Abstract: A protective shield for an electrically steered, high performance C Band antenna array is disclosed. The shield is of a multi-layer construction in which a sandwich is formed between two fiberglass layers and a central foam core to minimize electrical reflections; and in which an additional foam layer is provided for structural support and to minimize changes in mutual coupling, installed between the sandwich and planarly disposed dipoles of the array. In addition, a teflon layer is applied to the outer layer of the sandwich and coated with fumed SiO.sub.2. The hydrophobic properties of the teflon-fumed SiO.sub.2 combination minimizes the effects of rain on antenna performance.

Abstract: The invention relates to a low noise amplifier for use at microwave frequencies which may be fabricated using integrated circuit techniques. In accordance with the invention, critical components are made adjustable so as to simplify the design process and manufacturability of the amplifier. A two stage low noise amplifier is disclosed in which TEE networks are used as input and output networks in each stage, and in which one element of each TEE includes an adjustable spiral inductor. The value of each adjustable spiral inductor may be adjusted by removal of one or more air bridges disposed along the inner turn of the inductor. This permits one to "tune" the amplifier and optimize its performance.

Abstract: A point source spatial filter determines the quality of a central point source or pixel under test to thereby detect point sources and minimize the signals from all sources other than the desired point source. The spatial filter incorporates a buffer apparatus for receiving pixel signals, memory apparatus for storing pixel data for the test pixel and surrounding pixels, comparator apparatus for comparing test pixel values against a given number of surrounding pixel values to determine if the test pixel is a local maximum or minimum value, subtraction apparatus for subtracting the value of the nearest-valued surrounding pixel from the test pixel value when the test pixel is determined to be a local maximum or minimum, and apparatus for indicating the difference between the value of the test pixel and that of the surrounding pixel of closest value.

Abstract: A novel readout circuit for a charge injection device is disclosed permitting selection of the integration time to optimize performance. A primary application of the invention is to IR sensing in which performance is required at both low and very high levels of radiation. The readout circuit, in one practical configuration, utilizes a dump pulse recurring at the interval required to scan all elements, in advance of the read pulse also recurring at the scanning interval. The integration time may be adjusted in multiples of the readout period for a single element up to the frame scanning interval, or in approximate fractions of the readout period for a single element, or, at the limit, in a fraction of a microsecond.

Abstract: The invention relates to a charge injection device for optical sensing including a novel readout circuit facilitating an extended dynamic range. The invention has primary application to linear arrays for IR sensing.Sensitive, low-level operation is achieved in a primary readout means by allowing the charge to accumulate in the potential well of the individual sensor elements over the line period with each element being reset at the pixel readout rate and by using a charge injection pulse to clear stored charge from the individual sensor elements. A secondary readout means is also provided in which the charge is allowed to accumulate over a period not exceeding the pixel readout interval for unsaturated large signal operation and by sensing the change in depth of the potential well. The two readout means are combined in the eventual display to provide an improvement of typically three orders of magnitude in the dynamic range of the CID.

Abstract: A novel signal scaling MESFET of a segmented dual gate design is disclosed. The MESFET, which is monolithically integrated on a semi-insulating substrate capable of localized surface modification to form active semiconductor regions using MMIC (monolithic microwave integrated circuit) techniques, has a small AC signal transfer which is adjustable in selected discrete steps. For operation in the gigahertz range, the substrate is preferably of gallium arsenide.In applying the MMIC technique, the MESFET, including segment electrodes and segment interconnections, and the electrical connections, signal paths, and passive components connected to the MESFET are formed on the substrate and defined by a photolithographic process. The technique permits reproducable feature definition and very compact minimum reactance segment interconnections, reducing deleterious parasitics and facilitating virtual unitary MESFET operation to very high frequencies.

Abstract: A readout circuit for IR sensing charge injection devices (CID) is disclosed, the CID comprising a two-dimensional array of dual-gate sensing sites on an InSb or HgCdTe substrate. The novel readout circuit, which operates in the charge sharing mode (CSM) in extracting image information, is modified to correct for the subtractive effect present when the CSM mode is used. The readout circuit includes a plurality of processors, one for each column, from which a single serial output may be obtained by a demultiplexer, and into which signals derived from successive pixel sites on the associated column are coupled. A first quantity representing the subtractive error is obtained without injection from each column line by double sampling during a first interval. A second quantity representing the signal corrected for subtractive error is obtained with injection from a pixel site by double sampling during a second interval, the samples being increased by the error quantity.

