Abstract: The invention relates to an arrangement for determining a position (x) of a stopper relative to a container in a drug delivery device, comprising an acoustic source configured to emit an acoustic signal and an acoustic sensor configured to detect an acoustic signal, a processing unit for controlling the acoustic source and processing the detected acoustic signal for determining characteristics of the acoustic signal correlated with the position (x) of the stopper. Furthermore, the invention relates to a method for determining a position (x) of a stopper relative to a container in a drug delivery device, the method comprising the steps of emitting an acoustic signal from an acoustic source, detecting an acoustic signal caused by the emitted acoustic signal by means of an acoustic sensor, and processing the detected acoustic signal for determining characteristics of the acoustic signal correlated with the position (x) of the stopper by means of a processing unit.

Abstract: Methods and systems for an optical connection service interface may include, in an optical data link comprising an optical fiber, a local control system, first and second transceivers at ends of the optical fiber, generating a control signal for the local control system at frequencies <10 Hz and communicating, utilizing the optical fiber, an optical data signal at frequencies >10 kHz and an optical service signal for an Optical Connection Service interface (OCSi) at intermediate frequencies between 10 Hz and 10 kHz. An optical signal may be modulated at the intermediate frequencies for the OCSi, and may be modulated and communicated to the second transceiver. The communicated modulated signal and the optical data signal may be detected utilizing a photodetector in the second transceiver. The detected optical signal may be demodulated, and an optical power of the optical data signal may be configured based on the demodulated signal.

Abstract: A mobile device with an underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms. The portable device may be wearable.

Abstract: An underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms.

Abstract: An underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms.

Abstract: An underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms.

Abstract: An underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms.

Abstract: An underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms.

Abstract: An underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms.

Abstract: An underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms.

Abstract: An underwater navigation system comprising a transmitter having an electrically insulted magnetic coupled antenna for transmitting an electromagnetic and/or magneto-inductive signal, a receiver having an electrically insulated magnetic coupled antenna for receiving an electromagnetic and/or magneto-inductive signal from the transmitter, and determining means for determining the position of the receiver relative to the transmitter using the received electromagnetic and/or magneto-inductive signal.

Abstract: The present invention discloses a tagging and identification device and system for tracking and monitoring sea vessels as they enter sea ports, estuaries and/or other channels. The tagging device of the present invention comprises a receiver, for receiving an underwater electromagnetic signal transmitted by an underwater beacon. An acoustic transmitter is provided for transmitting an identification signal to an acoustic receiver deployed nearby. The acoustic identification signal is transmitted after an electromagnetic trigger signal is received from the underwater beacon. The tagging and device may further comprise a memory device which can store data relating to position and time of the see vessel to which it is attached. The tagging and identification device of the present invention is covert, compact and is capable of extended active deployment without replenishment of batteries etc.

Abstract: An underwater remote sensing system comprising a transmitter for transmitting an electromagnetic signal, a receiver for receiving an electromagnetic signal reflected from an object and determining means for determining the location of the object, wherein at least one of the transmitter and receiver is underwater. The determining means may be operable to determine the location of the object using signals received at three or more receiver positions. To do this, three or more receiver antennas may be provided. Alternatively, a single receiver antenna may be provided and moved between three or more different measurement locations.

Abstract: The present invention provides a communication device and a communication method of an underwater vehicle, which use an electromagnetic field (electromagnetic wave), having a higher propagation speed than that of an acoustic wave, for communication between an underwater vehicle and a mother vessel or the like so as to allow real-time control of the underwater vehicle and the like and further to make the communication little sensitive to noise and the like. The communication device performs wireless communication between an underwater vehicle in water and an object on land or on water, and is configured to compress data to be transmitted and transmit/receive the compressed data by the use of a low-frequency electromagnetic field.

Abstract: An underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms.

Abstract: An underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms.

