US2798902A - System and method for underwater communication - Google Patents

Description

July 9, 1957 D. R. KURSMA ET A1. 2,798,902

SYSTEM AND METHOD FOR UNDERWATER COMMUNICATION Filed June 15, 1956 DAN'MiL R.V NURSNAN am SIGNUND .P. ROSEN A IN VEN TORS SYSTEM AND METHOD FORUNDERWATER COMMUNICATION Daniel Richard Kursman, Philadelphia, and Sigmund P.

` Rosen, Plymouth Meeting, Pa.

Application June 15, 1956, Serial No. 591,615

12 Claims. (Cl. 179-1) The `present invention relates generally to the underwater transmission of intelligence, and more particularly to the underwater transmission of speech or othercomplex forms of intelligence by medium. f i

In general, it has been well known that the most eiicient mode of transmitting intelligence through a water medium is by the use of acoustic or compressional waveenergy, and numerous systems and methods have been developed for this purpose. The prior art development of underwater intelligence transmission has `been devoted principally, however, to the transmission of what may be termed coded intelligence, which may be embodied in a pulsed transmission of a selected and iixed frequency of acoustic energy, or possibly in a frequency variation of continuously transmitted acoustic energy. The foregoing developments may be characterized as coded transmission of intelligence, because the transmitted signals must be decoded in accordance with a predetermined code before being intelligible. It is sought here to distinguish between the foregoing coded type of intelligence transmission and the direct transmission of speech or other complex forms of intelligence, wherein the complex intelligence is itself directly transmitted and received. Although considerable advances have been made over the years in the underwater transmission of coded intelligence, there has heretofore been no development of a practical system and method for direct voice intelligence transmission under water, and this condition has persisted despite the recognized great need therefor in numerous industrial, commercial, sporting, and military underwater activities.

The present invention is directed toward the provision of a practical, ecient, and effective method and system for affording the desired direct transmission of voice or other complex intelligence by propagation of the intelligence through a water medium, and this result being had with reasonable power requirements for the effective transmission range obtained. Generally, it may be stated that propagation 1 through the water the purposes of the present invention are attained by -iirst` converting the speech, or other intelligence to be transmitted, into electrical energy. energy pattern is then mo-died into a different electrical signal pattern in accordance with a selected function to render it most effective for underwater transmission. This new pattern of electrical energy, however, retains in detectableform the characteristics ofthe original electrically converted intelligence. The ultimate electrical energy pattern is then converted into a corresponding form of acoustic or compressible wave energy, and in the form of this ultimate pattern is transmitted and propagated through the water. At the point of reception of the transmitted energy, the acoustic signal is reconverted into its electrical form or counterpart. Since this received signal contains the original electrical intelligence signal characteristics in detectable form, and the modification of the original electrical intelligence signal was had in accordance with a known selected function, the received signal can be readily converted electrically into its original intelligence form or The resultant electrical` Patented July 9, 1957 "ice pattern and transduced into intelligible speech in acoustic energy form, or any other desired presentation form.

1L Accordingly, it is one object of' the present` invention to provide for the direct transmission of intelligence, such as speech intelligence, under water.

Another object of the present invention is to provide for the direct underwater transmission of intelligence of a complex form, without the necessity of coding the intelligence.

Another object of the present invention is to provide for the direct transmission through water of speech and other intelligence in acoustic energy form.

t Another object of the present invention is to provide for the direct transmission and reception of speech intelligence through water, wherein the speech intelligence is `transmitted in an acoustic energy form best suited for 1 underwater transmission, and wherein the original speech intelligence is detected from the transmitted energy for presentation in a form substantially identical to the original speech intelligence. p

A still further objectof the present invention is to provide for the direct transmission and reception of intelligence of a complex form through water, wherein the intelligence is transmitted in an acoustic energy form best suited for underwater transmission, and wherein the original intelligence is detected from the transmitted energy for presentation in a form directly corresponding to the ment of the invention, had in conjunction with the accompanying drawing which is a block diagram of a transceiver operable for the purpose of the present invention.

Referring to the specific embodiment of the present invention illustrated in the accompanying drawing, there is presented a functional block diagram of a voice transceiver system adapted to the purposes of the present invention, and employing the principles of single-sideband suppressed-carrier transmission and reception. For intelligence transmission, the switch 2 is placed in the position shown in the drawing connecting switch contacts a and b. Speech picked up by the microphone l is converted into its electrical signal counterpart .and fed through switch 2 to the balanced modulator 3. Also fed into the balanced modulator is the output of a `fixed frequency oscillator 4. These audio or intelligence and oscillator signals are mixed in the balanced modulator to produce an upper and lower sidebands output, but no carrier as such. The sidebands output of the modulator, being the sum and difference frequencies 0f oscillator and audio or intelligence signal inputs to the modulator, are fed through a band pass filter 5. The band pass filter is designed to pass a range of frequencies constituting the upper sideband of the modulator output, and to attenuate all other frequencies. The transmitting output of the band pass lter thus constitutes an amplitude modulated signal whose frequency varies in .accordance with that of the audio signal plus a" lixed frequencythat of the oscillator 4. This signal is then power amplified at 6 and fed to the underwater transducer 7, from whence it is transmitted and propagated as acoustic or compressional Waveenergy into the surrounding water medium.

For intelligence reception, the switch 2 of the transceiver is set with its contact bar in the position joining contacts c and d. Whereupon, acoustic signals transmitted from a transmitter or transceiver operating as above described are picked up by the transducer 7 -and converted into the corresponding electrical pattern of energy. Thel., transmitting stations modulator output, whose frequencyn varies in accordance with that of the original audio or intelligence signal applied to the transmitting stations modulator plus the oscillator fixed frequency. This electrical output of the transducer 7 is then amplified by the listening amplifier 8 and passed by the band pass filter 5, where much extraneous noise is filtered. From the filter, this incoming signal is again mixed in the balanced modulator 3 with the fixed frequency output of oscillator 4, to again produce a carrier-free upper and lower sidebands output, comprising the sum and difference frequencies of the incoming and oscillator frequencies. With the oscillators 4 of the transmitting and receiving stations set for the same frequency, it will be apparent that the difference frequency or lower sideband obtained in the output of the modulator at the receiving station is the original yaudio or intelligence signal had at the transmitting station. The output of the modulator is then fed through the audio amplifier 9, whose frequency response is such as to reject the upper sideband coming from the modulator and pass only the lower sideband as an appropriately amplified signal to the headset or other speaker means 10.

Taking into account the attenuation characteristics of acoustic energy in water, and other factors such as noise level and distortion in operation, from the standpoint of optimum intelligibility at appreciable range the optimum frequency range for transmission or propagation of acoustic energy into water is approximately 8-11 kc. for a 3 kc. intelligence band. Applicants have found that excellent operating characteristics are had when utilizing the present system with a frequency range of transmission from the transducer into the surrounding water medium of 8.3 to 11.1 kc., where the microphone or other voice pickup response is in the range of 250 C. P. S. to 3 kc. In `order to obtain such a transmission frequency range with the stated intelligence frequency range, it is apparent that the oscillator frequency must be set at approximately 8.1 kc.

As a measure of the effectiveness of the present system for transmission of voice intelligence under water, it has been found that when operating at a frequency range of 8.3 kc. to 11.1 kc. of acoustic energy transmitted into the water medium, a directional 100 beam transmission has a range capability yof approximately 2,000 yards with a transmitter output of 0.6 watt and a receiver capable of delivering 6 milliwatts, reception over this range being comparable in clarity and fidelity with that of normal telephone communication.

The specific embodiment of the present invention shown in the drawing includes the additional feature of generating a constant frequency signal, useful for homing and direction finding functions, as will be apparent to those skilled in the art. For this purpose, the switch 11 is closed causing the oscillator to deliver a constant selected frequency signal to the power amplifier 6, Whose output is then applied to the transducer 7 and transmitted into the surrounding water medium. As will be readily apparent, switches 11 and 2 should in an actual system be appropriately ganged or unified into one selector switch, so that the constant frequency transmission will not coincide with intelligence listening or transmission operation.

In order that the instant constant frequency signal may be audible at the receiver, the chosen transmission frequency from the oscillator must be equal to some audible frequency plus the frequency of the oscillator during normal reception and transmission, in order to have an audible signal passed by the receiving station modulator 3. For example, if the constant frequency transmitted is 9.2 kc. and the oscillator output during normal reception and transmission is 8.1 kc., it is apparent from the preceding discussion that at the receiving station the balanced modulator and audio amplifier will pass a constant frequency signal of 1.1 kc.

Having thus described one specific embodiment of the present invention, it is intended that that embodiment is by way of example to enable a complete understanding of the invention. The present invention is therefore not limited thereto, for modifications will be apparent to those skilled in the art; and it is contemplated that the present invention embraces such modifications and other embodiments as come within the spirit and scope of the appended claims.

