Noise Or Unwanted Signal Reduction In Nonseismic Receiving System Patents (Class 367/901)
  • Patent number: 4388711
    Abstract: An apparatus for rejection of turbulence induced flow noise for towed hydhone arrays. Two adjacent hydrophones in the array are spaced less than flow noise coherence distance apart forming a flow noise cancelling module. The inverted acoustic/flow noise signal from the lead hydrophone of the pair is split, one side passing to the final stage of signal processing while the other side, filtered, amplified and inverted, is added to the combined signal from the lag hydrophone which has been filtered and amplified. The acoustic signal components cancel leaving only the lead hydrophone flow noise plus the lag hydrophone flow noise which has been shifted by a factor dependent upon tow vessel speed and hydrophone spacing.
    Type: Grant
    Filed: July 28, 1981
    Date of Patent: June 14, 1983
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventor: John W. Fay
  • Patent number: 4333169
    Abstract: Apparatus for suppression of water flow noises in connection with a keel nted sonar dome. A solution of water soluble polymer is ejected through a series of holes along the leading edge of the sonar dome under forward movement of the ship. The concentration and flow rate is chosen to "bathe" the dome in a very dilute dispersion (of the order of 10 parts per million by weight) of the polymer.
    Type: Grant
    Filed: October 4, 1966
    Date of Patent: June 1, 1982
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventor: Jack W. Hoyt
  • Patent number: 4322722
    Abstract: An intrusion detection apparatus including a sensor for sensing an objectionable interference phenomenon within a detection area and developing a pulse train coincident therewith, signal processing circuitry responsive to the pulse train and operation to actuate a Gunn diode microwave generator or the like in a pulsed manner causing it to transmit microwave energy into the detection area in synchronism with the interference phenomenon, a microwave receiver for detecting microwave energy reflected from the detection area and for developing detection signals indicating motion within the monitored area, and further signal processing circuitry responsive to the detection signal and operative to actuate an alarm or the like.
    Type: Grant
    Filed: June 20, 1980
    Date of Patent: March 30, 1982
    Assignee: DTI Security, a Division of Datura International, Inc.
    Inventor: Peter J. Kozdon
  • Patent number: 4310904
    Abstract: An ambient sea noise elimination system is disclosed in which the outputs of a directional hydrophone and an omnidirectional hydrophone are filtered and summed such that the effective receiving pattern below approximately 300 Hz is a vertically oriented dipole pattern having a null in the horizontal direction and such that the effective receiving pattern above 300 Hz is a cardioid having its null either pointing upwardly or pointing downwardly in a vertical direction. The option of simple omnicoverage at the high frequencies can also be easily implemented. This system thus takes advantage of the discovery that ambient sea noise under 300 Hz primarily travels in a horizontal direction whereas ambient sea noise above 300 Hz generally travels in a vertical direction.
    Type: Grant
    Filed: September 30, 1974
    Date of Patent: January 12, 1982
    Assignee: Sanders Associates, Inc.
    Inventors: Samuel S. Ballard, Ronald P. White
  • Patent number: 4293937
    Abstract: In a borehole acoustic telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise in the data stream is inherently high, making the use of precise frequencies advantageous to provide useful data. A first transmitter in the system operates at a precise frequency to transmit a signal over the pipe where it is received by a receive and retransmit circuit path. Components in the receive and retransmit section filter and amplify a data component of the signal and retransmit the data signal at a precise frequency. Crystal controlled oscillator clocks are operated in the system at a same frequency in the transmitter and receiver-retransmitter to insure precise frequency control of the system.
    Type: Grant
    Filed: August 10, 1979
    Date of Patent: October 6, 1981
    Assignee: Sperry-Sun, Inc.
    Inventors: H. Eugene Sharp, Octavio A. Vela, Mils A. Smither
  • Patent number: 4290058
    Abstract: The oscillations which are generated during an attempted instrusion at a protected area or surface, for instance a vault wall or fence, are received at a sonic receiver and processed by an evaluation circuit such that only the oscillations emanating from an intrusion attempt trip an alarm, not however spurious oscillations from the surroundings. The received oscillations are mixed with a carrier frequency whose frequency periodically and continuously passes through a certain frequency range. The mixed signals are filtered in a narrow band frequency range, so that at the output, during each frequency through pass period, there appears the entire frequency spectrum of the received sonic oscillations in the evaluated frequency range. The filtered signals are integrated and the integrated signal, after a brief period of time, is reset as a frequency throughpass if no further signal appears.
