Abstract: A feed-forward system for reducing the distortion products from a device such as an amplifier, wherein samples of the distortion products from the output of the device in one or more frequency bands whose bandwidths are less than that of the device are extracted, adjusted in amplitude and phase and subtractively combined with the device output to produce a system output in which distortion in the frequency bands is reduced.

Abstract: A canceler for decorrelating one set of signal samples called the main set rom another set called the auxiliary set taken from the same domain. It frequency-translates the signals on their intermediate frequency (i.f.) carrier down close to DC using a local oscillator outside one band edge of the signal and samples the resultant signal at a rate equal to twice the information bandwidth or greater and permits using real rather than complex samples. These samples are then converted to digital information in analog-to-digital converters and are processed digitally at a clock rate equal to twice the information bandwidth or greater. The main signal is processed as above but the auxiliary signal is translated down using the same local oscillator signal and, with the same local oscillator signal phase shifted 90.degree. to obtain an inphase and quadrature signal on the same carrier frequency prior to analog-to-digital conversion.

Abstract: A waveform recorder wherein surface acoustic waves excited in a piezoelecc-insulator-semiconductor layered structure produce a traveling electric field in the semiconductor substrate. Charges stored in the traveling potential wells and representing the instantaneous amplitude of a waveform to be recorded are transferred at high speed and density to different respective spatial locations. Because each successive well represents a different time instant of the waveform, the different spatial locations correspond to different times. The output signal from each of the locations can be selectively delayed before application to a display oscilloscope to enable display of the waveform at a rate many times slower than the actual frequency of the signal waveform.

Abstract: A feed-forward system for reducing the distortion products from a device h as an amplifier, wherein a sample of the device input signal is subtractively combined with a sample of the device output signal to produce a sample of the distortion products. The distortion sample is adjusted in amplitude and phase and subtractively combined with the device output to produce a distortion-reduced system output. A synchronous detector correlates a sample of the system output, in which the proportion of distortion has been increased, with another sample of the distortion products to produce control signals for a modulator which adaptively adjusts the amplitude and phase of the distortion sample subtractively combined with the device output.

Abstract: A power meter for non-destructively measuring the power of a high energy er beam. The power meter includes a cell disposed in the flow path of a gas containing a laser radiation-absorbing species. The absorption coefficient of the absorbing species is small enough to allow the beam to pass through the cell essentially unaltered. The concentration of the absorbing species is modulated to modulate its absorption of the laser beam power and produce acoustic waves in the gas which can be detected and measured to give an absolute measurement of the power in the high energy laser beam.

Abstract: A digital pulse expander-compressor for use in pulse compression radars and having the advantage of precompression bandwidth tolerance. The pulse expander-compressor exploys a discrete Fourier transform circuit and multi-stage delay line feeding inputs x(n) to the discrete Fourier transform circuit to generate outputs in accordance with the formula ##EQU1## where n is the sequence number of the clock pulse; N is the number of delay stages plus one; and k is the number of the output subpulse from the transform circuit. An arrangement of delay stages differentially delays the output subpulses from the discrete Fourier transform circuit, and a coherent summer adds the real and imaginary parts of the signals from the delay lines. The delay stages delay the subpulse s(k), O.ltoreq.k.ltoreq.N/2-1, by ##EQU2## clock pulse intervals, while delaying the subpulse s(k), N/2+1.ltoreq.k.ltoreq.N-1, by ##EQU3## clock pulse intervals. The subpulse s(k), k=N/2, is not used.

Abstract: An electron cyclotron maser high-frequency generator/amplifier having a cavity resonator positioned in an axial magnetic field. A spiralling beam of relativistic electrons is injected into the cavity and stimulated emission of radiation by the electrons takes place at the frequency of a wave mode supported by the cavity resonator. The transverse efficiency, defined as the average electron energy loss divided by its initial transverse energy, is maximized by disposing a shaped iron collar about the cavity resonator to provide an axial magnetic field in the cavity resonator whose amplitude increases in the beam direction-of-travel. In an alternative embodiment, the transverse efficiency is maximized by tapering the inner wall of the cavity in the axial direction to provide a wave-mode in the cavity resonator whose electric-field amplitude increases in the beam direction-of-travel.