Abstract: A system and method for relaying signals from a magneto-inductive system, which are normally used to communicate between magneto-inductive units using quasi-static magnetic fields, over a voice-band communication system. The magneto-inductive signals are modulated data signals having a carrier frequency typically between 300 Hz and 3 kHz. The voice-band communication system facilitates long distance communication of voice-band signals. By supplying the signals from one magneto-inductive unit to the voice-band communication system through an analog input port, the signals are transmitted through the voice-band communication system. They are output from the system through an analog audio output port to the other magneto-inductive unit.

Abstract: An underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms.

Abstract: An underwater communications system is provided that transmits electromagnetic and/or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text/audio/visible form. Similarly, the transmit system comprises appropriate audio/visual/text entry mechanisms.

Abstract: A receiver includes a controller which receives A/D sampled input signals and shifts the sampled digital signal to compensate for Doppler effect in the input signal prior to demodulation. The controller compensates for a Doppler increased frequency by shifting the sampled digital signal so as to skip a sample period every n samples. This may be achieved by decreasing a cycle of m samples by one sample period every n samples. The controller compensates for a Doppler decreased frequency by shifting the sampled digital signal so as to add a sample period every n samples. This may be achieved by repeating a sample every n samples to shift the sampled digital signal. The compensation is performed in software on a multi-threaded processor.

Abstract: The present invention provides an acoustic transmitter for sequentially transmitting a plurality of pulse signals by sound. Each of the plurality of pulse signals is a signal of at least one modulated carrier wave, which has a predetermined frequency. The carrier wave of each of the pulse signals has a mutually different frequency. The transmitter performs amplitude modulation and/or phase modulation based on transmission information, and modulation by a signal indicating a window function, for the carrier wave of each of pulse signals. Then the transmitter sequentially transmits the plurality of pulse signals by sound.

Abstract: Apparatus for Doppler correction in a wireless communications system, including a first frequency synthesizer for generating a carrier signal oscillating at a rate responsive to a first input, a counter coupled to the first input for generating a Doppler compensation signal, the counter having a clock input, and a second frequency synthesizer coupled to the clock input for generating a clock signal oscillating at a rate responsive to a rate input. The rate input is adjusted over time according to a predetermined sequence so that the Doppler compensation signal compensates for the Doppler effect experienced by, for example, ground-to-satellite communications in a satellite communications system.

Abstract: A mixer shifts the center frequency of a received signal to a baseband according to a center frequency detected by a center frequency detector or a center frequency estimated from ship speed, for example, by a center frequency estimator. The passband of a variable passband filter varies according to a bandwidth detected directly from the received signal by a bandwidth detector or a bandwidth estimated from the pulselength of a transmitting signal by a bandwidth estimator, whereby the bandwidth of a baseband signal output from the mixer is limited to remove undesired noise components in the received signal.

Abstract: An apparatus for phase coherent underwater communications includes a transmitter; a receiver, including a processor for jointly performing coherent diversity combining, carrier recovery, channel equalization and synchronization; and an antenna array that includes a plurality of antenna sub-arrays for alternately transmitting a signal generated by the transmitter and for receiving an incoming signal. Each of the antenna sub-arrays includes a plurality of underwater sensors positioned such that each of the sensors is spaced at about one half the wavelength of the receiver/transmitter operating frequency from any adjacent sensor in the same sub-array. At least one of the sub-arrays has a centerpoint vertically spaced apart from a centerpoint of an adjacent sub-array at a distance about equal to or larger than a vertical correlation length of a received signal. The individual sub-arrays are beamformed, e.g. using a plane-wave delay-and-sum (or phase-steering) method.

Abstract: A method for Doppler compensation in a phase coherent underwater communications system includes the steps of receiving a communications signal from a plurality of underwater communications channels, where the signal consists of a sequence of raw data; then applying a Doppler estimation to the data; demodulating the raw data; low pass filtering the demodulated raw data; applying resampling and downsampling to the data at a fractional sampling rate, for n samples per symbol, and generating a synchronized, Doppler-phase-corrected output signal; then applying the synchronized, Doppler-phase-corrected fractionally sampled signal to a phase locked loop and equalizer; then comparing an estimated symbol with a decision symbol and updating a plurality of tap coefficients; and h) outputting decision symbols.

