Abstract: The adverse effects of the impedance of long varying impedance connecting lines used in pulse width modulated power amplifier are eliminated by means of a dual input differential amplifier that senses the line voltage drops in the connecting lines and combines them into a line voltage drop compensation signal that is applied across the power amplifier inputs. This line voltage drop compensation signal raises the output of the power amplifier by the amounts needed to null out the line voltage drops.

Abstract: The linearity of group delay versus frequency in magnetostatic wave delay lines is improved by a linear variation of one of three discrete parameters in the region between the two delay line transducers. The parameter variation is applied to magnetostatic wave delay lines that have a ground plane, a magnetic garnet crystal film substrate that is spaced from the ground plane and has transmitting and receiving transducers engaged to it, and a magnetic bias field. The discrete parameters varied are the magnetic bias field; the distance of the substrate from the ground plane; and the thickness of the substrate. Appropriate linear variations of any one of the these parameters provides improved linearity of group delay versus frequency.

Abstract: A power circuit utilizing a switch comprised of Hall-effect-active resistive elements for interrupting a current flow in an inductive energy storage system. Interruption of the flow of current causes a high-voltage pulse which drives the current flow into a circuit leg which is parallel to the interrupting elements. The Hall effect switch is controlled by means of an exciter coil that is connected in parallel with the Hall-effect-active resistive elements to provide self excited operation.

Abstract: A universal timing array (UTA) comprising a branch and increment logic circuit and multiple 2-bit counter cells is fabricated as a single large scale integrated circuit and is adapted to implementing various timing and control functions in digital computers and radar signal processors. Implementation of the UTA functional design using emitter coupled logic circuitry and special circuit design features improves UTA performance by increasing operating clock frequency, widening operating temperature range and reducing on-chip complexity. A specific embodiment utilizes a standard universal digital array chip having specially selected cell placements and interconnecting routing patterns.

Abstract: The time of arrival of a constant speed moving object at a given location is calculated from data representing the time of arrival of the object at two preceeding locations and the relative physical distances between the three locations. An up-down counter counts up at a fixed frequency f.sub.1 during the time interval of the object's transversal of the distance between the first two locations and counts down at a pre-selected frequency f.sub.2 thereafter. The preselected frequency f.sub.2 is a function of the distances between locations and the fixed frequency f.sub.1. When the counter counts down to zero it produces an output pulse that occurs at the time the object reaches the given location. Operation of the time delay computer is independent of object speed.

Abstract: The plasma switching stage of a radar receiver protector is simplified and improved by the utilization of a halogen gas filled quartz container and a "keepalive" electron source. The container is configured as a capillary stem filled with low pressure chlorine gas and provides the active switching element in the signal waveguide portion of the receiver protector. An enclosed r.f. energy source in combination with the capillary stem creates a copious and steady free electron supply. The r.f. exciting field used to activate the "keepalive" plasma is enhanced by a coaxial re-entrant cavity located on the top wall of the receiver protector waveguide.

Abstract: The simulation of systems generated electromagnetic pulses in a space environment for satellite testing is accomplished by means of a spherical test chamber that is coupled with a pulsed x-ray source. Resonance damping is provided by a spherical resistive resonance suppression grid that is placed within the test chamber and spaced from its inner surface by a distance that effects optimum damping of electromagnetic wave energy at the fundamental chamber standing wave frequency. Electrons generated from surfaces within the chamber are suppressed by a spherical resistive electron backscatter suppression grid disposed between the resonance suppression grid and the chamber inner wall and by coating the inner chamber wall with electron emission suppression material.

