Jan Kracek

Jan Kracek
Czech Technical University in Prague | ČVUT · Department of Electromagnetic Field

Ph.D.

About

19
Publications
4,859
Reads
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265
Citations
Citations since 2017
8 Research Items
205 Citations
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2017201820192020202120222023010203040
2017201820192020202120222023010203040

Publications

Publications (19)
Article
Full-text available
A compact three-element shared-aperture waveguide antenna array for the 24–28 GHz microwave-frequency band is presented as a proof-of-concept of an array with steerable directional beam suitable for 5G telecommunication systems. The array is intended for use in a microwave photonic link and is sufficiently steerable only with the progressively phas...
Article
Full-text available
The theory of superdirective antenna arrays was discussed. The procedure for finding the excitation currents of fixed-geometry arrays, which maximizes the directivity, termed as superdirectivity, for a given direction and polarization, was described. The procedure was based on the solution of an eigenvalue problem including the directivity and matr...
Article
In this paper, we propose a novel frequency-domain reading method for the chipless radio frequency identification (RFID) tags. It is based on a single scalar measurement of transmission coefficient magnitude between two antennas by the presence of a tag. The method enables to reliably read the chipless RFID tags based on a dipole resonator array, w...
Article
Full-text available
The concept of source currents of a radiating source can be employed to express its directivity in some particular cases analytically. For an antenna array, this concept can be extended to the concept of a generalized directivity based on self- and mutual radiation intensities, self- and mutual radiated powers and excitation currents of array eleme...
Article
Full-text available
The analysis of capacitive wireless power transfer was conducted in a general manner. The circuit model of a capacitive wireless power transfer chain was presented. The derivation of the power transfer efficiency through the chain in question as well as the active power delivered to the appliance terminating this chain was shown. Both the case of t...
Article
This letter presents the novel 20 bit chipless radiofrequency identification transponder (tag) based on spiral capacitively loaded dipole scatterers of electrical size ka = 0.47, radar cross-section (RCS) σ = -29.3 dBsm, and bandwidth BW <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3dB</sub> = 20.9...
Article
The objective of this letter was to design a compact, battery-less system for an implantable semi-active UHF radio frequency identification (RFID) tag with inductive wireless power transfer for the human body. An RFID chip of the tag, combining powering from a reader by communication and from another source through inductive wireless power transfer...
Article
The analysis of magnetic field of a thin-wall air induction coil with a shape of finite cylinder of arbitrary cross section is described. The result of the analysis is a method for finding the scalar magnetic potential of the coil with the help of mutual inductance of the coil and the elementary loop. The magnetic flux density of the coil is found...
Article
Full-text available
Wireless power transmission (WPT) is an emerging technology that is gaining increased visibility in recent years. Efficient WPT circuits, systems and strategies can address a large group of applications spanning from batteryless systems, battery free sensors, passive RF identification, near-field communications, and many others. WPT is a fundamenta...
Article
This paper describes the method by which it is possible to construct simple algorithms for the calculation of the axial and transverse components of the intensity of the magnetic field of current loops and thin-wall air coils (solenoids). These are planar loops and tightly wound coils with a cross section of an arbitrary shape and parallel walls in...
Conference Paper
This contribution presents a measurement of harmonically changing magnetic flux density in the free space. The components of magnetic flux density vector are measured separately as effective value in the time. The measuring probe and its calibration are described in detail.
Article
Full-text available
The wireless power supply is motivated by sim-ple and comfortable use of many small electric appliances with low power input. This paper reviews the concepts that are suitable for wireless power transmission with respect to power supply of such appliances in small areas. The categorization of the concepts is made. The efficiency of the concepts is...
Article
The analysis of power balance for concepts of wireless power transmission based on electromagnetic induction is performed in general way. The derivation of power transmission efficiency is shown. The conditions for maximal efficiency and maximal active power delivered to the appliance are found. The maximal efficiency is expressed as a function of...
Conference Paper
This paper presents a part of a system for wireless power supply with the use of guided wave in the coupling surface. This system type is suitable for the supply of different devices with small power input in picocells. The main elements of the RF section of the system are slab dielectric waveguide which creates a coupling surface and adaptor to th...
Article
This paper presents an overview of the principles suitable for wireless power supply of devices with a small power input in picocells. This means predominantly different types of small electric devices in the space of rooms. Basic principles, namely electromagnetic induction and electromagnetic wave, are explained using examples of developed system...
Conference Paper
This paper presents set of software tool for the design and optimization of fractal patches described by the IFS.

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