Antenna compensation method using direct coupling wave in polarimetric borehole radar measurement

Crosshole borehole radar measurement is needed to compensate the antenna transfer functions in polarimetric single-hole radar measurement with combinations of a dipole antenna and a cylindrical conducting slot antenna. This paper presents a method to estimate the antenna transfer functions from the single-hole measurement alone. A small dipole model in a homogeneous medium is used to approximate the relationship between the direct coupling wave in the single-hole measurement and the direct wave in crosshole measurement (antenna transfer function). We show that the far field crosshole signal approximately has the same frequency dependency as the time derivative of the direct coupling signal measured via single-hole measurement. We experimentally demonstrate that the measured far field waveforms have good agreement with the time derivative of the measured direct coupling waveform for dipole-dipole and slot-slot arrangements with an antenna separation of 1.6 m.