Abstract: A beamformer for an array of sonar transducers, or electromagnetic radiating elements, includes mixers for translating the signals received by the transducers to a lower frequency. The beamformer incorporates delay lines operating at a clock rate which is reduced in proportion to the decrease in frequency. Each delay line provides delays to the signals of corresponding ones of the transducers in accordance with the time of arrival of a wavefront of radiation upon the respective transducers. Phase shifters coupled between the mixers and the delay lines impart phase shifts to the transducer signals proportional to the respective delays to compensate for the lowering of the frequency.

Abstract: A signal processor for use with an array of antenna elements comprises a plurality of pairs of receiver channels which receive signals from respective halves of the array. The component of the signals resulting from noise, such as the noise generated within the ocean, is substantially decorrelated between the respective halves of the array, while a component of the signal obtained from a source of a desired signal is coherent between the two halves of the array. The signals in each pair of channels are translated to intermediate frequencies by mixing the signals with reference signals of differing frequencies in each of the respective pairs of channels. The translated signals in each pair of channels are then multiplied together to produce a signal of substantially constant amplitude which is suitable for detection, or for a bearing deviation indication.

Abstract: A traveling wave tube (TWT) has a slow wave structure in the form of a helix for amplifying the forward electromagnetic wave. The TWT is provided with an outer slow wave assembly for attenuating a backward wave to provide stability to the TWT. A set of ceramic rods are uniformly spaced circumferentially around the helix for supporting the outer slow wave assembly which is formed by an electrically conducting wire wound around the supporting rods. The wire is wound in a helical fashion with individual turns of the helix being spaced apart to form the outer slow wave structure. An electrically conducting cylinder surrounds the outer slow wave structure and is in contact therewith only at the sites of the rods. Dielectric slabs, having a slow wave structure such as a meander line disposed thereon, are inserted periodically around the outer slow wave structure in spaces between the winding and the cylinder.

Abstract: An array of sonic transducers, useful for medical ultrasonic imaging, has individual sections thereof separately coupled for forming separate beams of sonic energy which converge, respectively, to separate foci along a common axis of the beams. The ratio of the diameter of the radiating aperture of the array relative to a wavelength of the sonic energy is chosen to provide a moderate degree of focusing so that the depth of field at one focus blends with the depth of field of the next focus. Thereby, there is formed a continuous region of substantially uniform intensity of sonic radiation along the common beam axis. Circuitry is provided for selecting one or more specific foci dependent on the bounds of a selected region to be insonified.

Abstract: Lens testing charts using a vernier pattern, a sawtooth pattern, and a sinusoidally varying reflectance pattern are described and are used in conjunction with a lens under test to be focussed by said lens onto suitable high contrast film to provide an image from which the quality of the lens may be determined.

Abstract: In a preferred embodiment of the invention the audio signal is bandwidth limited before being differentiated to provide either a positive or negative signal (depending on the slope of the audio signal) to a comparator which provides a corresponding logical one or zero at its output. A digital logic circuit connected to the comparator output is clocked to provide a digital output signal transition from a logical one to a zero or vice versa if its input has changed from a logical one to a zero or vice versa at least once during the clock period. The clocked digital output of the logic circuit is provided as an input to a computer where it is stored. The digital data is subsequently read out of the computer and provided to a filter and integrator to provide an audio signal replica of the filtered input audio signal.

Abstract: An eye chart having a plurality of rows of letters where each letter is composed of a line-stroke having a plurality of adjoining black and white segments to provide an average reflectance which is the same as the reflectance of the gray background of the chart. Each row of the letters utilizes a different width line stroke (the line segments thereof are proportioned correspondingly). The sizes of the letters of each row are geometrically decreasing and are preferably in proportion to the width of the line stroke.

Abstract: A beam of sound, of sufficient amplitude for inducing a finite amplitude effect in water, is directed into a field of sound for interaction therewith to produce intermodulation products. Energy is removed from the sound field in the formation of the intermodulation products resulting in an attenuation of sound in the sound field.

Abstract: A process for fabricating polyimide membrane x-ray lithography masks is described. Thin membrane of polyimide is formed by spinning polyamic acid on a glass substrate and polymerizing in situ. The glass substrate acts as a holder and efficient heat sink during formation of gold absorber patterns on top of the polyimide. A support ring is then bonded to the polyimide, and the glass etched in dilute HF. Optically smooth polyimide membranes with thickness from 0.5 to 5 .mu.m are readily achieved. The method and resulting product is not limited to the above materials or to masks.

Abstract: Representation of a speech signal by its short-time Fourier transform and the application of this representation to the problem of time compression and expansion of speech are presented. A time-frequency representation for linear time-varying systems is applied to a model for speech production to formulate a quasi-stationary representation for the speech waveform. This representation has the property that simple time scaling of the parameters of the representation corresponds to changing the rate of the speech. Given a real speech signal, short-time Fourier analysis provides a technique for estimating and modifying these parameters. The results of the theoretical analysis are used to design a high-quality speech rate-change system which are simulated on a general-purpose digital mini-computer.