Abstract: An optical system for frequency-modulation heterodyne detection of an acoustic pressure wave signal. An optical beam is directed into a Bragg cell outside of the fluid medium in which acoustic signals are to be detected. The Bragg cell modulates the incident beam such that two beams of different frequency exit the cell. The two beams are directed into an input optical fiber and the resultant combined beam is transmitted over a desired distance to a fiber optic transducer disposed in the fluid medium. The transducer includes two coiled optical fibers, a reference fiber and a signal fiber, each of which has a different sensitivity to incident acoustic pressure wave signals. The transmitted beam is directed from the input optical fiber through a power divider which splits the beam into two equal parts, one part passing through the reference fiber, the other part passing through the signal fiber. A filter in the signal fiber transmits only a fraction of the light at one of the two frequencies.

Abstract: An underwater sound generator composed of a ferrofluid contained within a toroidal container which has a rigid bottom and top and elastic cylindrical side walls. A coil of wire links the toroidal container and is adapted to be connected to a dc bias source to produce a biasing magnetic field, H.sub.BIAS, which drives the magnetization of the ferrofluid well into saturation. Two oppositely wound coils of wire respectively link the inner side wall and the outer side wall and are adapted to be connected in series to an ac signal source to produce a time-varying magnetic field, H.sub.AC, which modulates H.sub.BIAS. The wires are equally spaced in the volume occupied by the ferrofluid. The gradient of H.sub.AC in the radial direction provides the time-varying force on the ferrofluid. The resulting ferrofluid motion in the radial direction is transmitted through the outer elastic side wall to supply acoustic motion to the surrounding water.

Abstract: An apparatus for mounting a device defining a mounting plane so as to be ectively rotatable about mutually perpendicular axis with respect to a base member defining a base plane. The first axis is defined by a transverse pin fitted to the gimbal and rotatably secured to the base plane. The mounting plane is tilted about either axis by driving an associated, diagonally opposite pair of support arm members linearly so as to foreshorten one support arm member to the extent that the other is lengthened.

Abstract: A scanning radar system having the capability of taking a number of succeve looks at the same range and angle resolution cells with several millisecond time intervals between looks. The scanning radar system includes a pulsed transmitter, a receiver, and an array of energy beam radiators having individual beam paths with associated centerlines. A commutator switch and a duplexer sequentially connect a different one of the radiators to the pulsed transmitter at the beginning of each pulse repetition period and to the receiver during the subsequent interval between pulsed transmissions. A motor rotates the array of radiators as a unit to cause the beam path centerlines to rotate and scan the field of view.

Abstract: A magnetoplasmadynamic switch adapted to be coupled in parallel with an ictive energy storage circuit carrying current through an initially closed circuit interrupter. The switch includes an electrode spaced by a gap from an arcjet source which is triggered by a capacitor. The capacitor is connected to the arcjet source by a closing switch so that a plasma jet is created between the source and the electrode. The voltage on the capacitor is chosen such that the arcjet source current will equal the current in the energy storage circuit at the time when the circuit interrupter has completely opened. The circuit interrupter is opened after the plasma jet is established between the source and the electrode, and the energy storage circuit current is conducted by the magnetoplasmadynamic switch until the dielectric strength of the circuit interrupter reaches a satisfactory level. Another switch is then closed providing a low impedance conduction path parallel to the arcjet source current.

Abstract: A broadband directional transducer which provides a beam pattern that is essentially constant for all frequencies above a certain cutoff frequency, an acoustic pressure angular distribution that is virtually independent of the distance from the transducer and no side lobes, includes an array of isophase, omnidirectional electro-acoustic elements on a spherical shell, each element being amplitude-shaded according to the shading function ##EQU1## where n is a positive integer, and .theta. is an angle measured from the axis of the spherical surface to a shaded element.

