Accession Number : AD0776796

Title :   An Experimental ELF Receiver.

Descriptive Note : Technical rept.,

Corporate Author : MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB

Personal Author(s) : Bernstein,Steven L. ; McNeill,Dale A. ; Nackoney,Ogden G. ; Richer,Ira

Report Date : 11 SEP 1973

Pagination or Media Count : 130

Abstract : The advantages of utilizing the ELF band for communications to submarines are principally the low attenuation rate of ELF signals in seawater, and the low attenuation rate in the earth-ionospheric waveguide. ELF transmitters, however, require high input power. Therefore, efficient signaling schemes and sophisticated receiver designs which help minimize the required transmitter power, and hence system costs, are particularly important. This report considers one such signaling scheme - binary convolutional encoding with antipodal modulation of a band-spread minimum-shift-keyed (MSK) carrier -- presents the design and performance of an experimental ELF receiver which includes several unique features to maximize efficiency. The receiver includes several adaptive elements such as the compensation of the ocean propagation medium, nonlinear processing of the non-Gaussian ELF noise, tracking notch filters for interference rejection, and a sequential decoder for reliable decoding at low SNR. Receiver tests included real-time reception of test messages aboard a submerged submarine in the Atlantic Ocean. (Author)

Descriptors :   *Radio receivers, Extremely low frequency, Submarines, Underwater communications, Signal processing, Digital systems, Adaptive systems

Subject Categories : Radio Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE