The paper present a study of frequency shift of the reflection coefficient minimal absolute value dependence on antenna spacing in linear and circular arrays. The spacing of CB-band monopole antenna was in the range of 0.015 to 0.12 multiples of the antenna working wavelength. Number of elements in the antenna arrays ranged from two to four. Frequency dependence of minimal absolute value of the reflection coefficient was obtained by simulations and also experimentally confirmed in anechoic chamber. The research showed two facts. First, mutual impedance has the higher impact when antenna spacing is comparable with the reactive near field region. Second, circular antenna arrays are a better choice in applications for a small number of antennas with that spacing.
The use of programable logic controllers (PLC) technology in electrical networks 230 V causes electromagnetic radiation that interferes with other electrical equipment connected to the network [–]. Therefore, this article describes the issues of electromagnetic compatibility (EMC) of new PLC adapters used in IP broadband services in a multi-user environment. The measurements of disturbing electromagnetic field originated in PLC adapters were made in a certified laboratory EMC (laboratory of electromagnetic compatibility) in the Institute of Electrical Engineering at Faculty of Electrical Engineering and Information Technology of the Slovak University of Technology in Bratislava. The measured spectra of the radiated electromagnetic field will be compared with the results obtained when testing older PLC modems .
This article addresses the method of sensing mechanical quantities, in particular force and pressure, without the electrical connection of the sensing element and the electronics. The information about the mechanical quantity is transmitted only by evaluating the changes in the electromagnetic field created around the sensor. The sensor is designed on the basis of a flexible micro-electro-mechanical element (MEMS), the resonance of which carries the information about the measured quantity.