Abstract: A general absolute value circuit for developing a true, symmetric or bipolar, absolute value output signal from an input charge signal, compact enough to be used on a sensor chip incorporated into (or used in combination with) a pixel processor of the type used in imaging and other systems that collect electromagnetic radiation as part of on-chip circuitry, includes a balanced differential amplifier combined with a merged dual shelf transistor structure. The balanced differential amplifier, in response to an input charge signal, drives the merged dual shelf transistor structure which in turn generates the desired true absolute value output signal. Such circuitry may be used in imaging systems to implement focal-plane processing algorithms or may be used for performing a single read true absolute value computation by a pixel processor located on a sensor chip. The merged dual shelf transistor structure enhances performance and speed of the processor in which it is incorporated.

Abstract: Apparatus and method combine, in real time, weather radar data in digital format from multiple radar sites into a mosaic covering a regional or national area (e.g., the continental United States). Such apparatus and method are implementable as computer software that can be run on a general purpose computer such as a personal computer. Preferably, a database of "lookup tables" are used to project individual radar data bins directly to a grid of the desired coordinate system for that mosaic. Using these lookup tables, each of a plurality of radar data bins is converted to a corresponding grid location or box in a mosaic image. While each radar data bin is mapped to a grid box for the mosaic, not every such grid box within the coverage area of the radar may receive such a data bin.

Abstract: A signal processor is described for object detection systems such as radar and sonar systems in which wave energy is transmitted and received as a train of discrete pulses of frequencies stepped in predetermined sequence. The received signal processor comprises a plurality of processing channels of number corresponding to the number of sub-pulses in the transmitted pulse train, each channel including frequency selective means such that signal returns of frequencies corresponding to but one of the transmitted sub-pulses are processed by that channel. Means are provided for simultaneously sampling the signal levels in all channels and indicating that channel in which the signal level is greatest, this sampling process being serially repeated at times related to each of the times of transmission of one sub-pulse of the train.

Abstract: A signal processor for continuous wave (CW) sonars of the type using a doppler filter bank for target detection, in which improved detection capability under reverberation limited conditions and particularly at relatively low doppler values is accomplished by introduction of an adaptive filter providing a notch filter characteristic centered on the mean frequency of the reverberation spectrum and of width and depth continuously automatically adjusted to conform at least approximately to the inverse of the reverberation spectrum. For effecting this adjustment the notch filter is made voltage variable and is enclosed within an automatic notch control (ANC) loop in which the notch control voltage is derived by comparison of signal level on one doppler filter on which appears reverberation plus noise against signal level on another on which appears noise only, to thus derive a control signal providing a measure of reverberation level.

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 dual band IR scanning focal plane assembly includes two linear detector arrays in a close spaced configuration monolithically integrated on a common substrate. A medium wave IR staggered element linear array is formed on the front (111)B face of a (111) crystallographically oriented CdZnTe substrate in an MCT layer deposited by the molecular beam epitaxial (MBE) process. A long wave IR staggered element linear array is formed on the back (111)A face of the substrate in an MCT layer deposited by the liquid phase epitaxial (LPE) process. The sets of odd and even rows of the LWIR array on the back face are contiguous, while the sets of odd and even rows of the MWIR array on the front face are close-spaced, the spacing being just wide enough to allow a clear optical path to the underlying linear LWIR array. The arrangement provides simplified spectral separation of the simultaneously readout MWIR and LWIR images.

Abstract: An active array antenna for use, for example, in a radar system, includes elemental antennas, each with a T/R module, distributed over a circular aperture. For lowest cost, the aperture is thinned. The T/R modules are operated at maximum output, to achieve maximum DC-to-RF efficiency, and for simplicity. A phase controller controls the phase shift which is imparted by each module to its signal, to form a main beam and its associated sidelobes. A perturbation phase generator portion of a phase controller adds a perturbation phase shift selected, in conjunction with a particular thinning distribution, to form a relatively wide null in the sidelobe structure, in which signal transduction is reduced. In a radar context, this null may be placed on a source of ground clutter or a jammer.

