Showing papers by "Raytheon published in 1979"

The effects of noise on the autoregressive spectral estimator

Abstract: The autoregressive power spectral density estimator possesses excellent resolution properties. However, it has been shown that for the case of a sinusoidal autoregressive process the addition of noise to the time series results in a decrease in spectral resolution. It is proven that, in general, the effect of white noise on the autoregressive spectral estimate is to produce a smoothed spectrum. This smoothing is a result of the introduction of spectral zeros due to the noise. Finally, the use of a large-order autoregressive model to combat the effects of noise is discussed.

Coaxial electrical connector

Abstract: An electrical connector including a socket having an axis, a metal bellows connecting the socket to a support for adjustment of the axis in response to insertion within the socket of an axially misaligned plug or connector, the metal bellows further being an electromagnetic radiation shield between the plug or connector and the support.

Digital interpolation beamforming for low-pass and bandpass signals

Abstract: Digital time-domain beamforming requires that samples of the sensor signals be available at a sufficient rate to realize accurate time delays for beam steering. For many applications, this input rate, which may be significantly higher than the Nyquist rate required for waveform reconstruction, places stringent requirements on A/D converter hardware and transmission cable bandwidth. Recently, a technique referred to as digital interpolation beamfonning was introduced which greatly relaxes the sampling requirement and provides substantial hardware savings through more flexible design options. In this approach, the sensor channels need only be sampled at a rate which satisfies aliasing requirements. The vernier beam-delay increments are then synthesized using digital interpolation which can be implemented at the beamformer input or output to minimize digital processing complexity. Previously, this concept was presented for the case of "low-pass" signals. This paper extends this work by examining the relationship between interpolation and beamforming for the important class of "bandpass" signals. Specifically, sampling methods are discussed whereby the original waveform can be reconstructed from samples taken at a rate consistent with the bandwidth of the bandpass signal. Beamformer implementations are presented which utilize these bandwidth-sampling techniques in conjunction with interpolation and which compute beam output points at the generally low rate dictated by the signal bandwidth. The interpolation beamformer achieves time-delay quantization (beam-steering accuracy) independent of both the input and output sampling rates. This approach generally requires less hardware than conventional procedures. Interpolation falter characteristics dictated by the bandwidth-sampling procedure are described and efficient methods of implementation employing nonrecursive digital bandpass and low-pass filters are presented.

Interactive display system with touch data entry

Abstract: An interactive tabular display system having thin membrane switches positioned on the display surface around the periphery. The switches are categorized as select or function depending on the particular application software program in use. Touching one of the select switches causes a cursor to be displayed in the row adjacent to that switch; automatically, the cursor incrementally advances across that row sequentially underlining data items. When the switch is opened, the data item underlined is displayed in reverse video and additional data related to that item is displayed elsewhere on the display. The switches are provided with backlighting to provide illuminated touch points for use in dimly lit operational rooms.

Superresolution of uncorrelated interference sources by using adaptive array techniques

Abstract: By using adaptive techniques an antenna array can achieve an angular resolution of uncorrelated interference sources substantially greater than the aperture of diffraction limit. The antenna beam is scanned over the interference source locations, and for each scan condition the adaptive processor is allowed to reach its steady state. It is shown that for realistic ratios of interference strengths to system thermal noise, resolutions in excess of 0.25 times the Rayleigh limit can be achieved.

Laser gyroscope system

Abstract: A four-frequency laser gyroscope system having improved accuracy is constructed using a single solid block of low thermal coefficient of expansion material. A four-segment nonplanar propagation path provides a first frequency splitting. A second splitting is provided by a Faraday rotator having a thin slab of rare earth-doped glass positioned within an aperture in a permanent magnet. A narrow angle of incidence is provided for the beams of incident upon the output mirror to prevent cross coupling between beams within the output optics structure. Blocking the gaseous flow path reduces output frequency drift caused by contamininating particles.

Microprocessor having dual frequency clock

Abstract: A microcomputer having a microprocessor operative in response to a dual frequency clock, such microprocessor being adapted to read data stored in a programmable memory in response to address and read enable signals supplied to a programmable memory and being adapted to process such data in response to the clock pulses supplied by the dual frequency clock. The dual frequency clock produces clock pulses at a relatively low rate until such time as either a sensing device is activated or a time duration has passed, in which case the mine is to selfdestruct. When the sensor is activated the microprocessor commands the dual frequency clock to produce relatively high frequency clock pulses to enable the microprocessor to rapidly determine whether the mine should or should not be detonated. Relatively low power is consumed by the microcomputer during the period of time the processor is "counting time" and computing whether the predetermined period of time has arrived, i.e., whether the time for "self destruction" has arrived. When the sensor detects a potential enemy object, relatively rapid computation occurs in response to the relatively high frequency clock pulses to determine whether the mine should be detonated.

Laser pumped molecular lasers - Part I: Theory

Abstract: The density matrix formalism describing the interaction between a three level molecular system and two nearly resonant laser fields of arbitrary intensity is extended to include the molecular M -level degeneracy. Expressions for gain on the two possible relative polarizations of a laser pumped molecular laser are derived and its saturation behavior discussed. Numerical results for the 385 μm transition in D 2 O and 496 μm transition in CH 3 F are presented.

