Innovative possibilities in time domain reflectrometry

In this contribution we describe new possibilities regarding TDR measurements, related to the measurement of the electromagnetic characteristics of lossy and possibly magnetic and dispersive materials. The proposed advancement is related to the introduction of a spatial diversity in TDR measurements, achievable by means of extensible probes or alternatively by means of arrays of probes. The spatial diversity can replace the frequency diversity increasing the information achievable at single frequency, so allowing measurements immune from the effects of a possibly unknown dispersion law. Moreover, measuring the reflection coefficient at fixed frequency we can achieve information about both the propagation velocity of the electromagnetic wave along the line and about the intrinsic impedance of the line, which in its turn allows to discriminate between the dielectric permittivity and the magnetic permeability of the material, meant as complex quantities in order to include lossy cases too. There are several possible fields of application and in particular, with regard to the properties of the soil (of interest for archaeological prospecting), the attenuation of the waves in the soil can be estimated (which is important in relation with GPR prospecting), or the water content or in some cases the possible presence of some pollutant