Abstract: The invention relates to a dual frequency sonar transducer assembly which may be operated at low and/or high frequencies in a sonar array. The assembly comprises a low frequency unit of tonpilz design including a low frequency driver, a low frequency tail mass and a composite head mass, the composite head mass acting as a single low frequency water driving piston and comprising a plurality of high frequency units forming individual high frequency water driving pistons. The high frequency units are also of tonpilz design, with independent drivers, independent head masses, and a common tail mass. The use of a common tail mass simplifies the design without compromising high frequency operation. The design leads to more efficient operation at both frequencies by minimizing the head mass to tail mass ratios.

Abstract: A compact dual band IR focal plane assembly provides simultaneous, coincident two-dimensional image readout. It includes a MIS-CID MWIR detector array formed in an epitaxial layer grown by the MBE process on the (111B) front face of an IR transparent crystalline first substrate, the pixels thereof forming LWIR transparent windows, with opaque connections thereto lying in aisles framing the windows, and a PV diode LWIR detector array formed in an epitaxial layer grown by the LPE process on the (111A) back face of the substrate, the LWIR pixels being aligned with the transparent MWIR pixels. An MWIR MUX is provided on an IR transparent silicon second substrate arranged in front of the first substrate. The opaque switch portion of the MWIR MUX is arrayed with apertures and aisles in alignment with the windows and aisles of the MIS-CID array.

Abstract: An improved x-ray detector in the form of a p-i-n CdTe homojunction device is disclosed. The intrinsic ("i") layer is of high resistivity CdTe, while the n- and p-doped CdTe layers are epitaxially grown in a photo-assisted process in a molecular beam epitaxial apparatus. The n-dopant is conveniently indium, with an indium metal contact. The "i" layer is optionally epitaxially grown in a photo-assisted process. The p-dopant is preferably arsenic. A PAMBE formed mercury telluride contact layer enhances the ohmic contact to the p-layer, and a gold contact is provided to the contact layer. The use of the PAMBE technique facilitates high quality crystal growth and activation of the dopants. The resulting CdTe p-i-n homojunction device has a wide band gap (1.45 eV) essential to room temperature operation.

Abstract: The invention relates to apparatus for reducing the masking effect in the doppler frequency domain of wind sheared clutter upon the radar returns of moving targets. The invention consists in forming two beams from the elements of a radar antenna array by means of adjustable complex weights which are then summed. One of the two beams is then delayed by a predetermined amount and added algebraically to the other beam to form a composite beam containing a narrow trough-like depression in beam angle/doppler frequency space. Means are then provided for adjusting the weights to bring coincidence between the depression and the clutter to cause attenuation of the clutter with a minimum reduction in the usable doppler frequency domain.

Abstract: The present invention relates to a hydrophone and to a virtual array of hydrophones for sensing the amplitude, frequency, and in arrays, the direction of sonic waves in water. The hydrophone employs a laser beam which is focused upon a small "focal" volume of water in which natural light scattering matter is suspended and which matter vibrates in synchronism with any sonic waves present. The vibration produces a phase modulation of the scattered light which may be recovered by optical heterodyne and sensitive phase detection techniques. The sonic waves are sensed at locations displaced from the focusing lenses. Because of this remote sensing capability, the physical hardware of an array of hydrophones may be confined to a small area comparable to the dimensions of the lenses themselves while the sensing of the sonic waves virtually occurs at widely spaced, remote focal volumes.

Abstract: A low power consumption amplifier that is essentially insensitive to the process used to fabricate the active devices of the amplifier employs feedback to minimize variations in electrical characteristics of the devices. For weight-sensitive microwave applications, a high electron mobility transistor (HEMT) or a pseudomorphic high electron mobility transistor (PHEMT) may be selected as an active device for each stage of the amplifier. HEMTs and PHEMTs typically exhibit greater device gain than do MESFETs, especially at the upper portion of X-band and above, so that a HEMT- or PHEMT-based stage of an amplifier where additional overall gain is required, can be achieved without significantly adversely affecting power consumption demands, and attendant electrical energy storage/generation requirements while achieving and/or maintaining an overall flat gain characteristic of the amplifier.

Abstract: The invention discloses an apparatus for and a method of adaptively processing a sonar power spectrum for improving the display of narrowband line structure characteristic of a target in a background of broadband interference which is rippled due to multipath propagation arrival structure. The processor employs a first Fourier transformer to convert the sonar frequency data into a complex correlation format. The autocorrelation is then time difference sampled to separate the broadband ripple interference from the broadband trend interference. The separate time difference samples are then transformed back to their real frequency format to form a broadband ripple estimate and a broadband trend estimate of the interference background. The ripple estimate is subtracted from the sonar signal to remove the ripple component and the resulting difference is normalized by a division by the interference trend estimate.

