Authors:
Douglas A Abraham,
Page (NA) Paper number 1237
Abstract:
The probability of false alarm (Pfa) in active sonar systems is an
important system performance measure. This measure is typically estimated
by the proportion of alarms to opportunities over some finite window,
essentially forming the sample exceedance distribution function (EDF).
It is common for sonar systems to be `over-sampled'; that is, to have
a sampling rate higher than the minimum required for representing the
bandwidth of the received signal, resulting in reverberation data that
are correlated from sample to sample. The performance of the sample
EDF in Pfa estimation under such conditions is of interest. It is easily
shown that the estimator remains unbiased with correlated data. However,
it is shown in this paper that the variance of the estimator may be
reduced from that for independent data by oversampling. Further, the
variance is seen to fall between the Cramer-Rao lower bound based on
independent thresholded (binary) data and that based on the complex
matched filter output data.
Authors:
Donald W Tufts,
Edward C Real,
Page (NA) Paper number 2243
Abstract:
We present a method for estimating threshold values for signal detection
and classification systems in which a prescribed value of false alarm
probability is needed. The threshold values are determined directly
from observed test statistic data without knowledge of the probability
distribution of the data. Our method uses the concept of tolerance
intervals from nonparametric statistics.
Authors:
Zoi-Heleni Michalopoulou,
Page (NA) Paper number 1773
Abstract:
A signal propagating in a shallow water waveguide is subjected to (a)
multiple reflections off the ocean boundaries and (b) distortion because
of the dispersive properties of the propagation medium. Because of
these corruptions, the received signal differs substantially from the
transmitted signal. Although the transmission is sometimes exactly
known, the received signal cannot be described in detail because of
inadequate knowledge of the ocean impulse response. Ignoring the effects
of the ocean on the signal, or representing them inaccurately, can
lead to deterioration of the detection statistics. This paper compares
the performance of methods designed for distortion-free, multiple-reflection
transmission in realistic, dispersive environments. Two existing methods,
the RCI processor and the simple source-receiver matched-filter, and
a new detector are evaluated. The impact of distortion on signal transmission
is assessed by comparing the distortion-free methods to the optimal
processor, which models the effects of the propagation medium on the
signal.
Authors:
Biao Chen,
Peter K Willett,
Roy L Streit,
Page (NA) Paper number 1715
Abstract:
A simple yet effective statistic is proposed for detecting transient
buried in partially unknown ambient noise. The transient model is the
frequency scattered increased variance observations. We pose the transient
detection problem as homogeneity test and the statistic is derived
as the (generalized) likelihood ratio test of overdispersion when the
underlying observation sequence follows a double exponential distribution.
Numerical testing focuses on the comparison of this scheme with the
CFAR power-law detector.
Authors:
Aleksandar Dogandzić,
Arye Nehorai,
Page (NA) Paper number 1090
Abstract:
We present maximum likelihood (ML) methods for active estimation of
range (time delay), velocity (Doppler shift), and direction of a point
target with a radar array in spatially correlated noise with unknown
covariance. We consider structured and unstructured array response
models and compute the Cramer-Rao bound (CRB) for the time delay, Doppler
shift, and direction of arrival. We derive ambiguity functions for
the above models and discuss the relationship between identifiability,
ambiguity, and the Fisher information matrix.
Authors:
Stacy L Tantum, Department of Electrical Engineering, Duke University (U.K.)
Loren W Nolte, Department of Electrical Engineering, Duke University (U.K.)
Page (NA) Paper number 1805
Abstract:
The signal-to-noise ratio of real data is rarely known with complete
certainty. However, Bayesian matched-field processing techniques for
ocean acoustic source localization often require the signal-to-noise
ratio (SNR) to be known a priori. In this paper, the effects of SNR
mismatch on the performance of a Bayesian matched-field source localization
method, the optimum uncertain field processor [A. M. Richardson and
L. W. Nolte, J. Acoust. Soc. Am. 89(5), 2280-2284 (1991)], are investigated.
Theoretical and empirical analyses show that when the maximum a posteriori
(MAP) estimate is utilized as the source location estimate, the localization
performance is unaffected by the uncertainty regarding the SNR, provided
that the assumed SNR is sufficiently high.
Authors:
Arye Nehorai,
Petr Tichavsky, Institute of Information Theory and Automation, Academy of Sciences of the Czech Republic (Czech Republic)
Page (NA) Paper number 1401
Abstract:
We present two adaptive cross-product algorithms for tracking the direction
to a moving source using an electromagnetic vector sensor. The first
is a cross-product algorithm with a forgetting factor, for which we
analyze the performance and derive an asymptotic expression of the
variance of angular estimation error. We find the optimal forgetting
factor that minimizes this variance. The second is a Kalman filter
combined with the cross-product algorithm, which is applicable when
the angular acceleration of the source is approximately constant.
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