Measuring Mutual Coupling

[MobiNaz]

Hello all,

I am testing two patches resonant at 5.25 and 10.5GHz. They are placed at about 1mm a part such that their feed are next to each other. Their dimensions are different (as evident)

Like in the figure. Now if I want to measure Mutual coupling. For first patch I should measure S12 and for second S21? using network analyser.

Am I thinking in the right direction?

Thanks in advance.

 

[volker_muehlhaus]

S21 and S12 must be the same

 

[MobiNaz]

I was looking at this paper

**broken link removed**

It derives the foirmul afor mutual coupling using dimensions of the patch , Width and Radiation resistance of antenna. In my case Width of both are diffrent .. so what Width I should take, means of which antenna and why? similarly about Radiation resistance.

Secondly, the coupling is for E plane and H plane. Practical measurements would be by placing the antennas in horizontal and vertical plane?

Thanks in advance.

 

[vioamethyst]

hi, if i use only one port to excite all my array elements,
so is there any issue of mutual coupling? S21 or S12 is the result of using 2 port feeding, but how bout if using only single port?

i also confius with the terms current density, current distribution and surface current, are they most likely the same?

i try to search for info at the internet, but i still cannot get concrete answer. please give ur comment, im greatly appreciate it. thank u

 

[MobiNaz]

As far as my understanding is, when patches come close / next to each other there will be mutual coupling and the current densities will change , you can theoretically calculate it but am still seeking answer to how to measure them.

 

[vioamethyst]

i think so too (when patches closer , mutual coupling is exist and significant) BUT many papers i read, all of them speaks on mutual coupling describe in S21..as we know, S21 parameter is from multiport applications....
so i totally out of idea, how to calculate/simulate those mutual couplinga s my array only have 1 input port..what more to say to measure them...( i wish to measure too)
theoretically calculate it? can you suggest me any related links/books/references ?

thanx a lot,

if i found anything useful to be share, ill post them here later =]

 

[volker_muehlhaus]

all of them speaks on mutual coupling describe in S21..as we know, S21 parameter is from multiport applications....

Correct. To measure a transmission from one antenna to the other, you need 2 ports.

so i totally out of idea, how to calculate/simulate those mutual couplinga s my array only have 1 input port..

Very simple. You remove the feed network, and instead connect port 1 directly to one antenna and port 2 directly to the other antenna. That's it. Very simple.

 

[vioamethyst]

dear volker_muehlhaus:
thank for your kind reply....
so its really need 2 ports then..thx for the info...

about the use of simulation of antenna w/out feeding network...i get what you mean...
but, in my case ...my array have 8 elements with 1 single input port...

so what do u think?
erm, maybe i need to test each of the element alternately??
look forward fo ur reply. TQ

 

[volker_muehlhaus]

but, in my case ...my array have 8 elements with 1 single input port...

Change the model so that each patch has its own port. Now you can probe all the crosstalk values.

S21
S31
S41
...

 

[vioamethyst]

wow...ok thanx a lot =]