poor. and my structure is large, so cst simulator is better.

this is another problem for me

visit this link. This have tutorial of CST port creation ...

https://www.youtube.com/watch?v=k54XWrcI5Bc

@Dr.Pravin 

Thank you dear Professor. i try it. 

One software give high gain and another software is giving low gain means some problem is there either in your design or in the software. The problem is due to waveport dimension. Do not use waveport without SMA connector. Basically software is blind to solve a particular problem without proper guidance.One of our junior faced the same problem. Thats why, it is better to use HFSS. There, we do not have to give larger dimension of waveport than SMA connector

we have to use it to obtain results. What is size of your structure?

this link will be useful

http://www.emtalk.com/waveport_calc.htm

thanks

@Chaouki Hannachi

thank you dear. do you use this calculator? do you achieve a right answer? what are the base formulas of this calculator? 

thanks

Whenever I place a wave(guide) port onto a transmission line its nice (and easy) to check if the corrected mode shows up properly, and if its impedance was correctly computed - they can be analytically found and compared with the EM solver. By doing so one can be sure whether the port size/placement was alright. In CST there's an option where only the port simulation is performed (its very fast). The idea is to first check if the port is alright, if so the 3D long simulation can be started.

Some structures such as CPW are not so trivial to get it right, so this first quick port check is convenient.

@Marcelo B.Perotoni

thank you dear. i try it too. it is useful. 

Hi, Azita ... did you try to compare results witih waveport and lumped port? Usually i should do so if there are some doubts with sizes.

hi azita,

I would like to clarify that this calculator is used only for a 50 Ohm microstrip transmission line. you find further informations attached.

thanks

waveport size:

width=5 *microstrip feed width

Height=5* substrate height 

Hello Azita Gudarzi,

Port Width and Height Conditions:

5 times the width of microstrip line = width of port.

5 times the height of substrate  = port height.

These are the minimum required conditions for port width and height.

Radiation Boundary Size Conditions:

1. HFSS needs airbox to model free space radiation. A radiation boundary is used to emulate free space by truncating infinite free space to finite calculation domain. This minimize reflections from outer surfaces and ensures maximum absorption. This is very similar to an anechoic chamber.

2. For this, the distance from the radiator must be a minimum of λ/4 (or λ/2) for strong radiating surfaces. Here λ represents the wavelength for the minimum frequency used.

3. A distance of λ/4 from the radiating surface is taken for the reason that similar impedance mismatches can be cancelled at quarter wavelengths. This ensures that there are no reflected waves and thus the radiation boundary absorbs all the radiation.

4. Maximum absorption of energy occurs when the fields are perpendicular to the boundary.

These are for HFSS.

Regards,

Suhas. D.

Happy New Year Wishes in Advance!

@Suhas Dinesh

thank you dear 

it is useful for me. i simulate my antenna but the size of air box have an strong impact on radiation patterns and the gain. i change it from lambda/4 to lambda/2, but i cant get a fix answer, so i cant understand which result is correct. it makes me confuse. 

can i send you my antenna simulation?

happy new year too. thank you

Hi, Azita,

I think maybe you can use the hybrid boundary integral solver or the PML instead of the radiation boundary condition on the air box. 

Happy new year!

@Cheng-Yi Tian

thank you dear. but i think for antenna simulation, the radiation boundary is usual. and because of that i want to use such boundary. and so my radiation pattern is very variable by changing the air box size.

Happy new year too.

@Azita Gudarzi

The reasons that one usually uses the RBC are that it is quiet simple and computational efficiency. But it doesn't mean you cannot use the PML or even BIM. Compared to the RBC boundary, the PML or BIM is much more accurate and stable. Also, they usually need more computational resources.

If you want to get a reliable result, I think PML would be suitable for your case.

Happy new year (twice).

We are using HFSS17 where the radiation box automatically created after giving solution frequency. But waveport cant be defined within the radiation box itself. Any one have any idea?

No need to think about the size of waveport in HFSS. In the first run, one may get 100% correct results in he/she follows the following steps for wave port.

1. Draw coaxial probe as per practical dimensions (rad of inner conductor = 0.63mm and rad of outer conductor = 2.2mm and er = 2.2)

2. Draw a circle at the end of outer conductor (i.e. rad = 2.2mm)

3. Assign wave port on the circle.

Use this trick for any practical application in HFSS.

Wave port can be easily defined in CST but not in HFSS. HFSS will not accept wave port inside radiation box and so radiation box touched with the sides of the substrate. This box can be extended either at top or bottom of the patch. Whenever the antenna is fully covered by rad box, hfss will not accept wave port definition at the antenna feed. Also the size of rad box can be modified in HFSS but not in CST. So, in HFSS , chances of error may be higher. Any one put some suggestions on this.

Dear Anirban da, In every software, we have to draw structure as per their requirements and limitations. The position of waveport inside or outside the rad_box is not a matter if we know, in first run, we will get 100% correct results. As the question was on the size of wave port, I prefer to follow those steps. I got correct results in first run. If we follow the drawing procedure as per HFSS manual, there will be no error. From drawing point of view, CST is more user friendly and 4-5 times simpler compared to HFSS. But, I still prefer to use HFSS as it gives 25-300 times faster results than CST.

In build rf jack is available in HFSS. Can we use that for different substrate thickness. Even if we build our own sma, touching the pin and ground to antenna will be another challenging thing on which matching may vary.

Use the macro option as the figure

Anirban Karmakar Hello,

I got the solution to you problem. you need to create a 0.001mm thick rectangle at the back of your waveport (i use 0.0001mm thick) and it should be PEC. in that way you will have your port inside your radiation box ;)

Cheers