Specifications Of Raytran Material

Abstract: RAYTRAN infrared materials are formed by the chemical vapor deposition process which produces materials of unique characteristics and properties. This specification establishes optical and physical property requirements for polycrystalline zinc selenide and zinc sulfide made by this process.

Sources of and remedies for spectral line splitting in autoregressive spectrum analysis

Abstract: Spectral line splitting in autoregressive spectral estimation changes what should be a single spectral line into two or more displaced spectral lines. Fougere was the first researcher to note the existence of certain conditions for sinusoidal data for which splitting occurred. He proposed a complicated gradient-descent algorithm which seems to fix the problem for at least one sinusoid. It is shown that spectral line splitting is a result of estimation errors and is not inherent in the autoregressive approach. In particular, the interaction between positive and negative sinusoidal frequency components in the Burg reflection coefficient and Yule-Walker auto-correlation estimates and the use of the biased autocorrelation estimator in the Yule-Walker approach is responsible for spectral line splitting. Spectral line splitting may be alleviated for one sinusoid by using complex data and also, the unbiased autocorrelation estimator in the Yule-Walker case. Spectral line splitting for multiple sinusoids is discussed.

Boresight errors induced by missile radomes

Abstract: Radome induced boresight errors are defined in terms of antenna difference port to sum port voltage ratios. The antenna port voltages are derived using the reaction integral for the case of a planar waveguide slot array in the presence of a dielectric radome. Radome transmission uses planar slab results. Both the antenna reflection and the radome shadow contribution are taken into account. Although only linear copolarized comparisons are presented here, the analysis is kept arbitrary with respect to incident and seeker antenna polarizations. Measurements include a line source experiment that tests the antenna model sensitivity to geometry. A simple distributed source experiment, in the form of a planar slab radome with thickness corrugation, tests the influence of transmission through varying wall thickness. Effects of curvature are assessed with an offset hemisphere radome and finally a series of tangent ogive radome comparisons verify the limits of the analysis. A trend for the yaw errors to be less accurate than the pitch errors is consistently noted for the tangent ogive radomes, and this behavior is discussed.

Flue aspirated oven

Abstract: A gas-fueled oven which is capable of safely assuming high temperatures such as occur during pyrolytic self-clean cycles and which employs a single multi-purpose fan for directing cool air flows over wall surfaces, for providing aspiration and temperature dilution of hot flue products, and for providing combustion air for a power broiler burner.

Stabilized surface wave device

Abstract: A surface acoustic wave (SAW) device is provided with short-term and long-term stability by recessing the electrode structure into the surface of the piezoelectric crystal of the device. In addition, the surface is passivated with the silicon polymer, and a cover of the same crystalline material is placed above the electrode structure to prevent absorption of impurities into the surface from the atmosphere. The passivation is believed to reduce the effect of thermal agitation of the bonds of the crystal lattice structure, and thereby prevent the making and breaking of chemical bonds with hydroxyl ions that may have been entrapped from the atmosphere. The SAW device is particularly useful in the construction of stable oscillator circuits wherein the passivation provides improved short-term frequency stability and the cover provides long-term frequency stability.

Laser-pumped molecular lasers - Part II: Submillimeter laser experiments

Abstract: We report the first experimental determination of the gain spectrum of a laser-pumped submillimeter laser amplifier. Single-mode pump and submillimeter oscillators were used to determine the gain as a function of submillimeter laser frequency, pump intensity, relative polarization, and molecular gas pressure. The 385 μm transition in D 2 O and the 496 μm transition in CH 3 F, both pumped by a CO 2 laser, were investigated. The use of single-mode lasers allows a direct comparison with theory. Good agreement is obtained with our recent theory which takes into account two photon contributions to the gain as well as space orientation ( M -level) molecular degeneracy.

Polymeric piezoelectric microprobe with damper

Abstract: A probe detects sonic energy in liquids and in materials containing liquids such as the flesh of living beings, the probe being particularly adapted for medical ultrasonics. The probe is constructed of materials having acoustic impedances substantially equal to that of water to maximize the transfer of sonic energy in a living being to an electric signal within the probe for accurate detection of high frequency pulses having a duration less than a microsecond. A piezoelectric polymer serves as the transducer and is mounted at the end of the probe housing between a thin metallic window which serves as one electrode, and a metallized rubber rod which serves as the second electrode and sonically insulates the transducer from the housing. An acoustically absorbent ring affixed to the perimeter of the face of the probe, and a flaring of the back end of the probe, reduce the diffraction and reflection of acoustic waves for improved accuracy in the measurement of submicrosecond pulses.

Multiple correlator reference processor

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. Output signals of the respective multipliers are summed together and passed through a low pass filter having a pass band approximately equal to the reciprocal of the anticipated dwell time of the signal source within the beam width of the array of antenna elements. The uncorrelated noise results in an alternating component in the products of the respective multipliers which are substantially cancelled in the summing and filtering to produce a higher signal-to-noise ratio.

