Milos Mazanek

Wireless Power Transmission: R&D Activities Within Europe

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 fundamental enabling technology of the Internet of Things concept, as well as machine-to-machine communications, since it minimizes the use of batteries and eliminates wired power connections. WPT technology brings together RF and dc circuit and system designers with different backgrounds on circuit design, novel materials and applications, and regulatory issues, forming a cross disciplinary team in order to achieve an efficient transmission of power over the air interface. This paper aims to present WPT technology in an integrated way, addressing state-of-the-art and challenges, and to discuss future R&D perspectives summarizing recent activities in Europe.

Optimization of tapered slot Vivaldi antenna for UWB application

The paper deals with the optimization of the Vivaldi antenna, which is suitable for the measurement of impulse radiation characteristics. In case of particular ultra wideband applications (i.e. radar, positioning, etc.), it is crucial to know the transient responses of antennas. The optimization process searches for the Vivaldi antenna shape. The optimization accomplishes three required parameters - good matching, minimal distortion and smaller antenna dimensions. The parametric study and the manual step-by-step method were used in the process of antenna optimization. The main part of the paper presents the impulse distortion minimization by the feeding transition and the overall obtained results, which are compared with measured characteristics.

Modal Resonant Frequencies and Radiation Quality Factors of Microstrip Antennas

The chosen rectangular and fractal microstrip patch antennas above an infinite ground plane are analyzed by the theory of characteristic modes. The resonant frequencies and radiation are evaluated. A novel method by Vandenbosch for rigorous evaluation of the radiation is employed for modal currents on a Rao-Wilton-Glisson (RWG) mesh. It is found that the resonant frequency of a rectangular patch antenna with a dominant mode presents quite complicated behaviour including having a minimum at a specific height. Similarly, as predicted from the simple wire model, the radiation exhibits a minimum too. It is observed that the presence of out-of-phase currents flowing along the patch antenna leads to a significant increase of the factor.

A study of gas and rain propagation effects at 48 GHz for HAP scenarios

The atmosphere and rainfall significantly limit the performance of millimeter wave links and this has to be taken into account, particularly, during planning of high altitude platform (HAP) networks. This paper presents results from the measurement and simulation of these phenomena. A simulation tool from our previous analyses of terrestrial point-to-multipoint systems has been modified for HAP systems. Based on a rainfall radar database and gas attenuation characteristics as measured by a Fabry-Perot resonator, the performance of a simple link, two-branch diversity links, and more complicated HAP scenarios are discussed.

The Radiation

Closed-form equations are given for radiation quality factor of a thin-wire

Q

\lambda/2

-Factor of a Horizontal

dipole above an infinite electric ground plane. Particular results of interest include a simple formula for a small separation between the dipole and the ground and for one dipole in free space.

\lambda/2

This paper introduces the Fabry-Perot resonator designed for the frequency band 18-80 GHz. The Fabry-Perot improvement using a hyperbolical lens, which transforms the spherical wave, radiated by the standard horn antennas to the plane wave irradiating the coupling foil of the resonator is discussed. This approach helps to efficiently couple the energy into and out of the resonator. The quality factors (loaded as well as unloaded) were evaluated from the measured frequency responses of the resonances. These quality factors show the effectiveness of used lenses and functionality of the resonator within the frequency band 75-110 GHz, which is higher than the designed band.

Dipole Above Ground Plane

In case of the near-field measurement, the radiated field by the measured antenna is received by two- dimensional scanner in defined points. During the process of the field scanning, the cable between the VNA and the scanner antenna is moved and its parameters are changed. This paper deals with the evaluation of the cable parameters changes. The dominant change is represented by the phase deviation of the cable transmission coefficient. The paper also proposes the method of the cable errors correction and evaluation of the correction method efficiency. The correction can be based on the full calibration at the reference plane of the scanner antenna feeding in all points of scanned field. The aforementioned approach is more time consuming than the proposed method, where the full calibration is performed in one selected point, while the correction of the cable parameters is based on the estimation based on the input impedance of the cable loaded by the scanner antenna.

Dielectric Lens Utilization for Fabry-Perot Resonator Optimal Coupling

The theory of characteristic modes is a very useful tool to get physical insight into antenna behavior. It is possible to easily obtain resonant frequencies, modal radiation Q or bandwidth, modal currents and modal radiation patterns. The paper is intended to study well known linear antennas under this new point of view.