Abstract: A spectrometer capable of providing a predetermined wavelength of output light in accordance with a control voltage signal applied to a scanning element is described. The scanning element located at the grating image of the spectrometer is a small mirror attached to the rotor of a galvanometer whose angular position is accurately controlled by a closed-loop electronic control. The spectrum reflected from the mirror is passed through a slit to provide the output light of a predetermined wavelength. Selection of the waveform of the control signal allows the spectrometer to be operated as a dual wavelength spectrometer, to use a linear wavelength scan, or other wavelength scan patterns for absorbance analyses of a sample.

Abstract: An internally worn laryngeal prosthesis for laryngectomized patients is described. The prosthesis is worn internally at the end of a surgically constructed fistula leading to the base of the patient's vocal tract. Exhaled air powers a miniature vibratory mechanism whose output enters the vocal tract directly and supplies both a voiced and a voiceless sound source. A tube connects the other end of the prosthesis to the tracheostoma from which air from the lungs powers the prosthesis. The tube contains a valve which may be manually or automatically controlled to allow either speech or quiet breathing.

Abstract: Surface acoustic wave resonators are used to provide band pass filters. The length of each resonator is related to the lumped constant inductor and capacitor values of the components of the low pass filter equivalent. This invention allows high frequency s.a.w. type filters to be constructed by reference to already available inductor and capacitor values from tables of low pass filter designs.

Abstract: A hydrodynamically superior trawl door with increased efficiency in harvesting fish and reducing fuel expenditures is composed of curved steel panels, which may be of constant radius to allow for economy in manufacturing. The door approximates an ideal hydrofoil surface, presenting a streamlined surface to the flow of water and a relatively sharp hydrodynamic trailing edge, and allowing for a moderate angle of attack and a high lift coefficient. The door is hollow and may be airtight and contains a flood opening with a baffle to allow air to be trapped inside to provide, even when hydrostatically compressed, some measure of vertical stablity. Further, the water ballast is automatically jetisoned during hauling in. The bottom of the door is curved to allow easy clearance of seafloor obstructions.

Abstract: A planetarium projector and the method of making the projector is described wherein a light source is surrounded by an opaque enclosure having transparent spots or lines. The enclosure is fabricated from originally planar sheets of photographic film. The enclosure is preferably cylindrical however it may assume other shapes such as conical or a rectangular parallelepiped. The planar sheets of negative type of photographic film are patterned by exposure through a master transparent sheet of plastic on which star locations, zone plate lens, or lines representing geographical boundaries or other figures are drawn in opaque ink.

Abstract: A tone control circuit using only one potentiometer to provide bass or treble control is described. An integrator and a differentiator are connected to the input of the circuit and their outputs to the two ends of the potentiometer. Electrical connection between the potentiometer and the input is also made to provide a flat frequency characteristic component in the output signal.

Abstract: A process for fabricating polyimide membrane x-ray lithography masks is described. Thin membrane of polyimide is formed by spinning polyamic acid on a glass substrate and polymerizing in situ. The glass substrate acts as a holder and efficient heat sink during formation of gold absorber patterns on top of the polyimide. A support ring is then bonded to the polyimide, and the glass etched in dilute HF. Optically smooth polyimide membranes with thicknesses from 0.5 to 5 .mu.m are readily achieved. The method and resulting product is not limited to the above materials or to masks.

Abstract: A planar semiconductor optical waveguide, modulator, variable coupler and switch are described. The waveguide has an epitaxial layer on a semiconductor substrate. Two spaced strips of opposite conductivity type are implanted in the layer to form an optical waveguide channel in the space. By closely spacing two waveguide channels so that they have a common strip and a strip outside each channel, coupling is obtained between the channels. For a switch, the coupling length is such that substantially all the optical energy in the input channel is coupled to and emerges from the other channel. Reverse biasing one of the outside strips causes the optical energy to divide between the input channel and the output channel to provide output power modulation or variable coupling, and substantially complete transfer of power (switching) for a particular value of reverse bias.

Abstract: A method of selectively nickeling a layer of polymerized polyester resin is described. Patterns of electrically conducting nickel are produced on the resin surface by etching the surface of the resin prior to covering the etched surface with a patterned layer of unetched resin which exposes the etched resin in the regions in which metallization is to occur. A palladium plating solution followed by an immersion boron-nickel bath provide the metalization on the etched regions of the resin.

Abstract: A deceleration controlled and limited brake incorporates a deceleration sensor to limit the amount of braking torque which can be manually applied to a disc type brake. The deceleration sensor is a weighted lever which responds to deceleration by tending to disengage a disc clutch which the activated normal brake lever is engaging. The clutch force is applied at the end of a lever to provide the torque to engage the disc brake and provide deceleration of the vehicle containing the disc brake. Mechanical advantage together with deceleration control is provided by this clutch-brake assembly.