prof. Ing. Karel Hoffmann, CSc.

Measurement of extreme impedances, it is impedances with reflection coefficient close to 1, is in microwave frequency range a very new topic. The research was initiated in 2007 by the supervisor. Since that time new measurement systems for these measurements have been developed. Further development of these systems can be expected. Calibrations, measurement test fixtures and correction methods are very topical and yet not solved topics. Further research in this area is necessary for future measurement of perspective components based on carbon nano-tubes, tuning varactors with extremely low capacitance in the order of atto farad. Another applications can be supposed also in scanning microwave microscopy.

Development of microwave and mm-wave imaging systems is very fast in last years. Current systems are very complicated and expensive. The aim of the research is to find new possible system solutions with simpler construction and acceptable imaging properties.

A research in the area of microwave sensors for precise distance measurements and thickness measurement of metallic materials has been guided by the supervisor in last several years. A new microwave interferometric measurement method with theoretical distance precision in the order of microns has been developed. There is a great space for further research of calibration and correction algorithms for elimination of systematic errors and also for further circuit improvement of the measurement systems.

A research in the area of precise measurements on planar lines is going on at the department of electromagnetic field. A new earlier unknown source of systematic measurement errors has been discovered. It is radiation of the adapter between coaxial line and an open planar line like e.g., microstrip line. Many of significant findings has been discovered. However, a lot of space is still remaining for further research. The problematic of adapter radiations in the area of measurement on differential lines applied namely in digital circuits remains unmapped.