Abstract: A split-Stirling cryorefrigerator including a cylinder containing a movable displacer containing regenerator material and having an attached movable rod with a free end located in a housing enclosing a gas-spring chamber containing a gas. The cylinder has an orifice near its warm end which is in fluid communication with a gas source having a cyclic (typically sinusoidal) pressure. The movable rod slidably and generally sealably engages the housing and the warm end of the cylinder. The cryorefrigerator also includes a mechanism for adjusting the void volume of the gas-spring chamber, such adjustment allowing for increased cooling capacity of the cryorefrigerator when the amplitude of the cyclic pressure of the gas source is increased.

Abstract: A method for estimating target parameters of a target with respect to a platform such as ownship includes assigning predetermined initial values for the target parameters, wherein the target parameters are part of models having respective model probabilities. The models may include a Kalman filter. The models are updated in response to measured parameters of the target, wherein the measured parameters are different from the ones to be estimated. After a predetermined number of updates, the model having the highest updated model probability may be selected as the winning model. The updated values of the target parameters in the winning model at the time of winner selection are used as the estimated values for the parameters sought to be estimated. The updated parameter values may be refined by restarting the process using the updated values of the winning model as the basis for assigning new initial values for the target parameters.

Abstract: A typical source of cadmium and tellurium is as a by-product of copper mining. Although attempts are made to remove impurities such as copper prior to commercially supplying them for forming material like cadmium telluride, cadmium zinc telluride and cadmium telluride selenide for use as a substrate to support electronic circuitry, processing during formation of the circuitry causes the impurities from the substrate to segregate into the circuitry, resulting in unacceptable electrical performance of the circuitry. A method for purifying the substrate prior to circuitry formation includes forming a sacrificial layer of mercury telluride or mercury cadmium telluride on the substrate, annealing the combination at elevated temperature with an overpressure of mercury and removing the sacrificial layer along with a contiguous portion of the substrate, if desired. The sacrificial layer may be formed by vapor phase type processes or even by liquid phase epitaxy.

Abstract: A general absolute value circuit for developing a true, symmetric or bipolar, absolute value output signal from an input charge signal, compact enough to be used on a sensor chip incorporated into (or used in combination with) a pixel processor of the type used in imaging and other systems that collect electromagnetic radiation as part of on-chip circuitry, includes a balanced differential amplifier combined with a merged dual shelf transistor structure. The balanced differential amplifier, in response to an input charge signal, drives the merged dual shelf transistor structure which in turn generates the desired true absolute value output signal. Such circuitry may be used in imaging systems to implement focal-plane processing algorithms or may be used for performing a single read true absolute value computation by a pixel processor located on a sensor chip. The merged dual shelf transistor structure enhances performance and speed of the processor in which it is incorporated.

Abstract: A method for fabricating a hard faced fan blade containment system for turbofan aircraft engines, and the product resulting from that method. The product combines a hard facing material, a high strength fiber and an elastomeric binder to form a fan blade containment system which is lightweight and effectively retains fan blade fragments. The method consists of lightly bonding layers of high strength fibers together with a small amount of elastomeric binder so that they work in unison as a composite to contain a failed fan blade rather than as individual layers which are subject to sequential failure. In addition, a hard material such as ceramic or heat treated steel is encapsulated in an elastomer and bonded to the impact face of the containment system to blunt sharp edges of failed blade fragments and to spread the impact energy of the blade fragments over a larger area of the high strength fiber backing.

Abstract: A fuzzy logic based navigation module for use on a semi-autonomous vehicle computes the safety of moving from predefined local regions to adjacent local regions for the purpose of planning a safe path for the vehicle to take to reach its intended destination. Image understanding software provides the input to the system in the form of values for linguistic variables for each local region which impact the safe movement of the vehicle. Using a five level hierarchial rule base structure, the fuzzy inference process computes intermediate and final safety values which are affected not only by local conditions but also by nearby conditions in order to allow a minimum clearance for the vehicle.