Abstract: In-situ, non-destructive monitoring of semiconductors during laser annealing process is realized by a method the steps of which include: positioning a surface acoustic wave device adjacent to the semiconductor being annealed and in intercepting relationship with the annealing radiation, the surface acoustic wave device substrate being transparent to the annealing radiation; affixing an electrical contact to the top surface of the semiconductor; applying an r.f. input to the surface acoustic wave device; and measuring the transverse acousto- electrical voltage on the electrical contact. The surface acoustic wave propagation surface of the surface acoustic wave device is in close proximity to the bottom surface of the semiconductor and interaction of the electric field that accompanies the propagating surface acoustic wave with the charge carriers of the semiconductor produces the transverse acoustoelectric voltage. The transverse acoustoelectric voltage is thus a function of the semiconductor conductivity.

Abstract: The bandwidth limitation in space fed phased arrays (that results from the use of phase shifters to implement beam steering) is overcome by a lens arrangement in which independent feeds are provided at the focal plane of the lens. Each feed generates a collimated beam in a different spatial direction. Each beam can then be steered about its central position by means of phase shifters, while retaining a substantially improved bandwidth. An algorithm is derived for designing three-dimensional (3D) microwave lenses with line source feeds by stacking a number of identical two-dimensional (2D) parallel-plate, wide-angle constrained lenses into a cylindrical antenna structure. This lens design provides focused beams over a wide range of scan angles in both elevation and azimuth with only small optical aberration. A wide variety of lens designs can be achieved through this algorithm, dependent upon the constraints which are selected for the 2D lens counterpart.

Abstract: A mechanical sealing assembly for establishing a water-tight, rodent/insect-proof seal between a plurality of elongated members (e.g., cables, tubes, etc.) and a conduit carrying the elongated members. The sealing assembly includes a resilient, compressible, cylindrical rubber bushing and a pair of flat plates on opposite sides of the bushing. The bushing has a plurality of longitudinal receiving openings therein and a plurality of radial slots extending from the perimeter of the bushing into the receiving openings for enabling the elongated members to be forcibly inserted by way of the slots into the receiving openings. Each of the flat plates includes several sections which are assembled together in an interlocking fashion to surround the elongated members and define openings for the passage therethrough of the elongated members.

Abstract: Uniform background charge subtraction in a radiation sensing array is realized by removing the background charge from the array detectors several times during each array integration time. Radiation sensing arrays of the type to which the method of the invention can be applied include a radiation sensor with a charge storage reservoir to which there is coupled a CCD output register having a channel with multiple charge storage sites. Signal background and bias charge is accumulated in the charge storage reservoir and transferred to a CCD storage site by a transfer gate. Charge in the CCD storage site can be shifted to another storage site in the CCD channel or it can be dispersed to drain by means of a drain barrier gate. According to the method of the invention a number of times during each array integration period the charge accumulated in the charge storage reservoir is transferred to a CCD charge storage site and then returned in part to the reservoir leaving a metered amount in the charge storage site.

Abstract: Replication in a magnetic bubble device is realized by a method of operation that is based on the principle of stretching, then cutting the bubble by the control current pulses. In this mode of operation, the bubble is stretched, under the influence of a large amplitude current pulse in the control conductor, between the switch propagate element in the primary track and another propagate element in the secondary track. The bubble strip is let to propagate for a fraction of a field cycle after which a second large amplitude narrow pulse is applied to the control conductor to sever the bubble strip into two parts. One part propagates as would the original bubble in the primary track and the second part propagates in the secondary track.

Abstract: An electro-optical crystal slab defining an optical waveguide modulator between two parallel boundary regions. Each boundary region has electrodes next to the channel and a doped area immediately outside the region. An electric field applied via the boundary electrodes creates a low index of refraction and transmitted light remains in the waveguide. When boundary fields are removed some light is absorbed by the doped material. Fields applied to compensating electrodes lower the index of refraction of the doped area so that the light is directed into it and absorbed. Any light passing through the absorbing material is contained in an alternate channel.