Abstract: An underwater apparatus for transmitting and receiving high rate data and voice communication including a transmitter, a receiver, and a Doppler frequency shift compensator. The transmitter includes a data source comprising digital data to be transmitted by the apparatus through the water, a serial-to-parallel data processor for splitting the serial digital data into n parallel data channels, a n-channel modulator for receiving the n parallel data channels and for modulating those channels with n pairs of ultrasonic carriers to produce a modulated signal. The transmitter also includes a hydrophone for receiving and transmitting the modulated signal. The receiver includes a hydrophone for receiving a modulated signal.

Abstract: A terrain bias compensator for a Doppler navigation system utilizes an auxiliary beam with each beam of the Doppler system to form Doppler beam pairs. The axis of the auxiliary beam is slightly offset from the axis of the main beam and is positioned so that the two axes are in the same vertical plane. After slant range compensation, the amplitudes of the Doppler spectrum of each beam is averaged over a predetermined time interval. The difference between the mean amplitudes of the two beams is divided by the offset angle to establish an amplitude per degree correction factor which is applied to the main beam signal returns to establish a main beam amplitude corrected Doppler spectrum.

Abstract: A terrain bias compensator for a Doppler navigation system utilizes an auxiliary beam with each beam of the Doppler system to form Doppler beam pairs. The axis of the auxiliary beam is slightly offset from the axis of the main beam and is positioned so that the two axes are in the same vertical plane. After slant range compensation, the amplitudes of the Doppler spectrum of each beam is averaged over a predetermined time interval. The difference between the mean amplitudes of the two beams is divided by the offset angle to establish an amplitude per degree correction factor which is applied to the main beam signal returns to establish a main beam amplitude corrected Doppler spectrum.

Abstract: An automatic control system is disclosed herewith which causes the notch ter incorporated in a sonar system or any other appropriate utilization apparatus to be electrically by-passed in response to a predetermined minimum doppler present within a data signal being filtered thereby. It includes such uniquely combined elements as envelope detectors, rate-of-decay and rate-of-rise amplifiers, bistable multivibrators, an inverter, and an AND gate for adjusting the position of a selector switch connected for alternately electrically by-passing the notch filter. In addition, the gain of a variable gain amplifier disposed within an automatic gain control loop that includes the aforesaid elements and notch filter may be optionally employed to regulate the gain of the data signal supplied to said notch filter in correspondence with the by-passed and non-by-passed conditions thereof.

Abstract: A method for locating structure-borne sound events in pressure enclosures to be monitored in power plants, includes positioning sensors at various locations on a pressure enclosure. Signals are picked up with each of the sensors upon arrival of a sound wave generated by a structure-borne sound event and propagating along the pressure enclosure. The signals are stored in recording devices disposed downstream. A location of the structure-borne sound event is determined with a hyperbolic section method, from transit time differences resulting from different arrival times of the sound wave at two different sensors. Each range of possible speed values for the propagation of the generated sound wave is made a basis of one respective structure-borne sound event. The hyperbolic section method is performed separately for each speed value of the range for outputting a location indication with an error. The location with the least error is selected as the most likely location of the structure-borne sound event.

Abstract: A signal shift compensation system and method compensates for a shift in a ignal, such as a Doppler shift in an acoustic signal. The system includes a signal sampler for oversampling the shifted signal at a fixed oversampling rate to establish an oversampled shifted signal digital value sequence. The fixed sampling rate is greater than the typical sampling rate, such as the Nyquist rate, of the signals by an oversampling factor. The system further includes a compensation downsampler for decimating the oversampled Doppler shifted signal according to a downsampling factor to establish a decimated digital value sequence. The downsampling factor is determined according to the oversampling factor by which the signal is oversampled and an estimate of the (Doppler) shift value. In one example, the downsampling factor is equal to the oversampling factor divided by a Doppler multiplier reflecting the Doppler shift.

