DF reading is not used in the estimation of the emitter position. Since the position estimate is obtained only from the parameters of the trajectory of the observer, under the condition of constant apparent angle of signal arrival, any systematic error in the DF does not affect the estimate.A major advantage of the method discussed here is the complete absence of ambiguities. It not only does not introduce extra ambiguities such as the circulation method does; it even resolves the basic ambiguity present in DFs, thus eliminating the need for a sense antenna.The main drawback of the spiral method proposed in this work is that the trajectory required to be executed by the observer is somewhat complicated. However, the principle on which the trajectory is based, viz., keeping a certain system output constant, is fairly simple and is used in several navigation schemes, both automatic and manual.
This article derives the formula for random error versus signal-to-noise of an automatic bearing/time delay tracking system. The tracker is essentially a servosystem employing a clipper-type phase detector. Numerical results for the broadband (1 oct) case are presented and compared with the Cramer–Rao lower bound on time delay error. The characteristics of the phase detector and loop transfer function combine to provide a tracking filter that automatically decreases bandwidth with decreasing signal-to-noise ratio while maintaining essentially constant stability.
A formulation for the detection threshold of a sonar receiver operating with a reverberation background is derived. The similarity of the result to the noise-limited detection threshold is briefly discussed.
An analytical model for the detection performance of multiple channel time history display formats such as used with multibeam systems and spectrograms is presented. The resulting receiver operating characteristic (ROC) curves are presented as a function of the number of lines displayed. A typical comparison with the simple threshold excess decision rule operating on the same data is also presented.
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