Seasonal Variations of Polarization Diversity Gain in a Vegetated Area considering High Elevation Angles and a Nomadic User

Seasonal variations of the polarization diversity gain are addressed for a nomadic user in a vegetated area taking high elevation angles and nongeostationary satellites into consideration. Corresponding experimental data were obtained at a frequency of 2.0 GHz at Stromovka Park in Prague, the Czech Republic, within the full in-leaf and out-of-leaf periods of 2013 and 2014, respectively. By detecting copolarized and cross-polarized components of the transmitted left- and right-handed circularly polarized signals, the corresponding diversity gain was obtained for multiple-input single-output (MISO), single-input multiple-output (SIMO), and combined MISO/SIMO cases. It was found that tree defoliation results in a significant decrease of the polarization diversity gain achieved for low time percentages in particular scenarios

Clutter Loss Modelling for Low Elevation Link Scenarios

An analysis of the accuracy of several deterministic and semideterministic propagation models related to calculating clutter loss for low elevation links is presented. Predictions are compared with measurements carried out at 2 GHz over three locations. By comparing prediction and measurement techniques, improved predictive capabilities of deterministic models are demonstrated and quantified in cases where a description of the propagation environment exists and an air-to-ground scenario is considered

Obrazovanje na području antena, rasprostiranja valova i mikrovalova

The paper is focused on teaching of »applied microwaves«. Attention is turned to antennas, but the same structure of education process is possible to apply for e.g. radio-wave propagation, microwaves, EMC, and other »electromagnetic topics« in their whole. The structure of the education is based on the appropriate amount of the theory followed by the computer simulations, the theoretical and engineering design and development, the measurement and final evaluation, which acts as the feedback between the initial goals and the final results. Important role of laboratory experiments based on flexible experimental set-ups is introduced and the possibility of distant (internet) laboratory excess is mentioned.Rad je usredotočen na učenje »primijenjenih mikrovalova«. Pozornost je okrenuta antenama, ali se ista struktura obrazovnog procesa može primijeniti na rasprostiranje radijskih valova, mikrovalove, elektromagnetsku kompatibilnost i druge elektromagnetske sadržaje. Struktura obrazovanja osniva se na odgovarajućoj teoriji popraćenoj simulacijama na računalu, teorijskom i inženjerskim proračunima i razvoju, mjerenjima i konačnoj provjeri, koja djeluje kao povratna veza između početnih ciljeva i konačnih rezultata. Utvrđena je važna uloga laboratorijskih eksperimenata temeljenih na fleksibilnim eksperimentalnim modelima i spomenuta mogućnost učenja na daljinu

A Survey of Air-to-Ground Propagation Channel Modeling for Unmanned Aerial Vehicles

In recent years, there has been a dramatic increase in the use of unmanned aerial vehicles (UAVs), particularly for small UAVs, due to their affordable prices, ease of availability, and ease of operability. Existing and future applications of UAVs include remote surveillance and monitoring, relief operations, package delivery, and communication backhaul infrastructure. Additionally, UAVs are envisioned as an important component of 5G wireless technology and beyond. The unique application scenarios for UAVs necessitate accurate air-to-ground (AG) propagation channel models for designing and evaluating UAV communication links for control/non-payload as well as payload data transmissions. These AG propagation models have not been investigated in detail when compared to terrestrial propagation models. In this paper, a comprehensive survey is provided on available AG channel measurement campaigns, large and small scale fading channel models, their limitations, and future research directions for UAV communication scenarios

Penetration Loss Measurement and Modeling for HAP Mobile Systems in Urban Environment

The aim of this paper is to present the results of a measurement campaign focused on the evaluation of penetration loss into buildings in an urban area as a function of the elevation angle. An empirical model to predict penetration loss into buildings is developed based on measured data obtained using a remote-controlled airship. The impact on penetration loss of different buildings and user positions within the buildings is presented. The measured data are evaluated as a function of the elevation angle. The measurement campaign was carried out at 2.0 GHz and 3.5 GHz carrier frequencies, representing the frequency band for high altitude platform third-generation mobile systems and, potentially, next generation mobile systems, mobile WiMAX, for example, the new penetration loss model can be used for system performance simulations and coverage planning

Feasibility of UAV Link Space Diversity in Wooded Areas

Space diversity techniques provide an effective way to mitigate the deep fades in received power in a scattering environment. Space diversity influence on narrowband UAV links, which are unique due to the elevation angle and mutual position of a moving transmitter in homogeneous environment and static receiver in scattering environment, is analyzed in a wooded area using a remotely controlled airship at 2 GHz. The experimental link forms a 1x4 SIMO configuration with influence quantified by values of diversity gain and subsequent comparison with Rayleigh fading series. The mutual antenna distance and elevation angle influence is also studied as the difference between the wooded area and an open field or urban environment

EMC v oblasti radioreleovych spoju.

Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Wireless Mobile and Personal Communications.

Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi