USA As Represented by Secretary of the Navy

Timothy B Straw

Michael J Obara

Stephen A Caldwell

Thomas A Freehill

Dmitry Chizhik

Ahmed S Zaki

Mark B Moffett

James M Powers

Peter A Child

Kenneth R Galliher

Michael J O'Bara

Patricia M Eno

Richard L Miller

Joseph T Lucia

Thomas G Bucko

Philip G Danforth

A sonar system is provided with the system having comparatively reduced power consumption, data bandwidth and data storage requirements. A sensor array of the system is configured to a sleep mode, low-resolution mode and high-resolution mode. In the sleep mode, all sonar sensors are configured in the mode and no acoustic signals are detected or processed. In the low-resolution mode, a limited number of sonar sensors are powered and acoustic signals received by the sensors are processed with reduced bandwidth and dynamic range, and then stored on a data storage device. In the high-resolution mode, the acoustic signals detected by the sonar sensors are processed with full signal bandwidth and dynamic range and then stored on the data storage device. A 10 bit mu-Law encoding scheme is used to reduce the amplitude scale of measurement or dynamic range of the digitized acoustic signals.

Method for compressing the dynamic range of measured signals

A high performance solid-state heading sensor for underwater towed arrays is taught that combines high quality MEMS sensor components with data processing filters to resolve performance limitations present in prior art heading sensors. The heading sensor employs rate gyroscopes, accelerometers, magnetometers and a customized Kalman filter formulation implemented on a micro-controller to improve performance in determining the roll, pitch and heading of a towed array.

High accuracy heading sensor for an underwater towed array

An acoustic ranging system and method of use is provided that measures the magnitude of the separation of a pair of towed acoustic line arrays at a discrete point along the length of each array. One array acts as the measurement source, while the other array acts as a frequency-shifted echo repeater. The source array incorporates one sonar transmitter and two sonar receivers. The system further includes a configurable frequency shifter that enables one measurement source to make measurements with multiple repeater arrays.

Acoustic ranging system for multi-line towed acoustic arrays

A sonar sensor array is provided that has reduced power consumption, data bandwidth and data storage requirements. The sensor array may be configured to a sleep mode, low-resolution mode and high-resolution mode. In the sleep mode, all sonar sensors are configured in the sleep mode and no acoustic signals are detected. In the low-resolution mode, a limited number of sonar sensors are powered and acoustic signals received by the sonar sensors are processed with reduced bandwidth and reduced dynamic range, and then stored on a data storage device. In the high-resolution mode, the acoustic signals detected by the sonar sensors are processed with full signal bandwidth and full dynamic range and then stored on the data storage device.

Sonar sensor array and method of operating same

The calibration circuit is used with a differential input, monolithic integrated circuit preamplifier in a sensor system. The calibration circuit tests the integrity of the sensor, the preamplifier, and the wiring in the sensor system. The calibration circuit includes first and second calibration capacitors having different capacitances connected to the preamplifier input leads. A calibration signal source is connected between the capacitors. The capacitors are preferably implemented on the same integrated circuit as the preamplifier. In operation, a calibration signal of known amplitude is applied to the calibration circuit and the level at the preamplifier output is determined. The level at the preamplifier output indicates certain conditions relating to the integrity of the sensor and its wiring, for example, an open circuit condition or a short circuit condition.

Monolithic I.C. implemented calibration circuit

Calibration circuit for use with a differential input preamplifier in a sensor system

A calibration generator responds to a digital signal by generating a diffntial calibration signal with respect to a reference value established by a reference source. The calibration generator includes an input for receiving the digital signal and a differential output for transmitting the differential calibration signal. A voltage divider connects between voltage sources of opposite polarity and equal magnitude for generating a constant magnitude signal across one resistor in the voltage divider. A switch establishes alternate sets of paths from the voltage divider to the differential output. A control responds to the digital signal for controlling the switch thereby to alternate the paths from the voltage divider to the differential output and generate an alternating, fully differential, constant magnitude calibration signal.

