Define boundary condition in CST for circular patch antenna

circular patch antenna

Hi,

May I know how can I define the correct boundary condition for a circular patch antenna which has a circular ground plane? Here are my settings:
ymin, ymax= open
xmin, xmax = open
zmin = Et=0, zmax = open (added)

After setting up the boundary conditions, a boundary box can be seen. When I try to run the simulation, I get this error:

Inhomogeneous material at open boundary detected (The structure must be identical in the open boundary plane and the next two mesh steps)
Location(s): xmin xmax ymin ymax

I believe this error is due to the air meterial located at four edges of the box (since the ground plane is circular shape). therefore, may I know how to fix this? Please help. Thanks.

inhomogeneous material at open boundary detected

Can you send some picture from CST ?

adaptive mesh refinement cst

Hi zhiweisim

use open (add space) boundary condition for all directions and hopefully your problem will be resolved


regards
shahid

cst background material

hi shahid/mauloftin,

Attached is the boundary condition box of my circular patch antenna. I tried both methods, using

1) open for xmin, xmax, ymin, ymax

(by setting surrounding space for the background material)
lower x distance, upper x distance = 1cm
lower y distance, upper y distance = 1cm

2) open (add space) for xmin, xmax, ymin, ymax

and I get two different minimum S11 values (resonant frequencies), one being 867MHz and another one being 868MHz.

May I know which method is correct in setting up the boundary conditions?

Thanks.

cst open boundary

As you can see from the attached S11_all three cases.jpg result below, I got three different S11 values at one particular frequency when using three different boundary condition settings:

1) open
(1cm surrounding space for background material for xmin, xmax,ymin, ymax)
zmin = et=0, zmax =open added

2) open
(0.5cm surrounding space for background material for xmin,xmax,ymin,ymax) zmin = et =0, zmax = open added

3) open (added) (for xmin,xmax,ymin,ymax)

4) Also I did play around with the boundary condition settings where I set all directions as open added (xmin, xmax,ymin,ymax,zmin, zmax) and I did get a much smaller S11 values with different resonant frequency at 866MHz. Please see 'S11_all direction open added.jpg'.

Therefore, may I know which one is the correct approach? Which one is more accurate in getting the S11 values as well as the radiation pattern? I am getting a bit confused.

Please help. Thanks.

cst 1% circular latest

So,
first: use xmin, xmax, ymin, ymax open (add space), not only open, I think that is better.

second: 867 MHz is for set 1) and 868 for set 2) ? It is OK, CST is not absolutely precise , 1 MHz is not accuracy. Now you must use "Adaptive mesh refinement", is it in "Transient solver parameters". Try it and wait, you can see, that the resonant frequency will be jumping (you can see in Navigation tree - 1D results - Adaptive Meshing - S [dB])

I hope, that I helped you

Added after 6 minutes:

btw CST help:

Open: Operates like free space. It is available for the electrostatic magnetostatic and thermal solver.


Open (add space lf): Similar to the open boundary condition, with some extra space added between structure and applied boundary condition.

Added after 4 minutes:

and 2. btw:
try in help search: Circular Patch Antenna, it is
third result, there is inspiration for you

cst background material edaboard

Hi again,

I have something for you. It is about CST and boundary - is it in attachment, page 7.

cst boundary condition

Hi zhiweisim
In the Help of the CST, analysis of circualr patch had been discussed.
good luck

define cst @ 4% extra ?

hi

the example of circular patch antenna in CSt help is different in the sense that it has rectangular ground plane. while the person who posted this question has circular ground plane . so he cant use open boundary condition without introducing some additional space or using open (add) boundary conditions.

in my view rather than manually adding surruonding background space its best to use the opne(Add) boundary conditons for good results

i hope this helps

regards

setup antenna circula

Hi zhiweisim

use open (add space) boundary condition for all directions and hopefully your problem will be resolved


regards
shahid


I agree that. You must set open (add space) boundary condition for all directions when your work is antenna.

(^_^)"