Patent ID: 6130859
Filing Date: 2000-10-10
Classification: H04B,Y10S

Abstract:
An underwater modulator-demodulator (modem) apparatus for transmitting and receiving data at a high rate through water, said modem comprising:a. A transmitting section comprising:data source means, comprising digital data to be transmitted through water;serial-to-parallel data processing means, for splitting a serial data into n parallel channels;n-channel modulator means, for receiving data from said n parallel channels and for modulating the same with n pairs of ultrasonic carriers, thereby producing a modulated signal; andhydrophone means, for receiving said modulated signal from said n channel modulator means, and for transmitting same into water;b. A receiving section comprising:hydrophone means, for receiving a modulated signal from the water, and for conveying the same into an RF circuit;RF circuitry, for amplifying and shaping the received modulated signal, and for converting the received modulated signal to serial digital data and for conveying the same into serial-to-parallel means;serial-to-parallel means, for receiving said serial digital data from the RF circuit, and for splitting the same into n parallel channels;n-channel demodulator means, for demodulating said serial digital data conveyed to the demodulator from said RF circuit, and for outputting n parallel channels of digital data; andparallel-to-serial means for receiving n parallel channels of outputted data from the demodulator means, and for converting the data into serial data; andc. means for compensating for the Doppler effect on a transmitted signal propagating through water comprising, in the modulator means of the transmitting section, means for transmitting two unmodulated carriers and, in the receiving section, a frequency adjusting device for measuring the frequency of at least one of said two unmodulated carriers and for comparing said measured frequency with a predetermined frequency and for adjusting the n-channel demodulator means for any deviation between said measured frequency and said predetermined frequency.