Spread spectrum underwater location beacon system
AssigneeSandia Research Associates, Inc.
InventorSteven M. Shope
Life of this patent
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Abstract
An underwater location beacon emits a continuous wave signal which is phase-shift modulated by a pseudo-noise, spread spectrum code. This signal is detected with an exact replica of the transmitted code. To an unauthorized observer without the replica, the transponder's signal is indistinguishable from background ocean noise. The spread spectrum code allows extraction of the signal from high levels of ocean noise, providing an increased detection range, jamming resistance, covertness, and unique signals for each pinger. The outputs of the surface spread spectrum receiver are used with automated location algorithms. Several receivers at different surface positions provide the underwater coordinates of the pinger's location.
Claims19
Underwater location system, comprising:
- an underwater beacon apparatus having a housing, an attachment for attaching the housing to a device to be located underwater, an oscillator mounted in the housing for producing a continuous wave signal, a modulator connected to the housing for selectively phase-shifting the continuous wave signal, a sequence generator mounted in the housing and connected to the modulator for controlling the sequence of phase-shifts by the modulator, a driver connected to the modulator for receiving signals from the modulator and producing signals of sufficient power to drive a transducer, a transducer mounted in the housing and connected to the driver for receiving signals from the driver and transducing the signals to sound signals in water in which the apparatus is located;
- and
- a receiver for receiving the sound signals in the water, the receiver having a detector for detecting the sound waves and for converting the sound waves into electronic signals, a preamplifier connected to the detector for preamplifying the electronic signals from the detector, a bandpass filter connected to the preamplifier for eliminating noise in frequencies outside a beacon frequency, an analog to digital converter connected to the bandpass filter for converting signals from the bandpass filter in the beacon frequency to digital signals, a demodulator connected to the converter for demodulating the digital information from the converter for obtaining components of the beacon frequency signal and a matched filter for matching the modulation sequence produced by the beacon.
A receiver apparatus for detecting and locating an underwater beacon apparatus comprising a receiver for receiving sound waves in water from the underwater beacon apparatus, the receiver having a detector for detecting the sound waves and for converting the sound waves into electronic signals, a preamplifier connected to the detector for preamplifying the electronic signals from the detector, a bandpass filter connected to the preamplifier for eliminating noise in frequencies outside a beacon frequency, an analog to digital converter connected to the bandpass filter for converting signals from the bandpass filter in the beacon frequency to digital signals, a demodulator connected to the converter to demodulate the digital information from the converter to obtain components of the beacon frequency signal, a matched filter connected to the demodulator for matching the modulation sequence produced by the beacon.
An underwater location beacon apparatus, comprising a housing, an attachment for attaching the housing to a device to be located underwater, an oscillator mounted in the housing for producing a continuous wave signal, a modulator for selectively phase-shifting the continuous wave signal, a sequence generator for controlling the sequence of phase-shifts by the modulator, a driver connected to the modulator for receiving signals from the modulator and producing signals of sufficient power to drive a transducer, a transducer mounted in the housing and connected to the driver for receiving signals from the driver and transducing the signals to sound signals in water in which the apparatus is located.
The method of detecting and locating an underwater device, comprising generating a continuous wave signal, generating a spread spectrum code, phase-shift modulating the continuous wave signal by inserting a predetermined pseudo-random signal into the continuous wave according to the spread spectrum code, driving a transducer with the phase-shift modulated continuous wave signal, and creating phase-shift modulated sound signals.
An underwater locator beacon, comprising a case, a transducer mounted in the case, a power supply mounted in the case, a water switch connected to the power supply to activate the beacon, and an electronics module connected to the power supply for supplying a spread spectrum phase-shifted continuous wave signal to the transducer for driving the transducer and producing a spread spectrum phase-shifted continuous wave sound signal from the transducer
- wherein the electronic module comprises an oscillator for producing a continuous wave, a modulator connected to an output of the processor for phase-shifting the continuous wave output of the oscillator, a sequence generator connected to the modulator for controlling the modulator with a pseudo-random signal, spread spectrum code, and a driver connected to the transducer for driving the transducer with the phase-shifted continuous wave.
Dependencies are inferred from the claim text.