Maximum-likelihood narrow-band direction finding and the EMalgorithm
Miller, M.I.; Fuhrmann, D.R.
Acoustics, Speech and Signal Processing, IEEE Transactions on
Volume 38, Issue 9, Sep 1990 Page(s):1560 - 1577
Digital Object Identifier 10.1109/29.60075
Summary:Generalized EM (expectation-maximization) algorithms have been
derived for the maximum-likelihood estimation of the
direction-of-arrival of multiple narrowband signals in noise. Both
deterministic and stochastic signal models are considered. The algorithm
for the deterministic model yields estimates of the signal amplitudes,
while that for the stochastic model yields estimates of the powers of
the signal. Both algorithms have the properties that their limit points
are stable and satisfy the necessary maximizer conditions for
maximum-likelihood estimators. It is shown via simulation that the
maximum-likelihood method allows for the resolution of the
directions-of-arrival of signals at angular separation and noise levels
for which other high-resolution methods will not work. Algorithm
convergence does depend on initial conditions; however, convergence to a
global maximum has been observed in simulation when the initial
estimates are within a significant fraction if one beamwidth
(componentwise) of this maximum. Simulations also show that the
deterministic model has a significant impact on the angle estimator
performance
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