Hello Weston:
I have posted about this before. To obtain S-parameters, it is done is by
convolving a bunch of cosine functions with the analog impulse response of the
channel as follows:
y(t)ÿm [cos(wot)*h(t)] i.e. sum of convolutions in the time domain
what the VNA gives you in the frequency domain is
Y(s)ÿum [ (delta(w-wo) +delta(w+w0)xH(s ] multiplications of deltas times the
frequency response of an analog system
Hence, it is clear that is a sampling of an analog system on the frequency
domain. Taking the iFFT, it is assuming that H(s)ÿz), they are not the same.
What you have to do is vector fit the S-parameter, transfer it to z-domain by
bilinear transformation and then take the IFFT. This is independent of whatever
simulation tool you use. We have used the VF from the original source.
Cheers,
Aldo
_____________________________________________________________________________________________
Aldo W. Morales, Ph.D. IEEE Senior Member
IEEE Consumer Electronics Society 15-16 Distinguished Lecturer
Co-Director, Center of Excellence in Signal Integrity
C-PI NSF STEM grant
Professor of Electrical Engineering
Penn State Harrisburg
777 West Harrisburg Pike
Middletown, PA 17057
U.S.A.
Phone: (717)-948-6379
Fax: (717)-948-6352
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