VŠETULA, P. Anténní řady se syntetizovanou kmitočtovou závislostí zisku [online]. Brno: Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií. 2014.
Dissertation thesis written by Petr Všetula was focused on the synthesis of filtering antennas. A filtering antenna mimics a frequency filter which output port is replaced by the radiation into the environment. Whereas the transfer function of the filter depends on time derivatives of currents and voltages, the transfer function of the filtering antenna is given by integrals of currents on antenna elements. For this reason, a sharp shaping of the output quantity, i.e. the frequency response of gain in a gived direction, is rather difficult. The original contribution of the thesis can be found in two areas: 1. Multi-objective synthesis of filtering antennas. When synthesizing a filtering antenna, a prescribed frequency response of gain is not the only objective. The synthesis procedure has to also comprise impedance matching of the antenna, the sidelobe level, and the parasitic variation of the main lobe direction. Since the objectives are conflicting, multi-objective tools have to be used to identify the Pareto front of optimal solutions. According to my knowledge, a multi-objective synthesis of filtering antennas has not been published yet. For the multi-objective synthesis, the MOSOMA algorithm was exploited. Such a class of problems has not been handled by MOSOMA yet. So, this is the second important contribution of the thesis. 2. Exploitation of space-mapping in the synthesis. For a coarse design, simplified antenna models developed in MATLAB are used in the first step. In the second step, the refined 4NEC model is used to include mutual couplings among elements into the evaluation of antenna parameters. Finally, the CST model is applied to comprise even the construction details into the final tuning. So, the model is mapped from the simplest space to the most realistic space. That way, a high efficiency of the design procedure can be ensured. According to my knowledge, the three-step space-mapping has not been published yet. Initially, the thesis was intended to develop filtering antennas for on-body communication. From this reason, a long time was spent on developing special horn antennas with a dominant magnetic component in the aperture. This development was published in Microwave and Optical Technology Letters and at several conferences. Unfortunately, the development of a simple and efficient feeding network for a corresponding antenna array was not successful. For this reason, a horn array was replaced by the array of planar dipoles. The final structure was described in a paper submitted to IEEE Antennas and Wireless Propagation Letters. During his studies, Petr contributed to projects focused on the development of antennas for bio-medical application (funded by Czech Science Foundation), antennas for 75 GHz / 85 GHz wireless links (funded by Ministry of Industry and Trade), and antenna arrays for special application (funded by Ministry of Industry and Trade). Petr actively participated in the European School of Antennas and the International Traveling Summer School on Microwaves and Lightwaves. That way, he has built several international contacts. Links with Prof. Peter Hall from the University of Birmingham belong to the most important ones. I find the contribution of Petr to the research of my team very strong and highly important. For this reason, I fully support Petr’s thesis to be defended.
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