On the use of electromagnetic asymptotic methods for the estimation of communications propagation channel in complex environments

The ray tracing method and the high frequency theories this method is based on are recapitulated in chapter 1 in the formulation implemented in the software EMviroment-EMv used in this thesis to predict the electromagnetic propagation in complex environment. The estimation of channel parameters by asymptotic propagation model based software could show some drawbacks, such as long simulation times caused by the multipath reconstruction, and a huge memory dimension requirement to store the multipath info that is useful for the frequency analysis of the channel. A lot of energies were spent in optimizing and speeding up the ray tracing algorithms by researchers in the last decades. In the implementation of ray tracing based solver the study of the acceleration of the geometrical algorithm to predict the multipath has a great importance, because the physical coherence of this deterministic approach leads to a boost of the computational time. A method for speeding up a ray tracing based electric field prediction model suitable for urban environments investigation is described in chapter 2. The physical coherence of this high frequency method allows to accurately estimate the wireless communication channel frequency response and the antennas influence on the transmitted and received signals. A frequency analysis of the channel is required, for example, in ultra-wideband applications. In this case the frequency selective behavior of the channel needs to be estimate to correctly predict the communication link impairment. The frequency response definition by multipath prediction is shown in chapter 3 The Doppler frequency shift is caused by the presence of relative movement by the transmitter, the receiver and the complex objects present in the scene. The power distribution in the Doppler frequency shift domain can be derived by the spreading function estimation. By definition the spreading function could be calculated starting from the knowledge of the impulse response of a channel link by means of the Fourier transform. An alternative direct deterministic approach for its estimation avoiding the Fourier transform has been formulated and is presented in chapter 4 applied to the Munich airport complex scenario. The radar cross section evaluation of metal and dielectric objects needs to invoke the asymptotic techniques to overcome the limitations the full-wave techniques present at high frequencies. The method of moments, for example, needs a denser and denser mesh definition of the studied object as the wavelength decreases to respect the applicability constraints of the method. Because the complexity of this method is proportional to the currents on the facets, the number of unknowns can get to saturate the computer memory availability and increase the simulation time. The approximations that can be introduced with the assumption of far-field sources and observers at high frequencies allow to unburden the calculation procedures obtaining good estimations of the scattered field. The Physical Optics - PO theory is the most diffuse solution solving these kind of problems, often together with a ray bouncing analysis to predict the illuminated facets of the object. A PO based solver to predict the scattered field by a metallic or dielectric object and the radar cross section spectrum of rotating objects is presented in chapter 5

13th Annual Review of Progress in Applied Computational Electromagnetics at the Naval Postgraduate School, Monterey, CA, March 17-21, 1997, Conference Proceedings Volumes I & II

Includes Volumes 1 &

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Semi-automatic liquid filling system using NodeMCU as an integrated Iot Learning tool

Computer programming and IoT are the key skills required in Industrial Revolution 4.0 (IR4.0). The industry demand is very high and therefore related students in this field should grasp adequate knowledge and skill in college or university prior to employment. However, learning technology related subject without applying it to an actual hardware can pose difficulty to relate the theoretical knowledge to problems in real application. It is proven that learning through hands-on activities is more effective and promotes deeper understanding of the subject matter (He et al. in Integrating Internet of Things (IoT) into STEM undergraduate education: Case study of a modern technology infused courseware for embedded system course. Erie, PA, USA, pp 1–9 (2016)). Thus, to fulfill the learning requirement, an integrated learning tool that combines learning of computer programming and IoT control for an industrial liquid filling system model is developed and tested. The integrated learning tool uses NodeMCU, Blynk app and smartphone to enable the IoT application. The system set-up is pre-designed for semi-automation liquid filling process to enhance hands-on learning experience but can be easily programmed for full automation. Overall, it is a user and cost friendly learning tool that can be developed by academic staff to aid learning of IoT and computer programming in related education levels and field