| Summary: | The objective of the thesis is to evaluate the performance of two methods
recently proposed for scattering parameter (S-parameter) extraction using time-domain
optoelectronic vector network analyzers. Model-based simulations of an
electro-optic sampling experiment for a typical high-speed bipolar transistor were
used to investigate the accuracy of the techniques in the presence of experimental
non-idealities. In particular, the investigation focused on the effects of finite time
window, drift and noise. The methods use step-like signals and digital filtering
techniques to extract the S-parameters for one of two situations where signals are
either temporally overlapped or not. From the simulations, it was determined that
the approach for overlapping signals is not feasible. The experimental impairments
of drift and noise interfere with the separation of overlapping signals and result in
inaccurate S-parameter computation. Fair results may be obtained within a limited
range of frequencies for extracting the S-parameters with the approach for non-overlapping
signals. Although feasible, the latter method was not recommended over
existing optoelectronic methods which use pulse-like input signals for S-parameter
extraction.
The digital filtering technique common to both methods was validated by an
experimental measurement of signal propagation on a coplanar stripline fabricated
on a multilayer S1O2/S1 substrate. The attenuation and effective dielectric constants
were measured over a range of frequencies between 20 and 150 GHz. Elecromagnetic simulations of the structure performed by a collaborator were found to be in excellent
agreement with the experimental results. The results show high losses and dispersive
effects at low frequencies, which are attributed to the conductive substrate used.
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