Thank you for your response... Can you please elaborate further about e.g Active S(4,1).... here what does 4,1 mean? Infact simple s parameters s(1,1),s(2,2),s(3,3) makes sense but I am not sure in active s parameters !!
Why is it not like active S(1,1),ActiveS(2,2) rather than ActiveS(1;1),ActiveS(2;1),ActiveS(3;1) etc
They are usually the same, I mean both active S parameters and S parameters are the same. The only difference happens when you are optimizing a design, in this case active may refer to the current iteration or simulation run. You shouldn't worry about active or not active as long as your design is performing the way it supposes to.
Hope it helps.
Thanks for your response dear but no dear it did not help at all , It's not clear to me !!! What do you mean by they are the same... Jean Lambert Kubwimana
If you are using optimization feature in HFSS, then you may use active S-parameters. In optimization the design parameters are optimized as per the specified goal, then to monitor how the results(s-par here) are changing when the design parameters are being optimized by HFSS, you plot active s-parameters.
Thanks for reply Nitin Kumar...let me put forward a simple thing... if there are two antennas in an array each powered with 1watt... then according to definition of Active S parameters the corresponding active reflection coefficients would be just as below...
Active_S11= S(1,1)+S(1,2)
Active_S22=S(2,2)+S(2,1) where all reflections are passively evaluated (i.e in an array of antennas ,reflections at each port are evaluated when the rest of antennas are teminated with matched loads)...What is the use of these meaningless parameters in antenna arrays since they still represent passive S parameters...
Important: In multiport antenna array, when the antennas are scanning a beam, all antennas operate simultaneously and in that case the scattering represented by S parameters or active S parameters don't just suffice...
I am not sure if you can do that using HFSS, or even in practical world there will be only one power/signal source with power divided between multiple ports (Until you are applying different signals on each antenna/port, i don't know why to do that). If all antennas are operating simultaneously then there should be only one port with its power (amplitude and/or phase) divided to all your ports.
You are right Nitin Kumar.. we can't do that atleast via HFSS or CST but there must be someway and that is called re+search...
First of all I liked your comment about re-search. Now I almost forgot this, you may try an option, change the source of excitation which is by default the port number 1. If you want to change that you may do that by applying voltage/power/current to the desired port, or if you want all of the ports to be excited at once you can do that too. Just go to source option under excitation apply the value of voltage/power/current to the desired/all ports. I guess it helps.
Thanks Nitin for your feed back again... And ofcourse all antennas are supposed to be one watt each. That is the basic thing and how can I forget that in antenna array design!Infact, the problem lies in array scattering and its analysis which is based on passive paramters i.e to say that when s parameters of one antenna are evaluated,the rest of antennas are matched loaded...I hope I conveyed what I wanted to...
In HFSS, you can see the passive as well as active S-parameters. In a multi-port antenna array, when you ask for S-parameters (and not active s-parameters), e.g. S11, HFSS will only enable port 1 and treat all other ports as matched loads. In this way you'll only see the passive S-parameters. While if you ask for active S-parameters, HFSS will give you the results by taking into account the effect of mutual coupling with other ports/elements. In this case, HFSS will see what is the magnitude at other ports (1W or 0W). If it is 0W, it will be treated as matched load, but if it is 1W, the results shall be shown by taking that into account.
Irfan Ali Tunio The expression used to calculate the Active S-Parameter is (S11*a1 + S12*a2)/a1 where a1 is the complex excitation in volts incident on Port 1 and a2 is the complex excitation in volts incident on Port 2. So the explanation given by Imran Aziz above is correct.
What is the difference between S parameter obtained from network analyzers and from HFSS? Are they same?
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