Abstract: A multi-element antenna formed of symmetrical paired elements symmetrically positioned in a concentric arrangement. The proximate ends of the elements are interconnected through a switching network which, when properly biased, permits exciting the element of the antenna to obtain right-hand or left-hand circularly polarized radiation.

Abstract: The invention comprises a varactor tuning diode for use in a voltage controlled oscillator with a fast-hopping capability and short settling time for resonant frequency changes wherein the varactor tuning diode comprises an MOS structure with an oxide layer with thick and thin segments contiguous with and below the conductive metal layer, a permanently inverted P+ silicon area and a space-charge region terminating at the oxide layer a significant distance away from the planar PN junction such as to isolate the surface effects and bulk effect.

Abstract: A slant record/helical scan playback certifier for high speed magnetic tape certification including a signal generator for producing test data, a slant record head for recording the test data onto magnetic tape, a plurality of helical scan playback head for reproducing and transmitting the test data recorded in the magnetic tape, an error detector and error counter for detecting and counting the test data errors found on the magnetic tape and an error collection reporting system for collecting and reporting the test data errors found in the magnetic tape. Further disclosed are a preamplifier and an amplifier for amplification of the test data transmitted by the helical scan playback head.

Abstract: A discrete fourier transform direction finding apparatus for performing a direction finding function on signals received through two antennae separated by a known distance. The outputs of the respective antennae are connected to first and second receiver channels which convert the received signals down to baseband and provide orthogonal I and Q channel outputs. A common local oscillator is used to maintain phase coherency between the channels and AGC signals are provided to maintain identical delays in the receiver RF paths. The processed signals from each receiver channel are than fed into a respective charge coupled device Chirp-Z transform (discrete fourier transform) circuit to produce real and imaginary components of the received signals. These signals are then converted to digital form and are used by subsequent circuitry to determine the angle of arrival of the received signal.

Abstract: A microwave frequency synthesizer which simultaneously provides increased frequency coverage, reduced channel spacings and improved settling times with a single phase-locked-loop. A VCO and a parametric divider enables a wide frequency coverage to be used in a phase-locked-loop. The fast hopping capability is primarily derived from the wide loop bandwidth which, in turns, is permitted by using a high reference frequency. The small channel spacings are created by using a 90.degree. phase shifter installed in the feedback path of the phase-locked-loop. The 90.degree. phase shifter permits channel spacings as small as 1/4 the reference frequency value.

Abstract: A system is described for using the modulation of the phase of a RF carrier as means of transmitting information. The RF input is split into four quadrature components each of which is passed through individual amplitude control attenuators and then summed in a combiner to create the required phase-controlled RF signal. The resultant signal is then amplified in an RF signal amplifier chain as required to achieve the desired output level. The RF output level is sampled and routed back to an in-phase splitter the output of which is compared to the corresponding individual quadrature components of the unmodulated RF signal to generate a signal which is compared with a processor generated modulation reference signal in a control loop amplifier and the resulting error signal is applied to the individual attenuators to adjust the output amplitude of each quadrature component. The quadrature components are then combined to obtain the desired phase-modulated RF output signal.

Abstract: A method for establishing and maintaining a nodal network in a communication system is described using a network connectivity matrix at each node of the network. The network connectivity matrix has a plurality of channels each corresponding to a node of the network and storing nodal information about the connectivity status of the node in the network. Each channel (row) of the network connectivity matrix at each node includes a first field for storing data indicating whether a usable line-of-sight (LOS) transmission path exists between the node and each other node of the network, a second field for storing data indicating when the row was last revised, a third field for storing the identification of the most recent transmission received by the node and a fourth field for storing data indicating a quality of the transmission path between the node and each node within LOS of the node.

