Underwater navigation system

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 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.

1 . An underwater communications system for transmitting electromagnetic and/or magnetic signals to a remote receiver, comprising:
 a data input;   a digital data compressor for compressing data that to be transmitted;   a modulator for modulating the compressed data onto a carrier signal; and   an electrically insulated, magnetic coupled antenna for transmitting the compressed, modulated signals.   
   
   
       2 . The underwater communications system of  claim 1  wherein the data input includes at least one of: a text input; an audio input for capturing audio signals; an image input for capturing an image and a video input for capturing a video image. 
   
   
       3 . The underwater communications system of  claim 2 , further comprising:
 a display for allowing digital data to be viewed prior to transmission.   
   
   
       4 . The underwater communications system of  claim 1 , further comprising:
 a receiver that has an electrically insulated, magnetic coupled antenna for receiving compressed, modulated signals;   a demodulator for demodulating the signals, and   a de-compressor for de-compressing data.   
   
   
       5 . The underwater communications system of  claim 4 , further comprising:
 a display for displaying decompressed data.   
   
   
       6 . The underwater communications system of  claim 4 , further comprising:
 a device for generating sound representative of the data.   
   
   
       7 . The underwater communications system of  claim 1 , wherein the magnetic coupled antennas include at least one of, loops and solenoids. 
   
   
       8 . The underwater communications system of  claim 7  wherein the solenoid is formed around a high magnetic permeability material. 
   
   
       9 . The underwater communications system of  claim 1 , wherein the antenna is surrounded with a low conductivity material with a permittivity matched to that of the propagation medium. 
   
   
       10 . The underwater communications system of  claim 1 , wherein the transmitter antenna is operable to transmit signals having a frequency in the range of about 1 Hz to 100 MHz. 
   
   
       11 . The underwater communication system of  claim 1 , further comprising:
 a converter for converting captured speech to digital text for transmission.   
   
   
       12 . The underwater communication system of  claim 11 , wherein speech synthesis is used to reconstruct audible speech at the receiver. 
   
   
       13 . An underwater communications system, comprising:
 a receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal; and   a demodulator for demodulating the signal to reveal compressed data, and a de-compressor for de-compressing the data.   
   
   
       14 . The underwater communications system of  claim 13  further comprising:
 a display for displaying the de-compressed data.   
   
   
       15 . An underwater communications module of  claim 14  further including means for generating sound representative of the data. 
   
   
       16 . An underwater communications system, comprising:
 a transmitter for transmitting electromagnetic and/or magnetic signals,   a receiver for receiving signals from the transmitter, wherein at least one of the transmitter and receiver is underwater and includes an electrically insulated, magnetic coupled antenna.   
   
   
       17 . The underwater communications system of  claim 16 , wherein at least one transceiver is underwater and has an electrically insulated, magnetic coupled antenna. 
   
   
       18 . The underwater communications system of  claim 16 , wherein a plurality of intermediate transceivers are provided. 
   
   
       19 . The underwater communications system of  claim 18 , wherein at least one transceiver is above water and is operable to pass a signal from the transmitter to the receiver through an air propagation path. 
   
   
       20 . The underwater communications system of  claim 18 , wherein at least one of the intermediate transmitter and receiver is mobile. 
   
   
       21 . The underwater communications system of  claim 16 , wherein at least one of the transmitter and receiver is underwater and has an electrically insulated, magnetic coupled antenna, and the other is an above water station. 
   
   
       22 . The underwater communications system of  claim 21  wherein the above water station has an electrically coupled antenna. 
   
   
       23 . The underwater communications system of  claim 21 , further comprising:
 at least one transceiver positioned above a water surface for relaying signals between the transmitter and receiver.   
   
   
       24 . The underwater communications system of  claim 16 , wherein the transmitter is an underwater transmitter with an electrically insulated, magnetic coupled antenna for transmitting electromagnetic and/or magnetic signals, and the receiver is an underwater receiver having an electrically insulated, magnetic coupled antenna for receiving signals from the underwater transmitter, wherein the transmitter and receiver are operable to communicate in the near field. 
   