What is claimed is:

1. A system for underwater transmission and reception of voice intelligence: including a transmitter comprising a first transducer for converting voice intelligence into an electrical intelligence signal, an oscillator for generating a selected fixed frequency signal, a balanced modulator for mixing the oscillator output and said intelligence signal to produce an upper and lower sidebands suppressed-carrier amplitude modulated signal, a band pass filter for passing the upper sideband of the modulator output, and a second transducer for converting said upper sideband signal into corresponding acoustic energy and propagating the same into water; and including a receiver comprising a first transducer for receiving said propagated acoustic energy in water and converting it into a corresponding electric signal, a band pass filter for passing said signal, an oscillator for generating an electrical signal equal in frequency to that of the transmitter oscillator, a balanced modulator for mixing said filter passed signal and said oscillator output to produce an upper and lower sidebands suppressed-carrier amplitude modulated signal, an amplifier designed to reject the upper sideband frequencies and amplify the lower sideband frequencies of the modulator output, and a second transducer for converting the amplifier output to an audible intelligence; the output frequency of the two oscillators being chosen to provide for the second transducer output of the transmitter a frequency band of approximately 8-11 kc. when carrying intelligence having frequencies up to about 3 kc., thereby providing for optimum intelligibility of the transmitted intelligence.

2. A system for underwater transmission and reception of voice intelligence; including a transmitter comprising a first transducer for converting voice intelligence into an electrical intelligence signal, an oscillator for generating a selected fixed frequency signal, means for mixing the oscillator output and said intelligence signal to produce an upper and lower sidebands suppressed carrier amplitude modulation of said oscillator signal, means for selectively passing the upper sideband signal, and a second transducer for converting said upper sideband signal into acoustic energy and propagating the same into Water; and including a receiver comprising a first transducer for receiving said propagated acoustic energy in water and converting it into a corresponding electric signal, means for detecting the voice intelligence signal from the received signal, and means for transducing the detected signal to audible intelligence; the frequency of said oscillator being chosen to provide for the second transducer output of the transmitter a frequency band of approximately 8-11 kc. when carrying intelligence having frequencies up to about 3 kc., thereby providing optimum intelligibility of the transmitted intelligence.

3. A system for underwater transmission and reception of complex intelligence: including a transmitter comprislng means for converting complex intelligence into a corresponding complex electrical intelligence signal, an oscillator for generating a selected fixed frequency signal, means for mixing the oscillator output and said intelligence signal to produce a single sideband suppressedy signal, and means for converting the detected signal into a desired presentation form; the frequency of said oscillator being chosen to provide for the second transducer output of the transmitter a frequency band of approximately 8-11 kc. when carrying intelligence having frequencies up to about 3 kc., thereby providing for optimum intelligibility of the transmitted intelligence.

4. A system for underwater transmission and reception of complex intelligence; including a transmitter comprising means for converting complex intelligence into a corresponding complex electrical intelligence signal, modulator means for converting said intelligence signal into a single sideband amplitude modulation of a carrier signal, and a transducer for converting the sideband signal into acoustic energy and propagating the same into water; and including a receiver comprising a transducer for receiving said propagated acoustic energy in water and converting it into a corresponding electric signal, means for detecting the original intelligence signal from the received signal, and means for converting the detected signal into a desired presentation form; the modulator means being designed to provide a frequency band for said sideband signal of approximately 8-11 kc. when carrying intelligence having frequencies up to about 3 kc., thereby providing for optimum intelligibility of the transmitted intelligence.

5. An underwater transmitter for complex intelligence comprising means for converting complex intelligence into an electrical intelligence signal, an oscillator for generating a selected fixed frequency signal, a balanced modulator for mixing the oscillator output and said intelligence signal to produce an upper and lower sidebands suppressed-carrier amplitude modulated signal, a band pass filter for passing the upper sideband of the modulator output, and a transducer for converting said upper sideband signal into acoustic energy and propagating the same into water, the frequency of said oscillator being chosen to provide a frequency band for the second transducer output of approximately 8-11 kc. when carrying intelligence having frequencies up to about 3 kc., thereby providing for optimum intelligibility of the transmitted intelligence when received and demodulated.

6. An underwater transmitter for complex intelligence comprising a first transducer for converting complex intelligence into an electrical intelligence signal, an oscillator for generating a selected fixed frequency signal, means for mixing the oscillator output and said intelligence signal to produce a single sideband suppressed carrier amplitude modulation of said oscillator signal, and a second transducer for converting the sideband signal into acoustic energy and propagating the same into water, the frequency of said oscillator being chosen to provide a frequency band for the second transducer output of approximately 8-11 kc. when carrying intelligence having frequencies up to about 3 kc., thereby providing for optimum intelligibility of the transmitted intelligence when received and demodulated.

