Michal Mrnka

Enhanced-Gain Dielectric Resonator Antenna Based on the Combination of Higher-Order Modes

The combination of two higher-order hybrid electromagnetic modes ( HEM133 and HEM123) in a simple cylindrical dielectric resonator is exploited in the presented letter to enhance antenna gain. Both modes were excited by the same feeding aperture in the ground plane of a microstrip line. A linearly polarized, broadside radiation pattern with maximum realized gain of about 11.6 dBi was successfully obtained. The antenna was designed for the ISM band with central frequency 5.8 GHz and relative bandwidth of at least 2.6%. For fabrication, we used a layered Arlon AR600 substrate of relative permittivity 6.15. Experimental results showed reasonable agreement with simulations and validated the new concept of the high-gain dielectric resonator antenna.

Wide-band dielectric resonator antennas for RF energy harvesting

Energy harvesting seems to be a suitable solution for remote device powering in systems like wireless sensor networks, which are becoming ubiquitous. In presented paper, a wide-band Dielectric Resonator Antenna (DRA) for RF energy harvesting is studied. The frequency band of interest lies between 1.84 GHz and 2.445 GHz, covering three main wireless communication systems, namely Global System for Mobile Communications (GSM) operating on 1800 MHz, Universal Mobile Telecommunications System (UMTS) at 2100 MHz and wireless local area network (WLAN) based on 802.11 IEEE standard [9] at 2400 MHz. Two antennas based on identical bow-tie dielectric resonators with different feeding schemes are proposed. The aperture coupled DRA shows superior performance in terms of impedance matching and stability of the radiation pattern when compared to the probe coupled antenna. The simulation results of these two antennas are compared and experimentally verified by measurements.

3D-textile integrated corrugated horn antenna

The paper describes a corrugated substrate integrated horn antenna designed for surface wave excitation in the UWB band groups 3, 4, 5 and 6 (6-10 GHz). The antenna is optimized for integration into 3.4 mm thick textile of relative permittivity of 1.2. The corrugated substrate integrated waveguide is fed by a microstrip line and for connectivity a transition from microstrip line to coaxial line is designed. In order to enhance the impedance matching, we utilize thin strip lines placed in front of the aperture. The directivity of the antenna is 12.5 dBi at the 8 GHz and the antenna efficiency is about 70 %.

An Effective Permittivity Tensor of Cylindrically Perforated Dielectrics

In the letter, we propose a simple analytical effective permittivity model of perforated dielectrics composed of through-hole cylindrical perforations. As the perforated dielectrics are uniaxial media, the model respects the anisotropic properties of the material and the results are simple engineering formulas for effective permittivities of ordinary and extraordinary wave for polarization corresponding to parallel and perpendicular orientation with respect to the axis of perforations. The model is based on the 2-D Maxwell Garnett approximation of inhomogeneous media valid for circularly shaped perforations. The analytical results obtained for propagation of transverse electromagnetic wave are verified by unit-cell full-wave simulations of triangular perforations lattice, and a very good agreement is obtained.

Random gaussian rough surfaces for full-wave electromagnetic simulations

In the paper, we present a straightforward procedure to utilize random rough surfaces with Gaussian probability distribution in commercial full-wave electromagnetic simulation software CST Microwave Studio. Random, two dimensional (2D) matrices with desired size and statistical parameters such as correlation length and root mean square height of the profile are generated in MATLAB®. In order to obtain desired surface parameters, we employ a Gaussian random 2D matrix generator and subsequent filtering with Gaussian 2D filter. A macro in Visual Basic for Application is then developed to convert these matrices into continuous surfaces in CST MWS. Radiation patterns of horizontally and vertically polarized half-wave dipoles are finally evaluated above these surfaces and compared to analytical models.

Wireless body area networks numerical, experimental and approximate characterization

For the numerical design of on-body communication components, accurate and reliable models of a communication channel of a wireless body area network (WBAN) are needed. Whereas numerical models (volume-pixel ones, layered ones) can be very detailed, experimental models consist of a single layer of an agar gelatin usually. In the paper, an analytical model based on Norton surface waves is used to describe the surface wave propagating along the interface between the agar phantom and environment. For the frequency band of interest, electrical parameters of the analytical model of the agar phantom are optimized so that the propagation properties of the phantom can agree with properties computed by numerical layered models, volume-pixel models, or experiments.

Antenna Range Illuminator Based on a Septum Polarizer and a Dual-Mode Horn [Measurements Corner]

In this article, an original design of a range illuminator based on a stepped-septum polarizer and a dual-mode horn is discussed. However, the designed polarizer can also be used with other waveguide antennas, such as pyramidal horns and corrugated horns. A simple procedure for determining the initial septum geometry for the subsequent optimization is described, and based on this, a two-step septum polarizer is developed. A carefully designed dual-mode horn antenna with a rectangular aperture is then utilized to increase the illuminators gain and suppress sidelobe levels. Results of full-wave electromagnetic simulations are presented and compared to experimentally measured data with good agreement.

Gain improvement of higher order mode dielectric resonator antenna by thin air gap

The paper examines the influence of a thin air gap between a dielectric resonator and its ground plane on radiation parameters of the dielectric resonator antenna (DRA) operating with certain higher order modes. Gain improvement of about 1.6 dB is observed for optimal size of the gap, resulting in 13.2 dBi realized gain. Along with gain enhancement, the side lobe level suppression is improved as well. First, the effect is studied using full-wave simulation software and afterwards confirmed by experiments.

Rectangular dielectric resonator antenna with switchable radiation pattern

The paper is focused on a design of a rectangular dielectric resonator antenna with a switchable radiation pattern. A broadside or omnidirectional radiation pattern can be generated at the same frequency by feeding one of two input ports. In our work, the TEδ11 mode of the rectangular dielectric resonator is used to radiate in the broadside direction. On the other hand, the omnidirectional pattern is generated by a thick vertical monopole embedded inside the resonator. The interaction between two feeds is evaluated and taken into account during the design. The proposed antenna is manufactured and its performance validated by measurements with good agreement compared to simulation results.