Abstract: A monolithically integrated circuit is described for multiplexing parallel electrical data into a serial bit stream for transmission by fiber optics to a remote utilization apparatus and for demultiplexing a serial bit stream received from a fiber optics transmission path from a remote source. The integrated circuit uses a separate fiber for transmission and for reception, and in the transmission mode, encodes the data, which is clocked by on chip clocking into a self-clocking three-level code. The integrated circuit utilizes GaAs as the substrate material and is capable of transmitting data at bit rates in excess of 1/2 gHz.

Abstract: The invention relates to a read and clear readout circuit and a method of operation of an IR sensing array. The invention eliminates "readout circuit lag" which reduces transient response for an individual sensor, and reduces angular resolution of an array. "Readout circuit lag" also emphasizes longer duration IR background causing unwanted saturation and restriction of the dynamic range. Readout circuit lag arises from the capacitance of the sensor elements and the capacitance of the readout circuit at a node to which the sensor elements are periodically coupled for readout, the IR induced charge being partitioned between these capacitances, with that attributable to the sensor capacitance not being injected, causing readout circuit lag. Elimination of such lag is achieved by following each readout step, with a clear or clear and skim step that removes charge to the clear level or to the skim level, precluding the lag earlier described.

Abstract: A novel metal core printed circuit board and a method of making it are described. The circuit board comprises a metal substrate, a patternable metal foil, and an insulating layer of thermoplastic resin whose glass transition temperature is exceeded during assembly under pressure to bond the resin to the metal substrate and to the foil by high temperature wetting. The circuit board also provides holes whose interior is lined with a resin united fusing to the resin in the insulating layer by high temperature wetting accompanied by pressure. The thermoplastic resin is a polyetherimide engineering plastic. The layers of the printed circuit board described above, including any additional layers of insulating resin and foil, may be bonded in a single step in a laminating press.

Abstract: The invention relates to an arrangement for remote ultrasonic temperature measurement. The arrangement employs a sensor, which in turn comprises an electromechanical transducer, a sensing element, and a hollow ultrasonic waveguide for coupling the sensing element to the transducer. The transducer is designed to propagate surface waves of a torsional or a radial shear mode upon the internal surface of the waveguide. The walls of the waveguide are made sufficiently thick, such that supporting clamps applied to the exterior of the waveguide have no adverse affect on interior wave propagation. The sensing element may be of either a hollow construction using internal surface wave propagation for protection of the active interior surface of the sensing element or of a solid construction in which the active outer surface of the sensing element may be exposed to the environment.

Abstract: A planar array antenna is contructed of two sets of slotted rectangular waveguides positioned to have the slots of adjacent waveguides offset by half the slot spacing. A bidirectional feed is used with phase switching between inputs to produce four distinct output beams from the array.

Abstract: The decoder herein described recovers the clocking and the data in a binary format from a three level coded signal. The decoder has application to data rates in excess of one half gigabits per second, which are common to optical communication channels. The decoder employs a comparator for evaluating to two bit accuracy each state of the signal, a two stage, two bit per stage shift register, and decision logic for recovering the data in a binary format. The decoder is monolithically integrated using buffered FET logic on a gallium arsenide substrate. In the decoder, the comparator is optimized by the use of three zero crossing detectors, one of which has a zero input for reference purposes, in combination with two internal voltage dividers and two external voltage references for achieving an accurate drift free determination of the levels of the three level code (TLC) signal.

Abstract: The invention relates to an improved readout circuit and readout method for an IR sensing array. The invention, given a limited time interval for reading out the signal from a sensor element in an array of sensor elements, permits a longer time to be devoted to the injection of charges into the substrate, thereby reducing device "lag" (the retention of uninjected charges). The readout is carried out by a two step, direct coupled, injection process. The first step involves independent, but simultaneous resetting of the sensor elements and the preamplifier input (at a node having sufficient capacity to supply the charges required for injection). The voltages are suitable for IR induced charge storage in the sensor elements, and for subsequent injection by the nodal capacity. A first sample is taken by a correlated double sampling circuit from the preamplifier output during the first step as the resetting stabilizes.

