Wideband microwave imaging is of interest wherever optical opaque scenarios need to be analyzed, as these waves can penetrate biological tissues, many building materials, or industrial materials. One of the challenges of microwave imaging is the computation of the image from the measurement data because of the need to solve extensive inverse scattering problems due to the sometimes complicated wave propagation. The inversion problem simplifies if only spatially limited objects—point objects, in the simplest case—with temporally variable scattering properties are of interest. Differential imaging uses this time variance by observing the scenario under test over a certain time interval. Such problems exist in medical diagnostics, in the search for surviving earthquake victims, monitoring of the vitality of persons, detection of wood pests, control of industrial processes, and much more. This paper gives an overview of imaging methods for point-like targets and discusses the impact of target variations onto the radar data. Because the target variations are very weak in many applications, a major issue of differential imaging concerns the suppression of random effects by appropriate data processing and concepts of radar hardware. The paper introduces related methods and approaches, and some applications illustrate their performance.
In clinical routine there is a need of periodical recording of vital parameters in high risk groups, for example the intraocular pressure. A solution for this could be an intracorporeal sensor using a wireless radio frequency (RF) transmitter. Thereby the risk of an infection is reduced, because a percutaneous connection is not necessary. A limiting factor for some organs is the size of implants. For designing an energy efficient low power RF transmitter, the dielectric parameters of representative biological tissues have to be determined. In this article two methods of measurement are presented, the coaxial probe and transmission line method. With this information about the dielectric parameters a miniaturized RF transmitter was built for proofing tests on phantoms with equal properties like biological tissue.
For evaluation of extra-cellular recordings with multi-electrode arrays (MEAs) an algorithm is needed to detect different types of cellular activity. The algorithm presented in this paper is based on correlation. It is an efficient and simple algorithm which is compared with the wave_clus toolbox. In contrast this toolbox is using wavelets for clustering the cell activity.
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