Abstract: An apparatus for sensing acoustic signals in a liquid wherein an omnidirectional hydrophone exhibits a hemispheric response pattern. A hydrophone, including a transducer element and a transmitting cable, is mounted such that the transducer element is adjacent the forward face of an acoustic baffle including a layer of sound-absorbing material. The rear face of the acoustic baffle is positioned adjacent an acoustic shield including a layer of sound-reflecting material. The transmitting cable is positioned in an aperture in the acoustic baffle and the acoustic shield, and passes beyond the rear face of the acoustic shield. A flow fairing is positioned adjacent the forward face of the acoustic baffle and encloses at least the forward portion of the transducer element.

Abstract: When the scan interval or time between successive potential detections is long with respect to a potential target's maneuvering capability (say on the order of ten seconds for a radar system), there is the possibility that the target may be able to deviate far enough away from its last detected position at scan i-1 that correlation of the target with a detection in scan i may not be possible using conventional tracking methods. The present invention uses a maneuvering gate to monitor a volume in space. The volume is bounded by intersecting ellipsoids and is disposed, preferably uniformly about the target's last estimate velocity vector. The surfaces of the ellipsoids which bound the volume may be determined by determining the loci of a combination of a straight and turning maneuver at a predetermined acceleration, which acceleration may be selected to be the maximum acceleration expected to be achievable by a predetermined target. When target correlation is disturbed or lost, the volume is examined.

Abstract: The invention relates to a self monitoring/calibrating phased array radar in which the operating path for transmission and the operating path for reception may be monitored/calibrated by the addition of a corporate calibration network coupled at the plural end to the antenna elements and at the singular end to the exciter/receiver, and switching means to selectively route the monitoring/calibrating signal derived from the exciter in a transmit path to calibration path sequence or in a calibration path to receive path sequence.In one embodiment of the invention, a phase shifter common to transmit and receive paths is adjustable in increments under active logical control for calibration, while power and gain performance is monitored but not actively controlled. A novel T/R sub-assembly houses the operating electronics for four antenna elements in the form of four T/R modules with a one to four divider network in the transmit/receive path and in the calibration path.

Abstract: The invention relates to an air bridge and an evaporative process for making air bridges. A first layer of photoresist is patterned to create two openings over the contacts to be connected, separated by a strip of photoresist. The photoresist strip is hard baked to allow it to soften and to cause further cross linking. The softening allows surface tension to reshape the photoresist strip to create a gradually sloping arcuate surface between contact openings upon which a metal layer of nearly constant thickness may be evaporated. A second layer of photoresist is then applied, and patterned to create a single large opening embracing both contacts and the now arcuate hard baked photoresist strip. An arch within the large opening connecting both contacts is formed by evaporation. Excess metal and both photoresist layers are then removed, leaving a novel, arch shaped air bridge.

Abstract: An optical signal processing system includes a number of optical time delay units to generate differentially time-delayed optical signals. Each optical time delay unit includes at least an in put polarizing beam splitter (PBS) system having an input system Thompson prism and an output PBS system including an output Thompson prism. Each Thompson prism has a high extinction ratio and is positioned to act as a polarizing beam splitter, providing a high signal to noise ratio optical signal processing system. Selectively polarized light beams are deflected by the polarizing beam splitters onto predetermined paths that cause the respective light beams to be differentially time delayed dependent on the path that they follow through the optical signal processing system.

Abstract: An image processor for use in detecting and tracking a plurality of targets is provided including a plurality of memory locations for storing intensity images and a signal processor coupled to the memory locations. The signal processor comprises a closed loop feedback system for producing a plurality of intensity images for updating externally derived reference intensity images in response to at least one externally derived data image incorporating target detection signals.

Abstract: Each of the acoustic transducers (elements) of an array has a maximum dimension of less than .lambda.. They are located at the vertices of a regular polyhedron, which may be an icosahedron (12 elements), or a dodecahedron (20 elements). This placement effectively locates the elements on the surface of a sphere with diameter selected to provide an interelement spacing of .lambda./3 to 2.lambda./3. The signals are delayed for phasing to form directive "beams." A second array includes elements located at the vertices of a smaller polyhedron centered at the same point and included within the first array, and operated at a higher frequency than the outermost array. In order to reduce the effects of shadowing, the locations of the transducers of the smaller included array are selected to lie on radials passing through the centroids of the faces of the polygon defining the larger array.

