# CST MWS simulation of microstrip patc antenna

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#### leony

##### Member level 1
I am a new user of CST MWS 5. I have to learn how to simulate a rectangular patc antenna with microstrip line feed.Tutorial of the program is about how to design and simulate of circular with coaxial feed.And there is no help about line feeds.If you have any tutorial or link about my design, i will be very grateful.

#### plasma

Hi leony

in the directory examples there is simulation of microstrip patch antenna

PL

#### leony

##### Member level 1
Re: CST MWS simulation of microstrip patch antenna

Thanks, but that example is about coaxial feed technique with a circular patch.I want to learn to design a rectangular patch with a microstrip line feed.Can i also find this in the examples directory?

#### leony

##### Member level 1
I learned the answer of the question above.But now i am in trouble with the optimizer tool.I could not understand the way how it optimizes.I define the parameter and give a name and the value but i dont understand how this name make a connection with the shape i drew.Please CST masters.Help me.

#### eirp

leony said:
I learned the answer of the question above.But now i am in trouble with the optimizer tool.I could not understand the way how it optimizes.I define the parameter and give a name and the value but i dont understand how this name make a connection with the shape i drew.Please CST masters.Help me.

Hi

Why you don't take a closer look to manual which you have in install folder/Documentation ?

You have to first define the parameters such as Length, Width etc with some values - you know this already.
Then, when you are building a shape, use this parameters instead of numbers.
Let's say when you're drawing rectangular patch, use manual insertion of values (ESC after choosing brick) and type e.g.:
xmin:-Width/2, xmax:+Width/2
ymin:-Length/2, ymax:+Length/2
...
This is the connection with the shape

parametrisation of whole structure is highly recommended for easy manipulation of its dimension, not only for optimization!

Cheers,

e.

#### leony

##### Member level 1
Hello.I calculated the dimensions of microstrip patch antenna also feed point using formulas.The only objection for me was the inner and outer radius of the feed point( I use coaxial feed).I could not find how to estimate them.
And i built the antenna with the parameters i founded.I give some radius values and calculated the antenna at 2.4 Ghz.But not surprisingly s-parameters I obtained was not good.I could not find the way how to correct it.Also i could not obtain 50 Ohm line impedance.Any suggestions? If anyone wants i can mail all the project.It is important for me.Thanks for your help.

##### Full Member level 4
Hello leony,

It seems that you might have two problems, I'll try to help:

1. Design of 50ohm coax dimensions by the following formula :

Zo=(60/ √ε)×ln(D/(d*ks)),

D=Outer insulator diameter
d=inner conductor diameter
ks=hardness factor of coax (obtained from the manufacturer data sheet)

2. Check the port impedance CST calculates :

You can do this by going to 2D results->Ports->Port "x"->e"x"
Or , 1D results->SmithChart-> look at the upper right corner, you should be able to see the normalizing impedance of the chart, which is Zo.

3. If 1 is Ok but u still can't achieve 50 ohms, the problem can be the result of poor meshing.
Double click on the insulator -> right click->mesh properties-> divide it to at least 1/10 of its diameter at the length and width dimensions, the height should be at least three mesh steps (just from my experience).

Good luck,
P.

#### costox

##### Full Member level 4
Hi,

In CST MWS:
What does this message mean:
"sheet body will be ignored".

Does that mean I cannot use zero-thickness structure (infinitely thin microstrip) as PEC.

Thanks alot.

#### hajar2008

##### Newbie level 5
hi Eirp ..

l have seen the same way of using the Width/2 and lenght/2 to define the X and Y axis ... but how to define the values of the width and length them self ... are they the value for substrate or ground we have specified or for the working plane ....

thanx ..

eirp said:
leony said:
I learned the answer of the question above.But now i am in trouble with the optimizer tool.I could not understand the way how it optimizes.I define the parameter and give a name and the value but i dont understand how this name make a connection with the shape i drew.Please CST masters.Help me.

Hi

Why you don't take a closer look to manual which you have in install folder/Documentation ?

You have to first define the parameters such as Length, Width etc with some values - you know this already.
Then, when you are building a shape, use this parameters instead of numbers.
Let's say when you're drawing rectangular patch, use manual insertion of values (ESC after choosing brick) and type e.g.:
xmin:-Width/2, xmax:+Width/2
ymin:-Length/2, ymax:+Length/2
...
This is the connection with the shape

parametrisation of whole structure is highly recommended for easy manipulation of its dimension, not only for optimization!

Cheers,

e.

#### yafayez

##### Banned
For antenna radiation patterns and efficiencies, you can use EM-Core to simulate them.

https://www.pedasoft.com/