7. A transceiver for underwater transmission of voice intelligence comprising a first transducer for converting voice intelligence into electrical signals, an oscillator for generating a fixed frequency electrical output, a balanced modulator for mixing said oscillator output with a second electrical signal to produce an oscillator-frequency-suppressed amplitude modulated signal of upper and lower sidebands, a band pass filter means adapted to pass the upper side band frequencies connected to one side of said modulator, a second transducer connected to said band pass filter means for interconverting in water acoustic energy and electrical energy into their respective counterparts, a low pass filter means adapted to pass frequencies below that of the oscillator output and reject frequencles above that of the oscillator output, means for converting the output of said low pass filter means to an audible signal, and means for selectively connecting the first transducer means and the low pass filter means to the other side of said modulator for intelligence transmission and reception respectively, the frequency of the oscillator output being chosen to provide an upper sideband output of the modulator in the frequency range of approximately 8-11 kc. during transmission when carrying intelligence having frequencies up to about 3 kc., thereby providing for optimum intelligibility of the transmitted intelligence when received and demodulated.

8. A transceiver for underwater transmission of complex intelligence comprising a means for converting complex intelligence into electrical intelligence signals, an oscillator for generating a xed frequency electrical output, a balanced modulator for mixing said oscillator output with a second electrical signal to produce an oscillator- `frequency-suppressed amplitude modulated signal of upper and lower sidebands, a band pass filter means adapted to pass the upper side band frequencies connected to one side of said modulator, a transducer connected to said band pass filter means for interconverting in water acoustic energy and electrical energy into their respective counterparts, a low pass filter means adapted to pass frequencies below that of the oscillator outputand reject frequencies above that of the oscillator output, means for converting the output of said low, pass filter means to a desired presentation form, and means for selectively connecting the first mentioned means and the low pass filter means to the other side of :said modulator for intelligence transmission and reception respectively, the frequency of the oscillator output being chosen to provide for said upper side band during transmission a frequency band of approximately 8-11 kc. when carrying intelligence having frequencies up to about 3 kc., thereby providing for optimum intelligibility of the transmitted intelligence when received and demodulated.

9. An underwater transmitter for complex intelligence comprising means for converting complex intelligence into a corresponding complex electrical intelligence signal, modulator means for converting said intelligence signal into a single sideband amplitude modulation of a carrier signal, and a transducer for converting the sideband signal into acoustic energy and propagating the same into water, the modulator means being designed to provide a frequency baud for said sideband signal of approximately 8-11 kc. when carrying intelligence having frequencies up to about 3 kc., thereby providing for optimum intelligibility of the transmitted signal when received and demodulated.

l0. A transmitter as dened in claim 6, and further including means cooperating Withsaid oscillator for generating a second selected fixed frequency signal of frequency differing from that of the first mentioned fixed frequency signal by an audible frequency and for feeding said second fixed frequency signal unmodulated to said second transducer.

11. A transceiver for underwater transmission of complex. intelligence comprising a means for converting complex intelligence into electrical intelligence signals, an oscillator for generating a fixed frequency electrical output, a balanced modulator for mixing said oscillator output with a second electrical signal to produce an oscillatorfrequency-suppressed amplitude modulated signal of upper and lower sidebands, a first filter means adapted to pass one sideband of frequencies connected to one side of said modulator means, a transducer connected to said first filter means for interconverting in water acoustic energy and electrical energy into their respective counterparts, a second filter means adapted to pass only frequencies below that of the oscillator output, means for converting the output of said second filter means to a desired presentation form, and means for selectively connecting the first mentioned means and the second filter means to the other side of said modulator for intelligence transmission and reception respectively, the frequency 7 of the oscillator output being chosen to provide a frefrequency output by au audible frequency and for feeding quency band for said sideband of frequencies passed by said second xed frequency output unmodulated to said said rst lter means during transmission of approxisecond transducer. t

matel 8-11 kc. when carryin intelli ence havin frequencyi'es up to about 3 kc., theregby provigdng for optmum 6 References Cted m the me of this Pamt intelligibility of the transmitted signal when received and UNITED STATES PATENTS demodulated. 2

12. A transceiver as dened in claim 1l, and further 423,459 Mason July 8 1947 including means cooperating with said oscillator for gen- OTHER REFERENCES erating a second fixed frequency electrical output of fre- 10 Elements 0f Aoustical Engineering, by Harry F- Olsen, quency differing from that of the first mentioned Xed D' van Nostfand C0 1947 Pages 520521- rse Decision in Interference 902, D. R. Kurslnun mmuncaton, final as bo claims 10 Notice of Adve In Interference No. 91,257 involving Patent No. 2,798, and. S. P. Rosen, System and method for underwater eo judgment adverse to the patente/es was rendered Jan. 10, 1964,

and 1Q.

[Oficial Gazette A201-Z 28, 1.964.]

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