Abstract: A plasma antenna is provided having an ionizer, which when energized, generates a bounded or unbounded plasma column extending along a vertical axis. When ionization is initiated, the difference in the diffusion characteristics of ions and electrons and the resulting gas plasma produce a current pulse in a first direction. As the plasma extinguishes, the difference in relaxation times for the ions and electrons in the plasma produces a second current pulse of opposite direction. The alternating current pulses generate an electric field that radiates from the plasma column.

Abstract: A microstrip patch antenna with progressive slot loading is provided. A rectangular patch of electrically conductive material has a plurality of slots formed therein with each slot having its center aligned with the centerline of the patch's long dimension. Each slot further has its longitudinal axis perpendicular to the centerline. The slots are arranged in an order starting at a position n=1 that is furthest from the patch's feedpoint so that, for an n-th slot, the inequalities Ln>Ln+1 and Wn<Wn+1 are always satisfied. In general, the length decreases linearly with each successive slot while the width increases exponentially with each successive slot.

Abstract: A sonar array comprising a support structure, an acoustic projector attached to the support structure, and a plurality of directional hydrophones attached to the support structure and arranged so as to surround the acoustic projector. The directional hydrophones are equidistantly spaced about the acoustic projector. In one embodiment, the array includes means attached to the support structure that allows the support structure to be connected to a device that effects course steering of the sonar array.

Abstract: A three-dimensional array of acoustic sensors. The array can be used for both the transmission and reception of acoustic signals. The array comprises electroplated piezoelectric polymer layers that are laminated with a non-conductive epoxy to form individual multi-layer array transducer elements. Circuit support layer layers are incorporated between the multi-layer array transducer elements. Because of the three-dimensional configuration of the array, logical transducers can be created from multiple transducer elements, and transmission and reception of acoustic signals in any direction can be realized.

Abstract: A RF front end to an IF generator and post-processor whereby the IF generator output is variable. The transceiver up-conversion path includes an IF Filter, the output of which is input to a mixer with the output of a fixed Phase Locked Oscillator (PLO). The mixer output is input to a band-pass filter and amplified. With a single antenna configuration, the amplifier output connects to either an internal or external diplexer that interfaces to the antenna. With a dual antenna configuration, the amplifier output interfaces directly to the antenna. Similarly, the down-conversion path includes an internal or external diplexer in the single antenna configuration, a band-pass filter, a RF amplifier, a mixer that receives the RF amplifier output and the fixed PLO as inputs, an IF Filter, IF amplifier, and an attenuator for interfacing to the IF post-processor.

Abstract: A system and method are provided to measure relatively short distances between one or more moveable objects and with respect to an environment. The transponders may be affixed to other moveable objects and/or may be affixed in position within the environment. The transponders detect the query signal and respond with an acoustic response signal. A synchronized clock system establishes common timing between the transponders and the moveable objects such that the start time at which the acoustic response signal is sent is known. The moveable object detects a receipt time when the acoustic response signal is received. Knowing the start time and the receipt time, a transit time for the acoustic signal can be determined whereby a separation vector may be calculated. The system may be used to determine and transmit a table that contains the relative positions of all moveable objects in the environment.

Abstract: A piezoelectric embedded monolithic active surface for transmitting a directed acoustic beam comprising a monolithic active surface, a plurality of piezoelectric elements embedded on the surface forming an array comprising, a plurality of coupled frequency pairs comprising, a first primary frequency row extending in a frequency steered direction the first primary frequency row enabled to accept a first primary frequency signal, and a second primary frequency row extending in the frequency steered direction and located adjacent to the first primary frequency row the second primary frequency row enabled to accept a second primary frequency signal, wherein the plurality of coupled frequency pairs repeat in a delay-steered direction and wherein each of the coupled frequency pairs are enabled to accept a time delayed copy of the first and second primary frequency signals.

Abstract: A system and method is provided for determining the temperature to which a structure is subjected. An optical fiber having at least one pair of fiber sensors is attached to the structure. The fiber sensors comprise Bragg gratings and each is configured to have a particular coefficient of thermal expansion and be responsive to a particular wavelength. A broadband spectrum of light is launched into the optical fiber. The light returning from the fiber sensors is detected. The temperature to which the structure is subjected is then determined based on the difference in strain response of the fiber sensors as a result of the effects of temperature upon the fiber sensors. Coatings of different materials may be applied over the optical fiber to provide the fiber sensors with differing coefficients of thermal expansion.

Abstract: An optical hydrophone described herein includes a housing defining a chamber. The housing is acoustically transparent to acoustic waves at a frequency of interest. An optically transparent material fills the chamber and has air-filled voids defined therein that resonate within the material when an incoming acoustic wave impinges on the material. Light introduced into the material and passed therethrough is affected by the air-filled voids resonating within the material. Light is transmitted to and from the material by optical fibers which are coupled to the material on either side thereof. A plurality of these optical hydrophones can be configured in a linear array through which light is passed. Such linear arrays can be used to measure incoming acoustic signals.

