Abstract: A digital frequency synthesizer for synthesizing a selected frequency or a library of preselected frequencies in which a selected phase increment is fed at a clock rate to an adder and accumulating register in mutual cooperation as a digital integrator, the resultant period overflow of the register corresponding to the selected frequency of interest. An improvement is provided for reducing discrete spectral spurs in the spectral output of the synthesizer by means of preselectively randomly jittering the input to, or output of, the register, whereby the average periodicity of the register overflow for a selected frequency is not affected.

Abstract: A multiplexer for allowing multi-octave processing of sampled data by means of a common single-octave data processor. Sampled data is preselectively delayed, corresponding to delay-coding thereof, and a multiplex switch samples the progressively delayed delay-coded data at progressively reduced data sampling rates, corresponding to lower octaves of interest. In this way the several octaves of data are interleaved or time-multiplexed. Similar multiplexing within the single-octave data processor corresponds to frequency multiplexing of the time-multiplexed multi-octave data, whereby the single bandwidth limit processor may handle such multiple-octave data.

Abstract: A four-port digital complex multiplier useful for FFT butterfly arithmetic units and in which ROM's are employed as square function look-up tables. Each of the four ports is responsive to a respective one of the component values of two complex numbers. The square-function look-up memories are responsive to various ones of the input ports and cooperate with quarter-square-multipliers to provide component complex products. An output subtractor and an output summer, responsive to mutually exclusive pairs of the quarter-square multipliers, provide a respective real and imaginary component of the product of the two complex numbers.

Abstract: A device for the correction of signal distortion occurring in a signalling channel. Compensatory amplitude adjustment is made to a sampled signal in accordance with the statistical deviation of the signal from a preselected statistical model. Signal sampling means employs the sampled signal as a write-address for generating a statistical amplitude distribution function. Inverse distribution function means, responsive to addressing by the distribution function, provides an output signal of compensatorily modified amplitude.

Abstract: A fully-parallel digital arithmetic device for obtaining the square, C.sup.2, of a value, C, via parts of the value C and involving a reduction in memory requirements. Three square function ROM's are employed, one responsive to the most significant-bits half of a parallel input, the second ROM responsive to the least-significant bits half of the parallel input, and the third one responsive to the sum of said most significant bits and least-significant bits. The outputs of the square function ROM's are then combined and scaled to effect a square by parts of the applied input value, C. A pair of such arithmetic devices may be advantageously combined to economically effect the product AB of two values, A and B, in the manner of a quarter square multiplier.

Abstract: A position sensing element forms a reactance (inductive or capacitive) in the L/C tuning circuit of an oscillator. The reactance varies as a function of the position of the sensing element relative to a predetermined object. This causes the resonant frequency of the oscillator to vary as a function of the position of the sensing element. The output of the oscillator is squared to provide a square wave signal, the frequency of which is a direct function of the position of the sensing element relative to the predetermined object.

Abstract: A speed regulator or governor for an engine. The governor utilizes the approximate digital equivalent of a lead and a lag feedback network in combination with a stored, digital, nonlinear look-up table, or other nonlinear means, to control engine speed. The governor controls the engine at different fixed engine speeds in response to demand, or at continuously variable engine speeds in response to demand.

Abstract: An inertial measuring unit which precesses about the direction of apparent acceleration as a consequence of the introduction of a mass unbalance to each of the gyroscopes in the inertial measuring unit. The mass unbalances and the rotational moments of inertia of the gyroscopes are carefully controlled so that all gyroscopes within the inertial measuring unit precess at the same rate about any apparent acceleration. The precession of gyroscopes causes certain of the gyroscope errors to be averaged about zero thus reducing the error in the inertial measuring unit. The effect of precession upon the spatial orientation of the inertial measuring unit is compensated for by sensing the apparent acceleration and computationally compensating for the precession due to such acceleration.

Abstract: An improved organization for a FFT analyzer (or periodic function analyzer) having a reduced computing complexity. A modified organization comprises a simplified butterfly arithmetic unit in which the usual two coefficient registers or memories are required. By utilizing the registers as sources of a respective sum of and difference between sets of phase-shifted cosine values, the mechanization of the complex multiplier for such arithmetic butterfly unit in microcircuit or "chip" form may be further simplified to two controllable accumlators controlled by an exclusive-NOR gate logic system responsive to the states of the complex sampled inputs of a sampled signal epoch of interest. In this way, a more efficient and higher speed device is provided for the multiplication of complex variables.

Abstract: An error feedback circuit is employed in a digital filter to significantly lower noise in the output by feeding back the least significant (roundoff) output bits of the quantizer rather than throwing these bits away as is done in the prior art. The feedback circuit for accomplishing this end result includes a digital delay circuit which receives the roundoff bits and delays these bits for a sampling sequence (Z.sup.-1) (as is also done for the rounded bits), a multiplier which multiplies the output of the delay circuit by a predetermined integer and an adder which subtracts the output of the multiplier from the delayed filtered digital output signal which has been multiplied by a predetermined constant.

Abstract: Signalling means for enhancing the performance of automatic fingerprint identification systems by reducing system response to non-fingerprint-like regions within an image field pattern of interest. A two dimensional generalized sequency analyzer, such as a fast Fourier transform machine, responsive to a binary coded image signal identifies discrete frequency terms occurring within a selected bandwidth corresponding to a spatial frequency region of interest, associated with a fingerprint image. Logic means, responsive to the sequency analyzer, further identifies the relative energy levels of the bandwidth-limited spectral content of the binary coded image signal to signal the identity of a non-fingerprint-like region within the scanned image.

