Digitalno oblikovanje dijagrama zračenja dvodimenzionalnog antenskog niza za pojas frekvencija X

Our aim is to develop a microwave antenna whose radiation pattern is electronically controlled. The radiation pattern of regular antennas is determined by the Fourier-transform of the complex illumination function on the antenna aperture. This radiation pattern is mechanically fixed so its alteration is impossible. Therefore we construct an antenna system of several antenna elements. All elements are actuated by separate transmitters; we control the amplitude and the phase of the supplying currents of the antenna elements. This way, we are able to control the radiation pattern of the antenna system. The control is computerized so that there is a possibility to change the radiation pattern quickly.Naša je namjera razviti mikrovalnu antenu čijim se dijagramom zračenja može upravljati elektronički. Dijagram zračenja običnih antena odreden je Fourierovom transformacijom kompleksne funkcije pobude aperture antene. Taj je dijagram zračenja odreden izvedbom antene i njegova izmjena nije moguća. Stoga se naš antenski sustav sastoji od više antenskih elemenata. Svi se antenski elementi pobuduju odvojenim odašiljačima pa je moguće ugadati amplitude i faze pobudnih struja antenskih elemenata. Na taj način možemo upravljati dijagramom zračenja antenskog sustava. Upravljanje je izvedeno pomoću računala tako da je moguće vrlo brzo mijenjati dijagram zračenja

Mapping cost distance using air traffic data

Recent trends in transport and communication infrastructures have had a profound impact on the spatial organization of the world city network, which have long been of interest to geographers. Considering the former issue, our study is based on previous works on air transport geography and world city network studies. We introduce a new method to map the gap between geographical distance and cost distance by using air traffic data. In this paper, we created an international database for a large number of world cities and developed a way to map cost distance using conventional and Geographic Information System-based mapping techniques. The main result of this work is a set of maps showing the cost distances of world cities, which can be used as a significant source of information by world city network analysis