Resolving Phase Ambiguity in the Inverse Problem of Reflection-Only Measurement Methods

We have applied the phase unwrapping technique to resolve the phase ambiguity problem arising from complex expressions of scattering parameters, for re°ection-only measurement con¯gurations, since, at some instances, only one side of the sample under test is accessible for electromagnetic measurements. We considered two di®erent measurement con¯gurations for testing the applicability of the phase unwrapping technique as: 1) two identical samples with di®erent lengths °ushed by a short-circuit termination and 2) one sample shorted by a varying short-circuit termination. For each measurement con¯guration, the underlying expressions for the re°ection scattering parameters are derived. For both cases, we evaluated the suitability of the phase unwrapping technique by considering a highly-dispersive medium (distilled water) as our test sample. We note that continuity of the real part of the complex wavelength is a key issue in the unwrapping technique for (one-port) re°ection-only measurements.