Abstract: An antenna system and method for a plurality of plasma antennas driven by means of an optical driver. In one embodiment the driver comprises one or more lasers which may be modulated by one or more electro-optical modulators to produce a modulated laser signal. The modulated laser signal may be supplied to the plasma antenna by optical fibers whereby the photons from the modulated signal impart momentum to the plasma particles. The plasma particles, which may include unbound electrons, oscillate in accord with the modulated laser signal to radiate electromagnetic energy. In one embodiment, the plasma antenna is operated at a frequency near the resonant frequency of the plasma to form a more efficient radiator requiring a smaller size than to a metallic antenna. In another embodiment a plurality of closely spaced plasma antennas are operated with different plasma resonant frequencies such that one plasma antenna is electrically invisible with respect to another plasma antenna.

Abstract: The present invention relates to an elastomeric material thickness test fixture. The test fixture comprises a cylinder having an interior space for receiving at least one sheet of a material to be tested, and a piston movable relative to the cylinder for applying a holding force to the at least one sheet. The piston has a through hole to allow a test medium to be used to study chemical attack to come into contact with the at least one sheet. A process for allowing assessment of chemical attack on thick elastomeric materials using the test fixture is also described.

Abstract: A system and method for displaying sonar data are disclosed. In a presently preferred embodiment, each of N channels from a beamformer are separately processed utilizing a pair of passive broadband detection processors such as SCOT processors and SPED processors. The output of each SCOT processor and each SPED processor are scaled, aligned, and then compared. The maximum scaled and aligned output from each pair of processors is selected for input to a bearing time history display.

Abstract: A laser driven plasma antenna system utilizes a laser having an output for emitting a laser beam that is directed toward and is reflected from the ionosphere so as to produce an ionized column of air extending between the laser and the ionosphere such that electromagnetic radiation is conducted through the ionized column of air as electrical current, and a pulsing circuit for pulsing the laser in accordance with a predetermined pulse rate that corresponds to a particular frequency of interest such that electromagnetic radiation having the particular frequency is conducted through the ionized column as electrical current having a frequency equal to the particular frequency.

Abstract: A method and device to neutralize influence mines has a control module to generate signals representative of acoustic and magnetic signatures of a ship. These representative signals will either detonate the threat mines or ensure that transiting ships will not set off the mines. An acoustic transducer array is coupled to the module to transmit acoustic signals representative of the acoustic portion of the signatures. A magnetic signal transmitter is coupled to the module to transmit magnetic signals representative of the magnetic portion of the signatures. An anchor is connected to the module, acoustic array, and magnetic signal transmitter to hold them at the ocean bottom, and a buoy is connected to the module, acoustic transducer array, and magnetic signal transmitter to hold the device vertically.

Abstract: A propeller protector for a countermeasure vehicle having a propeller shaft, a propeller fixed to the shaft, radial fins fixed on the vehicle and extending outwardly from the shaft, and a shield fixed to the fins and surrounding the propeller. The propeller protector includes a sleeve having an end wall at a first end thereof, and an open second end engaged with the vehicle, the first end and side walls of the sleeve having perforations therein. The sleeve first end is provided with a central opening. A nut is fixed to the sleeve end wall, threadedly mounted on the shaft, and disposed around the central opening. Stop structure on the sleeve and the vehicle prevents rotation of the sleeve relative to the vehicle. Rotation of the propeller shaft unscrews the shaft from the nut, permitting the nut and the sleeve to move axially to disengage from the vehicle.

Abstract: A bottom activated retractable control device includes a fin member having a front edge, a trailing edge opposite to the front edge, a bottom edge between the front edge and the trailing edge, and an arm portion extending from and coextensive with the leading edge and away from the bottom edge. The arm portion includes a pivot pin extending in a perpendicular direction from each side of the arm portion. A pivot housing having an aperture is provided for receiving the pivot pin of the arm portion, the housing enabling both a vertical pivot of the fin member upon contact of the fin with, an object and axial rotation of the fin about the arm portion of the fin member. A well is formed in the bottom surface of an underwater vehicle corresponds in depth to a fully retracted position of the fin member and in width to any rotated position of the fin member.

Abstract: A flow meter strut assembly includes a strut portion having a first end plate, a second end plate, a longitudinally adjustable flow meter support structure between.the first and second end plates, and curved mounting surfaces formed on outer surfaces of each of the first and second end plates of the strut portion. At least one flow meter is adjustably mounted on the flow meter support structure. The flow meter support structure is adjustable longitudinally by a turnbuckle assembly connected between the flow meter support structure and the second end plate.

Abstract: A non-chromate conversion coating and method of applying same wherein the coating comprises a titanate, such as potassium titanate or sodium metatitanate, as a “drop-in replacement” for a chromate in an otherwise chromate-containing conversion coating.

Abstract: A method for making a piezoelectric composite transducer is disclosed. A block of piezoelectric material having a common base and a plurality of uniform-length rods is utilized. An electric conductor is positioned to extend through a side region of the block. Spaces between the rods are filled up to a first surface region with a viscoelastic material. The common base of the block is removed forming a second surface region. Electrodes are deposited at the first surface region to be in contact with the rods and in electrical contact with the electric conductors. A ground electrode is deposited at the second surface region to be in contact with the rods. The resulting piezoelectric composite transducer can be heated and shaped to conform to complex curves.

Abstract: An apparatus for determining the velocity of sound waves which includes a liquid medium having a plurality of gas bubbles. In the liquid medium, a laser transmits a light pulse to interact with the bubbles excited by the sound wave. Backscattered light from the interaction of the light pulse is received. A processor is then responsive to the detector to provide detection of the acoustic wave through the fluid medium.