Abstract: A method of determining electromagnetic scattering properties of a finite periodic structure has the steps: 1002: Calculating a single-cell contrast current density, within a unit-cell supporting domain of a single one of a finite collection of unit cells. 1004: Calculating a scattered electric field outside the finite collection of unit cells, by integrating, over the single unit cell's supporting domain, a Green's function with the determined single-cell contrast current density. 1006: The Green's function is obtained for observation points outside the finite collection of unit cells by summation across the finite collection of unit cells. The Green's function integrated with the determined single-cell contrast current density is obtained for observation points above the supporting domain with respect to a substrate underlying the finite periodic structure.

Abstract: A method of determining electromagnetic scattering properties of a finite periodic structure has the steps: 1002: Calculating a single-cell contrast current density, within a unit-cell supporting domain of a single one of a finite collection of unit cells. 1004: Calculating a scattered electric field outside the finite collection of unit cells, by integrating, over the single unit cell's supporting domain, a Green's function with the determined single-cell contrast current density. 1006: The Green's function is obtained for observation points outside the finite collection of unit cells by summation across the finite collection of unit cells. The Green's function integrated with the determined single-cell contrast current density is obtained for observation points above the supporting domain with respect to a substrate underlying the finite periodic structure.

Abstract: There is provided a method of predicting the response of an induction logging tool along an arbitrary trajectory in a three-dimensional earth model, wherein the method comprises a confinement of the electromagnetic field computations to a limited domain of the geology surrounding the induction logging tool. The magnetic field at a receiver coil is considered as a superposition of a primary background constituent and a secondary constituent. A single spherical scatterer approximation is used for the second constituent.

Abstract: The invention relates to a borehole radar tool comprising, in a housing (2) a transmitting antenna and a receiving antenna both of which comprise, near the housing wall (2), a dipole antenna (8) and a reflector (10) opposite thereto. Also provided are an algorithm, method and apparatus for determining electromagnetic contrast information of a site into which electromagnetic fields (27) are emitted. Signals (29) generated by induction are intercepted and, using a back-projection algorithm including a suitable weighting factor, are converted into contrast information. The algorithm and/or method can be recorded in a computer program or on a data carrier. Also disclosed is a method of determining said weighting factor. The invention further provides a method and apparatus for subsurface surveys in which electromagnetic pulse signals are emitted.

Abstract: The invention relates to a borehole radar tool comprising, in a housing (2) a transmitting antenna and a receiving antenna both of which comprise, near the housing wall (2), a dipole antenna (8) and a reflector (10) opposite thereto. Also provided are an algorithm, method and apparatus for determining electromagnetic contrast information of a site into which electromagnetic fields (27) are emitted. Signals (29) generated by induction are intercepted and, using a back-projection algorithm including a suitable weighting factor, are converted into contrast information. The algorithm and/or method can be recorded in a computer program or on a data carrier. Also disclosed is a method of determining said weighting factor. The invention further provides a method and apparatus for subsurface surveys in which electromagnetic pulse signals are emitted.