A method and apparatus for estimating a parameter of interest of an earth formation ahead of a carrier within borehole. The method including estimating one or more functions based on received signals that may reduce the sum of the signals received by a first receiver, and estimating the parameter of interest based on signals received by one or more additional receivers by applying the one or more functions and, if necessary, a defocusing factor, such that reception of information from downhole of a selected downhole location is enhanced relative to reception of information uphole from the selected location. The apparatus including two or more transmitters, two or more receivers, and a processor to estimate one or more functions, and, based on these functions, the parameter of interest.