Differential calibration signal generator

An analog signal conditioner for signals from high impedance sources adap for ready implementation as an integrated circuit. The signal conditioner includes a preamplifier, a step gain amplifier and a low-pass filter. A calibration generator can inject a calibration signal into the system. The step gain amplifier includes analog switches that control paths through a voltage divider network to provide negative feedback on both sides of a fully differential operational amplifier. The design of the feedback networks minimizes the total resistance on the integrated circuit.

Amplification of signals from high impedance sources

A monolithic CMOSFET integrated circuit which includes a first MOSFET integrant transistor having a gate area chosen to provide a desired range of resistance when operated in its triode region which constitutes (i) a preamplifier, (ii) a voltage controlled resistance (VCR) device, and (iii) a high-pass filter when capacitive with a transducer. Preferred operating characteristics are achieved by including an active CMOSFET linearization network including a pair of second and third integrant MOSFET transistors having only one-hundredth (1/100th) to one-tenth (1/10th) the gate area of the first transistor. The present invention operates with a reduction in distortion resulting from the filtering effect of the combined capacitive reactance of the sensor and the resistance of the resistor. This reduction in distortion occurs at frequencies greater than the corner frequency (the frequency which is equal to the inverse product of the capacitance in farads times the resistance in ohms) and is due to the high-pass filter formed by the sensor and the resistor. Stated in terms of well known capacitor-resistor pole theory, the high-pass filter effect is based upon the 'transducer capacitance-preamplifier input resistance pole' (i.e., such 'pole' with reference to the capacitance characteristic of the capacitive transducer and the preamplifier input resistance provided by a CMOSFET I.C. device or devices as aforesaid). This distortion is less than that which would have been expected as a consequence of the non-linearity of prior art MOSFET VCRS. Due to this high pass filter effect, the distortion rolls off at approximately 20 db/decade of frequency.

Preamplifier with adjustable input resistance

An omnidirectional ultrasonic microprobe hydrophone is disclosed. Applicans include underwater mine detection, explosive shock testing, high wave number measurements, medical imaging, and therapeutic systems. The apparatus includes at least two lead zirconate titanate (PZT) pressure sensing elements having a plurality of columnar voids formed therein. The pressure sensing elements are deposited on a metallic or nonmetallic substrate which provides mechanical support for the microprobe hydrophone. Electrical connection to the pressure sensing elements is made by deposition of conductors and insulators on the substrate material. Wire bonds are used to attach wire leads for connection to a supporting structure containing a preamplifier. Line arrays and planar arrays of microprobe hydrophone elements are also disclosed.

Omnidirectional ultrasonic microprobe hydrophone

A preamplifier for a piezoelectric sensor requiring a high-impedance, low ise interface circuit. The preamplifier is a single, monolithic integrated circuit that can be mounted directly onto or inside a miniature sensor without degrading the sensor's performance. The preamplifier performs signal amplification with a full-differential amplifier that includes common-mode feedback. A pair of feedback capacitors together with the sensor capacitance control the voltage gain of the preamplifier over much of it's useful operating range of 100 Hz to 100 kHz. The preamplifier circuit also has feedback resistors that discharge any accumulated DC voltage which might appear on the capacitors. Also the feedback resistors form a high pass filter which rejects low .frequency background noise from the sensor.

Monolithic low noise preamplifier for piezoelectric sensors

A stand-alone electronic simulator device for testing expendable bathythegraph (XBT) systems. The device is inserted into an XBT system in place of an expendable probe for purposes of checking the performance of the rest of the system with an active test signal. The test device simulates an operational XBT probe by switching a highly accurate and stable array of resistance values across its output. The switching rate is controlled by a stable internal time base such that the test pattern plotted on the strip chart recorder and transmitted to an external system will always look the same if the system is functioning properly. Temperature stability in the test device, essential because of the broad ambient temperature range which may be encountered in use, allows checks of the system for probe depth timing linearization in addition to temperature measurement.

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Narragansett, RI, United States of America

Timothy B Straw