    Type: Grant
    Filed: November 5, 1979
    Date of Patent: September 15, 1981
    Assignee: Cerberus AG
    Inventor: Gustav Bystricky
  • Patent number: 4283767
    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.
    Type: Grant
    Filed: May 3, 1979
    Date of Patent: August 11, 1981
    Assignee: Raytheon Company
    Inventor: Hoyt S. Rountree
  • Patent number: 4275460
    Abstract: A propeller modulation enhancement and display system which suppresses hull cho and displays propeller modulation of a return sonar signal in real time. The real-time operation is obtained through the use of a multichannel frequency spectrum analyzer having a plurality of narrow bandpass filters covering the frequency of interest. Suppression of the hull echo is obtained through the use of a narrow band-reject filter having a variable center frequency. The filter precedes the multichannel frequency spectrum analyzer.
    Type: Grant
    Filed: September 26, 1966
    Date of Patent: June 23, 1981
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventor: John P. Zirbel
  • Patent number: 4271491
    Abstract: The present invention relates to an intruder alarm system which compensates for background and other interfering noises. The system comprises dual amplifiers, one a main channel and the other a control channel wherein the control channel is responsive primarily to background and other interfering noises and develops a control signal which when applied as a control signal to modify the amplification characteristics of the main amplifier effectively removes the effect of the background and other interfering noises from the output of the main channel.
    Type: Grant
    Filed: November 20, 1978
    Date of Patent: June 2, 1981
    Inventor: Ronald R. Simpson
  • Patent number: 4232381
    Abstract: A noise-cancellation scheme in a system receiving acoustic information signals, where the system is carried in a vehicle having self-generated engine noise. An engine rotation sensor generates pulses driving a synchronous type filter device which passes only the engine noise frequency and its harmonics. The latter signal is then subtracted from the total input signal having information and noise combined. One filter circuit comprises a phase-locked loop with a multiplying counter whose output goes to a multiplexer having a plurality of grounded capacitors connected thereto.
    Type: Grant
    Filed: June 8, 1979
    Date of Patent: November 4, 1980
    Assignee: Northrop Corporation
    Inventors: Lyle V. Rennick, Julian W. Macias
  • Patent number: 4228531
    Abstract: Means are provided for reducing the dynamic range requirement of an underer sound system by minimizing the effects of noise interference. Computer means are provided to automatically rotate the pattern function of the combination of the dipole hydrophones in the system. A minimum noise pattern position is derived from hydrophone output information.
    Type: Grant
    Filed: September 17, 1970
    Date of Patent: October 14, 1980
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventors: Bruce P. Bogert, Peter Hirsch
  • Patent number: 4225954
    Abstract: An acoustical deverberator for eliminating the reverberation from a sound gnal originating with a transient sound source in shallow water. The sound signal is received by a single hydrophone and autocorrelated to determine the time differences between the direct signal and the bottom surface reflected signals. Together with the surface and bottom reflection coefficients and known depths of the hydrophone and water, the time differences are used to determine corrections which are applied to the received sound signal. The result is a clean sound signal free from interfering reverberation.
    Type: Grant
    Filed: December 21, 1978
    Date of Patent: September 30, 1980
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventor: Herman Medwin
  • Patent number: 4219888
    Abstract: A surface acoustic signal defader for optimizing the signal received from derwater sound scattered from the ocean surface. The bandwidth of the underwater sound source is monitored and the frequency of maximum signal strength is identified. When the maximum signal strength frequency fades a predetermined amount, reception is switched to the signal of maximum anti-correlation. This process is continuous such that when the new frequency fades the anti-correlation process will determine the optimum frequency for the new fading condition, thus resulting in optimum reception of surface scattered underwater sound.
    Type: Grant
    Filed: December 8, 1978
    Date of Patent: August 26, 1980
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventor: Herman Medwin
  • Patent number: 4218768
    Abstract: Each receiving or transmitting circuit for a respective transducer element includes an individually controllable buffer amplifier which is so operated as to avoid detrimental switching transients. For example, the buffer amplifiers in the receiving circuit may have input switches closed immediately after a transmit pulse and prior to the actual receiving phase. Then output switches of the buffer amplifiers to be activated are closed in the receiving phase, but transients so produced are blocked by the high reverse attenuation of the buffer amplifiers. The input switches may be actuated prior to activation of the transducer elements in receive mode and may serve to simultaneously supply operating voltage to the respective associated buffer amplifiers, the buffer amplifiers all being switched off during transmit mode to block transmit energy from non-active transducers.
