Abstract: A portable sonar surveillance system is disclosed which operates in the audible-frequency region where low attenuation loss minimizes the power requirement for achieving long-range detection capability. A light-weight, high-power transmitting transducer array approximately 1 ft. diameter, which operates efficiently in the 4-6 kHz range, is utilized in combination with a novel tri-cardioid hydrophone receiving array whose diameter is only a few inches to achieve a bearing resolution of 5.degree.. The inventive system replaces enormous sized conventional low-frequency scanning sonar systems weighing tens of thousands of pounds. The disclosed system can be very effectively used as a long-range, light-weight "dunking sonar" for submarine surveillance patrol operations from helicopters or small patrol craft.

Abstract: An airplane flies through the air because the forward speed of its wings through the air produces lift which is greater than the total weight of the craft. When the forward speed decreases below a certain amount, there is insufficient lift to counteract the weight of the plane and the plane will drop down (or stall). This is the ideal condition of speed at which an airplane lands, but it is important that the stall occur when the plane is only a very short distance (like three feet) above the ground. It is also very important that the plane remain well above the ground or other obstacles until a suitable landing field is reached.The device herein described uses "sonar" or reflections of sound pulses to give the pilot an audible indication of his exact distance from the ground so that he can know the correct moment to stall or "flare" the plane for a perfect landing.

Abstract: Apparatus for determining the bearing of an acoustic source from a selected ocation in an acoustic environment includes a plurality of discrete acoustic sensor elements and a flexible member, having first and second ends, which may be deployed in a linear configuration in the environment. The sensor elements are attached along the flexible member in spaced apart relationship, one of the elements, comprising a lead element, being closer to the first end than any of the other elements. A motion measuring device is coupled to the lead element when the flexible member is deployed in the environment to generate signals which indicate the velocity of the lead sensor element in the environment.

Abstract: Formation of channels for all-round passive sonar systems by the technique of charge-coupled devices. The shift register receives the multiplexed signals of the M transducers forming the listening base of the sonar system. The shift register has different series of sub-contacts, each series corresponding, at one moment, to the signal of one of the transducers. The adding of the weighted signals of one series gives an interpolated signal of the corresponding transducer. The such obtained delayed signals are weighted and added, such obtaining the preformed channels.

Abstract: A conical acoustic lens in conjunction with a ring of transducer elements located on a circle disposed above the lens is utilized to form a plurality of radial beams for imaging a target area beneath the apparatus. The transducers may occupy the fully 360.degree. of the circle or a sector less than 360.degree. in which the case the apparatus may be rotated to give full 360.degree. coverage.

Abstract: The present invention entails a multi-channel fishscope that includes an expandable microprocessor unit that is adapted to receive echo profile signals from one or more transmitter-receiver modules and through voltage comparatory networks generating an output video signal that is directed to a CRT of a television monitor. There the echo profiles are transformed into signature traces on the TV monitor that represent fish or other target objects. By the provision of a search/scan module with timing control provisions, the depth of the traces is scaled onto the TV monitor in order to indicate depth and relative position.

Abstract: A housing for an acoustic transducer includes means for dispersing internal reflections within the housing to minimize the incidence of such internally reflected acoustic pulses on the transducer itself, thereby avoiding the generation of spurious electrical signals for transmission to the translating circuitry.

Abstract: A compact, unitary sensor array support structure for use in a water medium omprises a plurality of scissor arms mounted on a support. The scissor arms are extended from the support to expand the sensor array, and are retracted to the support when the array is to be recovered. The support with the scissor arms retracted thereto is slidably housed within a container. Together, the support and the container form a hydrodynamic body which can be transported by towing in the water or removed from the water for transport or storage.

Abstract: Apparatus or a device for use in the jettisoning and flotation of a susped load, particularly an underwater listening buoy, comprises a parachute for suspending the load during descent between jettisoning and flotation, and at least one inflatable float for maintaining the load at a predetermined depth in a body of water. The float comprises a pillow-shaped inflatable ballonet fixed in the central portion of the parachute. It may have an inflation sleeve coupled at one end to the ballonet for inflating the ballonet with the superatmospheric pressure generated by the descent of the parachute. A tension member may be provided fixed at one end to the free end of the sleeve and at its other end to the load so as to extend the sleeve downwardly during descent. The inflation sleeve preferably is of frustoconical form and divergent toward its lower free end.

Abstract: A directivity display device and method are disclosed which involve a first saw-tooth generator producing a scan signal and a brilliance modulation circuit producing a brilliance modulated signal derived from the characteristic output of a test object with respect to a rotational angle of the test object. Thereby, the directivity display device makes it possible to display in graphic form a property of the test on a cathode-ray tube with a polar or other coordinate representation.