Abstract: A journal-type bearing the shaft member of which is divided into two or more cylindrical sections having their axes offset from each other and from the rotational axis thereof. As the shaft member rotates, viscous forces act upon said cylindrical sections to create a self-induced stabilizing load upon the bearing.

Abstract: A detection system for a ring laser gyro includes an array of photo-diodes mounted in the path of the laser beams, preferably on one of the laser mirrors. The outputs of the photo-diodes are selectively fed to first and second differential amplifiers to provide first and second outputs in quadrature relationship which represent the fringe or beat signal patterns generated between the clockwise and counter-clockwise rotating laser beams. An intensity signal for use in tuning and adjusting the laser for maximum output is generated from the very same diodes utilized for generating the quadrature related fringe signals. This end result is achieved by placing the terminals of the diodes not connected to the differential amplifier in parallel with each other and placing an amplifier in the current feed path for these elements, thereby providing a signal to the amplifier representing the sum of the photo-diode currents.

Abstract: A coherent optical adaptive system employs phase conjugation for locking the beam of a phased array of laser transmitter to a target, focusing the beam on the target and compensating for distortion and disturbances both within the system and in the propagating medium between the system and the target. A first diffraction-limited lobe of the beam is locked on a real target to track the real target. Simultaneously a second diffraction-limited lobe is directed to a location having a predetermined offset with respect to the target and relative energy of the two lobes is selectively adjusted. A signal component representing a fictitious target that is offset by a predetermined amount from the real target is summed with the signal received from the real target, the phase of the sum is compared with the phase of a reference, and the phase of the transmitted signal is adjusted so as to null the difference between the sum and the reference phases for each of a number of channels.

Abstract: An adaptive filter for sonar signals which operates on the complex spectral components of the received signal, which signal has been transformed into the frequency domain by means such as the Fast Fourier Transform. The adaptive filter consists of a plurality of component filters, each of which operates on a single spectral component of the received signals. The transfer coefficient of each component filter is described by a complex number and is adaptively adjusted by means of a computational feedback loop. The feedback loop compares the product of the transfer coefficient and the complex spectral component of the received signal from a prior frequency transformation cycle, with the present spectral component to obtain an error signal. The error signal, in turn, adaptively alters the magnitude and phase of the transfer coefficient.A plurality of such component filters operate together to adaptively filter, in the frequency domain, the entire spectrum of the received signal.

Abstract: This invention concerns a navigation system of the type utilizing proportional navigation guidance laws to guide an aerodynamically controlled body tracking a target, and particularly relates to a navigation system mechanization wherein necessary body-to-target line-of-sight rate-of-change information with respect to an inertial reference is developed implicitly, in part by using system optics and detector elements that are fixed to the guided body rather than to a body-mounted, inertially stabilized platform, to obtain stabilized guidance system tracking.

Abstract: A system, and method, is disclosed for substantially increasing the dynamic range of contrast of an input sequence of pixels representative of an image. In a preferred embodiment a first circuit is responsive to an input sequence of pixels representative of an image for developing bias and gain parameters. These bias and gain parameters are respectively utilized by first and second function generators to generate bias correction signals and gain correction signals, respectively. A delay circuit delays the input sequence of pixels to synchronize said input sequence with the bias correction signals and the gain correction signals. A first expansion circuit expands in a first direction the range of contrast of the delayed input sequence of pixels as a function of the bias correction signals to produce a first contrast expanded sequence of pixels.

Abstract: An autonomous navigational system for an airborne vehicle is disclosed which automatically updates its position and heading coordinates at each of a plurality of checkpoints along a preselected flight path. Prestored in a memory of the navigational system is a plurality of reference map images respectively associated with the plurality of checkpoints. Each reference map image is comprised of a plurality of terrain features associated with the terrain about an associated checkpoint. In operation, an acquisition unit senses an image of local terrain at each checkpoint. The relative sizes of reference and sensed map images vary with the mission requirements. A terrain feature extractor detects a plurality of terrain features contained in the sensed map image.

Abstract: A receiving system is described which has the capability of substantially cancelling broadband noise, such as impulse noise, atmospheric noise, electrical line noise and receiver front end noise, from a selected radio frequency passband. In a first embodiment, a desired radio frequency passband is selected and converted to a broadband intermediate frequency (IF) signal, which is applied in parallel to the inputs of first and second frequency channels. When broadband noise is present in the broadband IF signal, the first frequency channel develops a desired audio signal in the presence of an undesired first broadband noise signal, while the second frequency channel develops an undesired second broadband noise signal which is correlated with the first broadband noise signal. An adaptive transversal filter is responsive to the second broadband noise signal and to an output signal for adaptively developing an estimate of the first broadband noise.

Abstract: A monolithic solid state power controller generally comprises a power supply, zero voltage crossing detector, operator interface circuitry, current sensing and trip timing logic (having zero current detection capability), drive circuitry, and a power switch. The current sensing and trip timing logic functions are implemented in a monolithic device which provides flexible mode of operation of the switch, operator command validation, status and mode indication, drive enablement in synchronization with zero voltage crossing of the source voltage, and tripout operation in synchronization with zero current crossing in the load current. Both fast trip (in response to catastrophic overcurrent) and timed trip (in response to overcurrent conditions occurring over a period of time) capabilities are provided.