Integrated circuit manufacturing method

Abstract: A method for forming a semiconductor structure is disclosed wherein a masking layer used to form the gate contact of a Metal Electrode Semiconductor Field Effect Transistor (MESFET) is formed by selectively depositing particles into separated regions of the masking layer, diffusing the particles into the portions of the masking layer to reduce the separation between the regions to a predetermined separation and exposing the masking layer to a chemical etchant to selectively remove the portions of the masking layer which have a particle concentration below a predetermined concentration, producing an aperture in the masking layer having a predetermined width. With such method a well controlled diffusion process and selective chemical etching process are used to form such aperture which, in turn, is used to form a gate contact for a MESFET having a gate channel length in the order of a micron.

Microwave oven blower radiator

Abstract: A microwave heating system having a combination rotary blower and multiport microwave radiator positioned in a cavity and having radiating ports at different distances from the axis of rotation which direct overlapping radiation patterns at a body to be heated. A combination heater may be used having a resistive heater positioned in regions around the outside of the rotary structure to supply heat to the body.

Dynamically focussed array

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. Upon reception of sonic energy, circuitry is provided for selecting one or more specific foci as a function of the time of travel of an echo from a subject being observed to approximate a continuously varying focus in accordance with distance from successive points of reflection within the subject.

CRT Digital brightness control

Abstract: A digitally controlled CRT display system providing display intensity levels having equal ratios of luminances for consecutive steps over a plurality of brightness control settings. The digital video is added to a digital brightness code and the sum is converted to an analog signal that is coupled to the cathode of the CRT. The digital-to-analog converter provides a transfer characteristic such that the consecutive gray shade steps have a constant ratio of luminance.

Bowed elastomeric window

Abstract: A window for a sonar transducer housing is formed of an elastomeric plate which is bonded to a mounting ring for securing the window to the housing. The plate is bowed with a convex shape during the molding and the curing of the elastomer. During assembly of the housing, the convex surface of the plate faces inwardly and is depressed to a substantially planar configuration by the pressure of oil within the housing. The compression of the elastomer against the mounting ring inhibits separation of the elastomer from the ring.

Fire control system

Abstract: A fire control system is shown wherein the relative rotational motion between a modulated beam of infrared energy and a spinning projectile is used to determine the displacement of such a projectile during flight from the centerline of such beam so that the trajectory of such projectile may be corrected as required to enable a selected target to be hit.

Shifted sideband beamformer

Abstract: A fundamentally different time domain beamformer structure is described which can be used to process bandpass sensor signals efficiently. The beamformer operates directly on complex, frequency translated, single sideband representations of the input signals to obtain a similar representation of the beam output. Such representations are typically obtained by complex demodulation of the signals to facilitate the use of bandwidth sampling procedures. This new technique, which is referred to as the shifted sideband beamformer, is functionally a time-domain beamformer but it combines attributes of both time-domain and frequency-domain beamforming. Shifted sideband beam-forming has the advantage that beamformer vernier delay and throughput requirements depend on the frequency content of the translated band rather than of the original band. This paper discusses the potential hardware savings associated with shifted sideband beamforming in terms of analog to digital conversion, cable bandwidth, digital processing and, also, signal conditioning hardware. The impact of delay quantization on beam-pattern structure is compared for a shifted sideband and a conventional digital implementation. Beamformer throughput is also analyzed for both implementations. A further reduction in the beamformer throughput requirement is demonstrated by the use of digital interpolation in conjunction with the shifted sideband beam-forming concept.

Antitank weapon system and elements therefor

Abstract: An antitank weapon system is shown to include a projectile carrying at least one pulsed laser radar which periodically illuminates swaths of the underlying terrain, means for processing return signals to distinguish between the radar signatures of objects on such terrain and means for firing submunitions to impact on any object whose radar signature corresponds to that of a tank or other desired target.

Digital memory system

Abstract: A digital memory system adapted to store samples of a received radio frequency signal and enable retransmission of a radio frequency signal from such stored samples, such retransmitted radio frequency signal having a frequency related to the frequency of the received radio frequency signal. The received signal is heterodyned to a periodic sinusoid video frequency signal having a predetermined average level. A sequence of one-bit logical signals representative of the amplitude of the video signal relative to a predetermined level other than the predetermined average level is stored. The stored samples are returned and converted to a radio frequency signal having a frequency of the received signal. By using a non-average level as the threshold voltage, the spectrum of the signal retrieved from the memory will have reduced harmonic components relative to the fundamental frequency component.

Antitank weapon system and elements therefor

Abstract: An antitank weapon system is shown to include a projectile carrying at least one pulsed laser radar which periodically illuminates swaths of the underlying terrain, means for processing return signals to distinguish between the radar signatures of objects on such terrain and means for firing submunitions to impact on any object whose radar signature corresponds to that of a tank or other desired target.

Comments on "Frequency estimation by linear prediction "

Abstract: It is shown that contrary to the claims made in the above paper, the analytic signal frequency estimate can be severely biased. The bias manifests itself for short data records and low signal-to-noise ratios.