regarding s-parameters-tolerable values

hi all,

i extracted the s-paraMETRS of the transmission line strucyture say CPW or microstrip or stripline,etc.....how do i can makedecision that the s-parametrs of those structures is optimum?.......because in practice we wouln't get ideal values for those paramters?.....

Is there any standards for those parameters?.....how the values of s11,s21,s12?.....
give me tolerable limit of these paramters in practical environment?......

if u have links regarding this please reply....

with regards,
venkat.G.

The ideal value of S11(dB) is -∞. But if u can get simulated results around -20 to -25dB i think its sufficient for reasonable performance. I don't have any links. But i got these informations from experts in this field

hi jossion,
thanks for the reply...regrding S21 parameter?....
if u find any links please forward it to me....

with regards,
venkat.G.

There is no straight forward answer to it.
I would say it all depends on the bandwidth required and how your load varies in this bandwidth.
Practically, 30dB is a very good RL to be with, but if you get a RL of 25dB again one cant be sure if its because of the load or bad line.
Again on the IL issue, the factors that contribute are many; finite conductivity, dielectric loss and many others. I would say anything less than 1dB is ok, but one cant generalise, for even the co-axial cables we use with network analysers have a spec of more that 1dB at highfrequencies.

The answer is there is no generalised bench mark. It depends on the circumstances.

Hope this was useful.
Probably if you consider a specific case, an acceptable spec could be reached.

hi aswins,
thanks for the reply yaar....