Abstract: A short horn antenna (10) adapted for array use includes a rectangular waveguide with broad upper (12) and lower (14) walls and narrow side walls (16, 18), defining a radiating aperture (20) and a feed end closed off by a shorting plate (22). A stepped upper ridge (26) has a slot (50) adjacent the shorting plate, and a shorter stepped lower ridge (46) has a corresponding slot. An unbalanced transmission line (75) extends through the shorting wall, and the smaller conductor (76) extends into the waveguide as an electric probe (60). The probe includes a first portion (64), extending parallel to the waveguide axis (8) and into the slot in the upper ridge. The probe (60) also includes a second portion (66) extending at an angle (90.degree.) relative to the first portion (64) of the probe (60).

Abstract: A resistance strip heater includes a pair of elongated, mutually parallel electrical conductors or buses lying on a dielectric substrate. Each bus includes a conductive region extending toward the other conductor, and the locations of the conductive regions of the two buses alternate along the lengths thereof. An elongated resistance arrangement has its axis of elongation parallel to the buses, is physically supported between the buses, and is electrically connected to mutually adjacent ones of the conductive regions, so that the resistance arrangement is electrically connected across the buses. In a particular embodiment of the invention, the resistance arrangement is a plurality of elongated chip resistors arranged in an array. The substrate may be a polyimide sheet, and a corresponding cover sheet may be used. The strip heater can be cut virtually anywhere along its length without affecting its operability.

Abstract: An enemy radar or transmitter transmits a signal at frequency f1. A tag on a friendly forces target receives frequency f1 and, in response thereto, transmits a signal at frequency f2.noteq.f1 modulated by a code unique to the tag. A friendly forces receiver, in response to receiving frequency f2 provides an indication that (a) the tag has received frequency f1, meaning the enemy is operating in the area, and (b) which specific tag has received a signal at frequency f1. The friendly forces can then take appropriate action.

Abstract: A Kalman filter, for a dynamic system having a number N of different states and another number M of observational components, uses a fixed rectangular systolic array of N.times.(N+1) parallel data processing elements for a regular filter, and uses an array of (N+2).times.(N+3) processing elements for a fault-tolerant filter; the processing elements in either configuration are connected in a four-nearest-neighbors network. Each processor is capable of carrying out a commanded one of a plurality of different vector-data operations sets during each of eight passes through the array. The systolic array operates on the matrices in a pipeline manner, so that each pass through the processor array feeds the result back into the array to begin the next computation.

Abstract: The invention relates to a switchable bidirectional phase shift network exhibiting a desired differential insertion phase suitable for use as a phase bit in a multi-bit phase shifter. The design is economical in its use of components--six field effect transistors, three inductors and no capacitors, and provides in one switching state a band pass network of low insertion phase and in the other switching state a low pass network of high insertion phase. The rate of change of insertion phase over a range of operating frequencies is substantially equal for the two states.

Abstract: The invention discloses a novel method and apparatus for cleaving semiconductor wafers into individual die which comprises mounting the wafer upon an adherent resilient air impermeable membrane while the latter is flat. Cleaving is achieved by using air pressure to inflate the membrane to cause bending and tensile stresses on the wafer brought about by its adhesion to the inflating membrane. These stresses cleave the wafer along the scribe marks to form individual die. The die may be easily removed by the application of a vacuum to the underside of the membrane which draws it against a perforated undulatory grid dimensioned according to the die dimensions to reduce the surface contact. This reduces adhesion of the die to the membrane to facilitate a low stress pick-off of the die.

Abstract: An underwater viewing system includes a dry and wet end. Illumination energy is provided to the wet end where it is scanned and the resulting scanned illumination is directed to a scene of interest. Energy reflected from the scene is received by the wet end where it retraces the path of illumination to the dry end. The received energy is directed to a detector and ultimately to a video processor. The wet end may be disposed in a remote piloted vehicle with optical waveguide payed out from the dry end to supply the illumination and to conduct the received energy. Communication information may be transferred between the dry and wet end may be over the same path followed by the illumination energy but at a different frequency. The illumination and communication energy may be separated based on their frequency. A polarization device may be provided for maximizing the amount of received energy that is provided to the detector.

Abstract: A solar cell voltage regulating arrangement which is particularly advantageous for use in spacecraft includes a light valve such as a liquid crystal cell disposed before the solar cell, to thereby controllably vary the light transmission to the solar cell. A control arrangement varies the transmission of the liquid crystal to control the output voltage.

Abstract: A phased array antenna system having an optical signal processing system includes a number of optical time delay units to generate differentially time-delayed optical signals. Each optical time delay unit is configured to generate a time delay through the use of either an optical fiber or free-space optical propagation delay assembly. Differentially time delayed optical signals are generated by controlling, with a spatial light modulator, the polarization of each light beam entering each time delay unit so that each respective light beam is deflected along either a direct path or a delay path dependent on its linear polarization. Each time delay unit includes an imaging system having a selected imaging ratio, with spherical lenses disposed in the delayed and direct light paths of the unit to provide imaging between the spatial light modulator planes. High extinction ratio polarizers are positioned in each of the delayed and direct paths. Spatial filters are further disposed in each spherical lens pair.

Abstract: A beamformer for a main antenna and a plurality of auxiliary antennas converts the main and each of the auxiliary signals to digital form. Each of the real and auxiliary digital signals is applied to a pair of real multipliers, in which multiplication by beamforming weights is performed, to produce one weighted real main signal, one weighted imaginary main signal, and a plurality of weighted real and weighted imaginary auxiliary signals. The weighted real main and auxiliary signals are summed together by a cascade of summers, and the weighted imaginary main and auxiliary signals are likewise summed together by another summed cascade. A digital product detector is connected to the output of each summer cascade. The first digital product detector produces in-phase and quadrature components of real detected signals, and the second digital product detector produces in-phase and quadrature components of imaginary detected signals.

Abstract: A liquid crystal and acousto-optic based control system for phased array antennas provides independent control of scanning along two axes of the antenna. The optical control system includes a laser source providing polarized laser beams processed in an in-line interferometric optical architecture that uses two acousto-optic deflectors (AODs) driven by separate sidebands of a microwave signal that is a mixture of a drive frequency corresponding to the desired carrier frequency and a variable control frequency for determining a selected sideband frequency. The AODs and associated polarization rotators generate a plurality of optical signal pairs, each pair having one first order positive doppler shifted light beam deflected by a first sideband drive signal and one first order negative doppler shifted light beam deflected by a second sideband drive signal, the positive and negative doppler shifted beams being respectively orthogonally linearly polarized and traveling along almost collinear paths.

Abstract: Image data is subjected to a thinning process so as to derive a medial axis for each image. Boolean image data is reduced to lines and/or dots, each line generally being a centroid line of an image. The thinning process uses a change look-up table which is addressed using values from pixels in the neighborhood of a particular pixel which is the target for possible change. Pixels in the neighborhood which are to be evaluated are given a weight by use of a weight look-up table and the weight of the pixel is multiplied by the value of the pixel. Alternately, the weight of the pixel may be added to the pixel value. The pixels in the neighborhood of a target pixel (i.e., pixel which is being evaluated for possible removal) have their weights and values taken into account by a summation of the results of the multiplication (or addition) performed for each pixel so as to provide an address used to address a change look-up table which supplies an output indicative of change in the target pixel.

Abstract: An improved cold shielding arrangement for a scanned linear IR detector array normally having the pixels arranged in plural columns, is disclosed. The arrangement consists of a first slotted cold shield plate spaced from the array and designed to reduce the angular field of view for all pixels of the array in the scanning direction, and a composite cold shield in proximity to the individual pixels. The first part of the composite cold shield is a thicker plate, typically several mils thick having slots oriented to reduce the angular field of view in the resolution direction for the pixels in a common row.