Abstract: Parametric array Doppler sonar apparatus includes an acoustic lens containing a flat disk-like central portion and an annular outer portion serving as a convergent lens. Multiple transducers are positioned between the lens and the focal plane so as to launch collimated acoustic beams in specified directions through the central portion of the lens and to receive reflected energy propagating principally through the annular portion of the lens.

Abstract: A geophone testing apparatus includes a plurality of force detectors upon each of which is mounted a corresponding geophone. An electrical step function is applied to the active elements of the geophones to generate mechanical output transients. The mechanical output transients are detected by the force detectors which generate corresponding electrical signals. The signals are analyzed to determine the sensitivity, damping and natural frequency of each of the geophones under test. A multiplexer is provided so that all of the geophones may be tested at the same time.

Abstract: A radio buoy which can be jettisoned from an aircraft by a cable and which is intended to float on the surface of the ocean connected to a submerged hydrophone. During the drop a balloon is inflated by a forced intake of air through holes as a result of articulated openings in the form of scoops, the scoops unlocking by a bar the protective casing of the balloon and the safety device of the container, which is detached after impact with the water, the submerged container being linked with the electronics by a cable. The buoy can be used for underwater monitoring at depths up to 2,000 meters.

Abstract: A method of locating an object by wave energy reflection and an apparatus therefor in which receiving outer transducers provide directional receptivities represented by polar lobes diverging on opposite sides of a reference axis and an inner receiving transducer provide a directional receptivity represented by a narrower polar lobe centered on the reference axis. The signals received from the outer transducers are operated upon in channels of the receiver to modulate them with a frequency swept local signal derived from the transmitted signal and develop indicator signals of difference frequency between the transmitted and received frequencies and which represent the range of the object. The outer signals are displayed binaurally, to enable the user to achieve firstly approximate directional sensing by binaural effect, and thereafter more accurate directional sensing by the use of signals developed in a central channel and derived from the inner transducer or outer transducers simulating an inner transducer.

Abstract: A discrete transducer array of a plurality of discrete transducer elements, o connected as to achieve a good array directivity pattern with as narrow a beam width as possible for a given side lobe level, or as low a side lobe level as possible for a given beam width, or the most favorable combination of the two. This is to be done with the restriction that there is a discrete array of, say 24, elements that must be shaded discretely, for example by using a series-parallel combination of the elements.

Abstract: A device is structured to pass along a towed array of hydrophones, from the orward end thereof to the rearward end thereof. The device carries a small acoustic projector to project test signals to respective hydrophones as the device passes them by. The responses of respective individual hydrophones to the test signals are recorded to enable calibration of the array in situ, and additionally, or alternatively, are recorded to determine the departure of the array from the ideal straight, (generally) horizontal line.

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 fish detector capable of detecting species of fish. Two ultrasonic sounds at different frequencies and echoes are detected by receivers tuned to said different frequencies, respectively. The output signals from the receivers are converted into binary-coded signals and one of the binary-coded signal is divided by the other binary-coded signal. The ratio or quotient thus obtained is compared with a plurality of reference signals at different levels or strengths so as to detect whether or not the ratio or quotient is higher than the highest level or strength reference signal, lower than the lowest level or strength reference signal or between two reference signals at adjacent levels or strengths and subsequently to display in color depending upon a level of the ratio or quotient thus detected.

Abstract: A contour map underwater ultrasonic image system simultaneously uses a la time-bandwidth product signal waveforms for extremely fine range resolution, and an image memory organized as a three-dimensional data base of object reflectivity. The transmitted waveform is a pseudo-random coded signal. A plurality of correlator receivers produce a time-compressed pulse for each angular resolution cell. An image memory receives the output of the correlator receivers and builds up a three-dimensional data base of echoes in the form of a set of contour lines for each range cell. Standard computer-graphic techniques are used to accept the three-dimensional data base and generate displays to assist an operator in identifying the object.

Abstract: A method and apparatus is disclosed for use of a linear frequency chirp in a transmitter/receiver (14/16) having a correlator to synthesize a narrow beamwidth pattern from otherwise broadbeam transducers when there is relative velocity between the transmitter/receiver (14/16) and the target. The chirp is so produced in a generator (20) in bandwidth, B, and time, T, as to produce a time-bandwidth product, TB, that is increased for a narrower angle. A replica of the chirp produced in a generator (26) is time delayed and Doppler shifted for use as a reference in receiver (16) for correlation of received chirps from targets. This reference is Doppler shifted to select targets preferentially, thereby to not only synthesize a narrow beam but also aim the beam in azimuth and elevation.