383 research outputs found
Analytic Expressions for Stochastic Distances Between Relaxed Complex Wishart Distributions
The scaled complex Wishart distribution is a widely used model for multilook
full polarimetric SAR data whose adequacy has been attested in the literature.
Classification, segmentation, and image analysis techniques which depend on
this model have been devised, and many of them employ some type of
dissimilarity measure. In this paper we derive analytic expressions for four
stochastic distances between relaxed scaled complex Wishart distributions in
their most general form and in important particular cases. Using these
distances, inequalities are obtained which lead to new ways of deriving the
Bartlett and revised Wishart distances. The expressiveness of the four analytic
distances is assessed with respect to the variation of parameters. Such
distances are then used for deriving new tests statistics, which are proved to
have asymptotic chi-square distribution. Adopting the test size as a comparison
criterion, a sensitivity study is performed by means of Monte Carlo experiments
suggesting that the Bhattacharyya statistic outperforms all the others. The
power of the tests is also assessed. Applications to actual data illustrate the
discrimination and homogeneity identification capabilities of these distances.Comment: Accepted for publication in the IEEE Transactions on Geoscience and
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Habitats, abundância e ocorrência das espécies de aves do pantanal de Pocone, Mato Grosso, Brasil
Multi-beam 4 GHz Microwave Apertures Using Current-Mode DFT Approximation on 65 nm CMOS
A current-mode CMOS design is proposed for realizing receive mode multi-beams
in the analog domain using a novel DFT approximation. High-bandwidth CMOS RF
transistors are employed in low-voltage current mirrors to achieve bandwidths
exceeding 4 GHz with good beam fidelity. Current mirrors realize the
coefficients of the considered DFT approximation, which take simple values in
only. This allows high bandwidths realizations using simple
circuitry without needing phase-shifters or delays. The proposed design is used
as a method to efficiently achieve spatial discrete Fourier transform operation
across a ULA to obtain multiple simultaneous RF beams. An example using 1.2 V
current-mode approximate DFT on 65 nm CMOS, with BSIM4 models from the RF kit,
show potential operation up to 4 GHz with eight independent aperture beams.Comment: 7 pages, 4 figures, In: IEEE International Microwave Symposium 201
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