Mats Gustafsson

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In the present paper an iterative time-reversal algorithm, that retrofocuses an acoustic wave field to its controllable part is established. For a fixed temporal support, i.e., transducer excitation time, the algorithm generates an optimal retrofocusing in the least-squares sense. Thus the iterative time-reversal algorithm reduces the temporal support of(More)
A passive system is one that cannot produce energy, a property that naturally poses constraints on the system. In this paper there is a review of some results on linear, time translational invariant, continuous, causal and passive systems, where it turns out that Herglotz functions are related to the Fourier transform of the impulse response of such(More)
Antenna current optimization offers performance bounds and suggestions for the distribution of the desired antenna currents. Many current optimization problems can be formulated as convex optimization problems that are solved efficiently with explicit error bounds. The formulations as convex optimization problems are also illuminating as they can easily be(More)
We demonstrate a digital holographic method in which two different substances in a blend are discerned. The method requires only one set of exposures and one reconstruction in the plane of focus. The phase is unwrapped by Flynn's discontinuity algorithm to produce an image of the variation of the optical distance of the illuminating wave. Objects with(More)
Extraordinary transmission through subwavelength apertures is usually observed in a narrow bandwidth range, and the transmission outside this range is low, in agreement with classical results. The analysis presented here is based on the Babinet's principle and hence scattering by the complementary structure, where the apertures are replaced by finite(More)
In this paper, physical bounds on scattering of acoustic waves over a frequency interval are discussed based on the holomorphic properties of the scattering amplitude in the forward direction. The result is given by a dispersion relation for the extinction cross section which yields an upper bound on the product of the extinction cross section and the(More)
The purpose of this paper is to give an overview of some recent developments and future potentials regarding Fisher information analysis in microwave tomography. In particular, the Fisher Information integral Operator (FIO) is defined using the Fre¿chet derivative, yielding a gradient based formulation which is useful in connection with analytical Green's(More)
Antenna current optimization is a tool that offers many possibilities in antenna technology. Optimal currents are determined in the antenna design region and used for physical understanding, as a priori estimates of the possibilities to design antennas, physical bounds, and as figures of merits for antenna designs. Antenna current optimization is(More)
We have developed an Internet-based tool for remote realtime auscultation. The device was based on a commercially available electronic stethoscope and a PC which digitized and transmitted the signals. A voice and video channel were also available. The remote auscultation tool was evaluated between two sites in Sweden separated by a distance of 500 km. A(More)