An experimental ELF receiver

The Sanguine receiver must include sophisticated design features to permit extremely reliable operation at low signal-to-noise ratios. These features include nonlinear signal processing, compensation for the effects of the ocean channel, phase tracking at low signal-to-noise ratios, and sequential decoding. The entire receiver has been implemented on a small-digital computer, and extensive tests were conducted in order to optimize the design and to gather statistical data. Experiments with actual transmitted data indicate that the receiver can achieve the predicted performance. In this paper, the structure of the receiver is described, design tradeoffs are discussed, and the receiver performance is presented.