Communications – electrical: acoustic wave systems and devices – Underwater system – Telemetering
Patent
1993-12-23
1996-06-25
Pihulic, Daniel T.
Communications, electrical: acoustic wave systems and devices
Underwater system
Telemetering
H04B 1100
Patent
active
055306829
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of transmitting an information signal under water from a transmitter located at a first place to a receiver located distant therefrom at a second place, wherein a modulated ultrasound carrier signal delivered to the water is formed with a fixed value of the amplitude in the transmitter by modulation of an ultrasound carrier signal of a given frequency with the information signal, and the modulated ultrasound carrier signal picked up from the water is demodulated in the receiver for recovering the information signal, as well as to an apparatus for carrying out this method.
In a known method of this type (DE-A-2 656 969) the rectangular ultrasound carrier signal obtained by a push-pull circuit of monostable multivibrators is frequency-modulated and, subsequently, converted in a final stage into a sine-shaped frequency-modulated output signal which is radiated to the water. The radiated modulated ultrasound carrier signal has a fixed value of the amplitude as a result of its frequency modulation.
Another known method for underwater signalling between watercraft, in particular also for telephony operations, is based as well on the problem that conventional radio signalling techniques cannot be applied because of the bad transmitting capacity of water for electromagnetic waves (J. Matauschek "Einfuhrung in die Ultraschalltechnik" VEB Verlag Technik Berlin, 2nd edition, August 1961, pages 318 to 320). Particularly, by this method information can be transmitted also between submarine boats travelling underwater. The known method is based on amplitude modulation of the ultrasound carrier signal with the information signal to be transmitted. Thus, in this method a certain amplitude swing of the ultrasound carrier signal corresponds to the information signal to be transmitted. In this connection the problem arises, however, that cavitation of the ultrasound-conductive medium, i. e. the tearing of it and the formation of small bubbles, occurs above a certain amplitude value of the ultrasound carrier signal, resulting in considerable disturbances of the transmission of the information signal. On the other hand, if the amplitude of the ultrasound carrier signal were restricted to a value below that cavitation limit, only a correspondingly limited amplitude swing would be available for modulation, so that in particular those portions of the information signal that correspond to an amplitude swing that is small in proportion to the maximal amplitude swing show a very bad signal distance from disturbances, which gets worse as the distance between the transmitter and the receiver grows.
The use of ultrasound for information transmission is, for instance, also known for television receiver remote-controls. With this application, however, only simple switch signals for channels and control signals for sound and picture adjustment have to be transmitted, so that the demands in connection with the transmission of any information signal whatever with a complicated and differenciated information content do not arise here at all.
The object of the invention is to define a method of the type mentioned at the outset which is improved as far as its range and security against disturbances is concerned, and an apparatus for carrying out this method, which are in particular suitable for underwater communication between divers.
As far as the method is concerned, this object is achieved according to the invention in that modulation of the ultrasound carrier signal with the information signal is performed as pulse duration modulation in which the pulse leading edges are modulated with the information signal and the fixed value of the pulse amplitude of the modulated ultrasound carrier signal is below the cavitation limit of the medium.
Thus, in the method according to the invention, the cavitation limit of the medium `water` which serves for information transmission is approached only to a point necessary for the desired information transmission range. Thereby, an optimum of ultrasonic energy is on the on
REFERENCES:
patent: 3742440 (1973-06-01), Ehrlich et al.
patent: 3806862 (1974-04-01), Chao
patent: 3958215 (1976-05-01), Bianco
patent: 4039999 (1977-08-01), Weston
patent: 4044611 (1977-08-01), Kaname et al.
patent: 4231031 (1980-10-01), Crowther et al.
Peter Zastrow "Fernsehempfangstechnik" .
ITT, Ultraschallsender und Empfanger.
LandOfFree
Method and apparatus for transmitting an information signal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for transmitting an information signal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for transmitting an information signal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2195045