Mcdonnell Douglas Corporation

The Boeing Company

Arthur C Lind

Frederick Coleman Wear

Stephen C Buckner

Garret G Heil

Jeffry K Hoyt

John J Domalewski

A thin sheet impedance device and process for controlling the resistance, capacitance and inductive properties of a material through the use of a plurality of impedance elements of specific sizes, shapes and material on one side of a thin dielectric sheet in combination with a plurality of similar impedance elements and/or a layer of resistive material on the opposite side of the dielectric sheet.

Impedance sheet device

The bulls-eye mid-frequency impedance probe has probe electrodes of a larger surface area that conform to the test surface to provide a very low impedance coupling between the probe and surface, unlike other open end coaxial probes. This probe provides accurate measurement of the dielectric properties of dielectric materials in the mid-frequency range of 10 MHz to 1 GHz on flat and curved solid surfaces, while conforming simple or complex curved surfaces by providing a resilient means between the probe contact surface and the probe box.

Bulls-eye mid-frequency impedance probe

A sensor and method for identifying the surface properties of a workpiece includes a microstrip sensor for transmitting and receiving microwave signals and surface properties determining means for determining the surface properties of the workpiece, including the type of material from which the workpiece is constructed, based upon the strength of the detected microwave signals. The surface properties identifying sensor also includes a microwave generator for producing microwave signals at a predetermined frequency for transmission by the microstrip sensor and a detector for detecting the microwave signals received by the microstrip sensor from the workpiece. Thus, workpieces comprised of a conductive material, an insulative material and a conductive material coated with a radar absorbing material can be readily distinguished by the surface properties identifying sensor and method.

Microwave sensor for identifying the surface properties of a workpiece

There is provided by this invention an open-ended cavity microwave applicator apparatus for inducing current into an electrically conductive workpiece to be heated without need for the the applicator to be in contact with the workpiece. The microwave applicator is comprised of an open-ended housing that defines a cylindrical cavity which is coupled by an aperture to a waveguide which transmits the microwave energy from a microwave generator to the cylindrical applicator cavity. The microwave applicator is designed to operate in a subset of the circular TE.sub.mnp modes where m, n and p are the number of half wavelength variations in the standing wave pattern in the .theta., r,and z directions, respectively. The particular subset desired is the one in which m is equal to zero such that no current flows from the applicator to the electrically conductive workpiece. Of the subset of axially symmetric modes, TE.sub.0np, the preferred mode of operation is circular TE.sub.011. A conductive back plate forms one end of the applicator cavity while the other end is open so as to allow the microwave radiation to induce closed-loop currents in the workpiece being heated. The conductive back plate may be adjustable so as to vary the axial cavity length to accomodate variations in generator operating frequency and in the distance between the applicator and the workpiece. Furthermore, the applicator cavity may be filled or partially filled with one or more dielectric materials, either isotropic or anisotropic, to alter the physical size and shape of the cavity while supporting the same frequency of TE.sub.mnp circular mode microwave radiation.

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Chesterfield, MO, United States of America

Arthur C Lind