Theoretical Assessment of DEMON Performance
Abstract
Ships and submarines frequently radiate sounds underwater which exhibit distinct amplitude modulation. For example, the noise from a cavitating propeller is usually modulated at a frequency equal to the blade rate (i.e., the rate of rotation of the shaft multiplied by the number of blades of the propeller). This noise can be received by a passive sonar, and with training and in conjunction with other sounds, an operator can often, from the modulation, identify the type of vessel and estimate its speed. The operator can be greatly assisted by rectifying the sonar signals to extract the modulation and spectrum analyzing the result. This is termed "DEMON" processing. A block diagram of a DEMON processor is shown in figure 1. The writer is not aware of any published mathematical analysis of this processor. In this memorandum, an expression of its theoretical performance is derived. It should be pointed out that the processor shown in figure 1 is not necessarily the optimum detector for such modulated signals. Tuteur(1) has made an attempt to determine the optimum processor and its performance, but the simplifying assumptions he makes are unrealistic, and as a consequence his results should be regarded as useful only in giving an upper bound to the performance which might be achieved. The present writer has not yet succeeded in determining the optimum processor under realistic assumptions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1970
- Accession Number
- ADA482974
Entities
People
- H. A. D'assumpcao