Abstract: An ultrasonic ranging device for use in a vehicle having a high frequency oscillator supplying continuous sine wave signals to a power amplifier through a first gate controlled by a timer. A second gate controlled by the timer supplies an amplified sine wave signal from the power amplifier to a piezoelectric transducer mounted on an exterior portion of a vehicle. The transducer produces a series of repeated ultrasonic pulses and receives echoes from nearby objects converting the echoes into electrical return signals. A receiver amplifies the return signals and supplies them to a coincidence gate, which is enabled for relatively short time intervals by a timer. The coincidence gate supplies an output signal to an indicator when the return signal is detected during the interval that the gate is enabled.

Abstract: Indicator apparatus for determining the miss distance of a projectile in relation to a fixed or moving target, comprising pressure-sensing transducers intended to sense the pressure wave generated by the projectile in at least four points, and means for generating corresponding electrical signals therefrom. The apparatus further comprises computer circuits, calculating the distance to the point of origin of the wave, i.e. the so-called "bang generation point", in response to the characteristics of the pressure wave. This distance has been called the "miss distance" in previously known indicator apparatus, but in accordance with the invention the miss distance is defined as the shortest distance between the projectile and target, and one object of the invention is to indicate this distance and the exact position of the projectile when it is at the miss distance from the target.

Abstract: A depth sounder repeater providing a remote display of the depth of a body of water digitally or by meter movement, a depth alarm, a lost echo signal, and a meter scale expansion for shallow depth display in conjunction with a ship's sonar, display of "alarm depth" while setting. The depth display may be digital or analog and multiple displays are possible as required. The depth sounder repeater includes a signal processor for providing signals initiated with the main ultrasonic pulse transmission from the ship's sonar and terminated with the receipt of the first echo of the corresponding main transmitted pulses. The signal processor signals may then be used to initiate and terminate production of a train of clock pulse signals which are counted to provide a digital depth display, or alternatively the signal processor signal may be integrated in analog meter display apparatus.

Abstract: A deep water explosive echo ranging system capable of detecting high perfance submarines by using favorable acoustic paths available at deep depths. An umbrella hydrophone array is deployed from a sonobuoy to deep depths; an electrical subsystem transmits data from the hydrophone array to a transmitter housed in a surface float unit; a multichannel receiver and signal processing and display apparatus in an aircraft receives and processes radio data signals sent from sonobuoy transmitters; and an explosive underwater charge package is remotely triggered by a command generator in the aircraft.

Abstract: Apparatus for classifying the activity of an aircraft including the geophone proximate an airfield used by jet airplanes for generating a signal indicative of the existence of the jet aircraft. Amplifier means are provided for enhancing the signal. The signal is then passed through a low pass filter means for receiving the signal and passing only that portion having a frequency less than about 30 Hz. A high band pass filter also receives the signal and passes only that portion having a frequency ranging from about 90 Hz to about 120 Hz. Two demodulator means are provided which receive the low pass signal to provide a low pass envelope and receive the high band pass signal to produce a high band pass envelope. Threshold signal generating means are provided to receive the low pass envelope and the high band pass envelope, and generate a signal when either or both envelopes reach a predetermined threshold.

Abstract: An electronic range expander, such as for use on a sonar system, which has a rotating disc lamp or a rectilinear pen record, of the travel time, expressed as a certain distance from the transducer to an object and back again. The received signal is sampled periodically, and these samples are stored in a random access memory, in addresses which are determined by binary numbers successively outputted from a binary counter, which is stepped in accordance with a clock signal. As the binary number representing an address in the memory is incremented, the sampled value of received signal is stored in the corresponding address. The command to write in the memory is repeated at a selected number of clock counts. Intermediate the commands to write into the memory, the command is given to read the signal stored in a selected address and to send it to a latch and to the output display or printer of the sonar apparatus.

Abstract: This invention relates to a method and system for distinguishing between displacing targets and a surface of water by transmitting pulses from a transmitter that is submerged in the water, the pulses being reflected and received by a receiver, also submerged in the water. The variations in the distance to the reflecting surface for consecutive pulses are measured and compared with a first value, determined inter alia from the state of the sea, and with another value, determined from the size of the target.

Abstract: A selected increase in the farfield amplitude of the difference frequency am of saturation limited parametric sonar sources is obtained by an array of saturation limited parametric sources having a center-to-center spacing selected such that the primary beams launched by each source coexist in a common region where attenuation has reduced the amplitude of each primary beam to a level which precludes saturation. The selected center-to-center spacing depends upon the number of individual sources implemented and each doubling of the number of selectively spaced sources provides at least a 3 dB increase in the farfield difference frequency amplitude without changing the nominal directivity characteristics of the parametric source.

Abstract: A method for testing hydrophones in situ by means of a pulser for applying a repeatable low-level pressure pulse to individual hydrophones mounted in a marine seismic streamer cable. The transient output signal, due to the applied pressure pulse, from any one hydrophone under test is compared with the transient signals from other hydrophones under test to determine uniformity of response with respect to signal polarity, amplitude and period (reciprocal frequency).

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Abstract: This invention relates to a simplified pulse communication system for encrypting information to be transmitted over a communication link, which incorporates a novel randomizing and derandomizing procedure that is accomplished in the same step with PWM or PPM encoding and decoding.

