Abstract: A waveform generator is provided for generating a high frequency waveform. A pulse generator provides a pulse train at a low frequency. A pulse converter converts the pulse train into an alternatingly positive and negative groups of pulses. A bandpass filter passes the alternatingly positive and negative groups of pulses in a frequency band centered at the high frequency to output the generated waveform at the high frequency. When the groups of pulses are a pair of pulses, a sine wave is output from the bandpass filter. A pulse delay circuit can be used to variably delay the pulse train and thereby cause a phase change in the generated waveform.

Abstract: An apparatus for the determination of the wavelength and the detection of velength shifts in wavelength-encoded fiber sensors, such as Bragg grating sensors. The apparatus is implemented in fiber and uses a pair of tuned fiber gratings to provide a filter type function that tracks the wavelength component of a signal from a wavelength-encoded sensor.

Abstract: A fiber optic feed includes an optical circuit for providing at least one optical output signal modulated according to an RF source and an antenna interface for demodulating the at least one optical output signal and communicating with an antenna, wherein the optical circuit includes a coherent light source, an interferometer driven by the coherent light source for synthesizing a plurality of independently controlled planar beams, an optic modulator for frequency modulating at least one of the independently controlled planar beams according to the RF source and an optic pickup for producing the at least one optical output signal according to a superposition of the plurality of independently controlled planar beams, wherein the interferometer includes at least one beam deflector for angularly deflecting at least one of the plurality of independently controlled beams according to a beam control command.

Abstract: A heterojunction device, and a method for producing the device. A gate air bridge is formed at the mesa sidewall between the active region and the gate bonding pad to lower the gate leakage current. The device has a double recessed gate to reduce local fields in the vicinity of the gate. The fabrication method uses dielectric intermediate and final passivation layers to optimize the double-recess profile and control the extension of the high-field region between the gate and the drain. This combination increases the breakdown potential of the device, but minimizes the effective gate length of the device, preserving high frequency performance.

Abstract: An apparatus and method for optically testing an object, such as an optical etector whose pixels are an array of optically sensitive charged coupled devices. Two mutually coherent beams of light are interfered on the object to form an interference fringe pattern of sinusoidally varying intensity of preselected spatial frequency. The object's response at this spatial frequency is used to determine one point of the object's modulation transfer function at that frequency. This is preferably done by using the device's output to infer the coherence function of the fringe pattern, taking the Fourier transform of the coherence function, and determining the amplitude of the function at the spatial frequency of the fringe pattern. The process can be repeated for different spatial frequencies until one determines the entire modulation transfer function.

Abstract: A method for efficiently determining correlations between tracks and objects in a multi-target tracking system comprises defining a current track measurement estimate for each track, and building a measurement tree from the track measurement estimates. The estimates may be either point or volume measurement estimates. After defining the measurement tree, a measurement defining a volume measurement is taken of one of the objects. The measurement is correlated to one or more tracks by searching the measurement tree. The tree is searched by determining, at each node of the tree, if the volume measurement intersects the particular track point or volume measurement estimate associated with the particular node. Additionally, a search volume is associated with each node, such that the decision to search further paths emanating from a particular node is made by determining if the volume measurement intersects the associated search volume.

Abstract: A circuit link, and method for using link, for self initializing any device peratively connected to the link. An input signal is split into two portions, one of which is delayed so that the undelayed signal can transverse the circuit link before the delayed signal. A pair of quadrature splitters are operatively connected to one another to split and combine the undelayed and delayed signals in their turns, and recombine them in their turns, in a manner effective to cause one of the circuit link's outputs to be nonzero responsive to the delayed signal, and zero responsive to the undelayed signal, with the opposite result on the other circuit output. The undelayed signal is thus available to initialize any device requiring initialization, and the delayed signal, unperturbed by any such device, is thus available for use as the circuit link's ultimate output.

Abstract: A low frequency torsional transducer for the generation and/or reception of shear waves in a substantially solid medium. The transducer includes a spool like radiating structure to which are fixedly attached spaced piezoelectric elements. The elements undergo shear movement upon being electrically excited or upon receiving shear waves. This shear movement causes the opposite ends of the radiating structure to move torsionally. The torsional movement causes radiation of shear waves which can be detected by a sensor and used to determine the degree of support for shear wave propagation in the media.

Abstract: An interference photocathode includes a reflective substrate and interference layers disposed on said reflective substrate for selectively enhancing a first photoelectric yield of said photocathode when irradiated by radiation having a first wavelength relative to a second photoelectric yield of said photocathode when irradiated by radiation having a second wavelength. In one embodiment, the interference layers include a dielectric layer having a wavelength dependent effective thickness disposed on said reflective substrate such that said effective thickness for radiation having said first wavelength is an odd multiple of a quarter of said first wavelength and said effective thickness for radiation having said second wavelength is an even multiple of a quarter of said second wavelength. In another embodiment, the dielectric layer includes a layer of electrically conductive material and a dielectric material disposed between said layer of electrically conductive material and said reflective substrate.

Abstract: A field effect transistor having a buried gate, and one or more gates disposed along the channel between the source and drain, which cooperate to cause the electric field within the channel along its length to be more uniform, and have a lower field maximum. The geometry and/or doping of the channel can be varied to selectively vary the channel resistivity along its length, which also makes the field more uniform. Because of the more uniform field, electrons are exposed to a higher field strength nearer the source, and are accelerated to higher velocities more quickly, reducing the response time and increasing the frequency range of the transistor. Because the peak field is reduced, the transistor can carry more power without reaching breakdown potential within the channel.