Abstract: A method for predicting and monitoring the takeoff performance of an aircraft uses information from one or more previous takeoffs of the aircraft to generate a prediction of the takeoff performance for the current takeoff. In the preferred embodiment, a takeoff profile for the current takeoff is generated and includes information about predetermined characteristics of the aircraft and information about ambient conditions at an airport from which the takeoff is being monitored. Expected performance data for the current takeoff is then generated from the takeoff profile and used to select a set of actual performance data previously stored from the one or more previous takeoffs. A selected "best fit" actual performance data set is then displayed in an appropriate fashion. Upon takeoff, a set of monitored performance data is generated as a function of one or more of sensed takeoff parameters.

Abstract: A passive load mitigation system for supporting transducers on a body moving through a fluid stream is described. According to the invention, a streamlined aerodynamic surface for supporting the transducers is attached to the body via a pivot axis. The axis supports the surface in a torsionally unrestrained manner in at least one rotational degree of freedom about the pivot axis. Therefore, as the body moves through the fluid stream, the surface remains substantially parallel to the plane of the stream. Aerodynamic stability is ensured by forming the surface with substantially trapezoidal or parallelogram shaped sidewalls and by mounting the surface on the pivot axis such that the surface's aerodynamic center is located downstream of the pivot axis. Flutter is prevented or substantially reduced by increasing the surface's bending stiffness or by incorporating ballast weights on a tip pod attached to a portion of the surface.

Abstract: A direct drive servo valve includes a valve housing having a cylindrical bore and a valve spool mounted for movement in the bore for controlling fluid flow through said valve housing. The valve spool has a drive well located in the spool transverse of its longitudinal axis. A motor secured to the valve housing includes a rotor which is rotated in response to a drive signal applied to stator windings of the motor. A shaft attached to the rotor for rotation therewith includes a substantially spherical drive tip, the spherical tip positioned eccentrically to the longitudinal axis of the shaft and being close fitted into the drive well. In operation, as the shaft rotates through a given angular rotation, the spherical tip rotates in a circular path to provide linear displacement and rotational motion to the valve spool.

Abstract: A polarization twister for twisting the polarization of a wide angle incident electromagnetic wave is described. Specifically, the polarization twister includes a reflector for reflecting the wide angle incident electromagnetic wave, a dielectric substrate having a longitudinal axis, a spacer bonded on a first side thereof to the dielectric substrate and on a second side thereof to the reflector, and an array of meanderline conductive strips etched on the dielectric substrate. Each meanderline conductive strip has an axis extending at a 45.degree. angle with respect to the longitudinal axis of the dielectric substrate. In operation, the meanderline conductive strips serve to advance the phase of a parallel component of an incident E-field vector, and delay the phase of the perpendicular component thereof. Accordingly, the reflected field has its polarization twisted 90.degree. from the incident polarization.

Abstract: The back emf voltage of a motor is extracted from the applied motor voltage and motor current by means of a control system including a back emf sensor, an adaptive motor resistance circuit, and a position integrator. In the back emf sensor a corrected motor resistance signal, iR, a motor inductance signal, L di/dt, and applied motor voltage, V.sub.m, are input to a summing junction. The summing junction subtracts the motor resistance signal and the motor inductance signal from the applied motor voltage to compute the back emf voltage. To correct for variations in motor resistance, the adaptive motor resistance circuits demodulates and integrates the back emf voltage from the summing junction and the motor position signal input to the system. By integrating the back emf voltage from the back emf sensor in the position integrator a motor position output is obtained as a signal for servo position loop closure.

Abstract: A method for determining an acceptacle splice point is provided to facilitate splicing of a first segment of an audio signal to a second segment thereof. According to the method, an audio signal is converted into a sequence of samples and first and second edit points are selected along the sequence. The first edit point represents a nominal ending point of the first audio segment, and the second edit point represents a nominal starting point of the second audio segment. According to the method, a plurality of samples in a correlation window following the first edit point are weighted and correlated with a plurality of weighted samples in a correlation window following the second edit point for each position of the second edit point. The position of the second edit point is then shifted to the next sample in the sequence. After the correlation is calculated for each position of the second edit point, the location of an acceptable splice point can be determined.