Abstract: A Doppler shift compensation apparatus for compensating Doppler frequency shifts in an incoming signal to reproduce a highly accurate signal. The Doppler shift compensation apparatus has high frequency dissolution ability and can detect a frequency, an amplitude and a phase of the incoming signal accurately.

Abstract: The invention relates to towed sonars. It consists in compensating electronically for the movement of the antenna in order to suppress the Doppler shift of the fixed echoes. In order to do that in a towed linear antenna (203) comprising N sensors (205), M (M<N) successive sensors are selected which are switched electronically in order to make them travel synthetically over the antenna in the direction opposite to the movement of the latter at a speed equal to twice the forward speed of the antenna. In order not to have too large a number of physical sensors, the signals from the latter are interpolated in order to obtain synthetic sensors which are sufficient in number to reduce the increment of the movement of the synthetic sub-antenna in such a way as to suppress the parasitic lobes due to the incremental nature of this movement. It makes it possible to increase the sensitivity of sonars without increasing their power. FIG. 2.

Abstract: A method and apparatus for classifying objects based upon information conned in the fourth order cumulant derived from energy from the object. Successive pulse returns in active systems and samples in passive systems are converted into vectors based upon the fourth order cumulant information for each successive return or sample. The vectors for each such pulse are compared to corresponding class information based upon the corresponding fourth order cumulant information. The comparison uses loglikelihood ratios of the different pairs of classes. Decision making is based upon the value of each loglikelihood ratio in comparison with a class threshold.

Abstract: A laser transmitting and receiving system includes doppler compensation for large doppler shifts in frequency caused by relative motion between a collocated transceiver and a target or relative motion between separated transmitters and receivers. The system includes a tunable laser, a dithered laser optical frequency standard, and a computer for calculating the estimated doppler shift at a given time using platform navigation and attitude control inputs as well as inputs relating to pointing data controlling the direction of transmission. The frequency standard and the computer output are employed to develop a doppler compensation signal which may be used to shift the frequency of the laser transmitter or shift the bandpass of a laser receiver filter. The doppler compensation is provided by a feedback loop which may include r.f. components, a timing trigger from the computer, or wavemeters.

Abstract: A broadband adaptive Doppler estimator and canceller is described for adaptively removing a moving source of near field primary interference that is masking a weaker target. The estimator and canceller employs a distributed field of sensors, through which is moving the source of interference. The estimator and canceller takes the form of a canceller system, wherein the measured reference waveform is a Doppler shifted version of the interference. The estimator and canceller employ interpolating and decimating of the reference waveform to remove Doppler effects over a broadband. The interpolation is performed by oversampling (zero padding) and low pass filtering, and the decimation is a sample rate reduction. The adaption is performed in the decimation to minimize mean square error in the canceller output.

Abstract: A method of extracting target range and Doppler information from a Dopplepread signal is provided. An acoustic waveform is transmitted underwater and impinges upon a submerged Doppler-spread target. Doppler-spread sonar echoes resulting from the transmitted waveform are received and digitized. The received sonar echo is separated into its inphase and quadrature components thereby forming a complex vector function. A fourth-order cumulant spectrum is generated from the complex vector function based upon three time delays. In order to extract the range and Doppler information from the Doppler-spread signal, the first of the time delays is set equal to zero while the second and third time delays are set equal to one another.

Abstract: Doppler insensitive waveforms, such as portions of hyperbolas having the same asymptotes, may be used to modulate pulses or sub-pulses of energy for probing a determined environment so that when the modulated energy is transmitted and received, the received energy may be processed, such as by correlation with the transmitted energy without regard to any Doppler frequency shift between the transmitted energy and the received energy. The Doppler frequency shift may have been imparted by reflection of the transmitted energy from an object having a relative radial velocity with respect to a sensor of the received energy. Also included are apparatus for processing received energy by correlation with transmitted energy, a method for modulating energy that may be transmitted and a method for detecting an object without regard to Doppler frequency shift or relative radial velocity.

