HFSS modeling of cross-coupling in borehole radar

The total cross-coupling between UWB borehole radar antenna slots in a metal drill string were modelled using the high frequency structure simulator (HFSS). Methods of suppressing this coupling were also modelled and provided promising results. Ferrite sleeves were able to provide a 30 dB reduction of cross-coupling levels, and phased pairs of transmit slots provided a reduction of 20 dB. Both methods achieved poorer performance when the drill string was nonconcentric in the borehole however.