112 results about "Surface impedance" patented technology

An improved induction tool for formation resistivity evaluations. The tool provides electromagnetic transmitters and sensors suitable for transmitting and receiving magnetic fields in radial directions that are orthogonal to the tool's longitudinal axis with minimal susceptibility to errors associated with parasitic eddy currents induced in the metal components surrounding the transmitter and receiver coils. The present invention provides increased effective tool surface impedance by increasing self-inductance of the paths in which induced eddy currents flow on the surface of the multi-component induction instruments. The tool enables downhole tool designers to build more effective and better-protected radial induction arrays for existing and future downhole instruments operating in the frequency and / or time domains. In this case the array measurement results contain information primarily about the formation's vertical resistivity. The tool makes it possible to combine radial arrays with coaxial arrays that conventionally measure horizontal formation resistivity. This combination enables obtaining a full resistivity tensor to evaluate formation resistivity anisotropy. The tool provides a composite non-conductive housing to reduce or even avoid the effects of parasitic eddy currents flowing on the tool surface. The tool provides a non-magnetic housing that is conductive which reduces the effects of conductive materials near coils and, primarily, the receiver. The tool provides a non-conductive coating is placed over the housing to prevent high frequency eddy currents from leaking from the housing in the conductive mud of the adjacent wellbore and returning to the housing.

The present invention generally relates to the field of microwave antennas, and, more particularly, to a number of three-dimensional designs for the radiation element of an ultra-wideband monopole antenna with a symmetrical omni-directional radiation pattern operated in the frequency range between 3.1 GHz and 10.6 GHz. Said antenna is connected to the analog front-end circuitry of a wireless communication device used for transmitting and / or receiving microwave signals and meets the FCC requirements in terms of antenna gain, radiation pattern, polarization, frequency bandwidth, group delay, and size. It comprises a radiation element consisting of an air- and / or dielectric-filled cavity structure with a base plane and a radiator plane. A metallic ground plane having a relatively high surface impedance to electromagnetic waves within said frequency range, which is printed on a dielectric substrate, serves as a reflector. The monopole antenna further comprises an antenna feeding circuitry used for electronically steering the symmetrical omni-directional radiation pattern and a feeding line connecting the antenna feeding circuitry with the base plane of the radiation element. Thereby, parts of the analog front-end circuitry can optionally be placed within the air-filled part of the radiation element of the antenna.The proposed designs include a radiation element having the form of a truncated right circular cone, rotational-symmetric radiation elements with a convexly- or concavely-shaped 3D surface, respectively, a radiation element in the form of a truncated right regular pyramid with a square base plane, and radiation elements with a combined structure comprising a conical, pyramidal, convexly- or concavely-shaped first part and a closed cylindrical or cuboidal second part whose top plane is arranged on top of the congruent base plane of said first part. Further embodiments include radiation elements with the form of a radially notched cylinder or hemisphere as well as combined structures consisting of at least two convexly-shaped elements or two conical parts, respectively, stacked on top of each other.

Current flows in a three-dimensional conductive or dielectric body embedded in a substrate of a different material are modelled in terms of surface currents induced in planar surfaces bounding the body and composed of the same material as the substrate, the surfaces having appropriate values for surface impedance.