Abstract: A doppler compensated sonar system is disclosed as including a transmitter nd a receiver. The receiver of the disclosed preferred embodiment is a single channel receiver which incorporates a mixer and a narrow pass band filter connected in series therein. A phase lock loop of the negative feedback type is connected between the control input and the output of said mixer which effectively determines the occurrence of any doppler effects being processed in said receiver channel and compensates therefor by appropriate adjustment of the frequency of the signal supplied to the control input of said mixer, thereby causing the remainder of said receiver channel, including said narrow band pass filter, to process received target signals without any doppler effects being present therein.

Abstract: A precision Doppler effect compensator provides Doppler compensation in astic transmission by simultaneously sending a known reference signal with an information signal. The information signal and reference signal undergo identical Doppler effects. The compensator uses the Doppler shifted reference signal to sample the analog Doppler affected information signal. The analog information signals are digitally converted and stored in a first in first out shift register. The samples are read out of the FIFO at a rate corresponding to the frequency of a non-Doppler shifted reference signal so as to precisely reconstruct the information signal as transmitted. The samples read from the FIFO are reconverted from digital to analog form to be presented to a receiving modem for further information processing.

Abstract: The invention is a method of reducing phase distortion in a detected seismic signal resulting from Doppler shifting of the transmitted signal. An operator is convolved with the seismic data to correct the dispersion. The operator is determined for the particular transmitted signal and boat speed. The operator is normally determined in the frequency-wave number domain. The seismic data may be transformed to the frequency-wave number domain for performing the convolution. The transformed data may then be transformed back to the time-space domain. Alternatively, the determined operator may be transformed to the time-space domain and the convolution performed in that domain.

Abstract: A device for processing echoes back scattered from the surface of the sea bed in response to sound pulses transmitted by a fish towed while immersed, comprising at least one assembly for determining the components X.sub.C and X.sub.S of the complex envelope of the signals received by a reception chain or from a part thereof, obtained by selective filtering of a narrow band in the frequency spectrum, and computing, storage and display means for obtaining a representation of the variations in time of the complex amplitude of the signals received.

Abstract: An adaptable filtering device and method for filtering sonar signals to remove reverberation signals caused by the vehicle speed and trim and the sea surface and sea bottom. The vehicle itself has an antenna for transmitting and receiving sonar signals, a speed detector, a trim detector, a depth detector, and a distance-to-sea bottom detector and a sonar output device. The present invention forms paths corresponding to each distinct direction from which sonar signals are received by the antenna, each path having a path signal B.sub.i. For each path, a calculation is made to determine a central Doppler-shift frequency .DELTA.f.sub.i and a cut-off frequency f.sub.c.sbsb.i which are to be used to filter the path signal. This calculation is based upon the detected vehicle speed, the detected vehicle trim, the detected vehicle depth, and the detected distance between the vehicle and the sea bottom. The calculated frequencies .DELTA.f.sub.i and f.sub.c.sbsb.

Abstract: An acoustic telemetry system and technique are disclosed for remotely meaing the underwater depth and descent rate of a hydrographic package. Analog signals indicative of hydrostatic pressure exerted on the package and related to its underwater depth are periodically sampled and converted to an N-bit digital word representative of the value of pressure. Each bit of the digital word operates one of a plurality of tone generators of different acoustic frequencies in a narrow band, and the outputs of the tone generators are combined with a reference tone continuously generated to permit resolution of Doppler shifts. Acoustically projected through the water to a remote hydrophone, a composite signal representative of the combined tones is corrected for Doppler shifts by translating the frequency of the signal in accordance with shifts detected in the reference tone.

Abstract: Apparatus is disclosed for reproducing transmitted information which is subject to multipath delay spread effects and doppler frequency-shift effects. The information is transmitted as a series of modulated information pulses of differing nominal frequencies. The nominal frequencies of successive pulses are repeatedly shifted through a predetermined sequence of frequencies. Arrivals of the transmitted pulses are detected at a receiver and are processed to determine the frequencies to which the transmitted pulses are doppler shifted and the multipath delays of each pulse. This frequency and delay information is then used to reproduce the transmitted information from the arrival pulses.

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: 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 trandsducer 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: 1.

Abstract: 2.

Abstract: 1.