Abstract: A method and apparatus for wideband frequency discrimination uses a first power divider for dividing an input signal into first, second and third output signals. First and second delay circuits are provided for receiving the first and second output signals, respectively, and in response thereto generate time-delayed versions of these signals. A second power divider is connected to the first and second delay circuits and to the first power divider for receiving the time-delayed versions of the first and second output signals and for receiving the third output signal and in response thereto generating a vector sum output of these signals. Signal processing circuitry is provided to process the vector sum output to generate a frequency-discriminated signal.

Abstract: A method and system for delivery ordnance to a target via a remotely piloted or programmable aircraft including a yaw-to-turn guidance system, a deployment and launching system and packaging for the aircraft are disclosed.

Abstract: A high power RF resistor for use, for example, as an isolation resistor in an RF hybrid splitter/combiner is formed on a thermally conductive substrate. A first insulating beryllia (BeO) layer extends over the substrate and has a top surface and a bottom surface. A first metallization layer extends over the top surface of the first insulating layer and includes a longitudinally-extending gap. A second insulating BeO layer is positioned above the first insulating layer and includes a top surface, a bottom surface and first and second side surfaces. A second metallization layer surrounds the bottom surface and the first and second side surfaces of the second insulating layer and has a longitudinally-extending gap, the gap in the second metallization layer positioned to be in alignment with the gap in the first metallization layer. This structure forms a Faraday shield between the resistive layer and ground to thereby reduce the I.sup.

Abstract: A method and apparatus is provided for deriving the direction of a received signal from a signal source using first and second orthogonally-mounted loop antennas and an omnidirectional antenna. In operation, output signals from each of the antennas are generated and repeatedly supplied to signal processing circuitry in a cyclical fashion as the receiver is rotated to locate the transmitter. The amplitudes of the output signals from the first and second loop antennas are then compared to determine whether the signal source is located in a null of the second loop antenna. If so, a null indication signal is generated. The phases of the output signals from the second loop antenna and the omnidirectional antenna are compared to determine whether the received signal is being received in a predetermined region of the second loop antenna. If so, an ambiguity indication signal is generated.

Abstract: An adjustable, constant current power supply for use in electrically pumping negative impedance gas discharge lasers is disclosed. The power supply includes a voltage regulator and a constant current power source the output of the voltage regulator which is variable and controlled being connected to the input of the constant current power source. The output from the power supply is passed through a gaseous lasing medium located within a laser tube of the gas discharge laser in order to pump to the lasing medium. Be controlling the voltage fed into the constant current power source the current output therefrom can be altered in order to effectively vary the power output of the gas discharge laser.

Abstract: A digitally-controlled quadrature signal generator is provided having a frequency synthesizer for receiving a digital input signal and in response thereto generating an output signal having a predetermined frequency. The output signal is split to produce an in-phase (I) signal and a quadrature-phase (Q) signal. A first table look-up memory is provided for generating a predetermined phase correction signal for use in cancelling any phase error in the quadrature-phase signal. A mixer receives the phase correction signal and the in-phase signal and in response thereto generates a phase error signal. The phase error signal is then added to the quadrature-phase signal to thereby cancel the undesirable phase error. Moreover, programmable attenuator circuits or limiter circuits are provided to limit the in-phase and quadrature-phase signals and thereby cancel any undesirable amplitude error components therein.

Abstract: A high power tunable filter, for use in a frequency hopping system, is described and includes a transmission line having an input for receiving a high power level input signal to be filtered, and an output. The filter includes a plurality of resonators, each parallel-coupled to the transmission line, and driven by an associated electronic tuning network. Each of the electronic tuning networks includes a plurality of tunable reactive elements and PIN diodes, each PIN diode connected to one of the tunable reactive elements to enable this diode to connect its associated tunable reactive element in and out of the tuning network, thereby controlling the resonant frequency of the resonator associated with the tuning network. An electronic control circuit is also provided for controlling the frequency of the tunable filter.