Abstract: A system to measure geometric and electromagnetic characteristics of objects. Wave energy of a single frequency (or very narrow band of frequencies) is directed upon an object which reflects (or otherwise interacts with) the wave energy. The reflected wave energy is sensed by many spatially spaced sensors to provide electric signals whose amplitude and phase components are combined to give a quantity from which geometric and/or electromagnetic characteristics of the object can be ascertained.

Abstract: A circuit arrangement for forming a succession of group signals in the ranging art from received signals originating from an array of adjacent signal receiving transducers, each successive group signal being associated with a respective group characteristic and being based on the signals received by a respective group of adjacent transducers forming part of the array. The succession of group signals is processed to form a representation of the mean, or average, value of a predetermined number of successive group signals, and a representation of the ratio of the value of one of the group signals of that predetermined number of signals to the mean value is produced.

Abstract: The thinned arrayed transducer for a sonar system includes an array of sonar elements mounted in rows (layers) and columns (staves) on a structure, preferably cylindrical, to form a checkerboard pattern wherein the spacing between adjacent elements in the rows and the columns is equal to or greater than .lambda..sub.m /2, where .lambda..sub.m is the wavelength of the signal of frequency f.sub.o transmitted in the medium where the sonar is being used. The transducer structure is made from a layered cloth impregnated with a phenol based material, and includes openings in which the sonar elements are mounted. The sonar elements which are effectively a half wavelength in length consist of a cylindrical ceramic section fixed end-to-end to a cylindrical metal section. The metal section is made of a loading metal, such as brass. The transmit-receive circuitry energizes the elements by row using a modulated signal to form a variable sonar beam.

Abstract: An apparatus for determining the time of the closest point of approach of a taxiing aircraft comprising a microphone means for producing an input signal in response to the sound energy of a taxiing jet. A low pass filter is provided to receive the input signal and pass low signals having a frequency less than or equal to 1 KHZ while a high pass filter is provided to receive the input signal and pass high signals having a frequency greater than or equal to 1.5 KHZ. Demodulators are provided for receiving the signals from both the high and low pass filters, and are adapted to produce a low frequency envelope from the low signal and a high frequency envelope from the high signal. Finally, comparator apparatus is provided for receiving the low frequency envelope and the high frequency envelope and comparing the amplitudes so as to provide a signal at the point in time when the amplitude of the low frequency envelope exceeds the amplitude of the high frequency envelope.

Abstract: A device for forming beams for mulitple elements of a hydrophone array. An nalog multiplexer receiver sequentially obtains one signal from each hydrophone and supplies input voltages to an analog to digital converter. Digital words from the converter are applied to one input of a digital adder and the other adder input is from the output of a random access memory (RAM). The output of the adder is stored in the RAM at an address corresponding to the signal time delay required from a particular hydrophone in order to direct the beam of the hydrophone array in a desired direction.

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.

Abstract: A passive ranging system is disclosed wherein the transducer array has its eam pattern modulated so as to match the arrival angles of the different wave fronts arriving at the array from various target distances. The beams are formed by orientating a multiplicity of readout arms at appropriate angles with respect to a recording medium which has the individual signals detected by each transducer of the array recorded thereon in different horizontal tracks. The readout arms thus simultaneously scan all of the signals associated with the arrival angles for a particular range and produce a signal whose amplitude is a measure of the probability of a target at this range.

Abstract: A serial phase shift beamformer characterized by a charge transfer device for progressive clocked transfer of quadrature component analog samples of the scanned outputs of a multiplicity of transducer elements in a curved array. Weighting resistors effect scaling of the analog samples during parallel readout of X and Y component samples prior to summation of like components and derivation of the square root of the sum of the squares of the X and Y summations to provide formed beam amplitude signals.

Abstract: A directional hydrophone and electronic circuit combination giving a (cosp.2 .theta.) directivity pattern. A monopole transducer is placed coaxially within a ring transducer and the ring output is fed to a function-conversion electronic circuit which provides a (sin.sup.2 .theta.) output signal. This signal and the output signal of the monopole are fed to a weighted differential amplifier where they are subtracted. The output of the amplifier is a (cos.sup.2 .theta.) signal. By utilizing different components in the function-conversion circuit, the device can be made narrowband or broadband.

Abstract: A direction-finding array system which uses a plurality of hydrophones in a rossed dipole configuration and a phase-detection system. It is basically a time-of-arrival (TOA) system which is modified to act like a phase-detection system and is able to share much of the electronics of existing acoustic intercept receivers. Acoustic signals of a high frequency generated by an acoustic target under investigation are apparently heterodyned to obtain corresponding signals of an appropriate lower frequency. The apparently heterodyned signals are then processed in two identical processors giving rise to two outputs which are applied to X- and Y- axes of a cathode ray of oscilloscope or the like to obtain unambiguous bearing information about the acoustic target. Three dimensional bearing angle information is obtained by using a third processor which is identical to the two processors used in a two dimensional case.

Abstract: 6.

Abstract: A fixed array of three identical directional receivers, each having a carid directional pattern, are arranged in a symmetrical configuration with each receiver having its principal axis of maximum sensitivity oriented 120.degree. from the corresponding axes of its neighbors. By comparing the relative magnitudes of the voltages generated in each of the three cardioid receivers upon receiving a signal, the bearing of the signal source is automatically determined and displayed. The tri-cardioid receiving array overcomes the prior art need for large-sized directional receiving transducers, and also overcomes the need for mechanically rotating or electronically scanning the receiving array to find the bearing of the signal source.