How to test spatial diversity in MIMO configuratio antenna on FR4?

Hi to all!
I'm simulating a 2 antenna MIMO configuration printed on FR4 substrate.
To test spatial diversity separation should I use:

1)

(where

is vacuum wavelength)

2)

(where

is guided wavelength)

thanks

bye

Hi on1,
Where exactly are you using "d"? Is it the distance between the antennas?

If I assume that you have calculated the phase centers of the antennas for a given incident angle, then the antenna is already "de-embedded" out of this problem and you can use the first definition.

P.

thanks for your answer.
Sorry I forget to explain about d meaning: d is the phisical distance between the two antennas and I think that the right definition should be the second one.

Confirm?

thanks

hi on1...
i am also trying for such a mimo antenna...please can u help me in this too with the documents that you are actualy following ....so that i can also consider the same documents....as i havent started doing my project....please help

As the antennas are printed on a PCB there will be some coupling mechanism inside the dielectric but also just outside the PCB top layer. I'd say the mutual coupling is mostly coming from just outside the PCB since fields inside the PCB are more confined. So the antenna sees an effective dielectric constant with a value somewhere between that of the substrate and vacuum.

Now it doesn't reallty matter which definition you use, what matters is how close you can place the antennas. But I'd use the first one since the effective dielectric constant is closer to 1 than to that of the PCB. This also let you compare your separation distances with those in conventional arrays. If all space arround was filled with dielectric then one might choose the second option.