Abstract: A gyrotron providing first and second microwave frequencies comprises a dual frequency cavity coupled between an electron gun and a waveguide. The electron gun, the dual frequency cavity and a segment of the waveguide are surrounded by a variable magnetic source having first and second operating states. The first state provides microwaves at the first frequency, while the second state produces microwaves at the second frequency.

Abstract: A method to enhance target detectability on a radar plan position indicator s described which includes the receiving of coherent pulse-burst waveforms from a target so that at least one complete burst is included in each dwell of a scanning surveillance fan beam. A fast fourier transform is performed on each returned coherent burst to form Doppler channels in predetermined range cells. The largest signal of the Doppler channels in each range cell is then selected and color coded. The color coded signals are applied to a plan position indicator whereby target images are viewable. Preferably, the Doppler channels are color coded over a rainbow spectrum so that a white background is produced and target images appear as tracks on a microprocessor-based raster-type plan position indicator. A continuity test and threshold test are also utilized so that target velocity and position are determined.

Abstract: A transmit/receive layer is provided adjacent to an array of antenna elements. The transmit/receive layer has an array of transmit receive modules, each module associated with one of the antenna elements. An analog to digital converter and a digital to optical converter of one of the modules couple an RF signal from the associated antenna element to optical fibers. An optical to RF converter in each of the modules converts an amplitude modulated optical transmit signal from an optical fiber to an RF transmit signal for transmission by the associated antenna element. Frequency down and up converters can be added to perform super heterodyne frequency conversion based on a reference frequency control signal transmitted over the optical fibers. At the ends of the optical fibers opposite to the transmit/receive layer, a receive layer, a transmit layer, transmit and receive beamforming layers, dedicated signal synthesizer, control signals, and amplitude modulated optical diode lasers and photodiodes are provided.

Abstract: The invention relates to an apparatus and method for generating target range, azimuth angle, or elevation angle output signals corresponding to an apparent beam in a multiple-feed monopulse radar system. The multiple-feed monopulse radar system according to the present invention includes a transmitter/receiver unit, an adder/subtracter unit and a video comparator/adder unit. The transmitter/receiver unit is used to generate first and second actual antenna beams. Echoes caused by such actual beams are received and processed to provide first sum and first difference signals and second sum and second difference signals corresponding to the first and second actual beams, respectively. These signals are then supplied to the adder/subtracter unit which adds the first sum and first difference signals to provide a result .SIGMA..sub.1 +K.DELTA..sub.1, subtracts the first sum and first difference signals to provide a result .SIGMA..sub.1 -K.DELTA.

Abstract: The present invention relates to a method and system for determining target elevation angle, altitude and range and the like in a monopulse radar system with reduced multipath errors. A transmitter/receiver unit receives monopulse sum and difference signals caused by echoes from targets. The sum and difference signals are then logarithmically-amplified in a logarithmic amplifier unit. A selector selects one of the sum and difference signals having the largest amplitude, and generates a selection signal indicating which of the sum and difference signals has the largest amplitude. The selection signal is provided to a search radar target tracking unit which determines whether a target at a given range interval and azimuth interval, for example, has been selected for tracking by an operator.

Abstract: A parallel to serial converter converts parallel detected signals output m a linear array of photodetector cells to an uncorrected serial signal. A comparator compares the uncorrected serial signal from the parallel to serial converter with a previous offset stored in a shift register. An offset difference output from the comparator is added to a previous offset output from the shift register to provide a new offset for input to the shift register. An operate adder finally provides a corrected serial signal by adding the uncorrected serial signal from the parallel to serial converter and the new offset output from the learn adder.

Abstract: A thermal dilation type optical flow sensor includes an optical heating sce for heating a flowing fluid and a sensor disposed in a downstream direction from said heating source wherein the sensor includes a probe for varying a reflected light according to the temperature of the probe, a Michelson type interferometer for measuring the temperature of the probe according to the phase of the reflected light, and a calculating device for determining the flow rate based on the temperature of the probe, the distance between the heating source and the probe, and the amount of heat produced by the heating source. In an alternative embodiment, a thermal dilation type optical flow sensor includes a reflecting probe disposed in a flowing fluid for reflecting an incident light with a phase varied according to the probe temperature, an optical heater for heating the probe with a predetermined heat, and a calculating device for calculating a flow rate based on the predetermined heat and the phase of the reflected light.

Abstract: An all-weather aircraft landing system includes a plurality of ground based passive 90.degree. dihedral reflectors for producing two-bounce reflected signals without ground reflections, and an airborne radar system which may transmit and receive "same sense" circularly polarized radiation, while completely rejecting "opposite sense" polarization returns or else utilizing them to indicate weather conditions. Radar clutter from objects such as rain, buildings and trees which produce opposite sense reflections are rejected by the "same sense" receiver or switched to an "opposite sense" receiver to provide weather/obstacle condition information. By properly orienting a plurality of 90.degree. dihedral angle reflectors of a particular size in a predetermined array pattern and tilt-angle adjacent a runway, the reflections from airborne radar signals are processed and displayed to provide a visual means for determining glide slope deviation and approach vector of the landing aircraft.

Abstract: A new planar, fully ion-implanted indium phosphide junction FET (JFET) fabrication process, utilizing n.sup.+ source-drain implantation, Be and Be/P p.sup.+ gate implantation, and nitride-registered gate metallization.

Abstract: A space based radar antenna array is provided which includes a loop antenna, a narrow cylindrical central support column, and an erectable support structure for connecting the support column to the loop antenna. The loop antenna, the support column and the support structure together form a generally umbrella-like apparatus which is erected to deploy the antenna. When deployed, the loop antenna assumes a circular shape oriented in surrounding relation to the central support column. In the non-deployed state, the loop antenna is collapsed adjacent to the support column. The loop antenna comprises a plurality of printed circuit, end-fire YAGI-UDA antenna units.