Abstract: In a method and apparatus for surveying for nodular targets of a grain size of 1 to 15 cm present on the sea floor, pulse waves in each of three frequency ranges of 3 to 4, 10 to 14 and 25 to 50 KHz are radiated onto the sea floor from a ship navigating on the sea. The reflected sound waves of the three frequency pulse waves are received and the reflexibilities of the respective sound waves are measured from the reflected sound pressures and the reflexibilities are composed. The population of the nodular targets is determined from the composed reflexibility and, as required, the grain size of the nodular targets can be determined from at least one of the ratio of the reflexibility of the sound waves of the frequency range of 3 to 4 KHz to the composed reflexibility and the ratio of the reflexibility of the sound waves of the frequency range of 3 to 4 KHz to the reflexibility of the sound waves of range of 25 to 50 KHz.

Abstract: A circuit providing a ramp signal having dual slopes of increasing and decreasing magnitude is controlled to provide one of its ramp portions with a slope which varies in accordance with a signal perturbing effect and the other of which is constant. The dual slope ramp duration is modified in proportion to the perturbing effect and is used to compensate therefor.

Abstract: A device for determining the position of a sound source includes a plurality of sensors disposed on an object for which the sound source is to be detected and organized in the form of a matrix with N rows and M columns. The sensors are connected in parallel through respective uni-directional transmission elements with a common terminal for each row and each column. A signal processing circuit amplifies and carries out a designated output waveform generation process on detected signals produced by the sensors.

Abstract: A housing for an electroacoustic transducer includes a filling or access port for introducing an inert liquid into the chamber defined by the housing. The access port includes a bubble trap and a vent for extracting gaseous bubbles from the fluid fill. The structure of the access port also comprises a substantially zero spring pressure expansion cavity for the fluid.

Abstract: There is described a digital sonar receiver having a novel beamformer, own doppler nullifier (O.D.N.), and adaptive time varied gain controller. The beamformer interrogates a multi-element transducer by utilizing an interleaved sampling scheme which samples the elements in the transducer array sequentially, in such a fashion that continuous, uniformly spaced samples are obtained. The samples are subsequently converted into digital format, weighed and summed. The O.D.N. eliminates the own ship's doppler effect on the beam output signal resulting in a half beam output signal representative of the target doppler. The O.D.N. offsets the frequency of the beam output signal and a digital generated signal representative of the own ship's doppler. The O.D.N. multiplies these two offsetted signals resulting in a signal lying in each of the sum and difference frequency bands for which the signal lying in the difference frequency band corresponds to the target doppler.

Abstract: There is described a digital sonar receiver having a novel beamformer, own doppler nullifier (O.D.N.), and adaptive time varied gain controller. The beamformer interrogates a multi-element transducer by utilizing an interleaved sampling scheme which samples the elements in the transducers array sequentially, in such a fashion that continuous, uniformly spaced samples are obtained. The samples are subsequently converted into digital format, weighed and summed. The O.D.N. eliminates the own ship's doppler effect on the beam output signal resulting in a half beam output signal representative of the target doppler. The O.D.N. offsets the frequency of the beam output signal and a digital generated signal representative of the own ship's doppler. The O.D.N. multiplies these two offsetted signals resulting in a signal lying in each of the sum and difference frequency bands for which the signal lying in the difference frequency band corresponds to the target doppler.

Abstract: Serving as a hydrophone in the lower unit of the sonobuoy, two surface acoustic wave resonators for determining the resonant frequency of two independent oscillators are also used to sense pressure and thus sound. The outputs of the two resonators are mixed and then passed through a low pass filter to provide a low frequency hydrophone output signal and to remove temperature induced signal distortion. A line driver and low cost twin lead transmission line provides the signal to the upper floatation electronic unit of the sonobuoy for conversion to the desired RF carrier frequency. In a single-channel sonobuoy, this signal is multiplied and amplified for transmission to a distant receiver. In a multi-channel sonobuoy, this signal acts as a reference frequency for the frequency synthesizer section of the sonobuoy transmitter.

Abstract: An improved echo ranging system is disclosed which features improved circuitry for discrimination of received reflected pulses from noise. Discrimination is performed by comparison of the input pulses to a time-varying threshold voltage wherein the threshold function varies in accordance with the predicted attenuation of the transmitted echo signal over its path. In this way, variable gain elements used to amplify the received signal prior to comparison it with a fixed threshold height can be eliminated, thus rendering the circuitry less complicated, expensive, and calibration free.

Abstract: An inertial measurement underwater tracking system which determines range sition onboard an underwater vehicle using inertial navigation techniques. The system uses acoustic telemetry to relay the range position from the vehicle to an operations site. The position data is also recorded onboard the vehicle for post-run analysis. An onboard computer receives the inertial measurements from an inertial measurement unit and computes vehicle position with respect to an initialized reference. An acoustic transmitter receives the measurements, formats the data and transmits it by acoustic telemetry. An underwater hydrophone receives the acoustic telemetry and inputs the data to an acoustic processor to reconstruct the original position data. A range computer processes in real-time the data, and displays and records the time history of vehicle location on the range. After recovery the onboard recorded data is played back into the range computer to provide a maximum accuracy, continuous vehicle-run history.