Hrl Laboratories, LLC

Hughes Aircraft Company

John Jacob Ottusch

John L Visher

Daniel Frederic Sievenpiper

Joseph S Colburn

Bryan Ho Lim Fong

Jonathan James Lynch

Matthew W Ganz

Mark F Gyure

Geoffrey P McKnight

Chia-Ming Chang

Adour Vahe Kabakian

Harry Contopanagos

Bryan H Fong

Paul Richard Herz

Stephen M Wandzura

John F Visher

Vladimir Rokhlin

An acoustic absorber is disclosed. The acoustic absorber contains a plurality of adjacent passages defined by walls configured to generate alternating high and low pressure zones as an acoustic energy travels though the acoustic absorber.

Acoustic absorber

A method and system for determining an optimized artificial impedance surface is disclosed. An artificial impedance pattern is calculated on an impedance surface using an optical holographic technique given an assumed surface wave profile and a desired far field radiation pattern. Then, an actual surface wave profile produced on the impedance surface from the artificial impedance pattern, and an actual far field radiation pattern produced by the actual surface wave profile are calculated. An optimized artificial impedance pattern is then calculated by iteratively re-calculating the artificial impedance pattern from the actual surface wave profile and the desired far field radiation pattern. An artificial impedance surface is determined by mapping the optimized artificial impedance pattern onto a representation of a physical surface.

Method and system for determining an optimized artificial impedance surface

A method for designing artificial impedance surfaces is disclosed. The method involves matching impedance component values required for a given far-field radiation pattern (determined, for example, by holographic means) with measured or simulated impedance component values for the units of a lattice of conductive structures used to create an artificial impedance surface, where the units of the lattice have varied geometry. For example, a unit could be a square conductive structure with a slice (removed or missing material) through it. The measured or simulated impedance components are determined by measuring wavevector values for test surfaces in three or more directions over any number of test surfaces, where each unit of a given test surface has the same geometric shape and proportions as all of the other units of that test surface, but each test surface has some form of variation in the unit geometry from the other test surfaces. These test measurements create a table of geometry vs. impedance components that are used to design the artificial impedance structure. Since polarization can be controlled, the structure can be an artificial impedance surface characterized by a tensor impedance having complex components.

Method for designing artificial surface impedance structures characterized by an impedance tensor with complex components

An artificial impedance structure and a method for manufacturing same. The structure contains a dielectric layer having generally opposed first and second surfaces, a conductive layer disposed on the first surface, and a plurality of conductive structures disposed on the second surface to provide a preselected impedance profile along the second surface.

Artificial impedance structure

A method for guiding waves over objects, a method for improving a performance of an antenna, and a method for improving a performance of a radar are disclosed. The methods disclosed teach how an impedance structure can be used to guide waves over objects.

A computer program product, an apparatus, and a method for modeling equivalent surface sources on a closed, arbitrarily shaped object that result from the imposition of an arbitrary time-harmonic incident field (e.g., a radar wave) are provided. An object divided into by a plurality of patchesand parameters for the incident field and the properties of the objectare provided to the system. Next, the system produces a discretized representation of a well-conditioned boundary integral equation in the form of a well-conditioned matrix equation, modeling the interaction between the incident field and the object. The well-conditioned linear system is solved numerically to determine equivalent surface sources on the object. The equivalent sources may then be used to determine electromagnetic fields resulting therefrom. The invention provides improved computational efficiency as well as increased modeling accuracy by effectively reducing the numerical precision necessary.

Method and apparatus for modeling three-dimensional electromagnetic scattering from arbitrarily shaped three-dimensional objects

A photodetector produces an output signal in response to irradiation by an optical beam from a pulsed laser. A delay unit delays the output signal for a period corresponding to one-half of one cycle of a beat frequency generated by interaction of two frequency components in the optical beam corresponding to two predetermined longitudinal modes of operation of the laser. A differential mixer subtractively combines the output of the photodetector with the output of the delay unit, to produce an output signal having the main profile of the laser pulses suppressed, and the beat frequency component, if present, amplified. A resonant circuit and amplifier may be provided to further amplify the beat frequency component. The output of the amplifier is integrated to produce a DC signal having a magnitude which corresponds to the amplitude of the beat frequency component. The DC signal is compared with a threshold value to discriminate between single and multimode operation of the laser. An optical shutter may be closed in response to sensed multi-longitudinal mode operation to block the laser beam and protect equipment which would otherwise be damaged thereby.

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Malibu, CA, United States of America

John Jacob Ottusch