Abstract: A scanning system wherein a linear array of N detector elements having a form spacing of X cm between their centers is oriented parallel to the line scan dimension of a raster so that each element of the array optically scans the entire field of view at a rate of V cm. per second. The detector elements are sampled every t.sub.s seconds where ##EQU1## k being an integer, and each produces, when sampled, an output signal proportional to the integrated energy exposure thereof between samplings. The output signals of the various detector elements are delayed as a function of each element's position within the array and the line scan rate. The delayed imaging signals add to provide an improved signal to noise ratio. The variability of the waveform of the composite output signal for smallsized distant targets is minimized by introducing a progressively increasing phase shift in the relative timing of the sampling signals and initial contact of the image at successive detector elements.

Abstract: A clutter filter which reduces by (N-1) the number of input pulses required or operation of an N-pulse MTI canceler when L>N consecutive filtered outputs are desired. The clutter filter includes the two channels of an N-pulse MTI canceler which weight and sum the in-phase and quadrature-phase components of N radar returns, and a pair of delay circuits which introduce a delay of N interpulse time periods to the N and subsequent in-phase and quadrature-phase components of the radar returns. The stored outputs of the two channels of the canceler and the consecutive outputs of the delay circuits are combined in a complex multiplier to generate the consecutive in-phase and quadrature-phase outputs of the filter. The clutter filter has utility in a multiple-stage filter system employing a Doppler filter as the last stage.

Abstract: A pulse compression decoder which oversamples by two the signal elements of received phase-coded signal, performs a pairwise average on the signal elements at intervals equal to 1/2 the width of a signal element, reverse-codes the pairwise averages, combines the pairwise averages to form a sub-accumulation signal, and performs a pairwise average on the sub-accumulation signals at intervals equal to 1/2 the width of a signal element to produce a compressed pulse having a high peak-to-side lobe ratio.

Abstract: A method of manufacturing a field-emitter array cathode structure in which substrate of single crystal material is selectively masked such that the unmasked areas define islands on the underlying substrate. The single crystal material under the unmasked areas is orientation-dependent etched to form an array of holes whose sides intersect at a crystallographically sharp point. Following removal of the mask, the substrate is covered with a thick layer of material capable of emitting electrons which extends above the substrate surface and fills the holes. Thereafter, the material of the substrate underneath the layer of electron-emitting material is etched to expose a plurality of sharp field-emitter tips.

Abstract: A rectangular waveguide to circular waveguide coupler and vice versa. The upler includes a first section of circular waveguide spaced by a gap from a reflective-plane conducting wall, the latter having a hole for passage of an electron beam if the coupler is used in a traveling wave tube, and a second section of circular waveguide disposed external to, and coaxial with, at least a portion of the first waveguide section and extending to the wall to provide a conductive boundary surrounding the gap. The region between the first and second waveguide sections forms an input port of the coupler; the first waveguide section forms the output port of the coupler. Electromagnetic waves in a TE.sub.01 coaxial waveguide mode are applied to the input port from a rectangular waveguide supporting the dominant TE.sub.10 mode. The second waveguide section has a cut-off determining dimension r.sub.e proportioned to support both the TE.sub.01 and TE.sub.

Abstract: A speckle interferometer including a beam splitter, a mirror in the object beam arm, a phase-conjugate mirror in the reference beam arm, a converging lens and a photographic film. Laser light scattered retro-reflectively from a rough surface under investigation and passed through an imaging lens illuminates the interferometer. Fringes occur upon sandwiching a pair of exposures of the interference pattern made before and after deformation of the rough surface. The relative magnitude of the displacements from the original position at different points of the surface can be determined from the position of the fringes.

Abstract: An optically pumped laser which is operative by photolysis of a rare gas (RG)-halogne atom (X) compound (RGX.sub.2) which creates lasing from the RGX* molecule the RGX* molecule being diatomic. This type of laser is gaseous but a solid fuel is used to supply the gas; therefore the system is self contained.