    Type: Grant
    Filed: November 11, 1977
    Date of Patent: August 19, 1980
    Assignee: Siemens Aktiengesellschaft
    Inventor: Dieter Hassler
  • Patent number: 4213200
    Abstract: An improved position determining device using a delay line with energy absorptive terminations at the ends thereof and having a driver transducer coupled to the delay line for producing a traveling wave on the line and a first receiver transducer coupled to the delay line at the distance to be determined. A second receiver transducer, also coupled to the delay line, is displaced from the first receiver transducer by a distance preferably substantially equal to one-quarter wavelength of the traveling wave signal. Each of the receiver transducers detects the direct traveling wave signal from the driver transducer and a traveling wave signal component which is reflected from an end termination. The detected signals from the second receiver transducer are phase-shifted by a phase lag and the phase-shifted signals are combined with the signals detected by the first receiver transducer, whereby the reflected signal components in the combined output signal are effectively eliminated.
    Type: Grant
    Filed: March 8, 1979
    Date of Patent: July 15, 1980
    Assignee: The Charles Stark Draper Laboratory, Inc.
    Inventor: Leslie E. Matson, Jr.
  • Patent number: 4210970
    Abstract: An echo sounder has a transducer for transmitting and receiving pulses of energy, a rotary arm display and a meter or digital display. The rotary arm is arranged to cause the transducer to transmit a pulse of energy on each occasion it passes a datum position. The motor of the rotary arm display may be switched off while simultaneously energizing an oscillator having an output frequency equal to that of the rotational speed of the motor prior to deenergization.
    Type: Grant
    Filed: December 15, 1977
    Date of Patent: July 1, 1980
    Assignee: Space Age Electronics Limited
    Inventors: Walter M. Toubkin, Alan J. Mulley
  • Patent number: 4207624
    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.
    Type: Grant
    Filed: October 2, 1978
    Date of Patent: June 10, 1980
    Assignee: Rockwell International Corporation
    Inventors: Mauro J. Dentino, Harry M. Huey, Toni Letendre
  • Patent number: 4206510
    Abstract: 1.
    Type: Grant
    Filed: June 27, 1955
    Date of Patent: June 3, 1980
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventor: Robert D. Strait
  • Patent number: 4204280
    Abstract: 1.
    Type: Grant
    Filed: November 21, 1962
    Date of Patent: May 20, 1980
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventor: Jack H. Slaton
  • Patent number: 4195359
    Abstract: 1.
    Type: Grant
    Filed: June 28, 1954
    Date of Patent: March 25, 1980
    Inventors: Paul H. Miller, Tillman H. Schafer
  • Patent number: 4195360
    Abstract: In sound target detection equipment, at least three microphones are used in a broadside array manner to ascertain the presence of a selected sound source. The outputs of the three microphones all include the sought signal S and respectively contain noise components X, U and Y. These outputs are combined to provide X-U and X-Y. These two signals are then applied as separate inputs to a discriminator which applies the rules:(a) when the input signals are both of the same polarity, the discriminator selects the input closer to zero and presents it as the output;(b) when the input signals are of opposite polarity, the device presents zero as the output.The output from the discriminator is then subtracted from one of the original microphone outputs in a manner tending to cancel out the noise contents, and the resulting signal examined for the presence of the sought signal S. The invention is applicable also to non-aural signal detection equipment.
    Type: Grant
    Filed: October 16, 1973
    Date of Patent: March 25, 1980
    Assignee: Her Majesty the Queen in right of Canada, as represented by the Minister of National Defence
    Inventor: Noel O. Fothergill
  • Patent number: 4169255
    Abstract: An acoustic height sensor, particularly adapted for use in the foil-borne mode of operation of a hydrofoil, wherein sensitivity to noise pulses is materially reduced or essentially eliminated by monitoring for noise levels capable of producing interference and, if the noise persists for a sufficiently long period, suspending processing of any signal returns until the noise ceases. In the meantime, and as processing of signal returns is suspended, sample and hold circuitry maintains the output of the system at its previous level until the noise abates.
    Type: Grant
    Filed: April 1, 1974
    Date of Patent: September 25, 1979
    Assignee: The Boeing Company
    Inventors: Leonard A. Hulsman, Grant R. Montague