Positive S11 S21 in free space meas. with VNA Agilient,

[hufu42]

Need Help,
I have some planar samples and designed a free space measurement, I calibrated the rectangular horn antennas THRU-REFLECT than put the sample in the middle of system. The result gives S11 and S21, at some frequencies S11 and/or S21 have/has positive values. Is it correct ? does it have any physical meaning?
Thanks for your valuable helps...

same problem with coaxial waveguide measurement?

 

[biff44]

so you used some horn antenna setup with perhaps 10 db of insertion loss, and told the network analyzer to use it as a 0 dB loss thru section. Then you put some sample in the way and found a slightly positive S21. And, your question is what?

 

[hufu42]

thanks for your reply;
what should I do to obtain the exact S11 and S21 than I try to calculate the physciala parameters of samples such as permitivity permeability.