Abstract: A spread spectrum communication system having a correlation receiver for decoding an information signal transmitted on a pseudo-noise (PN) carrier. The receiver synchronizes to the transmitted signal by performing a continuous sequence of correlations until a correlation output exceeding a predetermined threshold level is detected. Thereafter, the receiver performs a plurality of correlations during a sampling interval which is timed to occur at approximately the time when high subsequent correlation output signals are likely to appear. After enhancement through adaptive filter processing, the correlation outputs generated during each sampling interval are accumulated (integrated and the summed output present at the end of the sampling interval is representative of the transmitted data message (a binary bit). The adaptive filter develops and stores weighting values representing the expected signal strength of the correlation outputs and the actual correlation outputs are multiplied by the weighting values.

Abstract: The invention relates to an arrangement for ultrasonic temperature measurement. The arrangement combines an ultrasonic temperature sensor and an electronic operating circuit. The ultrasonic temperature sensor comprises an acoustic waveguide, a second acoustic wave propagating resonant element, which is exposed to the thermal conditions under measurement, and whose resonant frequency becomes an indication of the temperature, and decoupling means inserted between the waveguide and the resonant element to facilitate high "Q" operation of the sensor. The arrangement utilizes torsional waves if a solid waveguide is employed, or internal surface waves with axial symmetry if a hollow waveguide is employed. The sensor is excited by a pulsed CW source, whose carrier is retuned to the resonant frequency of the sensor, and measured as the indication of temperature. The electronic operating circuitry achieves improved accuracy in temperature measurement as the "Q" of the sensor increases.

Abstract: A crucible is disclosed for use in molecular beam epitaxial processing exhibiting low flux transient behavior as shutters of individual furnaces are opened to initiate the process and with excellent flux uniformity over the surface being processed and over the processing time. The crucible is designed for liquid melts of Group III metals, including Gallium, Indium, and Aluminum.The crucible comprises a two member construction in which the outer member, which contains the melt, is typically cylindrical and of maximum capacity consistent with the furnace interior, and an inner member having a conical configuration with a small aperture at the bottom for optimum molecular beam formation. The conical member increases the thermal impedance between the melt surface and the interior of the MBE system to reduce the flux transient and increases the uniformity of the molecular beam over the area being processed, and over the time that the process is being conducted.

Abstract: The present invention deals with an optical transmission filter for effecting differential phase delay upon light in a beam polarized in a P dimension, as a function of position within the filter aperture for far field correction. The filter employs two lenses of birefrigent material, the crystal optic axes of the respective lens materials being oriented in mutually orthogonal positions and at a 45.degree. angle to the P dimension. The lenses have their adjacent surfaces respectively concave and convex with the same radius of curvature and their non-adjacent surfaces flat. The two lenses may be both spherical or both cylindrical.The correction provides an improvement in beam quality in laser systems operating with larger beam apertures or at higher powers.

Abstract: A digitally controlled wideband phase shifter is disclosed in which an input signal is resolved into two quadrature related components, the components are scaled in a stepped digital manner in proportion to the sine and cosine of the phase shifting angle, and then recombined to reconstitute a phase shifted replica of the input signal. The scalers are segmented MESFETS of a dual gate design in which each segment, has a predetermined transconductance and may be gated "ON" or "OFF" by a control signal to affect the overall transconductance of the scaler, and thereby the scaling factor.The phase shifter is implemented by a monolithic microwave integrated circuit technique in which the preferred substrate material is gallium arsenide, and in which all active device and circuit features are formed on the substrate by a photolithographic process.

Abstract: In side-lobe cancelling equipment direct jammer signals appearing in an auxiliary antenna channel are better correlated with reflected jammer signals in a main antenna channel by splitting the signal in the auxiliary channel into two parts, one of which is directly correlated with direct jammer signals in the main channel and the other is passed through a delay line to alter its timing to match the timing of the reflected jammer signals in the main channel.