   
       25 . The underwater communication system of  claim 16 , further comprising:
 an acoustic communication system having an acoustic transmitter.   
   
   
       26 . The underwater communication system of  claim 25 , further comprising:
 a device for selecting one of the electromagnetic/magnetic transmitter and acoustic transmitter to transmit a signal.   
   
   
       27 . The underwater electromagnetic communication system of  claim 16 , wherein information is transferred using multiple narrow frequency channels. 
   
   
       28 . The underwater communications system of  claim 16 ,
 wherein at least one of the transmitter and receiver includes a device for varying the signal gain.   
   
   
       29 . The underwater communications system of  claim 16 , wherein the underwater communications system implements data compression to reduce the bandwidth. 
   
   
       30 . The underwater communications system of  claim 16 , wherein the underwater communications system modulates data on to a lowest practical carrier frequency to minimize attenuation over distance. 
   
   
       31 . The underwater communications system of  claim 16 , wherein the underwater communications system is operable to vary the carrier frequency based on range of operation. 
   
   
       32 . The underwater communications system of  claim 31 , wherein the underwater communications system is configured to establish a connection; commence transmission at a first frequency; once communication is established, vary the frequency and select the frequency based on the received signal strength. 
   
   
       33 . The underwater communications system of  claim 16 , wherein the transmitter and receiver are both submerged, and arranged so that the signal path between them includes at least in part an air path that is above water. 
   
   
       34 . The underwater communications system of  claim 16 , wherein the transmitter and receiver are both submerged, the transmitter and receiver being arranged so that the signal path between them includes at least in part an air path that is above water. 
   
   
       35 . The underwater communications system of  claim 16 , wherein the underwater communications system increases frequency to increase attenuation for covert operation. 
   
   
       36 . The underwater communications system of  claim 16 , wherein the underwater communications system uses forward error correction techniques for underwater data transmission. 
   
   
       37 . The underwater communications system of  claim 16 , wherein the underwater communications system uses a sea bed as a low loss path for communication. 
   
   
       38 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to be at least partially positioned in a non-water fluid or gas. 
   
   
       39 . The underwater communications system of  claim 16 , wherein the underwater communications system provides narrow band frequency filtering to reduce effects of received noise. 
   
   
       40 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to use spread spectrum techniques to overcome multi path propagation, fading and dispersion effects. 
   
   
       41 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to provide direct transmission of base band signals without modulating a higher frequency carrier. 
   
   
       42 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to use directional antennas to improve signal strength directed from transmitter to receiver and improve received signals. 
   
   
       43 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to use directional antennas to allow re-use of frequencies in different directions. 
   
   
       44 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to use electric field coupled antennas as an alternative to magnetic coupled. 
   
   
       45 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to use electric coupled antennas as a supplement to magnetic coupled antennas. 
   
   
       46 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to use superconductivity for maximizing received signal and/or transmitted signals. 
   
   
       47 . The underwater communications system of  claim 16 , wherein the underwater communications system includes Josephson junction SQUID detectors for sensitive receivers. 
   
   
       48 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to transmit only when new relevant data is available at a transmit site. 
   
   
       49 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to transmit only periodically. 
   
   
       50 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to transmit only when a signal from a receive end requests data. 
   
   
       51 . The underwater communications system of  claim 16 , wherein the underwater communications system is configured to reduce transmit power to a lowest level necessary for reliable communication. 
   
   
       52 . The underwater communications system of  claim 16 , wherein the underwater communications system includes receive circuits that are dormant until a pre-timed wake up. 
   
   
       53 . The underwater communications system of  claim 16 , wherein the underwater communications system includes an array of multiple antennas to cover a larger area. 
   
   
       54 . The underwater communications system of  claim 16 , wherein at least one intermediate transceiver is provided to relay signals between an originating transmitter a terminating receiver.