Abstract: A submarine launched expendable radio navigation system (SSXRN) buoy method and apparatus. According to one embodiment, a method for determining a submarine geographic position using a SSXRN buoy system is disclosed. The method comprising launching a radio navigation-enabled buoy and recording a launch time and DRNS submarine position. The method further comprises recording a buoy breach time and searching for radio navigation RF signals. Then, recording a radio navigation position acquisition time and an initial radio navigation position. Further, recording a subsequent radio navigation position data and a subsequent time. Moreover, determining a DRNS correction factor using a DRNS position error, a buoy drift, radio navigation position data and DRNS position data. In addition, estimating the submarine geographic position using the DRNS correction factor and a DRNS geographic position. In another embodiment, a SSXRN buoy system is disclosed.

Abstract: An underwater acoustic communication system provides an operator with adjable frequency diversity so that data rates may be tailored to specific multipath environments. Transmitted messages are sent with precursor transmission/reception synchronization data and transmission parameter data so that the receiving communication end will recognize when message data starts, tone length as-well-as the frequency diversity of the transmitted message. Timing is extracted from the data to compensate for Doppler shift.

Abstract: A precision Doppler effect compensator provides Doppler compensation in astic transmission by simultaneously sending a known reference signal with an information signal. The information signal and reference signal undergo identical Doppler effects. The compensator uses the Doppler shifted reference signal to sample the analog Doppler affected information signal. The analog information signals are digitally converted and stored in a first in first out shift register. The samples are read out of the FIFO at a rate corresponding to the frequency of a non-Doppler shifted reference signal so as to precisely reconstruct the information signal as transmitted. The samples read from the FIFO are reconverted from digital to analog form to be presented to a receiving modem for further information processing.

Abstract: A hydroacoustic transducer provides an improved hemispherical radiation pern throughout a wide range of operating depths. A can-shaped transducer is nestled in the inside of a hat-shaped array of hollow spheres. Resiliently mounting the spheres with respect to each other and a hat-shaped shell holds the array away from the surface of the transducer and layering the hollow spheres assures the hemispherical pattern. Fashioning the spheres from hemispherical shells of aluminum and bonding them together makes the array insensitive to greater or lesser hydrostatic pressures and potting the array in polyurethane presents a more rugged structure capable of withstanding the routine abuses of the ocean environment.

Abstract: An undersea communications system provides for improved data transmission pabilities. Two separate sources of information respectively modulate the upper and the lower sidebands of an acoustic carrier. The discretely modulated sidebands are simultaneously transmitted without the acoustic carrier or the acoustic carrier can be added to allow asynchronous or synchronous demodulation and use of the two modulating informations. Separation of the information in the two discretely modulated sidebands is assured by shifting the modulating information to ultrasonic regions and filtering out upper and lower sidebands of modulating information. Next, the shifted sidebands are modulated by an acoustic carrier which, optionally, is transmitted along with the discretely modulated upper and lower sidebands. A phase locked loop in the receiver portion assures synchronous demodulation or a crystal oscillator allows asynchronous demodulation of the discretely modulated upper and lower sidebands.

Abstract: An adaptive slant range compensator, suitable for use with an optical mapg system for remote viewing, comprises a logarithmic amplifier which compresses an analog input signal having a wide range of values to a tractable range. An analog-to-digital (A/D) converter converts the compressed signal to a 10-bit binary number. The digitized compressed data is then used to address antilog programmable read-only memories (PROMs) which contain the antilog of the address data in scientific notation. Control and data processing circuits are used to accumulate sample scans from the antilog PROMs in a summing memory, calculate an average scan from the accumulated sample scans, and transfer this average to a working memory. The data stored in the working memory is used to drive an attenuation/amplification network that divides succeeding scans by the stored average scan. In this way, the inverse transfer function is applied to the analog input signal, which forms another input to the attenuation/amplification network.