Abstract: Nondestructive testing and analyzing of surface acoustic wave (SAW) interdigital transducers is accomplished by observing electro-optic changes in a layer of liquid crystals produced by the effects of electric fields resulting from an electrical potential applied to the transducer. A display cell comprising a liquid crystal layer covered with a gold coated glass coverplate is fabricated on the surface of the SAW substrate under test. The assembled display cell is positioned for viewing under a microscope equipped for vertical illumination by a light source and a beam splitter. Polarizers are positioned in the illumination and viewing paths. An electrical potential is applied to the SAW device transducers and in some instances to the coverplate gold coat. Electro-optic effects produced in the liquid crystal by the electric field effects of the applied electrical potential are viewed through the microscope and are analyzed and interpreted.

Abstract: Graphic data entry in an interactive graphic display system is achieved by means of an apparatus that provides automatic centering of a pointing laser beam on a hand held cursor. The graphic display system provides a means for displaying and comparing through superposition full size overlaid graphical data and projected graphical data on a common display screen. It includes a steerable pointing laser the beam of which scans the display screen in response to a laser beam deflection circuit. The system also includes laser beam position sensing and indicating circuits which accurately measure the laser beam position. Centering of the laser beam on the cursor at the display screen is accomplished by dithering the beam uniformly about its average position in a discrete dither pattern and utilizing the dither pattern to determine misalignment of the beam's average position with respect to the center of the cursor.

Abstract: The differential linearity of an analog-digital converter is measured by a test method that eliminates the need for precision calibrated test equipment. A triangle waveform with a pseudo random period is applied to the analog/digital converter input. The waveform has a uniform amplitude probability density function. Therefore, any analog/digital converter input voltage has an equal chance of being sampled by the analog/digital converter. The number of times each possible analog/digital converter output code word occurs is counted by a microprocessor. These numbers are a direct measure of differential linearity with an accuracy described by the theory of repeated random sampling.

Abstract: Adaptive filtering of narrow band interference is achieved by means of a circuit that automatically estimates the amplitude and frequency of narrow band interference in the presence of a wide band signal. The estimate of the interference is subtracted from the input signal. Sample data baseband signals are processed in order to estimate the frequency and amplitude of interfering signals. The filter employs two tracking loops which act together to provide a second order tracking function. The first tracking loop provides a smoothed estimate of the interference. The second tracking loop provides a signal that adjusts a phase shifter to track the interfering signal frequency. Subtraction of the estimated interference from the input signal provides an output signal with attenuated interference and that is only slightly distorted.

Abstract: Antenna alignment in troposcatter systems is accomplished by: (1) nutating the antenna receiver beam with a sinusoidal nutation signal to induce envelope modulation on the received signal; (2) crosscorrelating the envelope of the received signal with the nutating signal; and, (3) aligning the average angle of the antenna receiver beam into the position where the crosscorrelation goes to zero.

Abstract: A waveform capable of jamming some or all of the channels of a multiple channel receiver is developed by a multi-tone jammer that uses a digital counter and a digital/analog converter to generate a ramp voltage for a voltage controlled oscillator (VCO). The output of the VCO is modulated by a pin diode attenuator. The attenuator is controlled by a pattern generator synchronized with the digital counter to blank the retrace and any portion of the sweep to provide a partial band tone jamming spectrum. The digital counter is driven by a MHz reference signal generator and the sweep repetition rate is greater than the circuit bandwidth.

Abstract: Perceived atomic resonance frequency error resulting from microwave power level changes in atomic clocks is eliminated by controlling the device's microwave power source output in response to deviations from a fixed frequency relationship between the main atomic peak and a sidelobe peak of the atomic beam frequency spectrum. This is accomplished by a microwave power control servo system that includes a time sharing interrogation circuit for detecting and monitoring the frequencies of the main atomic peak and the sidelobe peak and a comparator that compares the frequencies of the main atomic and sidelobe peaks and generates a feedback control signal in response to frequency differences between the two that deviate from a fixed difference frequency. The feedback signal is used to control the microwave power source output in a manner that constrains the main atomic peak and the sidelobe peak at a fixed offset frequency.