Patch antenna, how can I use 2 ports?

[mitch81]

tem patch antenna

hello, I'm working on a conventional patch antenna. using CST microwaves studio, I want to find the S12 and S22 parameters, but I don't know how to put the second port as shown in figure. Where I can put the port2 ??? help me!

 

[tyassin]

Hi

Why do you need a second port?

Regards

 

[mitch81]

Hi

Why do you need a second port?

Regards

I need a second port because I want to represente s12 or s22 parameters. with one port, i can just represente s11

 

[tyassin]

Why do you need this for a single feed patch antenna?

I am not really sure what you want to do???? or measure.

 

[Azulykit]

s21 does not really make sense in the context of an antenna. Gain, efficiency, patterns, Axial ratio, etc. are measurements to characterize what comes out of the antenna and mirror s21.

 

[John_li]

Maybe..you make a mistake with the definition about the antenna paramters...

 

[mauloftin]

eee, I think, that is it some mistake, in CST MWS you can simulate only S11. Patch have not port 2, may be port is second antenna

Can you tell me, where you get the information about S21 and S22 of patch ??

 

[TerryADS]

why do you want to measure s12,s22 of patch antenna？

 

[mitch81]

to depart, I work on the antenna follows (see diagram) and I find that represents the coefficient S22! this means that there are two ports? or S22 is the same as s11

Added after 2 minutes:

why do you want to measure s12,s22 of patch antenna？

to depart, I work on the antenna follows (see diagram) and I find that represents the coefficient S22! this means that there are two ports? or S22 is the same as s11

 

[tyassin]

Hi

S11 and S22 or Sxx represent the same thing, the ratio of the reflected voltage/power to input voltage/power at a given port.

Usually when you only have one port you use S11. Using S22 usually indicates a having at least two ports. But you can donate a port whatever you want. The antenna in your figure seems to be a 1-port device, but they have donated the reflection coefficient S22, which is not the usual way. I would named it S11 otherwise you could be trying to find the 1-port.

But to your original question, S22 (S11) is the reflection coefficient at your port.
A simulation program like CST or any other EM-simulator do not calculate the gain of the antenna as S21.
You can use S21 or S12 if you have at least two ports in the antenna structure. But this only show the transmission between the ports and are not linked to the gain of the antenna.

You need to setup the simulator correctly with boundaries. The gain is then calculated by the program can give you the gain or other antenna properties directly.

Hope this helps.

 

[mitch81]

hi
thank you very much for all and tyassin, I think it is very clear. thank you again

 

[radiohead]

Thing is that S11 or more generally Sij are only defined when you are considering a mode at the port. This dominant mode is clear for microstrip: the quasi-TEM. For an antenna things are complicated a lot because the power is radiated in many directions as planar waves (out of the near-field region). Their power is expressed in W/m2.

You could capture this power over a certain area with a reflector antenna, and capture the aggregated power with a feed. This could lead you to some sort of S21, but then the link budget comes into play with all it's uncertainties about the link. Therefore it is better to measure or simulate the antenna patterns as discussed before. Polarization dependancy is an issue here.

Ciao.

 

[medaziz]

Hi

if your structure is symmectric you can say that S11 is equal to S22.

In your problem, patch antenna is an open structure, so S22 is not used.